Children who live in homes with vinyl flooring have double the chance of being autistic, research has discovered.
The finding - which amazed even the scientists conducting the study - provides one of the first clues as to a possible cause of the condition.
The study, by scientists in Sweden,
Denmark and the United States, stumbled across the connection almost by accident.
It is being taken seriously because autism has long been thought to result from environmental factors.
The number of babies born with the condition in California has risen more than seven times in 20 years, convincing scientists that pollution must be to blame.
The research, which traced nearly 5000 Swedish children from infancy to at least six years old, set out to investigate links between air pollution and asthma and other allergies.
The scientists - from Karlstad University in Sweden, the universities of Rochester and Texas in America, and the Technical University of Denmark - identified the type of flooring in each home at the start of the study, but only started to look at autism later.
Their paper, published in the journal Neurotoxicity, describes the findings as "puzzling, even baffling, and not readily explicable at this time".
But it adds: "Because they are among few clues that have emerged about possible environmental contributions to autistic disorders, we believe that they should be weighed carefully and warrant further study".
A possible explanation, they suggest, is that vinyl, or PVC, flooring produces dust full of phthalates, which are then breathed in.
Experts who have reviewed the study believe that, if this is the cause, the children may have been most vulnerable when their brains were developing in the womb.
If this is so, the threat may come from more than vinyl flooring. Californian research has also found high levels of the chemicals in home carpets.
- INDEPENDENT
