Eastern China is now being eyed as the most likely source of the higher levels of ozone-depleting chlorofluorocarbons (CFCs) detected in the atmosphere, countering a multi-year global effort to ban their use.

Under the Montreal Protocol, the global agreement to protect the ozone layer that took effect in 1989, the greenhouse gas trichlorofluoromethane, CFC-11, was to be phased out by 2010.  Late last year, however, the advocacy group Environmental Investigation Agency (EIA) published research showing that CFC-11 levels in the atmosphere had begun falling more slowly.

The declines in CFC emissions under the Montreal Protocol were expected to lead to a full recovery of the ozone layer by the middle of the 21^st century. However, the new emissions could delay that recovery by a decade or more, experts now say.

EIA’s findings initially pinpointed what it said was “significant new emissions of the gas” – according to calculations, between 11,000 and 17,000 t/y – in East Asia. A new paper published this week confirmed that the pollution most likely stems from “rogue factories” in eastern China.

Independent lab tests carried out last year suggested that the excessive CFC 11 came from three unidentified Chinese production facilities. Research by EIA and the US newspaper New York Times traced some of the emissions to a refrigerants plant in Shangdong, and a large share of emissions was shown to be concentrated in Hebei Province.

China has become a major producer and exporter of household appliances such as refrigerators, which consumed large amounts of CFCs before efforts to restrict them began in the 1990s.

The People’s Republic has denied that it is the main source of the emissions rise. As the country continues to build its position as a major chemicals producer, with the help of Western multinationals, Beijing said it has made a major effort to shut down unauthorized production facilities.

Moreover, authorities have repeatedly insisted that the extent of the CFC-11 emissions is simply too great to be solely from one source.

Sunyoung Park, a researcher at Kyungpook National University in Daegu, South Korea, and a lead author of the paper just published in the journal Nature, said that some of the emissions picked up could be coming from other countries however, there is no data to back that up.

Commenting on the paper, Avipsa Mahapatra, leader of the climate campaign at EIA, said the Chinese government has taken the CFC-11 issue very seriously.

“They have engaged with us and with the international community in a very constructive manner to ensure that they are not just treating the symptoms by clamping down a few factories, but are trying to address the systemic challenge,” she said. “However, the magnitude of emissions from this region now w scientifically shown in this paper show that much remains to be done.”