By Steven Reinberg
WEDNESDAY, Nov. 14 (HealthDay News) -- Exposure to common chemicals such as polychlorinated biphenyls (PCBs) may hamper a couple's efforts to conceive a child, a new study shows.
"This suggests that some environmental chemicals might be important for human reproduction, specifically the time it takes couples to get pregnant," said lead researcher Germaine Buck Louis, director of the division of epidemiology, statistics and prevention research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Rockville, Md.
Despite being banned, PCBs and other similar chemicals are still present in the environment. "The chemicals in this paper are commonly referred to as persistent environmental chemical compounds, meaning that when they get into the environment they don't break down," Louis explained.
Exposure often originates in the family kitchen, where processed and high-fat foods harbor the compounds. Heating plastic containers in the microwave oven also ups the risk of exposure, experts say.
"Humans are exposed largely through their diet," Louis said. "It takes a long time for these chemicals to clear from the body, but the key is to try to minimize new exposure."
One way to do that is to trim the fat from fish and meat, which is where some of these chemicals are absorbed, the researchers noted.
Their report was published online Nov. 14 in the journal Environmental Health Perspectives.
For the study, Louis' team collected data on 501 couples who gave blood samples so the researchers could measure the levels of these chemicals. In addition, the women kept a record of their menstrual cycles and the results of home pregnancy tests.
Over a year of follow-up, they found as the levels of chemicals increased, the odds of getting pregnant decreased. For women exposed to PCBs and the perfluorchemical known as perfluorooctane sulfonamide, the odds dropped by 18 percent to 21 percent.
Perfluorooctane sulfonamide belongs to a class of chemicals known as perfluoroalkyls, which have been used in fire-fighting foams.
For men, the odds dropped 17 percent to 29 percent for those exposed to PCBs and DDE, which is produced by degrading of the pesticide DDT. Although DDT was banned in the United States, it is still used in some countries, the researchers noted.
A previous study by this same group found high blood levels of lead and cadmium -- two common metals -- were also tied to delayed pregnancy.
PCBs have been used as coolants and lubricants in electrical equipment. They are in a category of chemicals known as persistent organochlorine pollutants and include industrial chemicals and chemical byproducts as well as pesticides.
These chemicals are ubiquitous and found in soil, water and in the food chain. They don't readily decay, and may stay in the environment for decades. Some of these chemicals, known as persistent lipophilic organochlorine pollutants, accumulate in fatty tissues.
Other chemicals, called perfluorochemicals, are used in clothing, furniture, adhesives, food packaging, heat-resistant, non-stick cooking surfaces and in the insulation of electrical wire.
Some of the delays in pregnancy may have been due to exposure to several chemicals, the researchers added.
"There is really no way to avoid exposure to these chemicals," said Shanna Swan, vice chair for research and mentoring in the department of preventive medicine at Mount Sinai School of Medicine in New York City.
"The best thing to do is keep your exposure down to a dull roar," she said.
Moreover, the effects of newer chemicals used to replace these older ones aren't yet known, Swan said.
To reduce exposure to these and other chemicals, Swan advises, eat pesticide-free food, don't eat processed food and don't microwave food in plastic containers.
In addition, Swan believes products should be labeled with their chemical contents.
Another expert, Dr. Christine Mullin, a reproductive endocrinologist/infertility specialist at the Center for Human Reproduction at North Shore-LIJ Health System in Manhasset, N.Y., commented that these findings are "not surprising."