Transpacific air pollution is worse than was suspected

provided by University of California, Davis

niversity of California, Davis researchers reported last month that rising industrialization in Asia is discharging millions of tons of previously undetected contaminants annually into the winds that travel across the Pacific Ocean. These aerosols make people sick and destroy crops in Asia, may be polluting American waters, and could dramatically change global climate.

The researchers also described their role in the forthcoming ACE-Asia project. ACE-Asia, for Aerosol Characterization Experiment, will be the world's largest attempt to identify the exact sources and destinations of those tiny particles of dust, sulfate and organic matter. This information does not exist for much of Asia and is badly needed by scientists trying to generate reliable predictions of global climate change.

"Previous research has shown that every spring there are massive dust storms in Asia that transport soil eastward to Japan and across the Pacific to the United States. Now we've found that sulfate and organic aerosols are also present, and in roughly the same amounts," said Thomas Cahill, a UC Davis professor emeritus of physics and atmospheric science and an international authority on the atmospheric transport of pollutants.

"That is very important for several reasons. First, the northern Pacific Ocean is one of the last really clean areas of the Northern Hemisphere. If we start to pollute the air above that ocean, we'll change the balance of heating and cooling of the ocean and that will produce changes in the weather.

"Second, there are increasing numbers of reports of what appear to be toxic Asian pollutants in the lakes and streams of North America.

"Finally, and perhaps most important, there is an established link between aerosol levels and rates of illness and death in people. Working with our Asian colleagues, we hope to help them efficiently address the causes of these aerosols and aid in developing mitigation. The findings may prompt Asian policy-makers to restructure developmental mandates to take into account the devastating air-quality problem they have," Cahill said.

Asia is the largest source of aerosols in the world, Cahill said. That's largely because the region burns millions of tons of coal annually from its abundant coal deposits. Aerosols are released from coal-burning power plants and coal-fired locomotives; heavy industry, such as metals production; automobile and truck exhaust; home heating; and the overtilling of dry-area farmland.

While releases of one key type of aerosol, sulfur dioxide, have been decreasing in the United States and Europe since tough air-pollution rules were enacted, the releases are increasing in Asia, particularly in China, Cahill said. Between 1990 and 2000, annual releases of sulfur dioxide into the atmosphere in the United States dropped from about 20 million tons to 13 million tons, but in China they have climbed to about 45 million tons.

Once released into the air, aerosols ride the wind over land and sea, rising to altitudes of several miles, where their travel is sped by the dry atmosphere and swift winds. Wherever they go, they retain a unique signature of their origins in their composition of trace elements, such as nickel, copper, zinc, arsenic and lead. Aerosols with these unique signatures from Asia have been detected all the way to the US Rocky Mountains, Cahill said.

The new data are the first results of a research project named the University of California Pacific Rim Aerosol Network, which was started in 1998 with $67,000 from the university system. Cahill said he expects the findings to suggest more Asian impacts.

Cahill also described the network's planned role in the large, multimillion-dollar ACE-Asia international research program. In ACE-Asia, the existing air samplers and some additions will gather data for six weeks in spring 2001. New samplers will be installed at sites in five Asian countries (China, Taiwan, the Philippines, South Korea and Japan), Mexico and the United States.

The heart of the network is the newly designed International Aerosol Sampler, which was designed and built at UC Davis. It is inexpensive, lightweight and low-tech for producing reliable data in undeveloped regions with unreliable power supplies. It collects air samples that can be chemically checked for unique signatures and tracked as they move around the globe. This method of developing chemical signatures has been put to intensive use at UC Davis since the early 1970s, when Cahill and colleagues were conducting the first studies to identify the origins of view-blocking haze in US national parks.

Those land-based machines will collect data in synchronization with aerosol detectors aboard ships, airplanes and satellites, Cahill said. The US National Science Foundation has granted UC Davis $350,000 over three years for its part of the ACE-Asia project.

After the ACE-Asia work concludes, the UC network will continue to deliver critical information, Cahill said. "The relationship between a smelter in Manchuria and aerosol pollution in Japan is not obvious. That's the understanding we're trying to achieve," he said.

Contact: Sylvia Wright,, (530) 752-7704.