China exporting pollution back to US: report

The U.S. may have outsourced much of its manufacturing to China, but it has regained the effects of air pollution as a result in some of parts the country. 

According to a study released by U.S. science journal Proceedings of the National Academy of Sciences, farming out manufacturing to China had resulted in poorer air quality carried across the Pacific Ocean into the western United States. 

"China is the world's largest emitter of anthropogenic air pollutants, and measurable amounts of Chinese pollution are transported via the atmosphere to other countries, including the United States," the study said. "However, a large fraction of Chinese emissions is due to manufacture of goods for foreign consumption."

It noted that, in 2006, 36 percent anthropogenic sulfur dioxide, 27 percent of nitrogen oxides, 22 percent of carbon monoxide, and 17 percent of black carbon emitted in China, were linked to production of goods for export. For each of these pollutants, about 21 percent of export-related Chinese emissions were attributed to China-to-U.S. export. 

"Pollution from China is having an effect in the U.S., and we need to recognize how that is affecting both our background ozone levels and also particulates that are reaching the West Coast," said Don Wuebbles, who is professor of atmospheric science at the University of Illinois at Urbana-Champaign, and one of the report's nine authors.

The study noted that while outsourcing manufacturing to China had led to reduced sulfate pollution in eastern U.S., it resulted in an increase in the western part including Los Angeles, which violated national ozone standards an extra day a year due to pollution from China. It added that Chinese pollution related to exports accounted for between 12 and 24 percent of the daily sulfate emissions in these areas. 

U.S. manufacturers of consumer electronic good such as smartphones and televisions are typically produced in China, including Apple which outsources the production of its iPhone to the Chinese industry.

The journal stated that while this did not cause most of the pollution in the U.S., it pointed to "westerlies" winds which could potentially send chemicals across the Pacific Ocean. "We know that the efficiency of industry in China is not as it is good in the U.S.," Wuebbles said, adding that higher efficiency manufacturing, alongside government controls on emissions and outsourcing, had significantly reduced U.S.-based emissions.

The Chinese government in August 2013 said it was investigating Apple-contracted manufacturers Foxconn and UniMicron over allegations they had released water tainted by toxic metals into rivers. Apple and Foxconn denied the charges. 

According to a study released in September 2013, some 80 percent of Chinese cities were unable to achieve a balance between economic growth, resource efficiency, and sustainable development. That same month, China's Ministry of Environmental Protection introduced more stringent laws on light vehicle emissions as well as subsidies to promote the use of eco-friendly vehicles in the country.