As severe drought threatens crops in northern China, a new study has suggested air pollution could be reducing valuable rainfall.

"Besides the health effects, acid rain and other problems that pollution creates, this work suggests that reducing air pollution might help ease the drought in North China," said lead researcher Yun Qian.

About 2.5 million hectares of crops are seriously affected by the drought and may face crop failure in the provinces of Liaoning, Jilin, Heilongjiang and Shanxi and in the Inner Mongolia autonomous region, the ministry of agriculture said over the weekend. Autumn grain output accounts for more than 70 percent of the country's total grain output.