Two-thirds of semen collected in a sperm bank in Shanghai is of inferior quality, a doctor in charge of the sperm bank said after collecting over the past decade, Shanghai Morning Post reported.

Only one-third of the semen is up to the standards set by the World Health Organization, and some of the sperm donators were diagnosed with oligospermia (low concentration of sperm) or aspermia (lack of semen), said the doctor Li Zheng.

Experts believed pollution may be a major culprit.