Health Effects of Ozone and Particle Pollution
New research reported in 2005 shows air pollution is even more dangerous than we had thought—dangerous, even deadly, at levels currently considered safe in the United States.
The American Lung Association State of the Air 2006 looks at the two most common and most hazardous air pollutants: ozone and particle pollution. Both are widespread and unhealthful at levels seen routinely in many parts of our nation. And, it turns out, both are more dangerous than we thought.
Particle pollution
Everyone has had this experience: You’re sitting in traffic or driving down a highway behind a large truck with black fumes spewing from the tailpipe. You wonder just what that exhaust is doing to you. Scientists have been asking the same question for some time now. What we’re learning is that those fumes contain many complicated ingredients that can do more damage to your health than you might realize.
Not only can that black plume of smoke from the tailpipe or the graying haze settling over the city make you cough and blink, but it can do much worse—it could help take months to years off of your lifespan. The evidence accumulates as the results of new research studies pour in each month. Analyses conducted over the past seven years link air pollution to shorter lives, heart disease, lung cancer, asthma attacks and serious interference with the growth and work of the lungs.
The dirty, smoky part of that stream of exhaust is made of particle pollution. Eighteen percent of the nation—53 million people—live where the air they breathe has so much particle pollution day in and day out that their health can be at risk. Twenty-two percent—64.3 million—live in areas where frequent spikes in particles lasting hours to days places their health at risk as well. But what is particle pollution? What can these particles do to your health? Who is most vulnerable? And what can we do about it?
What is Particle Pollution?
Particle pollution refers to a combination of fine solid particles and aerosols that are suspended in the air we breathe. But nothing about particle pollution is simple. First of all, the particles themselves are different sizes. Some are one-tenth the diameter of a strand of hair. Many are even tinier; some are so small they can only be seen with an electron microscope. Because of their size, you can’t see the individual particles. You can only see the haze that forms when millions of particles blur the spread of sunlight. Alarmingly, you may not be able to tell when you’re breathing particle pollution. Yet it is so dangerous it can shorten your life.
Because particle pollution ranges in size from the tiny to the microscopic, the differences in size make a big difference in how they affect us. Our natural defenses help us to cough or sneeze larger particles out of our bodies. But those defenses don’t keep out smaller particles, those that are smaller than 10 microns (or micrometers) in diameter, or about one-seventh the diameter of a single human hair. These particles get trapped in the lungs, while the smallest are so minute that they can pass through the lungs into the blood stream, just like the essential oxygen molecules we need to survive.
Researchers categorize particles according to size, grouping them as coarse, fine and ultrafine. Coarse particles fall between 2.5 microns and 10 microns in diameter and are called PM10-2.5. Fine particles are 2.5 microns in diameter or smaller and are called PM2.5. Ultrafine particles are smaller than 0.1 micron in diameter1 and are small enough to pass through the lung tissue into the blood stream, circulating like the oxygen molecules themselves. No matter what the size, particles can be harmful to your health.
Because particles are formed in so many different ways, they also can be composed of many complex compounds. Although we often think of particles as solids, not all are. Some are completely liquid; some are solids suspended in liquids. As the U.S. Environmental Protection Agency puts it, particles are really “a mixture of mixtures.”2 The mixtures differ between the eastern and western United States. For example, the eastern states have more sulfate particles than the west, largely due to the high levels of sulfur dioxide emitted by large, coal-fired power plants. By contrast, in Southern California, nitrate particles from motor vehicle exhaust form a larger proportion of the unhealthful mix.3
