China exports pollution alongside goods

China makes many of the products that people in other countries use every day. These include toys, clothes, furniture and electronics sold by American companies. U.S. companies make many of their goods overseas to save money. Producing goods in a foreign country at lower cost is known as outsourcing. A new study now finds that even when products are outsourced, the pollution produced in making them doesn’t remain in that foreign country. In fact, the study reports, much of the air pollution from Chinese manufacturing reaches the United States.

China’s cities have some of the dirtiest air in the world. Their factories and electric power plants burn huge quantities of coal, oil and natural gas. That creates pollution — mainly sulfur dioxide (SO₂), nitrogen oxides (NO_x), carbon monoxide (CO) and soot (sometimes called black carbon).

When they mix in the air, some of these pollutants create a hazy blend called smog. A chemical reaction between some of these air pollutants generates ozone. A colorless gas, ozone can irritate people’s eyes and lungs.

Last December smog in Shanghai, China, was so thick that airports grounded planes until pilots could see well enough to take off. On especially polluted days, government officials now warn people to stay indoors. Many people wear surgical masks when they leave home, trying to keep pollutants out of their lungs.

Thousands of U.S. companies build products in China and then export them (send them to other countries). One thing that makes China so popular with foreign companies: Its people will work for less money than those in wealthier nations. In addition, the cost of building a manufacturing plant is cheaper in China. Finally, China has fewer environmental laws and its laws for controlling pollution are weaker.

Nine scientists from China, England and the United States wanted to see how much of China’s air pollution came from making goods that would be sold in other countries. Activities such as generating electricity to run these factories produced 36 percent of China’s SO₂ emissions, 27 percent of its NO_x, 22 percent of its CO and 17 percent of its soot. And about 20 percent of these export-related pollutants came from making outsourced goods for the United States, the new study found.

The scientists published their findings on January 16 in the Proceedings of the National Academy of Sciences.

The scientists also used a computer program to model, or predict, where those air pollutants ended up. Called GEOS-Chem, this computer program uses data from weather satellites to build a three-dimensional picture of the atmosphere. It showed that some of China’s emissions from producing exports travel across the Pacific Ocean to the western United States.

How much of this pollution crossed the ocean varied from day to day. At its highest, pollution from Chinese production of goods for export accounted for 25 percent of sulfate concentrations and 11 percent of soot in the western United States. In some parts of California — and even as far off as the American Northeast— these emissions drove ozone levels above legally allowed limits at least once each year.

The computer model calculated that air over the eastern United States is cleaner now than it would be if it hadn’t outsourced some of its manufacturing to China. But western states are more polluted. The reason: That bonus pollution drifting over from China. (Most pollution in western states is still from U.S. sources, such as cars; Chinese emissions just make it worse.)

Most people who buy imported products don’t think about where they come from. But foreign shoppers who buy goods that were made in China contribute to air pollution in China, according to Steven Davis, a scientist who worked on the new study. He studies earth-systems science — interactions between the atmosphere, land and the oceans — at the University of California, Irvine. “We may not see soot in the air, but people somewhere else are breathing it,” Davis says.

China is serious about cleaning up its air, says Mark Levine. He created a group at Lawrence Berkeley Laboratory in California that studies Chinese energy use. China’s State Council — a group of leaders from government agencies — has pledged to use less coal, the country’s dirtiest fuel source. The Council has also vowed to modernize factories so that they produce less pollution. The Chinese are putting a lot of money and effort into controlling their pollution, Levine says. Still, “they have a long way to go,” he notes. “It will take a while for us to see improvements.”

Power Words

black carbon  Particles of carbon that are released when fossil fuel is burned.

carbon monoxide  A pollutant made of carbon and oxygen that forms when a fossil fuel is burned. Its scientific symbol is CO.

haze  Fine liquid or solid particles scattered through the atmosphere that make it hard to see. Haze can be caused by harmful substances such as air pollutants or by water vapor.

model A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes.

nitrogen oxides  Pollutants made up of nitrogen and oxygen that form when fossil fuels are burned. The scientific symbol for these chemicals is NO_x (pronounced “knocks”).

ozone  A colorless gas that forms high in the atmosphere and at ground level. When it forms at Earth’s surface, ozone is a pollutant that irritates eyes and lungs.

pollutant  A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.

sulfur dioxide  A pollutant made of sulfur and oxygen that forms when fossil fuel is burned. Its scientific symbol is SO₂.

smog   A kind of pollution that develops when chemicals react in the air. The word comes from a blend of “smoke” and “fog,” and was coined to describe pollution from burning fossil fuels on cold, damp days. Another kind of smog, which usually looks brown, develops when pollutants from cars react with sunlight in the atmosphere on hot days.