2010 March 31: CO Durango: Made in China: Asian pollution finds its way into the local airshed
by Allen Best
Beijing and Durango aren’t exactly sister cities, but they are linked in ways not so obvious as the ubiquitous “Made in China” tags in local stores. They share the same air, and that air that has become increasingly fouled with dust blowing westward from Asia’s expanding deserts and by fossil-fuel emissions resulting from China’s robust economic expansion.
Pollution has no boundaries. Not political boundaries. Not great oceans. Not even tall mountains.
This migratory stew includes tiny particulates called aerosols that originate in the wood-burning kitchen fires of rural Chinese villages, from cars and trucks now pouring into city streets and highways, and from the smokestacks of the smelters, chemical plants and coal-fired electrical plants that have sprung up to help propel the nation’s 13 percent annual economic growth.
The most immediate victims are the Chinese people themselves. A 2007 World Bank report estimated 700,000 people in China each year die prematurely because of the polluted air.
Many of the microscopic particulates get dispersed or washed out by rain before winds reach the West Coast. But not all. The danger is in the increment – of mercury, ozone and particulates from car exhausts, power plants and gas and oil well operations in the Durango area.
Think of Chinese pollution as a chaser of 80-proof whiskey after a pint or two of beer. The beer by itself may not challenge your sobriety. But the shot of bourbon on top of it could cause real trouble. That’s the threat represented by increasing pollutants from China.
That incremental threat, in turn, may force additional reductions in U.S. emissions to meet specified goals, says Richard “Tony” VanCurent, an associate researcher at the University of California, Davis.
VanCurent says measurements taken during the 1950s an 1960s at Hawaii’s Mauna Loa Observatory – just as the United States was getting serious about cleaning up pollution – first showed the presence of dust from Asia. In time, scientists realized the dust was reaching North America. In addition to dust, westerly winds carry up soot and other pollutants commonly called black carbon. A study conducted in 2004 found more than three-quarters of the black carbon over the West Coast during spring months comes from across the Pacific.
Scientists can monitor these trans-Pacific storms from images taken by orbiting satellites. A few times, they have also flown into the storms, to better analyze the contents.
In 2007, scientists boarded a specially outfitted small jet in Colorado that allowed them to fly up to 51,000 feet to study the composition of the plumes over the Pacific.
Dust particles themselves also have chemical signatures called isotopes that sometimes allow scientists to trace their origins. Studying air samples in California, soils scientist Stephanie Ewing of the U.S. Geological Survey found small particles of lead that clearly had originated in Asia.
Dan Jaffe, a professor of atmospheric and environmental chemistry at the University of Washington Bothell, first detected Asian pollutants arriving on the West Coast in 1997. To help peel back the identities of the invaders, he has established an observatory at Mt. Bachelor, the Oregon ski area with a top elevation of 9,000 feet.
Absent major cities nearby, “most of the time, the air atop Mt. Bachelor is the cleanest air in the United States,” he says. But especially during the spring storms, monitors spike with evidence of Asian pollution, he says.
Air in the West’s major cities, including Denver, Los Angeles and Salt Lake City, has improved enormously in recent decades. But those gains have been offset by increasing wildfires, which studies have shown can contribute both ground-level ozone and significant quantities of mercury.
In addition, the rural West isn’t quite as rural anymore. Automobile traffic has increased substantially as people choose to live in large-acreage, semi-dispersed exurban locations.
In other words, Asia alone is not the problem. It’s Asia in addition to local pollution. And it’s Asia on particular days.
Asia contributes only small amounts of microscopic pollutants called PM 10 and PM 2.5 on most days, says Jaffe, but as much as half of what is permitted by health standards on the West Coast is coming from overseas on a few days each year.
“Dust and pollution which is coming from 8,000 kilometers away will nearly always contribute less to your local air pollution than local sources,” Jaffe points out.
Most vexing to regulators is ground-level ozone. Again, say scientists, it’s a case of Asian pollution exacerbating local and regional problems.
When found in the atmospheric layer 20 to 30 miles above the earth’s surface, ozone very usefully blocks harmful ultraviolet rays. At ground level, given high levels and prolonged exposure, it poses problems especially to the young, the elderly, and people with respiratory diseases.
It can also damage high-elevation forests. Ozone causes some evergreens to lose their needles and suffer impaired ability to photosynthesize sunshine, carbon dioxide and water. Prolonged exposure can kill trees. Such damage has been documented for decades in California’s ponderosa and Jeffrey pine forests, particularly in areas downwind from the Los Angeles Basin.
Ozone is created when exhaust from cars and trucks, industrial emissions and chemical solvents combine in the presence of sunlight. But high ozone concentrations in valleys hundreds of miles from any city have been linked to expanded oil and gas drilling in the Rocky Mountains.
In early 2008, the Wyoming Department of Environmental Quality issued its first ozone advisory for the valley just west of the Wind River Range, where the nation’s two largest natural gas fields are located. Ozone levels there have reached as high as 122 parts per billion volume, well over the eight-hour average of 75 ppbv that was adopted by the U.S. Environmental Protection Agency as the safe health threshold.
Ozone is also an issue in the San Juan Basin of Colorado and New Mexico, where one monitor has recorded ozone at concentrations of 95 ppbv. The basin has 50,000 gas wells so far, plus two existing coal-fired power plants and the potential for a third.
In a 2007 paper, Jaffe and coauthor John Ray of the National Park Service reported a “significant increase” in ozone levels at seven of nine rural and remote monitoring sites they had studied – in all seasons of the year.
In a 2008 appearance before the U.S.–China Economic and Security Review Commission, Jaffe said computer simulations suggest Asia pollution is responsible for just 3 to 10 percent of ozone in the West on most days. On a few days each year, however, Asia contribution is as much as 37 percent of the federal standard. “While this contribution is relatively modest, it will certainly increase in the future and, when added to local pollution, it can push some areas over the air-quality standard,” Jaffee says.
The pollutant mercury has both local and global origins, mostly the result of coal combustion. “We know that most of the mercury that is falling out of the atmosphere is coming from coal combustion,” says Jeff Sorkin, assistant regional air program manager in Colorado for the Forest Service. But tracing mercury deposition to specific sources, even local ones, is more difficult, he says.
The challenge is illustrated in the San Juan Mountains. For several years, children and pregnant women in the area have been warned to limit their consumption of fish caught in Vallecito, McPhee, and other reservoirs and lakes because of mercury contamination.
Circumstantial evidence has pointed toward two existing power plants in the Four Corners area as sources of this mercury. Analysis of snow at Molas Lake, between Silverton and Durango, further suggests – but does not confirm – origins from the power plants.
But how much mercury from Asia is ending up in the San Juan, or other mountain ranges of the West, is still not clear. “That’s the $64,000 question,” says Jaffe. “That’s the one everyone wants to know.”
Mercury, he says, defies easy measurement, and its chemical transformations are not well understood. U.S. coal, however, contains much less mercury than coal burned in China.
Jaffe says he believes 10 to 30 percent of total deposition of mercury in the United States comes from Asia. Computer modeling of long-range transport estimates that Asia contributes 27 percent of mercury deposition in Colorado.
In recent years, China has begun to more actively develop wind and other so-called clean energy sources. Even so, in testimony during 2008 before the U.S.–China Economic and Security Review Commission, Jaffe projected an increase in emissions from China of 50 to 200 percent by the year 2020 – unless China adopted advanced pollution control technologies.
One way or another, there will be a cost – in the form of incremental pollution to U.S. cities, to damage sustained by high-elevation forests, even to the health of rural residents. Those plasma TV’s are cheaper these days, but there may be a surcharge now being incurred. •