By Steve Milloy
October 28, 2010, GreenHellBlog.com
A Kaiser Permanente-sponsored study of 514 Chinese workers reports that urinary levels of chemical bisphenol A (BPA) were associated with decreased sperm concentration, total sperm count, sperm vitality and sperm motility. The study was published in the journal of Fertility and Sterility. It may as well have been published in the journal of Futility and Stupidity.
First, the statistical associations are quite dubious. None of the reported associations between urinary BPA levels and semen quality are statistically significant. None of the p-values were reported, so it can be presumed that they all exceed the standard significance requirement of P =< 0.05. The confidence intervals (i.e., margins of error) are all quite wide — i.e., 160-200+% greater than the size of the reported association.
Next, the statistical associations were supposedly adjusted for age, education, history of chronic disease, previous history of exposure to other chemicals and metals, employment history, marital status, age at first intercourse, smoking, drinking and study site. But all these “data” were self-reported by the workers and the researchers made no effort to verify or validate any of it. Assuming for the sake of argument, for example, that smoking, drinking, and “exposure to other chemicals and metals” are true confounding factors for semen quality, no information was collected on the levels of such exposures. No doubt there are many other risk factors for reduced semen quality, but they weren’t considered. The researchers claim that study subjects complied with a 7-day sexual abstinence requirement but how certain can they be?
Also, the study population was not randomly selected. Of the 888 workers eligible to participate, only 514 did. Were these 514 the less healthy ones who opted for a free medical exam?
This effort was not designed or conducted so as to study the relationship of BPA exposure to semen quality. Not surprisingly, it doesn’t.
BPA has been used for more than 50 years with no real-world indication that it has ever harmed anyone. That’s why the anti-chemcial activists are forced to stoop to the depths of such junk science.
Steve Milloy publishes JunkScience.com and is the author of “Green Hell: How Environmentalists Plan to Control your Life and What You Can Do to Stop Them” (Regnery 2009).
For more on BPA, check out JunkScience.com’s Debunkosaurus.