Pollutants and Damage They Do

Read the latest news on this subject.

Bike riders get the full brunt of pollutants such as carbon monoxide, nitrogen oxides and particulate matter (soot) emitted at ground level by cars, buses and trucks. Because cyclists often breathe vigorously in the midst of traffic flow, they draw more pollutants into the lungs, causing coughing, fatigue and shortness of breath. Cyclists are stuck in a traffic catch-22: if they ride harder, to keep up safely with traffic flow, they wind up taking in more fumes through their mouths and straight into the lungs; if they ease up, they risk being sideswiped or blasted by the noxious back-end of a bus.

Ozone, the main constituent of smog, is the most insidious and constant air pollutant. The EPA classified New York City's ozone levels unhealthful on 19 days in 1991 — more than any year since 1988, [3] when record heat pushed ozone to the highest levels in a decade (ozone is formed when nitrogen oxides and hydrocarbons combine in sunlight). Actual exposures may be worse, because not all monitors are at street level.

Ozone is a highly reactive form of oxygen that damages body tissues and cells. After several days of exposure to high ozone levels, the body seems to recover from symptoms such as an itchy throat and a tight chest. But this apparent recovery may be just a temporary adjustment. Long-term or repeated exposure to ozone can produce fibrosis — scarring of lung tissue which can lead to emphysema and other chronic respiratory disorders. Ozone also weakens the body's ability to fight off sickness-causing bacteria and prevents the lungs from cleansing themselves of other trapped pollutants.

Inhaling tailpipe fumes exposes cyclists to carbon monoxide (CO), a notorious — though odorless and invisible — pollutant that impedes the body's ability to distribute oxygen. After a time cycling in heavy traffic, the cyclist may feel light-headed and fatigued due to overdoses of CO. Improved car exhaust systems and oxygenated fuels have led to reductions in CO nationwide. Indeed, for the first time in decades, CO levels in New York City did not violate federal standards in 1992, leading city officials to proclaim that no discouragement of auto traffic would be needed to clean the air. [4] Other considerations argue otherwise, however, including the limited number of CO monitors (four), the violations of CO standards in 1991 and prior years, and continued exceedence of smog limits. [5]

Acidic aerosols land in lung passages and may cause bronchitis, while nitrogen oxides damage the lungs and weaken the immune system, and particulates in diesel exhaust can cause lung cancer. New York City did not even measure particulate matter at street level until November 1990. [6] The Natural Resources Defense Council (NRDC) estimates that 3,000 tons of particulate matter are emitted every year by the 5,000 buses and tens of thousands of diesel trucks being operated in New York City. The combined effect of particulate matter and the other air poisons to which New Yorkers are exposed is probably greater than the sum of the parts, since each pollutant taxes the respiratory system's ability to repel and repair pollution damage.

Air pollution's damage extends beyond the metropolis. Ground-level ozone blankets the entire northeast U.S. Acid rain caused by sulfur and nitrogen oxides is destroying lakes, forests and buildings. Increasing carbon dioxide in the atmosphere caused by fossil-fuel burning is raising earth's temperature via the greenhouse effect.

NOTES: