Researchers testing urine samples of expectant mothers in the 28th week of pregnancy for evidence of phthalates or chemicals mimicking oestrogen, the female sex hormone, discovered foetuses with greater exposure to high doses of such chemicals, less willing to join the 'rough and tumble' of boyish games, including playing with 'male' toys, such as, cars.

According to Shanna H. Swan, lead author of the new report, boys who are born to mothers with above-normal levels of the controversial chemicals are less likely to exhibit masculine behavior. Phthalates by blocking the activity of male hormones, such as, androgens, could be altering masculine brain development,.

Widely used for softening plastics like polyvinyl chloride and for making them flexible, phthalates are used in food packaging, vinyl and plastic tubing, household products and many personal care products, such as, soaps and lotions.

While, the US Food and Drug Administration (FDA) considers them safe, a 2008 federal law has banned six different types of phthalates in toys like teethers, bath items, soft books, dolls and plastic figures.

Further, previous studies have also shown subtle changes to the size and anatomy of the genitals of some small boys and toddlers exposed to phthalates in the womb. Researchers are now planning to follow these boys into adulthood, in order to determine whether there are any changes in their sperm count, or whether they have reproductive problems.

For the study, the mothers who had given birth to 74-boys and 71-girls were once again contacted, and asked questions about the personalities of their children, now aged between four and seven, including what toys they played with and the type of activities they enjoyed.

The University of Rochester, New York found DEHP and DBP, two types of phthalate to be strongly linked with effeminate play in the boys, without impacting the girls.

According to the research published in the International Journal of Andrology, those boys who have been at the receiving end of higher doses of the chemical, were less likely to indulge in masculine play with cars, trains and guns, preferring 'gender neutral'activities like sports.

Like other researches, this study also adds to the mounting evidence that thousands of household products containing hormone-disrupting chemicals are interfering and having adverse effects on the development of children.

Despite, the plastics industry calling the phthalates safe, many of them have already been banned by the EU from cosmetics, teething rings and children's toys.