Microscopic particles of dust and soot are killing thousands of Californians each year. The Environmental Working Group - a Washington D.C.-based research and advocacy organization - reports that floating particles cause more than 9,300 deaths in the state each year. Most of them are from car exhausts and factories.
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Air pollution was responsible for more than 4,000 deaths in Hong Kong in 2000 and there are no signs the air quality will improve, A study conducted by Hong Kong University found that there were 4,262 deaths in 2000 due to cardiovascular and respiratory illnesses such as heart attacks and lung cancer arising mainly from air pollution. "We believe the death is precipitated by air pollution," says Anthony Headley, the university's chair of community medicine. "It is very clear even with the government's measures to improve air quality there is no improvements in the past two years."
Headley calls for "urgent and radical air-quality intervention to avoid further harm to health.
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Environmental monitoring stations on top of Hawaii's Mauna Loa, which is 13,677 feet high, have found arsenic, copper and zinc that came from smelting in China 5 to 10 days earlier, even though China is thousands of miles away.
When industrial pollution first showed up at Mauna Loa a few years ago, scientists were surprised. Now they know that the pollution from the world's largest cities affects the whole Earth. "It turns out Hawaii is more like a suburb of Beijing," says Thomas Cahill, a University of California atmospheric scientist.
Along the West Coast, scientists have been measuring pollutants as they land after traveling across the Pacific. They have used data gathered on the ground and from an airplane flying along the coast to measure aerosol pollutants that blow eastward each spring, carried by the prevailing winds. For the United States, China is a major source of dangerous pollutants. For Europe, it's the United States.
"It's kind of a natural human condition to point to someone else who is causing your problems," says David Parrish, a research chemist with the National Oceanic and Atmospheric Administration. "Each state points to the state upwind and says, 'You're causing our problems.'"
Scientists previously thought that only greenhouse gases like carbon dioxide were global in their reach and effect. They now understand that the microscopic, suspended particles of pollutants - generically called aerosols by atmospheric scientists - also travel around the world, even if they persist for just hours before settling to the ground. This class of pollutants includes soot, salts, dust and other byproducts of the burning of fossil fuels and vegetation, and have been shown to cause many deaths. "It happens on a small scale but the implications are on a global scale," says V. Ramanathan, an atmospheric scientist at the Scripps Institution of Oceanography.
During their time in the air, the particles affect everything from global warming to human mortality to the rainfall that ultimately washes them from the atmosphere. Given their tremendous variety in shape, size, composition and distribution, their effects are unpredictable.
Scientists used to assume that aerosols settled close to their point of origin, and this is sometimes true: The big cloud of smoke, dust and pollutants from the attack on the World Trade Center didn't travel very far. But beginning in the 1950s, scientists began noticing layers of haze in places like the Arctic, far from any significant source of pollution. The haze suggested aerosols were capable of traveling long distances.
Now, armed with satellites, airplanes, balloons, ship- and land-based observatories, scientists can accurately track pollutants and the winds that carry them. "If there's anything we've learned over the years, it's there is a lot of long-range transport up there that no one was ever aware of," says Ken Rahn, a professor of oceanography at the University of Rhode Island.
Large storms can blow particles high enough in the air to hook up with the jet stream. Once high enough, dust from the Sahara or smoke from big fires "can easily travel halfway across the globe," says Yoram Kaufman, a senior scientist with the National Aeronautics and Space Administration.
Sometimes the journeys of these clouds of pollutants can be mapped. The billowing clouds of dust each spring from Mongolia's Gobi Desert blows east, passing through cities like Beijing. There, the particles of dust are frosted by various pollutants, many of them toxic. This dangerous mixture continues to blow eastward, arriving in the United States within days. There, its effects are dramatic: In May 1998, Cahill and others measured the highest atmospheric concentrations of arsenic ever seen in the western United States in tiny Jarbidge, Nevada, population 12. "It's nothing that is going to get anyone sick. It's just that it shouldn't have been there," Cahill says.
The problem isn't just China. Aerosols have been tracked from the Sahara to the Caribbean, from Ontario to Rhode Island, and from Germany to Sweden. Within them are toxic metals, nutrients, viruses and fungi. "We live in a small world. We breathe each other's air," Cahill says. The problem isn?t new: Pollutants generated by the smelting of ores by the Greeks and Romans show up today, more than 2,000 years later, in trace amounts in ice cores drilled from Greenland.
"These dust plumes don't go away right away. They can be carried over great distances and are forcing people to take a global perspective on pollution," says Barry Huebert, a professor of oceanography at the University of Hawaii. The effects of aerosols are obvious in cities like Beijing, where in spring, a cloud of dust and pollution cuts visibility to a few feet. You can tell it's a sunny day if the sky is bright brown. If it's rainy, it's still brown, just a darker shade. "You're living in a sepia world," says Cahill.
The tiny particles make for spectacular sunsets, but they?re a serious health hazard, as they can lodge deep in the lungs, contributing to increased mortality. Aerosols may also harm agriculture by blocking portions of the spectrum of light from the sun, starving crops like wheat and rice of the energy they need to grow.
The biggest worry, and the one that?s least understood, is the effect aerosols have on weather and climate. Some aerosols can cool the planet by shading it from the sun. Others can warm it by absorbing and trapping the sun's heat. "(Aerosols) are clearly right at the center of some important climatic issues," says Huebert.
Aerosols may also have the ability to aid in the formation of clouds, while retarding their rainfall. Water drops surround aerosols in clouds, but they don?t clump together to form the larger drops that gravity pulls from the sky as rain. "We humans may be pushing precipitation away from populated regions," says NASA's Kaufman.
The dust is not all bad news: Dust clouds carry nutrients to regions that depend on them. In Hawaii, plant life relies on Asian phosphorus and calcium to grow. Phytoplankton in the waters off the Alaskan coast crave Asian iron, which blows eastward by the millions of tons.
Scientists can trace the origin of the pollutants by using the unique chemistry of aerosols as a fingerprint. Rahn, the oceanography professor, has developed a list of about 150 compounds, each with its own distinct signature so that scientists can distinguish between soot from a power plant burning low-sulfur coal in Colorado and a fire burning in the Brazilian rain forest.
"Once the scientists say these particles are coming from here, here and here, at that point it's finger-pointing," says Ramanathan. "That's something we have to leave to the politicians to figure out."
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