Most condoms contain a cancer-causing chemical and their manufacture should be subject to greater quality control, a German scientific research institute said Friday.

The Chemical and Veterinary Investigation Institute in Stuttgart, Germany, said it found the carcinogen N-Nitrosamine present in 29 of 32 types of condoms it tested in simulated conditions.

“N-Nitrosamine is one of the most carcinogenic substances,” the study’s authors said. “There is a pressing need for manufacturers to tackle this problem.”

The carcinogen is thought to be present in a substance used to improve condom elasticity. When the rubber material comes in contact with human bodily fluids, it can release traces of N-Nitrosamine, the study said.

Local government officials said condom users should not stop using rubber contraceptives based on results of the study because N-Nitrosamine does not present an immediate health danger.

But Germany’s Federal Institute for Risk Assessment said that daily condom use exposed users to N-Nitrosamine levels up to three times higher than levels naturally present in food.