Outdoor Air Quality Monitoring

Outdoor Air is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere.

The atmosphere is a complex dynamic natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth’s ecosystems.

Indoor air pollution and Outdoor air quality are listed as two of the world’s worst pollution problems in the 2008 Blacksmith Institute World’s Worst Polluted Places report.

Outdoor Air Pollutants can be classified as primary or secondary. Usually, primary pollutants are directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone — one of the many secondary pollutants that make up photochemical smog. Some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants.

• Sulfur oxides (SOx) - Since coal and petroleum often contain sulphur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2 leads to acid rain. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.
• Nitrogen oxides (NOx) – especially nitrogen dioxide are emitted from high temperature combustion. Can be seen as the brown haze dome above or plume downwind of cities. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants.
• Carbon monoxide – it is a colorless, odorless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.
• Carbon dioxide (CO2) – a colorless, odorless, non-toxic greenhouse gas associated with ocean acidification, emitted from sources such as combustion, cement production, and respiration
• Volatile organic compounds - VOCs are an important outdoor air pollutant. In this field they are often divided into the separate categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure. 1,3-butadiene is another dangerous compound which is often associated with industrial uses.
• Particulate matter - Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total amount of aerosols in our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.
• Particulate matter formed from gaseous primary pollutants and compounds in photochemical smog. Smog is a kind of air pollution; the word “smog” is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by ultraviolet light from the sun to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

Major source of indoor air pollution is the increased popularity of air conditioning units. Newer buildings are built to be more energy-efficient, but they also do not allow fresh air to circulate. Toxins that escape into the air are continually re-circulated through the air conditioning unit. These Air Conditioners also have a tendency of pulling in outdoor air through their condensers. Most air filters only remove about 10% of these pollutants. Dust, pollen, mold spores, animal dander and bacteria found in buildings is constantly circulated through the air conditioning system. To make matters worse, all these pollutants gather in the air conditioning duct work , a dark moist environment where they can continue to grow and be re-circulated throughout the building. It is a well known fact that allergies can be traced to the mold spores that grow in air conditioning units. Even dead mold can cause allergic reactions in individuals.