BEIJING - Pollution, stress, smoking and multiple abortions are all leading to a rise in infertility in China, which may affect up to one-tenth of Chinese couples, Xinhua news agency said on Monday.

Sperm counts had fallen noticeable since the 1970s, the report quoted Wang Yifei of Shanghai's Jiaotong University as telling a symposium on reproduction health in the eastern city of Hangzhou.

"A certain percentage of the sperm donated by seemingly healthy college boys to our sperm bank in Shanghai is not eligible in terms of sperm count or motility," Wang said.

Rising wealth resulting from the country's headlong economic boom over the past few decades had contributed to the problem in helping promote unhealthy lifestyles, said another academic.

"The problem deserves attention from all walks of life because it threatens the quality and structure of our future population," said Huang Hefeng of Zhejiang University.

Xinhua added that the issue could exacerbate China's ageing population crisis.

China is already home to more than half of the old people in Asia, and by 2050 the number of those over 60 will exceed 400 million, accounting for more than 30 percent of the population.

The government says China is in the unenviable and unique position of ageing before it becomes affluent, but it is trying to tackle the problem and believes the next 25 years are crucial.

Still, it has only relaxed slightly its strict family-planning policies, which limit many couples to just one child.