THE quality of donated sperm in the city has been falling for five years.

According to Shanghai Human Sperm Bank in Renji Hospital, the city’s only sperm bank, only a quarter of the donated semen it received in the first half of the year met the quality standard regarding the number and vitality of sperms.

The rate was 40 percent in 2013 and 35 percent in 2014.

“A 15 percent drop in five years is a quite noticeable figure,” said Chen Xiangfeng, deputy director of Renji Hospital’s reproductive medicine center. “But it doesn’t mean that people have to worry too much about infertility problems, since our standard for donor sperm is much higher than the normal standard for child-bearing.”

For child-bearing, the normal standard for the density of sperms is 15 million per milliliter. But for donors, the requirement is 60 million per milliliter. There is also a different criteria concerning the vitality of the sperm.

“But it’s true that the infertility rate saw a rise in the past few years, not only in China, but in other countries and continents too,” said Chen.

Working pressures and a faster living pace, as well as pollution and other environmental issues, are considered as partially responsible for the decline in sperm quality.

“The reasons are varied, including mind status, diet and living habits, inherited disease and excess use of plastics in daily life,” said Chen.

In 2014, the infertility rate in China was found to range between 12.5 and 15 percent.

According to Chen, Shanghai Human Sperm Bank receives about 10,000 semen samples a year, with just 500 to 600 of them able to meet the standard. Donors have to pass strict health checks.

Sperm donors usually receive up to 6,000 yuan (US$900) to help to cover the donor’s transportation and nutrition costs as they have to make multiple trips for eight to nine months.