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.
Plastic furniture
Phthalates have the ability to disrupt hormones, and have been banned in toys in the EU for some years.
However, they are still widely used in many different household items, including plastic furniture and packaging.
There are many different types and some mimic the female hormone oestrogen.
BBC NEWS | Health | Plastic chemicals 'feminise boys'