Health Effects of Ozone and Particle Pollution cont'd
Where Does Particle Pollution Come From?
Particles are so complex in part because they come from many sources. Particle pollution is generally produced through two separate processes: mechanical and chemical. Both processes can produce particles of a range of sizes, but the each procedure produces predominantly one size.
The simplest process is mechanical, which means the breaking down of bigger bits into smaller bits with the material remaining essentially the same, only becoming smaller. Mechanical processes form primarily coarse particles.4 Dust storms, construction and demolition, mining operations, agriculture and coal and oil combustion are some of the activities that produce coarse particles. They generally are already formed as particles when they enter the air.
By contrast, chemical processes in the atmosphere create most of the tiniest, the fine and ultrafine particles. Combustion sources burn fuels and emit gases. These gases can simply vaporize and then condense to become a particle of the same chemical compound. Or, they can react with other gases or particles in the atmosphere to form a particle of a different chemical compound. Particles formed by this latter process come from the reaction of elemental carbon (soot), heavy metals, sulfur dioxide (SO2), nitrogen oxides (NOx) and volatile organic compounds with water and other compounds in the atmosphere.5 Burning fossil fuels in factories, power plants, steel mills, smelters, diesel- and gasoline-powered motor vehicles and equipment generate a large part of the raw materials for fine particles. So does burning wood in residential fireplaces and wood stoves and burning agricultural fields or forests.
What can particles do to your health?
That dark smoke coming out of the truck’s tailpipe is probably directly emitting carbon particles and the raw ingredients for other fine particles into the air. That dark stream mixes with exhausts from other cars, trucks and heavy equipment, as well as the exhaust plumes from power plants, factories and many other sources to create the particle pollution problem we have in many places in the U.S. today.
In the early 1990s, dozens of short-term community health studies from cities throughout the United States and around the world indicated that short-term increases in particle pollution were associated with adverse health effects ranging from increased respiratory symptoms to increased hospitalization and emergency room visits, to increased mortality from respiratory and cardiovascular disease.
In 1993, a landmark study appeared in the New England Journal of Medicine, which documented the significant risk to human life from long-term exposure to particle pollution. Called the Harvard Six City study, it looked at six small towns in the eastern U.S. and found clear evidence of the increased risk of premature death from the particle pollution in the most polluted city studied, compared to the cleanest.6 Two years later, another group of researchers using the large nationwide database of personal histories from the American Cancer Society, came to similar conclusions.7 Additional thorough reviews8 have left no room for doubt: particles at the levels seen in the United States today are shortening lives.
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Tiny particles lodge deep in the lungs. |
| Partículas muy pequeñas se alojan en la profundidad de los pulmones. |
Particle pollution causes a broad range of health problems. Exposure worsens asthma and causes wheezing, coughing and respiratory irritation in anyone with sensitive airways. It also triggers heart attacks, cardiac arrhythmias (irregular heartbeat) and premature death.
Because of its very small size, particle pollution gets right through the nasal passage, past the trachea and deep into the lungs. The smallest of the particles can even enter the bloodstream via the lungs.9
For example, in a study published in 2003, researchers evaluated a series of autopsied lungs from Mexico City, a city with high particle levels, and compared them to lungs from Vancouver, where there is very little air pollution. The small airways in the Mexico City lungs showed markedly higher levels of fibrous tissue and muscle and microscopic evidence of particle accumulation in the respiratory bronchioles, the small airways in our lungs. The study demonstrates that particle pollution penetrates into and is retained in the walls of small airways. The resulting damage to the lungs was similar to that found in the lungs of cigarette smokers.10
