Chemicals in plastics alter the brains of baby boys, making them more feminine", say US researchers. Males exposed to high doses in the womb went on to be less likely to play with boys' toys like cars or to join in rough and tumble games, they found. The University of Rochester team's latest work adds to concerns about the safety of phthalates, found in vinyl flooring and PVC shower curtains. The findings are reported in the International Journal of Andrology. Phthalates have the ability to disrupt hormones, and have been banned in toys in the EU for some years. There are many different types and some mimic the female hormone oestrogen. The same researchers have already shown that this can mean boys are born with genital abnormalities. Now they say certain phthalates also impact on the developing brain, by knocking out the action of the male hormone testosterone. Dr Shanna Swan and her team ... found that two phthalates DEHP and DBP can affect play behaviour. Boys exposed to high levels of these in the womb were less likely than other boys to play with cars, trains and guns or engage in "rougher" games like playfighting. Elizabeth Salter-Green, director of the chemicals campaign group CHEM Trust, said the results were worrying. "We now know that phthalates, to which we are all constantly exposed, are extremely worrying from a health perspective, leading to disruption of male reproduction health and, it appears, male behaviour too."