A paper in the journal Human Reproduction adds weight to a long-held (by some) suspicion that the plasticising chemical bisphenol A (BPA) does bad things to the body’s hormone balance.

In this study, male workers in Chinese factories handling BPA were compared to a control group of Chinese factory workers who weren’t exposed to BPA over five years.

The results showed that the workers in the factories handling BPA had four times the risk of erectile dysfunction, and seven times more risk of ejaculation difficulty (press release).

This stark conclusion is the first direct evidence that exposure to BPA in the workplace could have bad health effects, the authors led by De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente’s Division of Research in Oakland, California.

For years BPA has been associated with a range of health problems, from cancer to diabetes and heart disease.

The suspicion was that BPA was an endocrine disruptor – a substance that mucks up the way hormones in the body, including sexual reproduction hormones – are made and regulated. This study, the authors say, provides the evidence that the US regulators have been after for years. They add that the levels in this study were very high – nothing like the levels people are normally exposed to in everyday life.

The chemical is already regulated. In Canada, for example, BPA is banned in baby bottle manufacture, and in France earlier this year members of the senate sought a ban on BPA. Of course, there is also perhaps a need for caution – don’t be terrified, not all plastics used in baby products or drinks bottles contain BPA, and no links between low exposure levels and adverse health effects have been found. In the US at least, it seems that it is easy to check whether BPA is present: there should be a number 7 printed on any bottle that contains the stuff.

Presumably the publication of this paper will now add much more weight to the arguments of campaigners calling for an outright ban on the chemical. The story has certainly got a lot of media coverage, from Packaging News to CNN.

Bad timing award goes to the Globe and Mail, which ran a column on Monday (the day before the study came out) saying that so far all BPA fears have been hyped by activists.