Jan. 28, 2009 -- Exposure to a type of chemical found in everyday items such as clothing, carpets, and food packaging may be adversely affecting women's fertility, delaying the time it takes them to become pregnant, according to a new study.
In the study, the higher the concentrations of these chemicals -- called perfluorinated chemicals (PFCs) -- in the women's blood samples, the more likely the women were to take more than 12 months to get pregnant.
"In our study, 75% of the women had concentrations that were associated with a longer waiting time [to pregnancy]," says study researcher Jorn Olsen, MD, PhD, professor and chair of epidemiology at the University of California School of Public Health. Olsen heads the Danish National Birth Cohort at the University of Aarhus in Denmark.
The study is published online in the journal Human Reproduction.
Meanwhile, representatives of manufacturers who use the chemicals say the study shows only an association, not a cause and effect, as Olsen also emphasizes. Major manufacturers who use the chemicals are participating in a voluntary phase-out of them.
Measuring PFC Levels
Olsen and his colleagues took blood samples from 1,240 women during their first pregnancy visit, when they were about four to 14 weeks pregnant, and measured concentrations of the chemicals. The researchers asked the women how long it took to become pregnant; they defined infertility as a "time to pregnancy" of longer than 12 months or the need for infertility treatment to become pregnant.
The women were part of the Danish National Birth Cohort, a study of women recruited from 1996 to 2002; most were 25 to 34. "We divided the women into equal size groups, lowest, higher, [even] higher, and highest values [of the chemicals]," Olsen tells WebMD. "We made the comparison between these groups'' in looking at the time to pregnancy.
They measured concentrations of two types of PFCs: PFOS (perfluorooctane sulfonate) and PFOAs (perfluorooctanoate). The chemicals are used to make such products as nonstick cookware and breathable clothing, among other items.
Compared to the women with the lowest levels of PFOS, women in the next three groups, with progressively higher levels of PFOS concentrations, had greater odds of taking more than 12 months to become pregnant. For instance, those in the group with the third highest concentration range of PFOS had a 2.34 times greater odds of taking more than 12 months to become pregnant than the women in the group with the lowest blood levels of the chemical.
The same was true for the concentrations of PFOAs, with women in the groups with the higher concentrations taking longer to become pregnant than women in the lowest concentration group. For instance, those with the next highest concentration of PFOAs had a two times greater odds of taking 12 months or more to become pregnant, compared to the women with the lowest concentrations of PFOAs.
"This is just an association study," Olsen says. It doesn't prove cause and effect, nor does it explain how the chemical exposures might affect fertility.
It's possible that high levels of the chemicals in the blood stream may affect the menstrual cycle, Olsen speculates, and that in turn could affect fertility.
In recent decades, the fertility rates in developed countries have declined, Olsen notes in the study report. While much of the decline can be explained by wishes to have a smaller family size and better contraception, he says some may also be due to reduced fertility. And chemical exposures may partially explain that reduction, he says.
Olsen hopes others will study the same association to see if they come up with the same findings. "If this finding can be replicated, I think we have one of the explanations for the frequent problem of long waiting times [to pregnancy]," he says.
The majority of Americans probably have concentrations of PFCs in their blood, says Olga Naidenko, PHD, a senior scientist at the Environmental Working Group, a nonprofit environmental research organization based in Washington, D.C., who reviewed the study for WebMD.
"It has been used very widely and has now contaminated the environment," she says of the chemicals. The new study adds information about the effects of exposure to the chemicals on reproduction, she says.
"What they are basically seeing is that the reproductive health of these women has been severely affected by the PFCs," she says. "It is a painful shock. I don't know if I would call it a surprise."
"This is a preliminary finding," says John Heinze, PhD, a special consultant to the Fluoropolymer Products Information Center of the Society of Plastics Industries, who also reviewed the study for WebMD.
Much follow-up research will be needed, he says, to demonstrate meaning for human health.
Dan Turner, a spokesman for DuPont, which makes the chemicals, issued a statement that says, in part: "We are reviewing the study. The weight of evidence continues to indicate to us that there is no health risk to the general population."
Goals to Reduce Use of PFOAs
Efforts are under way to reduce the use of the chemicals. In 2006, the Environmental Protection Agency (EPA) launched the 2010/15 PFOA Stewardship Program, in which eight major companies, including DuPont, agreed voluntarily to reduce the use of PFOA and related chemicals by 95% no later than 2010.
The plan is to eliminate use of the chemicals by 2015.
The EPA began to investigate PFOA "because it is very persistent in the environment,'' according to information on the EPA web site. ''It was being found at very low levels both in the environment and in the blood of the general U.S. population, and it caused developmental and other adverse effects in laboratory animals."
What can consumers do to minimize exposure, especially if they are trying to become pregnant?
"Exposures that come from products are very low," Heinze, the industry consultant, says. "It's not a reason to discontinue using consumer products." Exposure to environmental chemicals is more the issue, he says.
According to the EPA, routine use of household products made with the chemicals does not pose a concern, based on the information available to the agency.