A chemical commonly used to soften plastic and in lipstick, nail polish and other household items has been found to interfere with the development of healthy breast tissue, which could lead to breast cancer, according to a new study.

Butyl benzyl phthalate, or BBP, used in toys, has been linked in past studies to birth defects, kidney problems, infertility and stunted sex organ development in male babies, according to a report from French news agency AFP.

A study appearing this week in the online journal BMC Genomics found that lactating rats fed the man-made chemical, which mimics the female hormone estrogen, passed it on to their offspring via their breast milk.

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Scientists at the Fox Chase Cancer Center in Philadelphia said that BBP — which accumulates in fat cells — alter breast tissue in infants in a way that could increase the risks of breast cancer later in life. The rats were fed an amount of BBP estimated to be equivalent to the American Environmental Protection Agency's safe dose for humans.

"We are the first to report that neonatal/prepubertal exposure to BBP induced modifications in the gene expression of the mammary tissue," said team leader Dr Jose Russo, in a news release. "This is an indication that the same could happen in humans. Even if an individual is exposed to it in the beginning of life, BBP can cause alterations later in life."