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Atmospheric Environment 45 (2011) 3676e3684
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Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv
The AIRMEX study - VOC measurements in public buildings and schools/ kindergartens in eleven European cities: Statistical analysis of the data Otmar Geiss, Georgios Giannopoulos*, Salvatore Tirendi, Josefa Barrero-Moreno, Bo R. Larsen, Dimitrios Kotzias European Commission, Joint Research Centre, Institute for Health and Consumer Protection, Chemical Assessment and Testing Unit, Via E. Fermi 2749, Ispra 21027 (VA), Italy
a r t i c l e i n f o
a b s t r a c t
Article history: Received 7 December 2010 Received in revised form 8 April 2011 Accepted 15 April 2011
Indoor and outdoor air concentrations as well as personal exposure concentrations of volatile organic compounds (VOCs) have been measured during 2003e2008 in public buildings, schools, kindergartens and private homes in eleven cities over Europe covering geographic areas in north, central and south Europe during different seasons within the frame of the AIRMEX (European Indoor Air Monitoring and Exposure assessment) study. A database is presented containing the results for 23 VOCs based upon approximately 1000 samples taken from 182 different working environments (offices, classrooms, waiting halls) in public buildings, schools and kindergartens, from 103 private homeplaces and from adult volunteers (148 samples). The statistical analysis of the data demonstrated that sources in the indoor environment are prevailing for most of the investigated VOCs with indoor/outdoor (I/O) concentration ratios following the order: hexanal z D-limonene [ formaldehyde > acetone > 1butoxy-2-propanol > acetaldehyde > propanal > 1-butanol > n-undecane > methylcyclohexane > ndodecane. For aromatic hydrocarbons the main impact was shown to be penetration from outdoor air as indicated by I/O ratios near one and is characterised by significantly higher indoor as well as outdoor concentrations in the south of Europe with respect to the north. For the terpenes, the lowest indoor concentrations were measured during the warm season, which may be explained by higher ventilation rates and reactions with ozone penetrated from outdoor air. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: VOCs Database Indoor air quality Geographical variation Seasonal variation
1. Introduction Studies have shown that indoor exposure to volatile organic compounds (VOCs) can significantly contribute to adverse health effects (Dockery et al., 1993; Pope et al., 1995; Laden et al., 2001). The vast majority of human activities take place in indoor areas such as private homes, offices, shops and cars. Thorough investigations of the VOC pollution levels in such micro-environments are essential for the understanding of population exposure to harmful substances, for epidemiological work and the eventual amelioration of the indoor air quality. During the last decade three major VOC exposure studies have assessed European indoor microenvironments. In the frame of the EXPOLIS study, which took place in several European cities a wide range of VOCs were measured over 48 h in private homes, on the workplace, outdoors, and near to the breathing zone of volunteers (Edwards and Jantunen, 2001; Edwards et al., 2001a,b). In the MACBETH study
* Corresponding author. E-mail address: [email protected] (G. Giannopoulos). 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.04.037
(Cocheo et al., 2000) and the PEOPLE project (Ballesta et al., 2000) the focus was exclusively on benzene. In the former project, carried out in six European cities from 1996 to 1998, the exposure of 50 volunteers was studied by monitoring the concentrations in homes over a time range of 108 h. In the latter project a shorter sampling period (12 h) was used for personal exposure measurements in combination with a high number of samples for each city. Measurements were made during 2002e2003 outdoors, indoors and close to the breathing zone of volunteers. The AIRMEX study (Kotzias et al., 2009) aims at the identification and quantification of main indoor air pollutants in European public buildings - including schools and kindergartens - and at the estimation of human exposure to these pollutants while working and/or residing in these areas for a certain period of time. The study focuses on 14 VOCs (hydrocarbons, aromatic compounds, alcohols and carbonyls). Some of them have been identified in the INDEX project as priority compounds in indoor environments (Kotzias et al., 2005). VOCs were monitored in eleven European cities over a five years period and in dedicated campaigns with a 7 days duration outdoors, in public buildings and schools/kindergartens, in private homes and with personal sampling devices near the
O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
breathing zone of volunteers. Schools and kindergartens have been included in the present study since children spend a large amount of time in this type of public buildings and since children’s health is particularly susceptible to hazardous pollutants (Guzelian et al., 1992; Aprea et al., 2000; Commission, 2004). Studies done in the past in Munich, Hannover, Cologne and Leipzig have indicated that indoor concentrations for most VOCs are highest during winter and lowest during summer (Schlink et al., 2004; Ilgen et al., 2001). Schlink et al. (2004) concluded from their study on seasonal VOC concentration variations that a correct assessment of indoor air quality must take into account the season when the sampling takes place. For this reason the AIRMEX project included two campaigns in each city; one in the cold and one in the warm period of the year. A first analysis of the AIRMEX data with focus on the potential health effects of formaldehyde and benzene (Kotzias et al., 2009) indicated that air pollution concentrations are consistently higher indoors than outdoors for formaldehyde (and to a lesser extent for benzene) and that personal exposure concentrations are higher or similar to indoor concentrations and that in some cases, indoor concentrations in homes by far exceed those of public buildings and school/kindergartens, thus dominating personal exposures. Moreover it was indicated that noncarcinogenic responses from formaldehyde and benzene like inflammation may be enhanced by the presence of toluene in the indoor air VOC mixtures (Kotzias et al., 2009). In the current paper we provide detailed information on all measured concentrations of the compounds investigated within the AIRMEX study, which is intended to serve as a reference for future indoor air investigations and exposure studies. The statistical analysis of the dataset demonstrates the influence of geographical and seasonal variations on the indoor air concentrations of VOCs in public buildings, school/kindergartens and homes. 2. Materials and methods A detailed description of sampling and measurement techniques has been presented elsewhere (Kotzias et al., 2009). A short overview of the analytical procedures and the sampling strategy is given below. Measuring campaigns were carried out in public buildings located in urban areas with high traffic density, and in kindergartens/schools mostly situated in suburbs with reduced (medium) traffic impact. The characteristics of the studied indoor microenvironments were similar for all cities (for example buildings with public access). However, no attention was paid to the age of the buildings. In a very few exceptional cases samples were taken in single offices or entrance halls where smoking was allowed (Greece, Catania). Volunteers were identified among the employees and/or teachers working in the selected indoor environments for personal exposure monitoring. The cities included in this project were selected to give a good representation of typical European indoor environments. The cities are listed in Table 1. Measurements were done twice in each city: in the warm and in the cold season of the year and on average three public buildings and two schools were monitored in each city. The list of priority substances to be measured was defined following the selection criteria of the INDEX project (Kotzias et al., 2005), namely that the compounds had to be present in the indoor air and that they have shown adverse health effects being hence a potential hazard to European populations. Benzene, toluene, ethylbenzene, m/p-xylene, o-xylene, 1,2,4-trimethylbenzene, n-hexane, a-pinene, D-limonene, formaldehyde, acetaldehyde, propanal and hexanal were always measured in every campaign. Additionally a set of other chemicals were measured as well based on the characteristics of the area under evaluation (i.e. styrene,
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methylcyclohexane, 2-butoxyethanol, butanol, n-decane, nundecane and n-dodecane). 2.1. Sampling Simultaneous sampling of indoor/outdoor concentrations and exposure concentrations was carried out by diffusive sampling in campaigns with the duration of a full 7-day week including weekends. For exposure-concentration sampling devices were placed on the body of volunteers nearby the breathing zone during daytime and close to bed during night-time. For convenience, volunteers were asked to wear the exposures samplers for only three days. Only in a few cases did volunteers agree to wear two passive personalsamplers (one for VOC and one for carbonyls). For this reason the data coverage for personal exposure concentrations to carbonyls is lower than for the other VOCs. Indoor concentration samplers were distributed inside the buildings at a height of 2e2.5 m in order to cover the areas of main access by the occupants. In public buildings the samplers were placed in the entrance halls and offices. In kindergartens and schools the samplers were mounted in classrooms. In the homes of the volunteers the samplers were placed in the living room during the daytime and in the bedroom at night. Outdoor concentration samplers were placed at rain-protected positions in close vicinity to the studied buildings. For all measurements radial type diffusion samplers were used. Hydrocarbon and alcohol sampling was carried out with charcoal based cartridges (Radiello code 130, Supelco 3050 Spruce Str., St. Louis, MO, USA) whereas carbonyl sampling was done by 2,4-dinitrophenyl-hydrazine based cartridges (Radiello code 165, Supelco, St. Louis, MO, USA). The precision and accuracy of diffusive sampling of VOCs in air have been studied in detail (Ballesta et al., 2000; Strandberg et al., 2006; Meininghaus et al., 2003; Clarisse et al., 2003). For the utilised Radiello diffusive samplers the total measurement uncertainty has been found to be in the order of about 16% for a measuring time period of 7 days (Plaisance et al., 2008). 2.2. Sample preparation and analysis 2.2.1. Analysis of hydrocarbons and alcohols Samples were prepared and analysed following the ISO/FDIS 16200-2 method (ISO/FDIS 16200-2). The gas chromatographic system used was the Agilent 6890 (Agilent Technologies, Santa Table 1 Airmex locations and dates where measurement campaigns took place. City
Country Campaign
Arnhem/ NL Nijmegen Athens GR Brussels
BE
Budapest
HU
Catania
IT
Dublin
IE
Helsinki
FI
Leipzig
DE
Nicosia
CY
Thessaloniki GR
North South Warm Cold Comments
March 2004 August 2006 December 2003 October 2005 September 2004 March 2007
May 2007 January 2008 October 2003 May 2004 May 2007 February 2008 August 2007 April 2008 April 2005 July 2006 July 2004
January 2007 November 2004 May 2006
Only public buildings, no schools
In 2004 only schools
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O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
Table 2 Statistical information for each compound for all measurements done in the frame of the AIRMEX project. Values Min [n]
[mg m
Max 3
] [mg m
Arith. Mean 5th Percentile 25th Percentile Median 3
] [mg m
3
]
[mg m
3
]
[mg m
3
]
[mg m
75th Percentile 95th Percentile ] [mg m
3
3
]
[mg m
Acetaldehyde
Outdoor (Ambient) 105 Public Buildings/Schools 186 Private houses 96 Personal Inhalation 58
0.1 1.4 3.7 5.1
5.1 29.1 41.3 29.1
1.8 8.5 12.8 13.7
0.3 2.5 4.9 6.1
1.0 5.0 7.6 9.4
1.8 7.2 11.2 12.4
2.4 10.1 15.9 15.6
4.2 18.8 24.8 23.7
Acetone
Outdoor (Ambient) 66 Public Buildings/Schools 129 Private houses 88 Personal Inhalation 45
0.3 1.4 10.4 11.8
12.8 336.8 165.1 225.9
0.3 5.7 11.6 16.4
1.7 11.9 22.7 30.1
4.5 19.5 31.0 31.0
6.2 29.6 47.4 51.6
9.3 59.6 94.2 66.7
4.5 30.6 38.6 44.5
Benzene
Outdoor (Ambient) 108 Public Buildings/Schools 188 Private houses 96 Personal Inhalation 146
0.4 0.5 0.4 0.7
15.2 63.7 32.1 26.4
3.2 4.4 2.8 4.7
0.6 0.8 0.7 1.2
1.2 1.6 1.2 2.2
2.1 2.6 1.9 3.5
4.6 4.9 3.3 6.0
8.0 11.9 4.9 13.6
2-Butoxyethanol
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
41 74 50 53
0 0 0 0
0 136.5 11.0 7.9
0 4.5 0.6 0.5
0 0 0 0
0 0 0 0
0 0.25 0 0
0 1.3 0 0.25
0 8.3 2.7 2.4
1-Butoxy-2-propanol
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
12 21 8 e
0 0.5 1.9 e
1.6 33.9 39.6 e
0.4 4.7 12.5 e
e 0.5 e e
e 0.9 e e
e 4.7 e e
e 3.0 e e
e 18.6 e e
1-Butanol
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
46 82 46 40
0 0.3 0.4 0.4
10.9 41.4 9.8 8.2
1.5 3.7 2.5 2.8
0 0.5 0.6 0.5
0.2 1.1 1.0 1.4
0.6 1.8 1.8 2.3
1.7 3.7 3.5 3.5
5.0 11.2 7.5 6.8
n-Decane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
22 46 40 37
3.0 7.7 8.8 11.6
9.9 32.8 32.7 47.6
6.2 14.4 17.3 24.5
3.0 8.8 9.8 15.5
4.3 11.4 13.1 20.7
5.7 13.1 15.6 22.7
7.7 16.2 20.9 27.0
9.4 22.4 30.5 35.2
n-Dodecane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
22 46 40 37
3.0 7.7 8.8 11.6
9.9 32.8 32.7 47.6
6.2 14.4 17.3 24.5
3.0 8.8 9.8 15.5
4.3 11.4 13.1 20.7
5.7 13.1 15.6 22.7
7.7 16.2 20.9 27.0
9.4 22.4 30.5 35.2
Ethylbenzene
Outdoor (Ambient) 108 Public Buildings/Schools 178 Private houses 88 Personal Inhalation 146
0.2 0.2 0.2 0.4
17.9 26.9 12.8 44.7
2.2 2.4 1.5 3.2
0.3 0.5 0.4 0.5
0.6 0.7 0.6 1.1
1.1 1.3 1.1 1.8
2.6 3.0 1.7 3.8
6.1 7.4 3.8 8.2
Formaldehyde
Outdoor (Ambient) 105 Public Buildings/Schools 185 Private houses 97 Personal Inhalation 58
0.3 1.5 3.9 7.4
7.3 49.7 57.2 29.9
2.6 16.7 21.5 16.6
0.6 4.5 7.9 8.3
1.7 10.4 13.6 12.7
2.4 14.1 19.7 15.3
3.2 22.7 25.3 19.7
4.9 31.5 44.2 25.7
n-Hexane
Outdoor (Ambient) 73 Public Buildings/Schools 134 Private houses 84 Personal Inhalation 92
0.3 0.3 0.2 0.6
6.0 33.3 78.4 50.8
1.6 3.0 2.5 4.0
0.4 0.5 0.5 0.9
0.8 1.0 0.9 1.5
1.1 1.7 1.4 2.4
2.2 3.1 2.1 4.2
3.6 7.6 3.5 9.7
n-Heptane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
22 46 40 37
0 0.2 0.2 0.5
0.7 9.7 8.9 10.5
0.4 1.0 1.2 1.4
0 0.3 0.3 0.5
0.3 0.5 0.5 0.8
0.4 0.6 0.7 0.9
0.6 1.0 1.2 1.2
0.7 3.1 2.4 3.8
Hexanal
Outdoor (Ambient) 102 Public Buildings/Schools 185 Private houses 96 Personal Inhalation 66
0.2 1.2 6.2 1.0
3.3 159.6 198.1 68.0
0.9 16.4 32.3 22.2
0.3 3.0 8.5 1.8
0.5 6.8 14.8 14.0
0.8 11.4 24.4 20.2
1.4 21.6 39.4 28.3
2.1 39.6 82.0 44.1
D-Limonene
Outdoor (Ambient) 102 Public Buildings/Schools 179 Private houses 96 Personal Inhalation 146
0 0 0 0.4
2.4 175.7 492.9 276.9
0.3 9.4 29.2 26.1
0 0.3 1.6 1.4
0 1.2 4.9 4.3
0.2 2.6 9.5 10.4
0.3 9.1 31.0 32.1
1.2 33.0 87.6 88.4
Methylcyclohexane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
44 86 68 67
0 0.1 0 0
2.0 36.6 6.2 23.0
0.4 2.9 0.9 2.2
0 0.1 0.1 0.3
0.1 0.4 0.3 0.5
0.3 0.7 0.5 0.8
0.5 1.2 0.9 1.6
1.2 14.1 3.7 9.2
Propanal
Outdoor (Ambient) 104 Public Buildings/Schools 185 Private houses 96 Personal Inhalation 58
0 0.5 0.4 1.5
1.9 26.0 12.7 28.0
0.7 3.0 3.0 4.5
0.1 0.8 0.9 1.5
0.3 1.4 1.8 2.3
0.6 2.3 2.7 2.6
0.9 3.0 3.3 3.7
1.4 9.1 5.9 18.0
3
]
O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
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Table 2 (continued ) Values Min [n]
[mg m
a-Pinene
Outdoor (Ambient) 89 Public Buildings/Schools 160 Private houses 97 Personal Inhalation 129
0 0 0.2 0
Styrene
Outdoor (Ambient) 66 Public Buildings/Schools 128 Private houses 88 Personal Inhalation 83
0 0 0 0
Toluene
Outdoor (Ambient) 108 Public Buildings/Schools 188 Private houses 96 Personal Inhalation 146
Max ] [mg m
3
Arith. Mean 5th Percentile 25th Percentile Median 3
] [mg m
1.5 47.3 214.1 58.9
0.1 3.2 14.5 8.3
2.0 3.2 22.1 5.4
0.1 0.2 0.4 6.4
0.8 1.0 1.3 1.4
207.8 103.8 160.6 291.0
1,2,4-Trimethylbenzene Outdoor (Ambient) 105 Public Buildings/Schools 185 Private houses 96 Personal Inhalation 143
0.2 0.2 0.3 0
n-Undecane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
m/p-Xylene
o-Xylene
3
]
[mg m
3
]
[ mg m
3
]
[ mg m
0 0 0.6 0.5
0 0.6 2.6 2.3
0 1.5 6.1 4.5
0 0 0 0
0 0 0 0
11.5 12.6 11.7 22.4
1.2 1.7 2.5 3.4
16.3 44.3 58.9 35.1
2.2 3.3 2.7 3.1
0 0 0 0
2.7 19.5 113 11.1
Outdoor (Ambient) 108 Public Buildings/Schools 188 Private houses 96 Personal Inhalation 146
0.5 0.7 0.5 0.8
Outdoor (Ambient) 108 Public Buildings/Schools 188 Private houses 96 Personal Inhalation 146
0.2 0.2 0.2 0.4
22 46 40 37
75th Percentile 95th Percentile ] [mg m
3
3
]
[mg m
0.2 3.1 16.9 9.2
0.6 12.3 47.3 32.2
0 0 0 0
0 0 0 0.1
1.1 2.4 1.0 2.5
2.3 3.3 4.5 6.7
4.8 7.1 6.5 11.7
12.9 15.5 11.1 27.5
33.2 47.6 28.4 55.3
0.2 0.3 0.3 0.5
0.4 0.6 0.6 0.8
0.9 1.2 1.1 1.6
2.0 3.1 2.9 3.0
8.2 13.6 6.6 8.8
0.6 2.2 7.2 3.0
0 0 0.8 0
0 0.9 1.2 1.6
0.5 1.4 2.3 2.4
0.8 2.1 5.0 3.2
1.9 6.3 20.0 8.4
36.5 75.1 28.1 144.2
5.7 6.2 3.8 10.5
0.6 1.1 0.9 1.3
1.4 1.8 1.7 2.8
2.5 2.9 2.8 4.7
7.2 7.1 4.6 12.2
16.2 21.5 9.3 31.0
12.3 22.2 20.5 61.6
2.0 2.2 1.8 4.2
0.3 0.6 0.5 0.6
0.5 0.9 0.9 1.4
0.9 1.2 1.2 2.0
2.6 2.4 2.0 5.0
5.5 7.1 3.7 11.3
Clara, CA, USA) equipped with a flame ionisation detector. Chromatographic separation was achieved using a J&W Scientific capillary column (DB-5, 60 m, 0.25 mm i.d., 1 mm film thickness, Agilent J&W columns, Santa Clara, CA, USA). The detection limit for all compounds ranges from 0.2 to 0.3 mg m 3. 2.2.2. Analysis of carbonyls Samples were prepared and analysed following the ISO/FDIS 16000-4 method (ISO/FDIS 16000-4, 2004). Analysis of carbonyl compounds was conducted using the Agilent Series 1100 liquid chromatographic system (Agilent Technologies, Santa Clara, CA, USA) coupled to a diode array detector (DAD) set at 360 nm. Chromatographic separation was achieved using a Waters NovaPak C18, 60 Å. 4 mm (3.9 300) mm column (Waters Corporation, 34 Maple Street, Milford, MA, USA). The detection limit for all carbonyls ranges from 0.2 to 0.3 mg m 3. 2.2.3. Fitting of the experimental data Experimental data obtained through the measurement campaigns are plotted using cumulative probability plots. Additionally, fitted plots have been also elaborated using the mean and standard deviation values calculated from the measured data. The data follow a log-normal distribution. The fitting has been produced using MS-ExcelÒ. Using the random number generator function with a defined number of data and providing the type of distribution (log-normal) and the corresponding standard deviation and mean values, it has been possible to reproduce the theoretical form of these distributions. 3. Results and discussion Table 2 summarises all data collected within the frame of the AIRMEX project. The table contains minimum, maximum,
3
]
arithmetical averages and percentiles of concentrations observed in all eleven cities for each compound and in each micro-environment (outdoors, indoors, personal). The information contained in the table may serve as reference for typical European exposure scenarios and is essential for probabilistic exposure assessment through timeeactivity analysis. The data are not claimed to be exhaustive and representative for all European possible situations. However, it can be used for exposure assessment in the investigated areas and may also give a good indication for the average European exposure to VOCs. VOCs with the highest absolute concentrations include acetone (median concentration in private houses 47.4 mg m 3 and 51.6 mg m 3 in personal samples), n-decane (median concentration in personal inhalation samples 22.7 mg m 3), n-dodecane (median concentration in personal samples 22.7 mg m 3), formaldehyde (median concentration in private houses 19.7 mg m 3) and hexanal (median concentration in private houses 24.4 mg m 3 and 20.2 in personal samples). In Table 3 the levels of selected VOCs measured in AIRMEX study are compared with a similar study (Expolis-Helsinki). First of all, it is clear that concentrations measured in the two studies are on a similar level. However, some minor differences are worth noting, namely that the outdoor concentrations in the AIRMEX study tend to be higher for the aromatic compounds than in the Expolis-Helsinki study, and vice-versa for the residential, workplaces and personal exposure concentrations. This can be explained by differences in the traffic fleet as discussed later in the paper and by differences in ventilation rates. Furthermore differences of only minor nature can be observed for terpenes. This is confirmed by the cumulative probability plots discussed in Section 4.2. The data obtained in the AIRMEX study are comparable to the indoor data from similar studies in Oxford (Lai et al., 2004) and
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O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
Table 3 Comparison of mean VOC concentrations (mg m
3
) from the AIRMEX study and the Expolis-Helsinki study.
Airmex (Arithmetic Mean)
Benzene Toluene Ethylbenzene m/p-Xylene Hexanal n-Decane n-Undecane 2-Butoxyethanol a-Pinene D-Limonene
Expolis-Helsinki (Arithmetic Mean) (Edwards et al., 2001a; Jantunen et al., 1999)
Outdoor
Residential
Workplace
Personal
Outdoor
Residential
Workplace
Personal
3.2 11.5 2.2 5.7 0.9 6.2 0.6 n.d. 0.1 0.3
4.4 11.7 1.5 3.8 32.3 17.3 7.2 n.d 14.5 29.2
2.8 12.6 2.4 6.2 16.4 14.4 2.2 4.5 3.2 9.4
4.7 22.4 3.2 10.5 22.2 24.5 3.0 n.d 8.3 26.1
1.7 5.6 1.0 3.1 2.1 1.1 0.7 e 2.1 e
2.2 20.4 2.9 7.8 11.6 5.3 5.1 2.5 16.1 31.6
3.9 32.3 16.1 38.8 5.0 13.9 13.0 e 5.5 14.2
3.4 25.3 7.7 25.0 8.2 16.5 14.3 e 10.2 18.7
a number of German cities (Schlink et al., 2004). The biggest differences found from these studies are the somewhat higher concentrations in the German study for toluene and lower concentrations for n-decane and n-dodecane, which might be attributed to local sources but needs to be further studied. Using the data provided in the Table 2, indoor/outdoor (I/O) and private house/office (Ho/Of) ratios were calculated with the aim to identify compounds that are typical for these micro-environments. 3.1. Indoor/Outdoor (I/O) ratios and home to office ratios The I/O ratio shown in Fig. 1 was calculated by dividing the median indoor concentrations (offices and classroom) by the median outdoor concentrations for each location and compound. The data are extracted from Table 2. A practical implication of the findings shown in Fig. 1 and Table 4 may be that when investigating indoor pollutants the sampling strategy should especially focus on those compounds which have an I/O ratio of >2. However, from the I/O ratio values the compounds can also be divided into categories ranging from being predominantly indoor pollutants (ratio > 6) to being pollutants not deriving from indoor sources (ratio approaching 1). In Table 4 these ratios are listed. In the first category we find formaldehyde, D-limonene and hexanal, which are mainly originating from indoor sources. The findings for formaldehyde and hexanal are in agreement with Barguil et al. (1990) who confirmed the existence of indoor aldehyde sources in residential homes and
identified formaldehyde and hexanal as being among the main aldehydes detected in indoor air. Formaldehyde has recently been identified as carcinogenic to humans (IARC, 1982, 2006), and its median I/O ratio of approximately 6 underlines the need to minimize emissions from building products, household products and furnishings inside closed environments. Other compounds of concern are 2-butoxyethanol and Dlimonene that are skin contact allergens (class III and IIB, respectively NKB, 1994). 2-butoxyethanol is used as a solvent in spray lacquers, enamels, varnishes, and latex paints and as an ingredient in paint thinners, paint strippers, and varnish removers (ATSDR, 1999), whereas D-limonene is widely used in cleaning products (Steinemann, 2009; Rodrigues et al., 2009). Besides its contactallergenic properties, D-limonene has been proven to add ultrafine particles to indoor environments through formation of ozone mediated secondary aerosol (Weschler and Shields, 1999), which has also been connected with sensory irritation in office environments (Wolkoff et al., 2006). In the category of compounds with a ratio of almost 1 we find benzene, toluene, the xylenes and the trimethylbenzenes. The levels found for these compounds indoors originate predominantly from the polluted outdoor air penetrating into the indoor environment and they are associated with automobile emissions (Chan et al., 1991; Barrefors and Petersson, 1993; Lawryk et al., 1995). Benzene is of concern as known human carcinogen, and the common practice of improving indoor air quality by opening windows is not applicable for this pollutant. The only practical way to abate this category of compounds in the
Fig. 1. Ratio median concentration indoor working/school environment against median concentration outdoors for all data collected in the frame of the AIRMEX project.
O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684 Table 4 Ratio-categories obtained by dividing median indoor concentration of offices/ classrooms by median outdoor concentrations.
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Table 5 Ratio-categories obtained by dividing median indoor concentrations in private houses by median indoor concentrations in offices/classrooms (Ho/Of ratios).
Category
Compounds
Category
Compounds
Ratio > 6a
Formaldehyde, hexanal, D-limonene, a-pinene, 2-butoxyethanol Acetaldehyde, acetone, 1-butoxy-2-propanol n-Undecane, propanal, methylcyclohexane, n-dodecane, 1-butanol Benzene, ethylbenzene, n-hexane, n-heptane, toluene, 1,2,4-trimethylbenzene, m/p-xylene, o-xylene
Ratio > 2 Ratio 2 > x < 1
Hexanal, D-limonene, a-pinene n-Decane, n-undecane, acetone, acetaldehyde, formaldehyde, propanal, n-heptane, n-dodecane Benzene, methylcyclohexane, ethylbenzene, n-hexane, toluene, 1,2,4-trimethylbenzne, 1-butanol, m/p-xylene, o-xylene
Ratio 6 > x < 4 Ratio 4 > x < 2 Ratio < 2 a
Ratio 1
Ratio > 6 or ambient air concentration close to zero.
indoor environment is through forced ventilation with filtering of the air. Analogue to the I/O ratio, a home to office ratio (Ho/Of) is obtained by dividing the median concentrations calculated for each compound in the private homes by the median concentration calculated for offices/classrooms. The Ho/Of ratio is displayed for all compounds in Fig. 2 and Table 5. It is evident that the two most abundant compounds in the private-house micro-environment are the terpenes a-pinene and D-limonene. Apparently such uses are more common in private homes than in offices/classrooms. a-Pinene is frequently used in perfumes, cleaning products and fragrances (Steinemann, 2009; Rodrigues et al., 2009) and just as D-limonene it may cause skin and eye irritation and contributes to the formation of strong airway irritants in terpene/ozone reaction mixtures (Wolkoff et al., 2006). Although a large number of terpene ozonolysis products have been identified (Calogirou et al., 1999; Glasius et al., 2000) it is not known, which are responsible for the irritation of skin, eye, and airway. However, the present findings of high Ho/Of as well as I/O ratios for terpenes may be of relevance for future indoor air quality guidelines (Kephalopoulos et al., 2007). 4. Geographical and seasonal variations in indoor concentrations of the measured compounds 4.1. Introduction
4.2. Geographical variation The geographical variation was analysed by dividing the data into two groups (Central-North and South Europe) and visualized in the form of cumulative probability plots of observed concentrations and fitted curves assuming log-normal distributions. In Table 7 the utilised parameters are presented. A clear difference between north and south was evident for the indoor concentrations of aromatic hydrocarbons (Fig. 3). In absence of indoor sources for this group of compounds (Table 4) the northesouth difference is attributed to a similar trend for outdoor concentrations. In fact the ambient air pollution levels around the investigated public buildings were notably higher in the southern European cities of Athens, Thessaloniki and Catania. Higher concentration of aromatic hydrocarbons in outdoor environments in the south of Europe may be explained by different traffic patterns
fi
A number of variables must be taken into account when setting up probabilistic European exposure scenarios. Data on different body characteristics (e.g. bodyweight) for the various populations
in Europe (EXPOFACTS) is important together with timeeactivity patterns and may differ between geographical locations and between seasons of the year. However, also potential geographical and seasonal variations in indoor concentrations must be considered. The degree of scattering in the present indoor air concentration dataset for individual compounds and for individual indoor micro-environments can mask geographical and seasonal trends. Thus data were pooled for public buildings, private homes, schools and kindergartens assuming that any geographical and seasonal variation would equally affect concentrations in these indoor environments. Furthermore, three groups of individual compounds were examined as the sum of the individual concentrations, namely aromatic hydrocarbons, terpenes and aldehydes (Table 6).
Fig. 2. Distribution of home/office ratios.
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Table 6 Groups of substances evaluated for geographical and seasonal variations. Group
Compounds
Aldehydes Aromatic HC
Formaldehyde, acetaldehyde, hexanal, propionaldehyde Benzene, toluene, 1,2,4-trimethylbenzne, ethylbenzene, m/p-xylene, o-xylene a-pinene, D-limonene
Terpenes
Table 7 Parameters used for data fitting: Log-Normal distribution (mg m Substance group Geographical Mean Median SD seasonal
).
95% confidence interval
Aldehydes
Warm Cold North South
58.869 47.400 56.307 44.837
52.000 41.400 49.400 43.200
30.793 31.669 32.606 27.921
5.138 5.173 4.508 6.080
Aromatic HC
Warm Cold North South
24.613 31.863 15.559 59.051
15.900 22.723 18.500 36.126 13.300 9.051 49.650 40.385
3.764 5.963 1.258 8.741
Warm Cold North South
13.357 6.300 16.358 2.823 35.975 18.450 60.669 10.510 23.994 11.350 47.338 6.696 26.478 12.000 40.749 9.906
Terpenes
3
and a significant amount of passenger vehicles not equipped with a catalytic converter (Karakitsios et al., 2006, 2007). The observed trend for aromatic hydrocarbons is in agreement with recent studies on benzene, which investigated the relation between pollution levels and the latitude of the place the samples were taken from (Ballesta et al., 2000; Cocheo et al., 2000). In the latter, the observed increase in annual average benzene concentrations from north to south was explained with the difference in prevailing meteorological conditions, such as local wind speeds. However, the Cocheo study was conducted in Copenhagen, Antwerp, Padua, Murcia and Athens and did not include cities from eastern Europe, what makes a direct comparison difficult. For the group of terpenes there was no substantial difference between north and south (Fig. 4), which may be due to the fact that their indoor sources are related to modern lifestyle which clearly does not differ substantially between the various areas of Europe that have been included in the present study (terpenes sources: fragrances, cleaning products).
Fig. 3. Geographical variation of aromatic HC.
Fig. 4. Geographical variation of terpenes.
There is a difference in the aldehydes concentrations between north and south of Europe (Fig. 5), which fits well with the extended use of wood products in north Europe. Aldehydes sources are predominantly pressed wood products and furniture made with pressed wood products, ureaeformaldehyde foam insulation (UFFI), combustion and environmental tobacco smoke, durable press drapes, other textiles, and glues (WHO, 1989; Health Canada, 2005). In particular for hexanal a major source has been demonstrated to be the chemical reaction of oxidants in the air with linoleic acid (Svedberg et al., 2004) deriving from wood products. 4.3. Seasonal variations In the work of Diez et al. (2003) a general increase of VOC concentrations in the cold season is reported, mainly due to lower ventilation and air exchange rates. However, this effect depends on the specific VOC, of the emission sources, the building type, the geographic location, the outdoor air quality and other factors (Schlink et al., 2004). To identify a possible seasonal variation of the indoor air concentrations the division of the data into two groups was complicated by the fact that the measurement campaigns for each city did not take place simultaneously but they were spanned over a period of several years. Thus, as criterion for the categorisation of the data, the ambient temperature of the city during the campaigns was utilised. For each geographical location data were pooled together for the warmest of the two campaigns and classified as the
Fig. 5. Geographical variation of aldehydes.
O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
Fig. 6. Seasonal variation of terpenes.
warm period, whereas the rest of the data have been used to form the so called cold period. In Table 1 the geographical and seasonal division is presented. For terpenes the analysis shows a clear difference between warmer and colder seasons (Fig. 6) with indoor concentrations being lower during the warm season. Terpenes react rapidly with oxidants in the air such as ozone, which is much more abundant in the warm season due to the higher photochemical activity and penetrates from the outdoor air. This finding provides a good indication of the importance of indoor air chemistry for the concentration levels of various substances. An additional explanation could be the increased ventilation rates during the warm season. No difference between the warm and the cold season was evident for the aromatic hydrocarbons (Fig. 7), which is expected from the fact that they do not have significant indoor sources and therefore an increased ventilation rate does not really influence their indoor concentration. During the warm season the indoor concentration of aldehydes appeared to be slightly higher than during the cold season (Fig. 8), which may support the hypothesis of ozone penetration (formaldehyde is an oxidation product in the terpene/ozone reaction (Calogirou et al., 1999) and hexanal is an oxidation product of ozone with linoleic acid). However, also increased emission/evaporation/desorption rates from their indoor sources may play a role.
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Fig. 8. Seasonal variation of aldehydes.
5. Conclusions The AIRMEX project is the most recent of a series of panEuropean projects aiming to assess personal exposure and taking an inventory of VOC levels in indoor environments in several European cities. Results presented in this work represent an elaboration of the whole set of raw-data and are hereby made publicly accessible via a database (http://web.jrc.ec.europa.eu/airmex/). Moreover, the statistical analysis of the data in the present paper provides a good indication of a possible influence of indoor air chemistry on the concentration levels of reactive substances, which should be taken into consideration in future indoor air quality guidelines. Attention should be taken in indoor air quality monitoring campaigns to pollutants with an indoor/outdoor ratio higher than 2. A clear difference between north and south was evident for the indoor concentrations of aromatic hydrocarbons which can be attributed to the different kinds of vehicle fleet in the studied cities. For terpenes no similar trend was revealed for geographical variation but there was a significant difference between the values obtained for the warm and the cold period with concentrations being lower during the warm period. Besides potentially increased ventilation rates in the warm period, this can be attributed to the reactivity of terpenes with ozone penetrating from outdoor air, which is more abundant during warm periods. Our findings of higher concentration of aldehydes (ozone oxidation reaction products) during the warm period support this hypothesis.
Acknowledgements
Fig. 7. Seasonal variation of aromatic HC.
The authors wish to acknowledge all participants at this project. Without the on-site local coordination this project could not have been realized. Namely the coordinators are: Dr. Cuccia and Dr. Nastri from the Regione Siciliana, Azienda Unita Sanitaria Locale N.3 in Catania, Italy; Dr. Bloemen and his collaborators from the RIVM in Bilthoven, Netherlands; Prof. Herbarth and his collaborators from the Umweltforschungszentrum in Leizpig, Germany; Dr. Kalabokas from the Research Centre for Atmospheric Physics and Climatology Acacedmy of Athens in Greece; Dr. Nikolaou from the Organisation for the Masterplan & Environment in Thessalonica, Greece; Dr. Michael and his collaborators from the Ministry of Health in Nicosia, Cyprus; Dr. Kauppi and her collaborators from the Finnish Environment Institute, Dr. Putus from the Ministry of Social Affairs and Health, Dr. Säteri and her collaborators from the Ministry of Environment; Dr. Nurminnen and Dr. Jylkkä from the City of Helsinki in Finland; Dr. McLaughlin and his collaborators
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from the University College Dublin, Dr. Fitzpatrick, Dr. Healy and Dr. McCartan from the Dublin City Council in Dublin, Ireland; Prof. Zaray and Dr. Mihucz from the Eötvös Lorand University in Budapest, Hungary. References Aprea, C., Strambi, M., Novelli, M.T., Lunghini, L., Bozzi, N., 2000. Biologic monitoring of exposure to organophosphorus pesticides in 195 Italian children. Environmental Health Perspectives 108, 521e525. ATSDR, 1999. Toxicological Profile for 2-Butoxyethanol and 2-Butoxyethanol Acetate. PB/99/102527/AS. Ballesta, P., Field, R., Connolly, R., Cao, N., Baeza-Caracena, A., De Saeger, E., 2000. Population exposure to benzene: one day cross-sections in six European cities. Atmospheric Environment 40, 3355e3366. Barguil, S., Le Moullec, Y., Person, A., Laurent, A.M., Festy, B., 1990. Chemical characterisation of indoor air quality in Parisian homes. Aerobiologia 6, 28e31. Barrefors, G., Petersson, G., 1993. Assessment of ambient volatile hydrocarbons from tobacco smoke and from vehicle emissions. Journal of Chromatography 643 (1e2), 71e76. Calogirou, A., Larsen, B.R., Kotzias, D., 1999. Gas phase terpene oxidation products: a review. Atmospheric Environment 33A, 1352e2310. Chan, C.-C., Ozkaynak, J., Spengler, J.D., Sheldon, L., 1991. Driver exposure to volatile organic compounds, CO, ozone, and NO2 under different driving conditions. Environmental Science and Technology 25 (5), 964e972. Clarisse, B., Laurent, A.M., Seta, N., Le Moullec, Y., El Hasnaoui, A., Momas, I., 2003. Indoor aldehydes: measurement of contamination levels and identification of their determinants in Paris dwellings. Environmental Research 92, 245e253. Cocheo, V., Boaretto, C., Sacco, P., De Saeger, E., Ballesta, P.P., Skov, H., et al., 2000. Urban benzene and population exposure. Nature 404, 141e142. Commission of the European Communities, 2004. Communication from the Commission to the Council, the European Parliament, the European Economic and Social Committee The European Environment & Health Action Plan 2004e2010. (COM/2004/416). Diez, Ulrike, Rehwagen, Martina, Rolle-Kampczyk, Ulrike, Wetzig, Heide, Schulz, Rita, Richter, Matthias, Lehmann, Irina, Borte, Michael, Herbarth, Olf, 2003. Redecoration of apartments promotes obstructive bronchitis in atopy risk infants - results of the LARS study. International Journal of Hygiene and Environmental Health 205 (3), 173e179. Dockery, D.W., Pope III, C.A., Xu, X., Spengler, J.D., Ware, J.H., Fay, M.E., Ferris Jr., B.G., Speizer, F.E., 1993. An association between air pollution and mortality in six US cities. New England Journal of Medicine 329, 1753e1759. Edwards, R.D., Jantunen, M.J., 2001. Benzene exposure in Helsinki, Finland. Atmospheric Environment 35, 1411e1420. Edwards, R.D., Jurvelin, J., Saarela, K., Jantunen, M.J., 2001a. VOC concentrations measured in personal samples and residential indoor, outdoor and workplace microenvironments in EXPOLIS-Helsinki, Finland. Atmospheric Environment 35, 4531e4543. Edwards, R.D., Jurvelin, J., Koistinen, K., Saarela, K., Jantunen, M.J., 2001b. VOC source identification from personal and residential indoor, outdoor and workplace microenvironment samples in EXPOLIS-Helsinki, Finland. Atmospheric Environment 35, 4829e4841. http://expofacts.jrc.ec.europa.eu (accessed 19.10.10.). Glasius, M., Di Bella, D., Lahaniati, M., Calogirou, A., Jensen, N.R., Hjorth, J., Kotzias, D., Larsen, B.R., 2000. Carboxylic acids in secondary aerosols from oxidation of cyclic monoterpenes by ozone. Environmental Science & Technology 34, 1001e1010. Guzelian, P.S., Henry, C.J., Olin, S.S., 1992. Similarities and Differences between Children and Adults: Implications for Risk Assessment. ILSI Press, Washington, DC. Health Canada, 2005. Proposed Residential Indoor Air Quality Guidelines for Formaldehyde. Health Canada, Ottawa, Canada. H128e1/05-432E. International Agency for Research on Cancer (IARC), 1982. IARC monographs on the evaluation of the carcinogenic risk of chemicals to humans. In: Benzene, vol. 29. IARC, Lyon, France. International Agency for Research on Cancer (IARC), 2006. IARC monographs on the evaluation of the carcinogenic risk of chemicals to humans. In: Formaldehyde, vol. 88. IARC, Lyon, France. Ilgen, E., Karfich, N., Levsen, K., Angerer, J., Schneider, P., Heinrich, J., Wichmann, H.E., Dunemann, L., Begerow, J., 2001. Atmospheric Environment 35, 1235e1252.
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Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv
The AIRMEX study - VOC measurements in public buildings and schools/ kindergartens in eleven European cities: Statistical analysis of the data Otmar Geiss, Georgios Giannopoulos*, Salvatore Tirendi, Josefa Barrero-Moreno, Bo R. Larsen, Dimitrios Kotzias European Commission, Joint Research Centre, Institute for Health and Consumer Protection, Chemical Assessment and Testing Unit, Via E. Fermi 2749, Ispra 21027 (VA), Italy
a r t i c l e i n f o
a b s t r a c t
Article history: Received 7 December 2010 Received in revised form 8 April 2011 Accepted 15 April 2011
Indoor and outdoor air concentrations as well as personal exposure concentrations of volatile organic compounds (VOCs) have been measured during 2003e2008 in public buildings, schools, kindergartens and private homes in eleven cities over Europe covering geographic areas in north, central and south Europe during different seasons within the frame of the AIRMEX (European Indoor Air Monitoring and Exposure assessment) study. A database is presented containing the results for 23 VOCs based upon approximately 1000 samples taken from 182 different working environments (offices, classrooms, waiting halls) in public buildings, schools and kindergartens, from 103 private homeplaces and from adult volunteers (148 samples). The statistical analysis of the data demonstrated that sources in the indoor environment are prevailing for most of the investigated VOCs with indoor/outdoor (I/O) concentration ratios following the order: hexanal z D-limonene [ formaldehyde > acetone > 1butoxy-2-propanol > acetaldehyde > propanal > 1-butanol > n-undecane > methylcyclohexane > ndodecane. For aromatic hydrocarbons the main impact was shown to be penetration from outdoor air as indicated by I/O ratios near one and is characterised by significantly higher indoor as well as outdoor concentrations in the south of Europe with respect to the north. For the terpenes, the lowest indoor concentrations were measured during the warm season, which may be explained by higher ventilation rates and reactions with ozone penetrated from outdoor air. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: VOCs Database Indoor air quality Geographical variation Seasonal variation
1. Introduction Studies have shown that indoor exposure to volatile organic compounds (VOCs) can significantly contribute to adverse health effects (Dockery et al., 1993; Pope et al., 1995; Laden et al., 2001). The vast majority of human activities take place in indoor areas such as private homes, offices, shops and cars. Thorough investigations of the VOC pollution levels in such micro-environments are essential for the understanding of population exposure to harmful substances, for epidemiological work and the eventual amelioration of the indoor air quality. During the last decade three major VOC exposure studies have assessed European indoor microenvironments. In the frame of the EXPOLIS study, which took place in several European cities a wide range of VOCs were measured over 48 h in private homes, on the workplace, outdoors, and near to the breathing zone of volunteers (Edwards and Jantunen, 2001; Edwards et al., 2001a,b). In the MACBETH study
* Corresponding author. E-mail address: [email protected] (G. Giannopoulos). 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.04.037
(Cocheo et al., 2000) and the PEOPLE project (Ballesta et al., 2000) the focus was exclusively on benzene. In the former project, carried out in six European cities from 1996 to 1998, the exposure of 50 volunteers was studied by monitoring the concentrations in homes over a time range of 108 h. In the latter project a shorter sampling period (12 h) was used for personal exposure measurements in combination with a high number of samples for each city. Measurements were made during 2002e2003 outdoors, indoors and close to the breathing zone of volunteers. The AIRMEX study (Kotzias et al., 2009) aims at the identification and quantification of main indoor air pollutants in European public buildings - including schools and kindergartens - and at the estimation of human exposure to these pollutants while working and/or residing in these areas for a certain period of time. The study focuses on 14 VOCs (hydrocarbons, aromatic compounds, alcohols and carbonyls). Some of them have been identified in the INDEX project as priority compounds in indoor environments (Kotzias et al., 2005). VOCs were monitored in eleven European cities over a five years period and in dedicated campaigns with a 7 days duration outdoors, in public buildings and schools/kindergartens, in private homes and with personal sampling devices near the
O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
breathing zone of volunteers. Schools and kindergartens have been included in the present study since children spend a large amount of time in this type of public buildings and since children’s health is particularly susceptible to hazardous pollutants (Guzelian et al., 1992; Aprea et al., 2000; Commission, 2004). Studies done in the past in Munich, Hannover, Cologne and Leipzig have indicated that indoor concentrations for most VOCs are highest during winter and lowest during summer (Schlink et al., 2004; Ilgen et al., 2001). Schlink et al. (2004) concluded from their study on seasonal VOC concentration variations that a correct assessment of indoor air quality must take into account the season when the sampling takes place. For this reason the AIRMEX project included two campaigns in each city; one in the cold and one in the warm period of the year. A first analysis of the AIRMEX data with focus on the potential health effects of formaldehyde and benzene (Kotzias et al., 2009) indicated that air pollution concentrations are consistently higher indoors than outdoors for formaldehyde (and to a lesser extent for benzene) and that personal exposure concentrations are higher or similar to indoor concentrations and that in some cases, indoor concentrations in homes by far exceed those of public buildings and school/kindergartens, thus dominating personal exposures. Moreover it was indicated that noncarcinogenic responses from formaldehyde and benzene like inflammation may be enhanced by the presence of toluene in the indoor air VOC mixtures (Kotzias et al., 2009). In the current paper we provide detailed information on all measured concentrations of the compounds investigated within the AIRMEX study, which is intended to serve as a reference for future indoor air investigations and exposure studies. The statistical analysis of the dataset demonstrates the influence of geographical and seasonal variations on the indoor air concentrations of VOCs in public buildings, school/kindergartens and homes. 2. Materials and methods A detailed description of sampling and measurement techniques has been presented elsewhere (Kotzias et al., 2009). A short overview of the analytical procedures and the sampling strategy is given below. Measuring campaigns were carried out in public buildings located in urban areas with high traffic density, and in kindergartens/schools mostly situated in suburbs with reduced (medium) traffic impact. The characteristics of the studied indoor microenvironments were similar for all cities (for example buildings with public access). However, no attention was paid to the age of the buildings. In a very few exceptional cases samples were taken in single offices or entrance halls where smoking was allowed (Greece, Catania). Volunteers were identified among the employees and/or teachers working in the selected indoor environments for personal exposure monitoring. The cities included in this project were selected to give a good representation of typical European indoor environments. The cities are listed in Table 1. Measurements were done twice in each city: in the warm and in the cold season of the year and on average three public buildings and two schools were monitored in each city. The list of priority substances to be measured was defined following the selection criteria of the INDEX project (Kotzias et al., 2005), namely that the compounds had to be present in the indoor air and that they have shown adverse health effects being hence a potential hazard to European populations. Benzene, toluene, ethylbenzene, m/p-xylene, o-xylene, 1,2,4-trimethylbenzene, n-hexane, a-pinene, D-limonene, formaldehyde, acetaldehyde, propanal and hexanal were always measured in every campaign. Additionally a set of other chemicals were measured as well based on the characteristics of the area under evaluation (i.e. styrene,
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methylcyclohexane, 2-butoxyethanol, butanol, n-decane, nundecane and n-dodecane). 2.1. Sampling Simultaneous sampling of indoor/outdoor concentrations and exposure concentrations was carried out by diffusive sampling in campaigns with the duration of a full 7-day week including weekends. For exposure-concentration sampling devices were placed on the body of volunteers nearby the breathing zone during daytime and close to bed during night-time. For convenience, volunteers were asked to wear the exposures samplers for only three days. Only in a few cases did volunteers agree to wear two passive personalsamplers (one for VOC and one for carbonyls). For this reason the data coverage for personal exposure concentrations to carbonyls is lower than for the other VOCs. Indoor concentration samplers were distributed inside the buildings at a height of 2e2.5 m in order to cover the areas of main access by the occupants. In public buildings the samplers were placed in the entrance halls and offices. In kindergartens and schools the samplers were mounted in classrooms. In the homes of the volunteers the samplers were placed in the living room during the daytime and in the bedroom at night. Outdoor concentration samplers were placed at rain-protected positions in close vicinity to the studied buildings. For all measurements radial type diffusion samplers were used. Hydrocarbon and alcohol sampling was carried out with charcoal based cartridges (Radiello code 130, Supelco 3050 Spruce Str., St. Louis, MO, USA) whereas carbonyl sampling was done by 2,4-dinitrophenyl-hydrazine based cartridges (Radiello code 165, Supelco, St. Louis, MO, USA). The precision and accuracy of diffusive sampling of VOCs in air have been studied in detail (Ballesta et al., 2000; Strandberg et al., 2006; Meininghaus et al., 2003; Clarisse et al., 2003). For the utilised Radiello diffusive samplers the total measurement uncertainty has been found to be in the order of about 16% for a measuring time period of 7 days (Plaisance et al., 2008). 2.2. Sample preparation and analysis 2.2.1. Analysis of hydrocarbons and alcohols Samples were prepared and analysed following the ISO/FDIS 16200-2 method (ISO/FDIS 16200-2). The gas chromatographic system used was the Agilent 6890 (Agilent Technologies, Santa Table 1 Airmex locations and dates where measurement campaigns took place. City
Country Campaign
Arnhem/ NL Nijmegen Athens GR Brussels
BE
Budapest
HU
Catania
IT
Dublin
IE
Helsinki
FI
Leipzig
DE
Nicosia
CY
Thessaloniki GR
North South Warm Cold Comments
March 2004 August 2006 December 2003 October 2005 September 2004 March 2007
May 2007 January 2008 October 2003 May 2004 May 2007 February 2008 August 2007 April 2008 April 2005 July 2006 July 2004
January 2007 November 2004 May 2006
Only public buildings, no schools
In 2004 only schools
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Table 2 Statistical information for each compound for all measurements done in the frame of the AIRMEX project. Values Min [n]
[mg m
Max 3
] [mg m
Arith. Mean 5th Percentile 25th Percentile Median 3
] [mg m
3
]
[mg m
3
]
[mg m
3
]
[mg m
75th Percentile 95th Percentile ] [mg m
3
3
]
[mg m
Acetaldehyde
Outdoor (Ambient) 105 Public Buildings/Schools 186 Private houses 96 Personal Inhalation 58
0.1 1.4 3.7 5.1
5.1 29.1 41.3 29.1
1.8 8.5 12.8 13.7
0.3 2.5 4.9 6.1
1.0 5.0 7.6 9.4
1.8 7.2 11.2 12.4
2.4 10.1 15.9 15.6
4.2 18.8 24.8 23.7
Acetone
Outdoor (Ambient) 66 Public Buildings/Schools 129 Private houses 88 Personal Inhalation 45
0.3 1.4 10.4 11.8
12.8 336.8 165.1 225.9
0.3 5.7 11.6 16.4
1.7 11.9 22.7 30.1
4.5 19.5 31.0 31.0
6.2 29.6 47.4 51.6
9.3 59.6 94.2 66.7
4.5 30.6 38.6 44.5
Benzene
Outdoor (Ambient) 108 Public Buildings/Schools 188 Private houses 96 Personal Inhalation 146
0.4 0.5 0.4 0.7
15.2 63.7 32.1 26.4
3.2 4.4 2.8 4.7
0.6 0.8 0.7 1.2
1.2 1.6 1.2 2.2
2.1 2.6 1.9 3.5
4.6 4.9 3.3 6.0
8.0 11.9 4.9 13.6
2-Butoxyethanol
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
41 74 50 53
0 0 0 0
0 136.5 11.0 7.9
0 4.5 0.6 0.5
0 0 0 0
0 0 0 0
0 0.25 0 0
0 1.3 0 0.25
0 8.3 2.7 2.4
1-Butoxy-2-propanol
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
12 21 8 e
0 0.5 1.9 e
1.6 33.9 39.6 e
0.4 4.7 12.5 e
e 0.5 e e
e 0.9 e e
e 4.7 e e
e 3.0 e e
e 18.6 e e
1-Butanol
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
46 82 46 40
0 0.3 0.4 0.4
10.9 41.4 9.8 8.2
1.5 3.7 2.5 2.8
0 0.5 0.6 0.5
0.2 1.1 1.0 1.4
0.6 1.8 1.8 2.3
1.7 3.7 3.5 3.5
5.0 11.2 7.5 6.8
n-Decane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
22 46 40 37
3.0 7.7 8.8 11.6
9.9 32.8 32.7 47.6
6.2 14.4 17.3 24.5
3.0 8.8 9.8 15.5
4.3 11.4 13.1 20.7
5.7 13.1 15.6 22.7
7.7 16.2 20.9 27.0
9.4 22.4 30.5 35.2
n-Dodecane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
22 46 40 37
3.0 7.7 8.8 11.6
9.9 32.8 32.7 47.6
6.2 14.4 17.3 24.5
3.0 8.8 9.8 15.5
4.3 11.4 13.1 20.7
5.7 13.1 15.6 22.7
7.7 16.2 20.9 27.0
9.4 22.4 30.5 35.2
Ethylbenzene
Outdoor (Ambient) 108 Public Buildings/Schools 178 Private houses 88 Personal Inhalation 146
0.2 0.2 0.2 0.4
17.9 26.9 12.8 44.7
2.2 2.4 1.5 3.2
0.3 0.5 0.4 0.5
0.6 0.7 0.6 1.1
1.1 1.3 1.1 1.8
2.6 3.0 1.7 3.8
6.1 7.4 3.8 8.2
Formaldehyde
Outdoor (Ambient) 105 Public Buildings/Schools 185 Private houses 97 Personal Inhalation 58
0.3 1.5 3.9 7.4
7.3 49.7 57.2 29.9
2.6 16.7 21.5 16.6
0.6 4.5 7.9 8.3
1.7 10.4 13.6 12.7
2.4 14.1 19.7 15.3
3.2 22.7 25.3 19.7
4.9 31.5 44.2 25.7
n-Hexane
Outdoor (Ambient) 73 Public Buildings/Schools 134 Private houses 84 Personal Inhalation 92
0.3 0.3 0.2 0.6
6.0 33.3 78.4 50.8
1.6 3.0 2.5 4.0
0.4 0.5 0.5 0.9
0.8 1.0 0.9 1.5
1.1 1.7 1.4 2.4
2.2 3.1 2.1 4.2
3.6 7.6 3.5 9.7
n-Heptane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
22 46 40 37
0 0.2 0.2 0.5
0.7 9.7 8.9 10.5
0.4 1.0 1.2 1.4
0 0.3 0.3 0.5
0.3 0.5 0.5 0.8
0.4 0.6 0.7 0.9
0.6 1.0 1.2 1.2
0.7 3.1 2.4 3.8
Hexanal
Outdoor (Ambient) 102 Public Buildings/Schools 185 Private houses 96 Personal Inhalation 66
0.2 1.2 6.2 1.0
3.3 159.6 198.1 68.0
0.9 16.4 32.3 22.2
0.3 3.0 8.5 1.8
0.5 6.8 14.8 14.0
0.8 11.4 24.4 20.2
1.4 21.6 39.4 28.3
2.1 39.6 82.0 44.1
D-Limonene
Outdoor (Ambient) 102 Public Buildings/Schools 179 Private houses 96 Personal Inhalation 146
0 0 0 0.4
2.4 175.7 492.9 276.9
0.3 9.4 29.2 26.1
0 0.3 1.6 1.4
0 1.2 4.9 4.3
0.2 2.6 9.5 10.4
0.3 9.1 31.0 32.1
1.2 33.0 87.6 88.4
Methylcyclohexane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
44 86 68 67
0 0.1 0 0
2.0 36.6 6.2 23.0
0.4 2.9 0.9 2.2
0 0.1 0.1 0.3
0.1 0.4 0.3 0.5
0.3 0.7 0.5 0.8
0.5 1.2 0.9 1.6
1.2 14.1 3.7 9.2
Propanal
Outdoor (Ambient) 104 Public Buildings/Schools 185 Private houses 96 Personal Inhalation 58
0 0.5 0.4 1.5
1.9 26.0 12.7 28.0
0.7 3.0 3.0 4.5
0.1 0.8 0.9 1.5
0.3 1.4 1.8 2.3
0.6 2.3 2.7 2.6
0.9 3.0 3.3 3.7
1.4 9.1 5.9 18.0
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]
O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
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Table 2 (continued ) Values Min [n]
[mg m
a-Pinene
Outdoor (Ambient) 89 Public Buildings/Schools 160 Private houses 97 Personal Inhalation 129
0 0 0.2 0
Styrene
Outdoor (Ambient) 66 Public Buildings/Schools 128 Private houses 88 Personal Inhalation 83
0 0 0 0
Toluene
Outdoor (Ambient) 108 Public Buildings/Schools 188 Private houses 96 Personal Inhalation 146
Max ] [mg m
3
Arith. Mean 5th Percentile 25th Percentile Median 3
] [mg m
1.5 47.3 214.1 58.9
0.1 3.2 14.5 8.3
2.0 3.2 22.1 5.4
0.1 0.2 0.4 6.4
0.8 1.0 1.3 1.4
207.8 103.8 160.6 291.0
1,2,4-Trimethylbenzene Outdoor (Ambient) 105 Public Buildings/Schools 185 Private houses 96 Personal Inhalation 143
0.2 0.2 0.3 0
n-Undecane
Outdoor (Ambient) Public Buildings/Schools Private houses Personal Inhalation
m/p-Xylene
o-Xylene
3
]
[mg m
3
]
[ mg m
3
]
[ mg m
0 0 0.6 0.5
0 0.6 2.6 2.3
0 1.5 6.1 4.5
0 0 0 0
0 0 0 0
11.5 12.6 11.7 22.4
1.2 1.7 2.5 3.4
16.3 44.3 58.9 35.1
2.2 3.3 2.7 3.1
0 0 0 0
2.7 19.5 113 11.1
Outdoor (Ambient) 108 Public Buildings/Schools 188 Private houses 96 Personal Inhalation 146
0.5 0.7 0.5 0.8
Outdoor (Ambient) 108 Public Buildings/Schools 188 Private houses 96 Personal Inhalation 146
0.2 0.2 0.2 0.4
22 46 40 37
75th Percentile 95th Percentile ] [mg m
3
3
]
[mg m
0.2 3.1 16.9 9.2
0.6 12.3 47.3 32.2
0 0 0 0
0 0 0 0.1
1.1 2.4 1.0 2.5
2.3 3.3 4.5 6.7
4.8 7.1 6.5 11.7
12.9 15.5 11.1 27.5
33.2 47.6 28.4 55.3
0.2 0.3 0.3 0.5
0.4 0.6 0.6 0.8
0.9 1.2 1.1 1.6
2.0 3.1 2.9 3.0
8.2 13.6 6.6 8.8
0.6 2.2 7.2 3.0
0 0 0.8 0
0 0.9 1.2 1.6
0.5 1.4 2.3 2.4
0.8 2.1 5.0 3.2
1.9 6.3 20.0 8.4
36.5 75.1 28.1 144.2
5.7 6.2 3.8 10.5
0.6 1.1 0.9 1.3
1.4 1.8 1.7 2.8
2.5 2.9 2.8 4.7
7.2 7.1 4.6 12.2
16.2 21.5 9.3 31.0
12.3 22.2 20.5 61.6
2.0 2.2 1.8 4.2
0.3 0.6 0.5 0.6
0.5 0.9 0.9 1.4
0.9 1.2 1.2 2.0
2.6 2.4 2.0 5.0
5.5 7.1 3.7 11.3
Clara, CA, USA) equipped with a flame ionisation detector. Chromatographic separation was achieved using a J&W Scientific capillary column (DB-5, 60 m, 0.25 mm i.d., 1 mm film thickness, Agilent J&W columns, Santa Clara, CA, USA). The detection limit for all compounds ranges from 0.2 to 0.3 mg m 3. 2.2.2. Analysis of carbonyls Samples were prepared and analysed following the ISO/FDIS 16000-4 method (ISO/FDIS 16000-4, 2004). Analysis of carbonyl compounds was conducted using the Agilent Series 1100 liquid chromatographic system (Agilent Technologies, Santa Clara, CA, USA) coupled to a diode array detector (DAD) set at 360 nm. Chromatographic separation was achieved using a Waters NovaPak C18, 60 Å. 4 mm (3.9 300) mm column (Waters Corporation, 34 Maple Street, Milford, MA, USA). The detection limit for all carbonyls ranges from 0.2 to 0.3 mg m 3. 2.2.3. Fitting of the experimental data Experimental data obtained through the measurement campaigns are plotted using cumulative probability plots. Additionally, fitted plots have been also elaborated using the mean and standard deviation values calculated from the measured data. The data follow a log-normal distribution. The fitting has been produced using MS-ExcelÒ. Using the random number generator function with a defined number of data and providing the type of distribution (log-normal) and the corresponding standard deviation and mean values, it has been possible to reproduce the theoretical form of these distributions. 3. Results and discussion Table 2 summarises all data collected within the frame of the AIRMEX project. The table contains minimum, maximum,
3
]
arithmetical averages and percentiles of concentrations observed in all eleven cities for each compound and in each micro-environment (outdoors, indoors, personal). The information contained in the table may serve as reference for typical European exposure scenarios and is essential for probabilistic exposure assessment through timeeactivity analysis. The data are not claimed to be exhaustive and representative for all European possible situations. However, it can be used for exposure assessment in the investigated areas and may also give a good indication for the average European exposure to VOCs. VOCs with the highest absolute concentrations include acetone (median concentration in private houses 47.4 mg m 3 and 51.6 mg m 3 in personal samples), n-decane (median concentration in personal inhalation samples 22.7 mg m 3), n-dodecane (median concentration in personal samples 22.7 mg m 3), formaldehyde (median concentration in private houses 19.7 mg m 3) and hexanal (median concentration in private houses 24.4 mg m 3 and 20.2 in personal samples). In Table 3 the levels of selected VOCs measured in AIRMEX study are compared with a similar study (Expolis-Helsinki). First of all, it is clear that concentrations measured in the two studies are on a similar level. However, some minor differences are worth noting, namely that the outdoor concentrations in the AIRMEX study tend to be higher for the aromatic compounds than in the Expolis-Helsinki study, and vice-versa for the residential, workplaces and personal exposure concentrations. This can be explained by differences in the traffic fleet as discussed later in the paper and by differences in ventilation rates. Furthermore differences of only minor nature can be observed for terpenes. This is confirmed by the cumulative probability plots discussed in Section 4.2. The data obtained in the AIRMEX study are comparable to the indoor data from similar studies in Oxford (Lai et al., 2004) and
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O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
Table 3 Comparison of mean VOC concentrations (mg m
3
) from the AIRMEX study and the Expolis-Helsinki study.
Airmex (Arithmetic Mean)
Benzene Toluene Ethylbenzene m/p-Xylene Hexanal n-Decane n-Undecane 2-Butoxyethanol a-Pinene D-Limonene
Expolis-Helsinki (Arithmetic Mean) (Edwards et al., 2001a; Jantunen et al., 1999)
Outdoor
Residential
Workplace
Personal
Outdoor
Residential
Workplace
Personal
3.2 11.5 2.2 5.7 0.9 6.2 0.6 n.d. 0.1 0.3
4.4 11.7 1.5 3.8 32.3 17.3 7.2 n.d 14.5 29.2
2.8 12.6 2.4 6.2 16.4 14.4 2.2 4.5 3.2 9.4
4.7 22.4 3.2 10.5 22.2 24.5 3.0 n.d 8.3 26.1
1.7 5.6 1.0 3.1 2.1 1.1 0.7 e 2.1 e
2.2 20.4 2.9 7.8 11.6 5.3 5.1 2.5 16.1 31.6
3.9 32.3 16.1 38.8 5.0 13.9 13.0 e 5.5 14.2
3.4 25.3 7.7 25.0 8.2 16.5 14.3 e 10.2 18.7
a number of German cities (Schlink et al., 2004). The biggest differences found from these studies are the somewhat higher concentrations in the German study for toluene and lower concentrations for n-decane and n-dodecane, which might be attributed to local sources but needs to be further studied. Using the data provided in the Table 2, indoor/outdoor (I/O) and private house/office (Ho/Of) ratios were calculated with the aim to identify compounds that are typical for these micro-environments. 3.1. Indoor/Outdoor (I/O) ratios and home to office ratios The I/O ratio shown in Fig. 1 was calculated by dividing the median indoor concentrations (offices and classroom) by the median outdoor concentrations for each location and compound. The data are extracted from Table 2. A practical implication of the findings shown in Fig. 1 and Table 4 may be that when investigating indoor pollutants the sampling strategy should especially focus on those compounds which have an I/O ratio of >2. However, from the I/O ratio values the compounds can also be divided into categories ranging from being predominantly indoor pollutants (ratio > 6) to being pollutants not deriving from indoor sources (ratio approaching 1). In Table 4 these ratios are listed. In the first category we find formaldehyde, D-limonene and hexanal, which are mainly originating from indoor sources. The findings for formaldehyde and hexanal are in agreement with Barguil et al. (1990) who confirmed the existence of indoor aldehyde sources in residential homes and
identified formaldehyde and hexanal as being among the main aldehydes detected in indoor air. Formaldehyde has recently been identified as carcinogenic to humans (IARC, 1982, 2006), and its median I/O ratio of approximately 6 underlines the need to minimize emissions from building products, household products and furnishings inside closed environments. Other compounds of concern are 2-butoxyethanol and Dlimonene that are skin contact allergens (class III and IIB, respectively NKB, 1994). 2-butoxyethanol is used as a solvent in spray lacquers, enamels, varnishes, and latex paints and as an ingredient in paint thinners, paint strippers, and varnish removers (ATSDR, 1999), whereas D-limonene is widely used in cleaning products (Steinemann, 2009; Rodrigues et al., 2009). Besides its contactallergenic properties, D-limonene has been proven to add ultrafine particles to indoor environments through formation of ozone mediated secondary aerosol (Weschler and Shields, 1999), which has also been connected with sensory irritation in office environments (Wolkoff et al., 2006). In the category of compounds with a ratio of almost 1 we find benzene, toluene, the xylenes and the trimethylbenzenes. The levels found for these compounds indoors originate predominantly from the polluted outdoor air penetrating into the indoor environment and they are associated with automobile emissions (Chan et al., 1991; Barrefors and Petersson, 1993; Lawryk et al., 1995). Benzene is of concern as known human carcinogen, and the common practice of improving indoor air quality by opening windows is not applicable for this pollutant. The only practical way to abate this category of compounds in the
Fig. 1. Ratio median concentration indoor working/school environment against median concentration outdoors for all data collected in the frame of the AIRMEX project.
O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684 Table 4 Ratio-categories obtained by dividing median indoor concentration of offices/ classrooms by median outdoor concentrations.
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Table 5 Ratio-categories obtained by dividing median indoor concentrations in private houses by median indoor concentrations in offices/classrooms (Ho/Of ratios).
Category
Compounds
Category
Compounds
Ratio > 6a
Formaldehyde, hexanal, D-limonene, a-pinene, 2-butoxyethanol Acetaldehyde, acetone, 1-butoxy-2-propanol n-Undecane, propanal, methylcyclohexane, n-dodecane, 1-butanol Benzene, ethylbenzene, n-hexane, n-heptane, toluene, 1,2,4-trimethylbenzene, m/p-xylene, o-xylene
Ratio > 2 Ratio 2 > x < 1
Hexanal, D-limonene, a-pinene n-Decane, n-undecane, acetone, acetaldehyde, formaldehyde, propanal, n-heptane, n-dodecane Benzene, methylcyclohexane, ethylbenzene, n-hexane, toluene, 1,2,4-trimethylbenzne, 1-butanol, m/p-xylene, o-xylene
Ratio 6 > x < 4 Ratio 4 > x < 2 Ratio < 2 a
Ratio 1
Ratio > 6 or ambient air concentration close to zero.
indoor environment is through forced ventilation with filtering of the air. Analogue to the I/O ratio, a home to office ratio (Ho/Of) is obtained by dividing the median concentrations calculated for each compound in the private homes by the median concentration calculated for offices/classrooms. The Ho/Of ratio is displayed for all compounds in Fig. 2 and Table 5. It is evident that the two most abundant compounds in the private-house micro-environment are the terpenes a-pinene and D-limonene. Apparently such uses are more common in private homes than in offices/classrooms. a-Pinene is frequently used in perfumes, cleaning products and fragrances (Steinemann, 2009; Rodrigues et al., 2009) and just as D-limonene it may cause skin and eye irritation and contributes to the formation of strong airway irritants in terpene/ozone reaction mixtures (Wolkoff et al., 2006). Although a large number of terpene ozonolysis products have been identified (Calogirou et al., 1999; Glasius et al., 2000) it is not known, which are responsible for the irritation of skin, eye, and airway. However, the present findings of high Ho/Of as well as I/O ratios for terpenes may be of relevance for future indoor air quality guidelines (Kephalopoulos et al., 2007). 4. Geographical and seasonal variations in indoor concentrations of the measured compounds 4.1. Introduction
4.2. Geographical variation The geographical variation was analysed by dividing the data into two groups (Central-North and South Europe) and visualized in the form of cumulative probability plots of observed concentrations and fitted curves assuming log-normal distributions. In Table 7 the utilised parameters are presented. A clear difference between north and south was evident for the indoor concentrations of aromatic hydrocarbons (Fig. 3). In absence of indoor sources for this group of compounds (Table 4) the northesouth difference is attributed to a similar trend for outdoor concentrations. In fact the ambient air pollution levels around the investigated public buildings were notably higher in the southern European cities of Athens, Thessaloniki and Catania. Higher concentration of aromatic hydrocarbons in outdoor environments in the south of Europe may be explained by different traffic patterns
fi
A number of variables must be taken into account when setting up probabilistic European exposure scenarios. Data on different body characteristics (e.g. bodyweight) for the various populations
in Europe (EXPOFACTS) is important together with timeeactivity patterns and may differ between geographical locations and between seasons of the year. However, also potential geographical and seasonal variations in indoor concentrations must be considered. The degree of scattering in the present indoor air concentration dataset for individual compounds and for individual indoor micro-environments can mask geographical and seasonal trends. Thus data were pooled for public buildings, private homes, schools and kindergartens assuming that any geographical and seasonal variation would equally affect concentrations in these indoor environments. Furthermore, three groups of individual compounds were examined as the sum of the individual concentrations, namely aromatic hydrocarbons, terpenes and aldehydes (Table 6).
Fig. 2. Distribution of home/office ratios.
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O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
Table 6 Groups of substances evaluated for geographical and seasonal variations. Group
Compounds
Aldehydes Aromatic HC
Formaldehyde, acetaldehyde, hexanal, propionaldehyde Benzene, toluene, 1,2,4-trimethylbenzne, ethylbenzene, m/p-xylene, o-xylene a-pinene, D-limonene
Terpenes
Table 7 Parameters used for data fitting: Log-Normal distribution (mg m Substance group Geographical Mean Median SD seasonal
).
95% confidence interval
Aldehydes
Warm Cold North South
58.869 47.400 56.307 44.837
52.000 41.400 49.400 43.200
30.793 31.669 32.606 27.921
5.138 5.173 4.508 6.080
Aromatic HC
Warm Cold North South
24.613 31.863 15.559 59.051
15.900 22.723 18.500 36.126 13.300 9.051 49.650 40.385
3.764 5.963 1.258 8.741
Warm Cold North South
13.357 6.300 16.358 2.823 35.975 18.450 60.669 10.510 23.994 11.350 47.338 6.696 26.478 12.000 40.749 9.906
Terpenes
3
and a significant amount of passenger vehicles not equipped with a catalytic converter (Karakitsios et al., 2006, 2007). The observed trend for aromatic hydrocarbons is in agreement with recent studies on benzene, which investigated the relation between pollution levels and the latitude of the place the samples were taken from (Ballesta et al., 2000; Cocheo et al., 2000). In the latter, the observed increase in annual average benzene concentrations from north to south was explained with the difference in prevailing meteorological conditions, such as local wind speeds. However, the Cocheo study was conducted in Copenhagen, Antwerp, Padua, Murcia and Athens and did not include cities from eastern Europe, what makes a direct comparison difficult. For the group of terpenes there was no substantial difference between north and south (Fig. 4), which may be due to the fact that their indoor sources are related to modern lifestyle which clearly does not differ substantially between the various areas of Europe that have been included in the present study (terpenes sources: fragrances, cleaning products).
Fig. 3. Geographical variation of aromatic HC.
Fig. 4. Geographical variation of terpenes.
There is a difference in the aldehydes concentrations between north and south of Europe (Fig. 5), which fits well with the extended use of wood products in north Europe. Aldehydes sources are predominantly pressed wood products and furniture made with pressed wood products, ureaeformaldehyde foam insulation (UFFI), combustion and environmental tobacco smoke, durable press drapes, other textiles, and glues (WHO, 1989; Health Canada, 2005). In particular for hexanal a major source has been demonstrated to be the chemical reaction of oxidants in the air with linoleic acid (Svedberg et al., 2004) deriving from wood products. 4.3. Seasonal variations In the work of Diez et al. (2003) a general increase of VOC concentrations in the cold season is reported, mainly due to lower ventilation and air exchange rates. However, this effect depends on the specific VOC, of the emission sources, the building type, the geographic location, the outdoor air quality and other factors (Schlink et al., 2004). To identify a possible seasonal variation of the indoor air concentrations the division of the data into two groups was complicated by the fact that the measurement campaigns for each city did not take place simultaneously but they were spanned over a period of several years. Thus, as criterion for the categorisation of the data, the ambient temperature of the city during the campaigns was utilised. For each geographical location data were pooled together for the warmest of the two campaigns and classified as the
Fig. 5. Geographical variation of aldehydes.
O. Geiss et al. / Atmospheric Environment 45 (2011) 3676e3684
Fig. 6. Seasonal variation of terpenes.
warm period, whereas the rest of the data have been used to form the so called cold period. In Table 1 the geographical and seasonal division is presented. For terpenes the analysis shows a clear difference between warmer and colder seasons (Fig. 6) with indoor concentrations being lower during the warm season. Terpenes react rapidly with oxidants in the air such as ozone, which is much more abundant in the warm season due to the higher photochemical activity and penetrates from the outdoor air. This finding provides a good indication of the importance of indoor air chemistry for the concentration levels of various substances. An additional explanation could be the increased ventilation rates during the warm season. No difference between the warm and the cold season was evident for the aromatic hydrocarbons (Fig. 7), which is expected from the fact that they do not have significant indoor sources and therefore an increased ventilation rate does not really influence their indoor concentration. During the warm season the indoor concentration of aldehydes appeared to be slightly higher than during the cold season (Fig. 8), which may support the hypothesis of ozone penetration (formaldehyde is an oxidation product in the terpene/ozone reaction (Calogirou et al., 1999) and hexanal is an oxidation product of ozone with linoleic acid). However, also increased emission/evaporation/desorption rates from their indoor sources may play a role.
3683
Fig. 8. Seasonal variation of aldehydes.
5. Conclusions The AIRMEX project is the most recent of a series of panEuropean projects aiming to assess personal exposure and taking an inventory of VOC levels in indoor environments in several European cities. Results presented in this work represent an elaboration of the whole set of raw-data and are hereby made publicly accessible via a database (http://web.jrc.ec.europa.eu/airmex/). Moreover, the statistical analysis of the data in the present paper provides a good indication of a possible influence of indoor air chemistry on the concentration levels of reactive substances, which should be taken into consideration in future indoor air quality guidelines. Attention should be taken in indoor air quality monitoring campaigns to pollutants with an indoor/outdoor ratio higher than 2. A clear difference between north and south was evident for the indoor concentrations of aromatic hydrocarbons which can be attributed to the different kinds of vehicle fleet in the studied cities. For terpenes no similar trend was revealed for geographical variation but there was a significant difference between the values obtained for the warm and the cold period with concentrations being lower during the warm period. Besides potentially increased ventilation rates in the warm period, this can be attributed to the reactivity of terpenes with ozone penetrating from outdoor air, which is more abundant during warm periods. Our findings of higher concentration of aldehydes (ozone oxidation reaction products) during the warm period support this hypothesis.
Acknowledgements
Fig. 7. Seasonal variation of aromatic HC.
The authors wish to acknowledge all participants at this project. Without the on-site local coordination this project could not have been realized. Namely the coordinators are: Dr. Cuccia and Dr. Nastri from the Regione Siciliana, Azienda Unita Sanitaria Locale N.3 in Catania, Italy; Dr. Bloemen and his collaborators from the RIVM in Bilthoven, Netherlands; Prof. Herbarth and his collaborators from the Umweltforschungszentrum in Leizpig, Germany; Dr. Kalabokas from the Research Centre for Atmospheric Physics and Climatology Acacedmy of Athens in Greece; Dr. Nikolaou from the Organisation for the Masterplan & Environment in Thessalonica, Greece; Dr. Michael and his collaborators from the Ministry of Health in Nicosia, Cyprus; Dr. Kauppi and her collaborators from the Finnish Environment Institute, Dr. Putus from the Ministry of Social Affairs and Health, Dr. Säteri and her collaborators from the Ministry of Environment; Dr. Nurminnen and Dr. Jylkkä from the City of Helsinki in Finland; Dr. McLaughlin and his collaborators
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