Liz Szabo, USA TODAY
Although industrial chemicals called PCBs have been banned for more than three decades, a new study suggests that the pollutants could be making it harder for some people to have a baby today.
Couples with high levels of certain chemicals in their bodies took about 20% longer to conceive compared with those with lower exposures, says the study from the National Institutes of Health.
That type of delay is similar to the effects of other factors known to reduce fertility, such as smoking, obesity and older age, according to the findings, published today in Environmental Health Perspectives.
PCBs, or polychlorinated biphenyls, were widely manufactured from 1929 to 1979, with hundreds of uses, such as coolants and lubricants in electrical equipment, according to the Environmental Protection Agency.
Although they're no longer manufactured, PCBs still may be present in older products, such as caulking, oil-based paint, floor finish and insulation. PCBs persist for years in the environment - in soil, water and the food chain - as well as in body fat, the EPA says. PCBs also are found in breast milk.
Studies have shown that PCBs and other chemicals, such as the banned pesticide DDT, can alter the hormone system, according to the Natural Resources Defense Council, an environmental group.
People can reduce their future exposure to PCBs by limiting their consumption of animal products, especially fatty meat, says study author Germain Buck Louis, a researcher at NIH, which funded the study. Yet because these and other chemicals are stored in fat, it's not possible to completely eliminate the pollutants, says Shanna Swan, a professor at the Mount Sinai School of Medicine in New York.
Swan called the $10 million project "an amazing study" and "unprecedented in its cost, scope and details." Researchers tried to contact more than 424,000 households, in order to find 500 couples who were going to try to conceive a baby within the next two months.
The study followed the couples for a year, and followed women through the end of any pregnancies. Only 0.1% of couples contacted were planning to try to conceive in that time, Louis says. Scientists asked couples to provide blood and urine samples before conceiving, as well as keep daily diaries, undergo frequent interviews and pregnancy tests.
Researchers measured levels of 63 environmental chemicals. Virtually everyone had detectable levels of PCBs and a breakdown product of the banned pesticide DDT, Louis says. The couple's chances of conceiving each month then were calculated and showed that the likelihood of a pregnancy fell by about 20% among men and women with high exposure to certain types of PCBs.
Louis found that five chemicals affected women's fertility, along with 12 chemicals that affected men's. "People always look at women, but we need to be looking at the men, too," for questions about infertility, she says.
Other environmental pollutants also were related to a lower chance of conceiving. Women with high levels of a flame retardant also had a 20% lower chance of conceiving. Men with high levels of a breakdown product of the pesticide DDT also had a 17% lower rate of conception, the study says. DDT has been banned in the USA since 1972, but is still used in other countries, according to the EPA.
In another study published in June, Louis and her colleagues also found that couples took longer to conceive when men had high levels of lead in their blood. Louis says she hopes her findings won't further stress couples trying to conceive. She notes that 81% of couples conceived within 12 months.
One of the study authors, Anne Sweeney of Texas A&M Health Science Center, hopes to follow the children, as well. In future papers, Louis says she hopes to evaluate whether the couples' consumption of such things as vitamins, alcohol or caffeine affected their fertility.
Although the study was ambitious and carefully designed, authors called its results "preliminary." A study such as this can't definitively prove that high chemical exposures delayed pregnancy, says Kathryn Murray St. John, spokeswoman for the American Chemistry Council. "Many factors can affect when or if a pregnancy occurs and, while this study attempted to address some of those outside issues, not all were taken into account," she says. "The authors themselves note that the study has significant limitations, including lack of data on specific exposures to some chemicals. Given the large number of statistical analyses involved in this report, it is not surprising that some associations were found."
In the paper, authors acknowledge that their findings will be more convincing if other scientists repeat the experiment and get similar results. In earlier research, PCBs have been shown to cause a number of health problems in animals, the EPA says, including cancer and problems with the immune system, reproduction, nervous system and hormonal system.