WOMEN whose bodies contained high levels of certain chemicals found in plastics and cosmetics experienced menopause two to four years earlier than women with lower amounts in their systems, US researchers said Wednesday.

While the study in the journal PLOS ONE did not prove that the chemical exposures caused earlier menopause, study authors said the associations they uncovered merit further research.

"Chemicals linked to earlier menopause may lead to an early decline in ovarian function, and our results suggest we as a society should be concerned," said senior author Amber Cooper, an assistant professor of obstetrics and gynecology at the Washington University School of Medicine.

The findings were based on a nationally representative sample of 1,442 menopausal women, whose average age was 61.

None of the women were taking estrogen-replacement therapies, nor had they undergone surgery to remove their ovaries.

Researchers examined the women's blood and urine for signs of 111 chemicals that are suspected of interfering with the natural production and distribution of hormones in the body, the study said.

They found 15 chemicals that were significantly associated with earlier menopause and declines in ovarian function.

They included nine polychlorinated biphenyls (PCBs), three pesticides, two phthalates --- which are typically found in plastics, common household items, pharmaceuticals, lotions, perfumes, makeup, nail polish, liquid soap and hair spray -- and a toxic chemical known as a furan "that warrant closer evaluation," the study said.

Ovarian function is important because without it, women are infertile and may be at risk for earlier development of heart disease, osteoporosis and other health problems.

"Many of these chemical exposures are beyond our control because they are in the soil, water and air," Cooper said.

"But we can educate ourselves about our day-to-day chemical exposures and become more aware of the plastics and other household products we use."

She recommended people use glass or paper containers when microwaving food, and minimize their exposure to harmful chemicals in the cosmetics and personal care products they choose.

The study was funded by the US National Institutes of Health.