When coal or other fossil fuels are burned by power plants in economically booming central China, they spew pollution like ozone precursors and particulates high into the air, which mix with sunlight and become smog. While some of the ozone produced in the smog stays near the ground, some continues upward and commingles with a flowing air stream, starting a global journey.

Typically, the noxious cocktail of air pollution and dust rises a few thousand feet, then joins an air current moving east toward Beijing. High over Beijing, some of the pollutants may drop toward the ground, but the city adds even more to the pollution mix before it continues to rise a thousand-or-more feet higher into swifter moving currents. This current flows eastward over Korea, picking up more ozone and particulates from industrial and other sources there, and continues east.

After Korea, the pollution stream bends north, streams over Japan and finds the Pacific Ocean’s strong air currents, where it moves like a freight train over Hawaii, into the free troposphere and on to California and the western United States. Along the way, some smog particles and gases will drop to ground level, affecting air quality in western North America, while the rest moves inland, creating so-called “Asian dust events” in Colorado and Arizona.

In Boulder, Colo., government scientist Russ Schnell, the deputy director of the National Oceanic and Atmospheric Administration’s (NOAA) Earth System Research Laboratory’s Global Monitoring Division, helps coordinate efforts to measure and monitor these global air pollutants. The ESRL has been collecting atmospheric composition data for decades, documenting an increasing global mixture of ozone, the main component of smog, particulates, mercury and other pollutants that flow in a constant stream high in the atmosphere. This mixture defies borders or a specific country’s air quality laws, with one country’s industrial exhaust sometimes becoming another’s air. It’s a concept as old as Industrialization -- one booming nation’s air pollution increases along with production and population, sending more for their neighbors to breathe.

“In essence, California is living in the air sewer of China. Western Europe is living in the air sewer of North America,” Schnell said. “Whatever you put up in San Francisco or Beijing goes around the world in a few weeks or so.”

Soon, according to NOAA data, the amount of ozone wafting across the Pacific Ocean to western North America may exceed levels allowed by the U.S. Environmental Protection Agency (EPA). And while progress is being made toward some international standards that might help rein in this cross-border conundrum, as of now there’s not much anyone can do.

Tracking global air pollution

The amount of time it takes a pollutant to navigate the globe is startlingly short: if you put a monitoring balloon up in San Francisco it may take only three or four days to move over Washington D.C., then it can be in Europe in three to five more days, Schnell said. And then it moves on to Asia and the air comes around again. And by no means is Asia’s share of this global pollution a new phenomenon: smog and other pollutants from the United States have been polluting Western Europe for decades, and Canada and Mexico also send a good amount of air pollution into bordering U.S. states, and vice-versa.

On California’s rugged far northern coast, one of NOAA’s observatories sits on Trinidad Head, a point that juts out into the Pacific Ocean. The site was chosen for its remoteness from the dirtier air of Southern and Central California -- the nearest town has only 400 residents -- which makes it perfect for measuring incoming global air pollution.

Trinidad Head is just one in a network of observatories run by NOAA that are measuring and studying cross-border air pollutants. They collect jars of air weekly that can be studied and stored and use lasers at night to measure particles.

“It’s like a flashlight in a dark room -- you can see all the particles floating around,” Schnell said of the lasers. “It tells us their size and shape and something about their composition.”

On each step of a pollutant’s journey there is either a large observatory -- Mauna Loa, Hawaii; Barrow, Alaska; American Samoa; the South Pole and Summit Greenland -- or a smaller monitoring station there to capture and study its makeup.

On October 7, 2011, the first of four planned missions by unmanned, high-altitude planes was launched from California, with another scheduled to be launched from Australia. Two other flights in areas to be determined are also being planned.

These white, windowless aircraft can fly at high altitude autonomously without landing. They can carry large payloads of scientific equipment, and are being sent up to measure ozone, greenhouse gases and other global air pollutants in another of a constant effort to understand what effect the burning of fossil fuels around the world is having on the environment.

Measurements of ozone -- which at ground level is the main component of smog and can cause respiratory and heart problems in humans -- and carbon dioxide, or CO2, have been consistently rising for the past half century since NOAA began monitoring it globally.

With these monitoring tools it is also easier for scientists to identify where a specific type of pollutant originates -- sometimes down to the actual facility it comes from.

“You can get a fingerprint, and you know one or two of these (gases) are coming from a certain location,” Schnell said. “So if you had a box of 100 marbles of different colors and shapes, one is ozone, and the other marbles say ‘Made in China or India,’ one can assume the other ozone marbles in that mix were made there too.”

A study published last year in the journal Nature by NOAA scientist Owen Cooper found that springtime levels of ozone over the western United States were rising due to air flowing in from Asia, and concluded that these incoming pollutants would make it more difficult for the United States to comply with its own Clean Air Act laws. The data was collected as far back as 1984 to 2008.

While the United States also contributes to this global ozone pollution stream, the rising levels over the western U.S. were not being driven by local sources, the study found. The study also found that when airflows from Asia decreased, ozone levels still rose over North America, but not as much. So Cooper concluded that other areas might also be contributing to this increase in ozone.

What can be done about it?

A state or country where air pollution worsens because of activities elsewhere cannot do much about it. The United States, Canada and European countries have been working together on this issue since the 1970s and have agreed to some pollution standards. But the rising levels of smog coming from south and east Asia are not covered by any such policy, officials said.

“For ground-level ozone and fine particles, the main components of smog ... there is currently no global agreement,” said Enesta Jones, a spokeswoman for the EPA.

Air-quality officials and advocates say local sources of emissions like cars and power plants are still much more harmful to human health in the United States than pollution from Asia. But concerns are growing as air-quality data show increasing pollution traveling across the sea.

Yet, there are a number of efforts under way to change this by adding new teeth to an existing international air pollution agreement. The effort is attempting to get climate and air quality scientists from around the globe to collaborate on studies so that all nations can better understand how pollution is moving around the earth. The hope is that this collaboration will result in better science, and therefore better air pollution regulations in countries like China.

The main thrust of this work is being done by the Task Force on Hemispheric Transport of Air Pollution, a group chaired by the United States and European Union. The task force operates under an international air pollution convention created in 1979 called the Long-range Transboundary Air Pollution, or LRTAP Convention, which covers the United States and Canada, all of Europe and central Asia. This agreement currently addresses a number of pollutants: sulfur oxides, nitrogen oxides, volatile organic compounds, ammonia, heavy metals and persistent organic pollutants.

The EPA said more than 750 experts from 38 countries have participated in task force meetings, but a real agreement is still a long way off. That said, negotiations are currently under way on obligations related to fine particle pollution.

David McCabe, an atmospheric scientist with the Clean Air Task Force, said discussions are just beginning in earnest among LRTAP members and Asian countries to address the smog being sent across the sea.

“The Asian countries have begun to have these discussions, and there's a lot of interest in science and policy circles about how we take these successful efforts like LRTAP, which is considered the most important air pollution treaty, and use that model in different venues," McCabe said. "Obviously that's a negotiation process, and that discussion is just beginning.”

Still, there is some cause for hope coming from China. NOAA’s Schnell and others said recent developments in China spurred by citizen groups angry over air quality in cities like Beijing are starting to make a difference. While Beijing’s smog has been so bad at times it has forced flight cancellations, the government and private groups are doing better monitoring, which has led to real changes.

“As economies grow they become more concerned about air quality,” Schnell said. “For example, they can't burn coal in Beijing anymore, but before every house or apartment had a coal pollution source. Now they are switching to natural gas.”

Meantime, officials in the United States, Europe and Asia are working toward more international collaboration, but local laws are still most effective at reducing air pollution that travels beyond a certain state’s borders.

“Officials are working to improve collaborations between U.S. scientists at NOAA, EPA and NASA and ... Asian scientists,” McCabe said. “There’s been a good deal of participation from China and Japan. So, it appears (better collaboration) is a big goal of theirs.”

Photo: Will Hart/Flickr

This post was originally published on Smartplanet.com