Motor vehicles emit a toxic stew of pollutants, which cause a host of environmental and health problems, ranging from acid rain to asthma. Below is a primer, providing the nuts and bolts on local emissions.

What are local emissions?

Sulfur Dioxide - Sulfur Dioxide forms when fuels containing sulfur are burned. It can irritate the eyes and the respiratory tract. Prolonged inhalation can cause asthma and other respiratory diseases, including chronic bronchitis. It can cause premature death. Children, the elderly, and the infirm at the most at risk groups.

Nitrogen Oxide - Produced during combustion, Nitrogen Oxide, when combined with volatile organic compounds and sunlight, causes smog. It also reacts with other substances in the air to produce acid rain, which damages forests and lakes and corrodes buildings. It effects the human resperitory tract, resulting in asthma, bronchitis, and emphysema. Nitrous oxide is a greenhouse gas and contributes to global warming.

Carbon Monoxide - Carbon monoxide is an odorless, colorless gas that results from incomplete combustion. Exposure to Carbon Monoxide causes flu-like symptoms include headaches, dizziness, disorientation, nausea and fatigue. At high concentration Carbon Monoxide can be fatal.

Particulate Matter - Also known as PM, Particulate Matter is a complex combination of extremely small compounds, including dust, acids, and metals. The smaller the particles, the more dangerous they are. It can cause asthma, irregular heart beats, bronchitis, and premature death for people with lung diseases.
*Source: US EPA.

Why Are They Called Local Emissions?

Unlike Carbon Dioxide, the leading greenhouse gas that causes climate change, local emissions like the ones listed above primarily impact the immediate environment. People who live and work closest to areas that emit local pollutants - places like freeways, coal burning power plants, etc - are most likely to suffer health impacts.

Dr. Yifang Zhu, an Assistant Professor at Texas A&M University, has shown that in Los Angeles concentrations of carbon monoxide and ultra-fine particles dropped by 60-80% within 100 meters of the road (Zhu et al., 2002).

Not So Local Anymore?

Power lines and pollution in northern China. Photo by AdamCohn.

Massive brown plumes of smog, resulting from the burning of fossil fuels and biomass, now stretch from the Arabian Peninsula to China, an indication that local pollution has become so concentrated and intense that it is starting to have global implications.

While these clouds, which are visible by satellite and from airplanes, also hover over North America and Southern Africa, they are most prominent in Asia.

The clouds have such a strong environmental impact because they prevent light from passing through, affecting crop yields and forests that depend on photosynthesis.

At some points, clouds can be as much as a mile thick with yellow haze blotting out the sun.

Charts & graphs

NOx Emissions by Sector - United States