US researchers at the University of Rochester have found that chemicals in certain household plastics knock out testosterone in boys as they grow up.

Phthalates are contained in items such as vinyl flooring and PVC shower curtains. Previous research into chemicals and the effect they may have on hormones in the human body has led to the EU banning certain plastics from use in children’s toys. However use in household items and in plastic wrapping and packaging is still permitted.

BBC News reports that the researchers have already found that contact with such materials can lead to genital abnormalities in newborn boys. The team has now discovered that phthalates can act on the developing brain by ‘knocking out’ the male hormone testosterone.

Lead researcher Dr Shanna Swan and colleagues tested urine samples from mothers-to-be who were midway through their pregnancies. The women gave birth to 74 boys and 71 girls and were followed up when the children were aged between four and seven years.

The researchers studied the toys the children chose to play with and found that boys exposed to high levels of two phthalates, DEHP and DBP, were less likely to play with traditional ‘male’ toys, such as cars, trains and toy guns. They were also less likely to engage in traditionally masculine games such as playfighting.

Director of the chemicals campaign group CHEM Trust, Elizabeth Salter-Green, called the findings ‘worrying’ – although she acknowledged that the boys may have been followed up at too early an age. However, she said there were concerns that exposure to the chemicals might lead to male children developing other ‘feminised’ traits as they grew up.

‘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. This feminising capacity of phthalates makes them true ‘gender benders’', said Ms Salter-Green.

Tim Edgar of the European Council for Plasticisers and Intermediates said there were ‘many different phthalates’ in use and the study concerned ‘two of the less commonly used types that were on the EU candidate list as potentially hazardous and needing authorisation for use’.

DBP, for example, has been banned in cosmetics such as nail varnish in the EU since 2005.

Mr Edgar added:

‘We need to get some scientific experts to look at this study in more detail before we can make a proper judgement.’

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