Air Pollution Could Be Damaging Your Lungs

Free radicals that are attached to small particles of air pollution may cause lung damage, including the possibility of lung cancer. This discovery may explain why nonsmokers develop tobacco-related diseases such as lung cancer.

Free radicals have long been known to be present in the atmosphere in the form of atoms, molecules and fragments of molecules, which can damage cells. Until now, it has been believed that these particles are most often produced by combustion and exist for less than a second before dissipating. However, according to lead researcher H. Barry Dellinger, the Patrick F. Taylor Chair of environmental chemistry at Louisiana State University, combustion-generated particles that contain environmentally persistent free radicals can apparently exist for an indefinite period of time. Dellinger says that the chemical methods used to detect free radicals accidentally converted PFRs into molecules that were mistaken for other pollutants.

As Dellinger explained it, these free radicals are very similar to those found in cigarette tar, implicating that you can have the same environmentally related diseases by exposure to airborne fine particles that you can get from cigarettes. He also noted that a person would have to smoke about 300 cigarettes per day to be exposed to the same level of environmental free radicals found in moderately polluted air. "This is a staggering but not unbelievable result, when one considers all the diseases in the world that cannot currently be attributed to a specific origin," Dellinger stated.

These persistent free radicals (PFRs) discovered by Dellinger's team attach themselves to small particles of air pollution as they rise from smokestacks, car exhaust and chimneys. Then they continue to remain in existence as free radicals. Those particles of air pollution that contain metals are more likely to remain in the atmosphere and carry PFRs for great distances. "We now have evidence that these PFRs are pervasive in the environment and may exist in higher concentrations than most organic pollutants," Dellinger says.

The reserch team used a technique called "electron paramagnetic resonance" to determine if free radicals existed in air particles. They found free radicals in each sample measured, at concentrations that varied from the equivalent of smoking one cigarette per day to smoking 100 cigarettes per day. They also found that even air that meets federal standards set by the Environmental Protection Agency exposes people to as many harmful free radicals as smoking at least one cigarette. However, breathing heavily polluted air may expose a person to free radicals equaling 100 cigarettes in one day.

PFRs are absorbed by the lungs as well as other tissues when inhaled and cause cell damage leading to conditions such as asthma, emphysema and lung cancer. However, there is currently no direct evidence that links PFRs to these diseases. More research is needed to definitively link PFRs to human disease.

According to the American Cancer Society, over 500,000 Americans die of cardiopulmonary disease linked to breathing fine air particle pollution annually with 10 to 15 percent of lung cancers occurring in nonsmokers that have been linked to air pollution. Dellinger believes that it is possible that persistent free radicals are the real culprit in these deaths. "You basically have to be in certain places to inhale transient gas-phase radicals," Dellinger said. "You'd have to be right next to a road when a car passes, for example. Whereas we found that persistent radicals can last indefinitely on airborne fine particles. So you're never going to get away from them."

Dellinger said that smokers might get a double dose of PFRs each time they light up, since tobacco smoke also contains these free radicals. A smoker will breathe in an equal number of PFRs from the air and the smoke itself, compounding the damaging effects, in the five minutes it normally takes smoker to have a cigarette.