Bisphenol-A, a chemical responsible for the clear hard plastic found in many plastic bottles and other items, appears to adversely affect sperm in men, according to new research.

The study of more than 200 Chinese factory workers found that those who were exposed to bisphenol A, or BPA, were more likely to have lower sperm counts and poorer sperm quality. The men who didn't handle products with the chemicals contained were found to have the same level of BPA in their urine samples than that of the average American man.

The study, published in the journal Fertility and Sterility, is the first to produce evidence that the chemical could adversely affect sperm quality in humans. De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland, Calif., conducted the study with funds from the National Institute of Occupational Safety and Health.

In the new study, Li and his colleagues found that those with detectable BPA levels in their urine were two to more than four times as likely to have poor semen quality, including low sperm concentration, low sperm counts, fewer sperm that were alive and more sperm that did not move normally, known as poor sperm motility. BPA was not associated with lower sperm volume or deformed sperm.

The study is the third in a series of reports Li has published examining the effects of BPA exposure among Chinese factory workers. The two previous papers produced evidence that BPA exposure was associated with erectile dysfunction and other sexual problems in men.

BPA is found in thousands of consumer products, ranging from dental sealants to canned food linings. It is so ubiquitous that it has been detected in the urine of more than 90% of the U.S. population. Concern about the substance has been increasing as evidence has accumulated, primarily in laboratory animals, that it may be associated with health effects including infertility, weight gain, behavioral changes, premature puberty and diabetes.

After long maintaining that BPA is safe, the Food and Drug Administration in January reversed itself, saying it was concerned about the compound's health risks, especially in the development of fetuses, infants and young people.

In the meantime, many manufacturers have pledged to take BPA out of baby bottles, water bottles and other products, and a handful of jurisdictions across the country have banned BPA from baby products.