The Challenge

Breathing smog and soot are dangerous to health

Nearly four decades after the passage of the Clean Air Act, more than half of all Americans still live in areas that don't meet clean-air standards.

Dirty air increases the risk of heart disease, stroke, cancer and respiratory problems. While everyone suffers some harm, the 22 million Americans with asthma are particularly vulnerable.

The two primary sources of air pollution are tailpipes and smokestacks. The Environmental Protection Agency (EPA) sets different standards for various pollutants. In the U. S., ozone (smog) and fine particles (sometimes called soot) pose the biggest health threats. Large power plants, cars and trucks are major sources of the pollutants that form ozone and fine particles.

Air is cleaner overall, but 'hot spots' pose health threat

In recent years, EPA has placed stricter pollution controls on power plants, cars and trucks. The good news is that we are seeing successful results from these measures in many places. (Read a Q&A with Dr. John  Balbus, our chief health scientist on air quality, red alert days and public health.)

The bad news is that recent studies show that smog and fine particle air pollution harms our health at lower levels than we used to think. So living downwind of a large power plant or near a major roadway can lead to higher exposures and greater health risks, and contribute to heart and lung problems.

Ozone (smog)

Ozone, the main component of smog, forms in the lower atmosphere when nitrogen oxides (NOx) and various volatile organic compounds (VOCs) interact in the presence of sunlight, heat and relatively stagnant air.

Exposure to ozone can have serious effects on respiratory health. Inflammation and irritation of the respiratory tract can cause shortness of breath, throat irritation, chest pains, coughing and asthma attacks.  These consequences are more severe if exposure occurs during physical activity.

Particulate pollution (soot)

Particulate pollution is a mixture of soot, smoke and tiny particles formed in the atmosphere from sulfur dioxide (SO2), nitrogen oxides NOx) and ammonia (NH3). Sooty particles are most dangerous when very small as they are easily inhaled and reach deep into the lungs where they can trigger an inflammatory response.

Breathing in air heavy with tiny particles can be dangerous even over a short time. Because these particles are so minuscule, they can enter the circulatory system and damage blood vessels. Children are especially vulnerable because their lungs are still developing.

Particulate pollution is associated with heart attacks, irregular heartbeat, asthma attacks, reduced lung function and bronchitis. These impacts result in tens of thousands of premature deaths from heart and lung disease annually, as well as hospital admissions, emergency room visits, absences from school or work, and restricted activities related to asthma attacks.

Posted: 08-Aug-2007; Updated: 08-Nov-2007