Part I-It's a Small, Small World
December 5, 1952, dawned clear and cold in London, England. h e air was damp and stagnant. Heavy black smoke rose from chimneys as Londoners lit the coal they burned to cook and heat their homes. Fog began to roll in. By dusk, the smoke-fi lled fog had turned an impenetrable yellowish black.
By the time the smoky fog lifted four days later, 2000 Londoners were dead of heart and lung complications. Another 2000 died during the following two weeks, as the persistent health impacts of the fi ve-day fog continued. When researchers compiled statistics, they estimated that during the next two months, 8000 more died of causes directly related to that deadly fog.
the culprit in London's killer fog wasn't the fog itself. It was thousands of tons of tiny particles that clung to the stagnant fog and fi lled residents' lungs. h ick soot from the city's coal-burning home hearths, diesel buses, and factories hung near the ground, trapped by a slow-moving temperature inversion. Black smoke concentrations measured during those five days reached more than 50 times normal levels.
For hundreds of years, Londoners have experienced discomfort related to particles in smoky fog (dubbed smog in 1905). Recently, it has become clear that those fi ne particles are more than uncomfortable.
The most serious eff ects of small particles are associated with aggravation of heart or lung disease. Numerous studies have related particles in the air to increased hospital admissions, emergency room visits, and mortality. Aggravation of lung diseases, including asthma attacks and acute bronchitis, has been correlated with short-term exposure. In people with heart disease, particles have been linked to heart attacks and irregular heart rhythms.
According to Dr. Joel Schwartz of the Harvard School of Public Health, it's not a small problem. By one estimate, 70,000 people in the U.S., primarily older adults, die prematurely each year when fi ne particle pollution increases to unhealthy levels. "h is," says Schwartz, "is larger than the death rate from breast and prostate cancer combined."
Minnesota is a long way from the London of the 1905 s-or even the troubled cities of the industrial northeast United States. It has its own unique problems with smoke-related pollution, however, as documented in the following article.
Regardless of their source, trying to describe fi ne particles is like trying to describe animals to someone from another planet. Just as animals can be large or small, feathered or furred, dangerous or benign, particles can be varying sizes, solid pieces or liquid droplets, man-made or natural, dangerous or benign.
Some particles are emitted directly into the air, and some form in the air from chemical reactions of nitrogen oxides, sulfur oxides, volatile organic compounds, and ammonia. Particles can cling to moisture droplets or simply drift in the air. Scientists call particles "particulate matter," abbreviated pm. Regulators generally divide particulate matter into two categories on the basis of size: pm10 and pm2.5.
Questions
1. What do "pm10" and "pm2.5" mean?
2. Which of these particles are the most harmful?
3. How do fi ne particles cause health effects?
4. What groups are most vulnerable to fi ne particle air pollution?
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