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 containe
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