Air Pollutants

Air Pollutants There are many types of air pollutants. The exact composition and concentration of pollutants depend on the source activity or process, the type of fuel and/or chemicals involved, and in some cases the meteorological conditions under which the pollutant is emitted. Air pollutants are pervasive, and are responsible for a range of adverse health and environmental effects. These pollutants include hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM), sulfur dioxide (SO2), ozone, volatile organic compounds (VOCs), hydrogen sulfide (H2S), and toxic air contaminants such as lead (Pb). Greenhouse gases such as carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and high-global warming potential gases (e.g., perfluorocarbons, sulfur hexafluoride, hydrofluorocarbons, nitrogen trifluoride, hydrofluoroethers, and ozone depleting substances) have been implicated in global warming effects. Sources of air pollution also emit quantities of other substances which are often referred to collectively as toxic or “hazardous” air pollutants (HAPs). These pollutants can have more serious health impacts than some of the general pollutants, depending on the level of exposure. In many cases, toxic pollutants constitute a small fraction of the total HC or PM emissions. Related links about Air Pollutants Subtopics Greenhouse Gases One of the key contributors to global warming is the increased emissions of greenhouse gases (GHGs). When solar radiation passes into the Earth’s atmosphere, most is absorbed by the Earth and some is reradiated back into the atmosphere. GHGs trap the heat, keep it from passing through the atmosphere to space, thus causing the lower atmosphere to warm. Some GHGs occur naturally in the atmosphere, while others are emitting strictly by human activity. CO2 is emitted by combustion of fossil fuels (oil, natural gas, and coal), solid waste, biomass (e.g., wood products), and by industrial processes (e.g., cement kilns). Also, CO2 can be removed from the atmosphere (or “sequestered”) when it is absorbed by plants as part of the biological carbon cycle. CH4 is emitted during the production and transport of fossil fuels, and can be emitted through livestock and other agricultural practices and by the decay of landfill wastes. N2O is emitted by fossil fuel and solid waste combustion, and during agricultural and industrial activities, Hydrofluorocarbons, sulfur hexafluoride, and perfluorocarbons are emitted from a wide range of industrial processes, including during their production as well as their use in refrigeration and air conditioning, during semiconductor manufacturing, and as substitutes for ozone depleting substances (ODCs). Although these gases are typically emitted in smaller quantities relative to CO2, they have a higher global warming potential (GWP), and are sometimes referred to as “high GWP gases”.

Related links about Greenhouse Gases Mercury and Other Toxic Air Pollutants Toxic air pollutants are substances that cause or may cause cancer or other serious health effects, such as reproductive or birth defects, and neurological, cardiovascular, and respiratory disease. They can be found in gaseous, aerosol, or particulate forms. Some toxic air pollutants, such as mercury (Hg), are persistent bioaccumulative toxics (i.e., they are stored indefinitely in the body and increase over time). These toxics can deposit onto soils or surface waters, where they are taken up by plants and are ingested by animals, with concentrations increasing as the toxics move up through the food chain to humans. Sources of hazardous air pollutants include stationary sources such as factories, dry cleaners, and hospitals, as well as mobile sources such as cars, buses, and construction equipment. Related links about Mercury and Other Toxic Air Pollutants Ozone Ozone (O3) is created by a chemical reaction between NOx and VOCs that is generated by heat and sunlight. A large share of ozone-generating pollutants are produced by motor vehicles, although any fuel combustion source emits the pollutants that can contribute to ozone formation. Ozone is a major problem in many urban areas around the world where it can reduce lung capacity and increase susceptibility to respiratory illnesses, especially in infants and the elderly. Related links about Ozone Particle Pollution Particulate matter can be either emitted directly by sources (primary) or formed in the atmosphere from precursors (secondary). Primary particles are generated by combustion such as the burning of diesel fuel, and by mechanical generation such as the churning of road dust, brake wear, and construction activities. Secondary particles form in the air due to complex chemical reactions that convert gaseous precursor pollutants into particles. Most dangerous are the fine particles (PM2.5) which can be absorbed deep in the lungs, causing aggravated asthma, decreased lung function, lung cancer, cardiac problems, and premature death. Related links about Particle Pollution

Climate Change Global climate change refers to any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). Global warming, a term which refers to an average increase in the temperature of the atmosphere near the Earth’s surface, can contribute to changes in global climate patterns and is influenced by both human activities and natural causes. One of the key contributors to global warming is the increased emissions of greenhouse gases (GHGs) resulting from human activities. Human activities, such as the burning of fossil fuels, deforestation, and agricultural practices, have caused the concentrations of heat-trapping GHGs to increase significantly in the atmosphere. Since the beginning of the industrial revolution, atmospheric concentrations of greenhouse gases (GHGs) have increased at an accelerating pace because of human activities. According to the 2007 findings of the Intergovernmental Panel on Climate Change, concentrations of carbon dioxide (CO) have increased 35%, methane (CH4) concentrations have increase almost 150%, and nitrous oxide (N2O) concentrations have risen by 18% since the pre-industrial era. These increases have enhanced the heat-trapping capability of the earth's atmosphere. According to NOAA and NASA data, the Earth’s average surface temperature has increased by about 1.2 to 1.4 degrees since 1900. There is general consensus among the world’s leading climate modelers that the buildup of GHGs will lead to further increases in the worldwide average temperature, with potential impacts that may include rising sea levels, erosion of coast lines, increased storm intensity, changing rainfall patterns, and loss and migration of species. In 1993, most world countries joined an international treaty -- the United Nations Framework Convention on Climate Change (UNFCCC) -- to begin to consider what can be done to reduce global warming and to cope with whatever temperature increases are inevitable. In 2005, an addition to the treaty known as the Kyoto Protocol formally entered into force. The Kyoto Protocol contains quantified, country-specific emission reduction targets for the period of 2008-2012 and legally binding commitments to these reductions for 36 countries. In January 2005 the European Union Greenhouse Gas Emission Trading Scheme (EU ETS) commenced operation as the largest multi-country, multi-sector Greenhouse Gas emission trading scheme world-wide. The aim of the EU ETS is to help EU Member States achieve compliance with their commitments under the Kyoto Protocol. The Prototype Carbon Fund, a partnership between seventeen companies and six governments and managed by the World Bank, became operational in April 2000. This fund helps establish the market for project-based greenhouse gas emission reductions while promoting sustainable development. In 2004, the international Methane to Markets Partnership was launched as a voluntary, non-binding framework for international cooperation to advance the recovery and use of methane as a valuable clean energy source. Under the Partnership, countries make formal declarations to minimize methane emissions from key sources, stressing the importance of implementing methane capture and use projects in developing countries and countries

with economies in transition. The Asia-Pacific Partnership on Clean Development and Climate is an innovative new effort to accelerate the development and deployment of clean energy technologies. There have also been a number of regional, state and local initiatives to address climate change in the United States. In 2005, Governors of seven Northeast States signed a Memorandum of Understanding to develop a CO2 cap and trade initiative known as the Regional Greenhouse Gas Initiative (RGGI). In 2006, California became the first state to pass a comprehensive GHG emission reduction regulation under legislative bill AB32, which has the potential to cover a wide range of source categories depending on how significant sources are ultimately defined. The recently established national Climate Change Registry is a collaboration between states, provinces and tribes aimed at developing and managing a common GHG emissions reporting system that is capable of supporting various GHG emission reporting and reduction policies for its member states and tribes and reporting entities. Many states have also developed their own individual climate change action plans to identify and implement specific activities and responses to potential climate change impacts within their states. Control Strategies Reductions in air pollution can be achieved by a variety of methods including pollution prevention, control technologies, and control measures, and may be implemented through regulatory, market-based or voluntary programs. A control strategy may include a combination of different voluntary measures or mandatory controls, may focus on one or several pollutants or sources of air pollution, and can be implemented on a local, regional, national, or international scale. Energy efficiency, process changes,, and solventless coatings are examples of pollution prevention strategies. Many of the air quality improvements to date have been achieved through technological developments. Air pollution control technologies have achieved stunning results in reducing emissions from the manufacturing and mobile source sectors by as much as 90 to 99 percent. Continuing advances in both pollution prevention and air pollution control technology should enable further emissions reductions to offset increased emissions caused by continued population growth and worldwide economic development. Related links about Control Strategies Subtopics Mercury and Other Toxic Air Pollutants Control of mercury emissions is based upon reduction of the emissions and pollutant releases into the atmosphere by the industries that use mercury within their processes, emit mercury or dispose of products containing mercury, such as thermometers. In the U.S., national emission standards for hazardous air pollutants (NESHAPS) have been established for industries emitting toxic air emissions that require the use of Maximum

Achievable Control Technology (MACT) for compliance. For example, mercury NESHAP/MACT standards have been promulgated for hazardous and municipal waste incineration, commercial/industrial boilers, chlor-alkali plants, and portland cement kilns. Strategies for controlling mercury and other toxic air pollutants include pollution prevention measures, including product substitution, process modification, work-practice standards and materials separation; coal cleaning (relevant to mercury control); flue gas treatment technologies; and alternative strategies. Significant sources of toxic air pollution are motor vehicles, so programs to reduce emissions from cars, trucks and buses also decrease concentrations of toxic air pollutants. These programs include reformulated gasoline, the national low emission vehicle (NLEV) program, and gasoline sulfur control requirements, among others. Related links about Mercury and Other Toxic Air Pollutants Ozone Ozone control strategies generally target nitrogen oxides (NOx) and volatile organic compounds (VOCs), the primary contributors to ozone formation in the troposphere. Control strategies may comprise a set of regulations that specify emission limits and/or control equipment that are deemed to be reasonable available control technology (RACT), best available control technology (BACT), lowest achievable emission rates (LAER), depending on the severity of the air pollution problem in the area. NOx and VOC control equipment or programs may address specific industrial processes;on-road vehicles; nonroad equipment such as locomotives; or nonpoint sources such as small industrial boilers, dry cleaners, and consumer solvents. Pollution prevention measures such as use of non- or low-VOC content solvents and coatings can also be part of an effective ozone control strategy. Related links about Ozone Particle Pollution Particle pollution, or particulate matter (PM) pollution control strategies reduce primary PM emitted directly by a source, or PM precursor emissions (NOx, SOx, VOC, and ammonia) that react in the atmosphere to form fine PM. Control strategies could include a set of regulations that specifies emission limits in either mass or opacity units. PM control equipment or programs may address specific industrial processes; nonroad equipment such as locomotives and other equipment that burns diesel fuel; and nonpoint sources such as dust from agricultural activities and travel on paved and unpaved roads, and smoke from fireplaces and woodstoves. Related links about Particle Pollution

Indoor Air Pollution Indoor air can become polluted if contaminants accumulate inside buildings. Common contaminant groups include dusts (particulates), vapors and gasses, as well as biological agents. Some indoor contaminants occur naturally, but most are generated by materials or activities in or around the building. Certain indoor air pollutants, such as asbestos, formaldehyde, carbon monoxide, and lead, cause great health risks to individuals. Indoor air pollution can occur in any type of building, including homes, offices, and schools. Incomplete or inadequately controlled combustion is a major cause of indoor air pollution world-wide. Sources of polluting combustion include fireplaces, wood stoves, kerosene heaters, natural gas stoves, furnaces, and water heaters. When these sources are worn, improperly adjusted, or inadequately vented, they burn inefficiently and produce increased levels of smoke, deadly carbon monoxide gas, and other substances. Different materials burn with different characteristics, but as a general rule, a hot blue flame indicates an adequate mix of fuel and air, while a persistent yellow-tipped flame is associated with increased pollutant emissions and need for adjustment. Routine inspection and maintenance by a qualified technician helps maximize appliance efficiency, reduce unwanted byproducts of combustion, and identify dangerous conditions that should be corrected by venting to the outdoors. Two other products of combustion, second-hand tobacco smoke and diesel exhaust, are also frequent indoor pollutants. Second-hand tobacco smoke is associated with increased number and severity of asthma attacks in children. Diesel exhaust, which is also associated with increases in respiratory disorders, can enter buildings when vehicles idle near windows and air intakes. The problem is particularly severe when the building ventilation system air intake is located near a busy loading dock or an electrical power generator that runs on diesel fuel. Where this condition exists, building owners may request that drivers turn off their engines while making deliveries, the loading area can be relocated, or the building air intake duct can be extended or routed away from the source of contamination. Paint, cleaning products, and other household chemicals can also produce unacceptable levels of indoor air pollution. Components of these substances are released during normal use and also if containers leak or are not closed tightly in storage. Because containers can deteriorate, leak, and contribute to indoor pollution over time, limit stored supplies to that which will be used in a reasonable amount of time. Properly dispose of aging containers and excess or unused products. Certain building materials also contribute to indoor air pollution under some circumstances. Common construction materials that are associated with indoor pollution include asbestos insulation, formaldehyde resin pressed wood products, lead paint, and certain volatile organic compounds, such as those associated with some carpets. Naturally occurring radon gas, molds that grow on wet or damp building materials, and dust mites can pose health hazards if they are allowed to increase indoors. Radon gas is

gradually formed below ground in some types of geological formations and rises up through soil. The gas enters buildings through cracks in the foundation or basement and accumulates in areas with poor air circulation. Adding fans to increase air exchange usually prevents this radioactive gas from building up in occupied spaces. Mold spores and other parts can trigger asthma and allergies if they become airborne. Active mold growth is best controlled by keeping building surfaces dry. This is particularly challenging in hot, humid environments where moisture in air condenses on cool building surfaces. Mold management typically involves construction, maintenance, insulation, and ventilation combined. Dust mites are also associated with asthma and allergy symptoms. Structures (body parts) of these very small organisms can become airborne and constitute another component of indoor air pollution in dusty environments. Regardless of the pollutant or its source, modern energy-efficient building practices have inadvertently increased the problem by increasing the extent to which the building is sealed from the outdoor environment. With less air leaks in and out of the building, more heated or cooled air is retained, but so are the indoor air pollutants. Building owners and occupants find that the best way to minimize air pollution in these buildings is by reducing the amount of polluting sources (for example by purchasing furnishings that give off lower levels of volatile organic compounds), taking steps to keep ventilation systems operating effectively or improve venting when necessary, and improving routine maintenance and venting of equipment and appliances that can contribute air contaminants. Measuring Air Pollution Air pollution can be directly measured as it is emitted by a source in mass/volume of emission (e.g., grams/m3) or mass/process parameter (e.g., grams/Kg fuel consumed or grams/second). Air pollution can also be measured in the atmosphere as a concentration (e.g., micrograms/m3). Ambient air monitoring data is used to determine air quality, establish the extent of air pollution problems, assess whether established standards are being met, and characterize the potential human health risk in an area. Alternatively, air pollution concentrations can be simulated using computer models, and then validated using data collected from direct measurements at selected monitors or sources. Air pollution data and models are used together to examine the impacts of control strategies on the ambient air. Related links about Measuring Air Pollution Subtopics Air Quality Modeling As an alternative to or in conjunction with direct monitoring, computer models are often used to predict the levels of pollutants emitted from various types of sources, and how these emissions eventually impact ambient air quality over time. The models themselves

vary in terms of sophistication, accuracy and precision of their outputs. Different models are used to estimate emission rates, source activity levels, and ambient air quality impacts. For example, models are available for estimating emissions from mobile and stationary sources, predicting meteorological factors, locating potential emission point sources, and the likely photochemical and dispersion characteristics of air pollution, as well as predicting traffic patterns and congestion. In addition, emissions models and preprocessors can be used to provide input data for air quality models that need emissions based on chemical species, and broken down into very fine temporal (e.g., grams/second) and spatial (1 km x 1 km grid) resolution. Related links about Air Quality Modeling Monitoring Air pollution monitoring activities are typically separated into two classifications: source monitoring and ambient air monitoring. Monitoring can be made directly using continuous measurement instrumentation or manual methods, or remotely using optical sensing systems. Source monitoring involves the measurement of emissions directly from a fixed or mobile emission source, typically in a contained duct, vent, stack or chimney. Stationary source data is used to determine control technology performance, confirm established permit limits are being met, and as input to ozone and/or health risk prediction models. Major stationary sources may have continuous emissions monitors (CEMs) installed to report real-time emissions based on pre-established reporting cycles. Ambient air monitoring involves the measurement of specific pollutants present in an immediate surrounding atmosphere. Most Major urban areas often operate several ambient air monitoring instruments, each dedicated to measuring specific target pollutants. Vehicles and Fuels Motor vehicles are a major source of air pollution worldwide. In many urban areas, motor vehicles collectively produce 50 to 90 percent of local air pollution, depending upon the pollutant. Vehicles can also produce a significant amount of the toxic or hazardous pollutants found in our air. Motor vehicles are typically divided into on-road and nonroad categories for regulatory purposes. Most nations set standards for both engines and fuels in order to reduce air pollution. In the U.S., only EPA and the State of California are permitted to establish new vehicle and fuel standards; other states may adopt California standards if they choose. In addition to engine and fuel characteristics, mobile source emissions are also affected by ambient conditions, driving behavior, and transportation system characteristics. Related links about Vehicles and Fuels Subtopics

Cars, Trucks and Buses Automobiles, motorcycles, trucks, and buses are commonly referred to as “on-road” mobile sources. Automobiles and light-duty trucks are a major source of air pollution all over the world. Emissions from these vehicles come from the tailpipe. Gasoline powered vehicles also generate evaporative emissions from fuel tanks, out of the oil reservoir, and around engine seals. Gasoline refueling vapors are also a significant source of emissions. Most cars and light-duty trucks are fueled by gasoline, and generate large quantities of volatile organic compounds (VOCs), nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide (CO2) emissions. Motorcycles represent a large part of the vehicle fleet in developing countries. Two-stroke motorcycles are especially polluting and can emit more air pollution than a small fleet of modern automobiles. Most heavy-duty trucks and buses are powered by diesel fuel, which can generate significant amounts of NOx and sulfur oxide (SOx) emissions (especially in areas with high-sulfur content fuels), as well as potentially cancer-causing particulate matter. Emission controls for modern gasoline vehicles are capable of reducing vehicle emissions by more than 95 percent compared to uncontrolled carbureted vehicles. Diesel vehicle controls have also provided substantial reductions, especially for particulate matter (PM), although further NOx reductions require highly advanced engine technologies or retrofit of aftertreatment devices. Related links about Cars, Trucks and Buses Fuels Gasoline and diesel fuels are complex mixtures of many different chemicals. The precise combination of chemicals determines key fuel properties such as energy content, volatility (i.e., ability to vaporize), and the fuel’s ability to ignite and burn in the engine. In turn, the various fuel properties effect vehicle emissions, performance, and fuel cost. Fuel producers have developed different gasoline and diesel formulations designed for specific vehicle and engine technologies to provide adequate vehicle performance and decreased emissions at a reasonable cost. In fact, a vehicle and its fuel should be viewed as an integrated system, with fuel properties designed to match specific engine technologies, and vice versa. Fuel standards can also be designed to control specific pollutants. Depending upon the air quality conditions in a particular local area, fuel properties can be adjusted to reduce CO, hydrocarbon, NOx, or even PM emissions from vehicles. Some areas change their fuel formulations on a seasonal basis to address wintertime CO and summertime ozone problems. In many instances adopting new fuel standards can bring about immediate, cost-effective emission reductions, without making changes to an area’s vehicle fleet. Other fuel changes may be designed for the introduction of new, cleaner vehicles over the long-term. Alternatives to traditional fuels include compressed natural gas, biodiesel, ethanol, liquefied natural gas, methanol and propane. Hydrogen has been identified as a potential “fuel of the future,” with little to no net emissions. The advent of fuel cells as a potentially viable power source for vehicles has further raised the interest in hydrogen as a fuel.

Related links about Fuels Other Engines and Equipment Offroad mobile sources are defined as motorized equipment that is portable or selfpropelled, but not certified for operation on roadways. Typical offroad equipment includes construction and farm equipment, airplanes, ships, locomotives, lawn and garden equipment, mobile generators and pumps, among many others. Increases in air traffic and shipping, along with construction activities, have resulted in significant emissions from nonroad sources in recent years. As emission controls on automobiles, trucks, and buses become more prevalent, the relative amount of air emissions generated by nonroad sources is becoming more significant. In general, smaller, lighter equipment is dominated by gasoline engines, while larger equipment relies heavily on diesel engines. In most cases offroad equipment is not centrally registered. In addition, offroad equipment operation profiles can vary widely depending upon the specific application and operator. For these reasons, engine populations, use patterns, and resulting emissions from these sources are much more uncertain than for on-road sources. Related links about Other Engines and Equipment