Using a modeling system called GEOS-Chem, the scientists estimated that in 2006, sulfate concentrations in the Western United States increased as much as 2 percent, and ozone and carbon monoxide levels also increased slightly because of the transportation of pollutants from emissions that resulted from the manufacture of goods for export to the United States. Because the Eastern United States has a much denser population, the outsourcing of manufacturing to China still resulted in “an overall beneficial effect for the U.S. public health,” even if Western states suffered, the scientists wrote.

The amount of air pollution in the Western United States resulting from emissions from China is still very small compared with the amount produced by sources in the United States that include traffic and domestic industries.

The study’s scientists also looked at the impact of China’s export industries on its own air quality. They estimated that in 2006, China’s exporting of goods to the United States was responsible for 7.4 percent of production-based Chinese emissions for sulfur dioxide, 5.7 percent for nitrogen oxides, 3.6 percent for black carbon and 4.6 percent for carbon monoxide.

The interdisciplinary research project was begun two and a half years ago by scholars in Britain, China and the United States. The group included economists as well as earth and environmental scientists. The methodology applied various analyses and modeling to the Chinese economy and to the earth’s atmosphere and weather patterns.

The scholars who gave emissions estimates for China’s export industries, a significant part of the country’s economy, looked at data from 42 sectors that are direct or indirect contributors to emissions. They included steel and cement production, power generation and transportation. Coal-burning factories were the biggest sources of pollutants and greenhouse gases, which contribute to global warming.

In recent years, scholars have been studying the impact of China’s total emissions on global air pollution and warming. Residents of nations in the path of winds carrying pollutants from China have grown alarmed at what they believe to be deteriorating air quality in their countries because of that pollution. In Japan, for instance, an environmental engineer has attributed a mysterious pestilence that is killing trees on Yakushima Island to pollutants from China.

Alex L. Wang, a law professor at the University of California, Los Angeles, who studies Chinese environmental policy, said after reading the new paper: “This is a reminder to us that a significant percentage of China’s emissions of traditional pollutants and greenhouse gas emissions are connected to the products we buy and use every day in the U.S. We should be concerned, not only because this pollution is harming the citizens of China, but because it’s damaging the air quality in parts of the U.S.”