China’s finally starting to reckon with the health consequences of decades of pollution. An official at the top economic planning agency just acknowledged pollution’s toll on people’s mental and physical health. But for many, that’s too little too late. Such as for China’s youngest lung cancer patient (link in Chinese), an 8 year old girl. And for the 40 million people between 20 and 40—about 12.5% of that population—who have fertility problems.

It’s also why Chinese men are increasingly shooting blanks (link in Chinese), says Dr. Li Zheng, a doctor who runs Shanghai’s main sperm bank. “To figure out whether and ecosystem is stable or not, all you have to do is test the sperm,” Li tells the Shanghai Morning Post (h/t The Telegraph).

When environmental pollution is severe enough, it causes the sperm to become long and “ugly,” such that they can even stop swimming, says Li.

Increasingly “ugly” sperm are what Li and his colleagues at Shanghai’s Renji Hospital witnessed in their 10-year study of male infertility. The just-completed research found that two-thirds of the semen specimens at Shanghai’s biggest sperm bank failed to meet World Health Organization sperm-count standards. The finding is consistent with what other studies have found, reports China Real Time.

That’s especially bad news given the dire straits of China’s sperm banks. Quality problems aside, China has long grappled with a donor shortage. Even though government banks keep upping what they pay donors, sperm are so scarce that women will pay up to 30,000 yuan ($4,900) for sperm on China’s booming black market.

The news of Li’s research broke just as an unusually thick blanket of haze hit Shanghai on Nov. 7 (paywall). Authorities urged residents to stay indoors and alerted schools to avoid outdoor activities.

This is, of course, bad news for a country struggling with an aging crisis. Unless the government can dramatically reduce pollution, this will only worsen, Li told the Shanghai Morning Post. If China “does not protect the environment,” he said, “human beings will face an infertility catastrophe.”