Man-made chemicals present in homes, schools, offices, cars and food are probably contributing to the sharp rise in obesity and diabetes in Western societies, according to a review of scientific literature published yesterday.
Until now lifestyle factors such as lack of exercise and poor diet were believed to be the primary causes of the increased incidence of both conditions, whose proliferation has strained global health budgets.
While these remain undisputed factors, the review of 240 scientific papers by two leading experts, Professor Miquel Porta, of Spain, and Professor Duk-Hee Lee, of South Korea, suggests chemicals in plastics and other surfaces play an important and avoidable role.
Their study assessed the impact of chemicals including the now banned PCBs, the plastic-softeners phthalates, and the plastic-hardener Bisphenol A, or BPA, a common substance in food packaging and plastic bottles.
All 240 studies they reviewed - whether in test-tubes, on animals or on humans - had been peer-reviewed and published in scientific journals.
The paper, the Review of the Science Linking Chemical Exposures to the Human Risk of Obesity and Diabetes, found some of the chemicals appeared to have a causal effect on obesity, some on diabetes and some on both.
Many are endocrine disruptors, which can change human hormones, including the stimulation of appetite and fat storage and regulation of sugar.
Porta, of the Hospital del Mar Research Institute, Barcelona, said: "The epidemics in obesity and diabetes are extremely worrying. The role of hormone disrupting chemicals in this must be addressed. The number of such chemicals that contaminate humans is considerable.
"We must encourage new policies that help minimise human exposure to all relevant hormone disruptors, especially women planning pregnancy, as it appears to be the fetus developing in utero that is at greatest risk".
Some of the chemicals studied - organo-chlorine pesticides, PCBs used to lubricate electrical equipment and to make plastics fireproof; and many brominated flame retardants - have now been banned but others such as BPA and phthalates are still widely used in everyday products.
BPA is commonly found in the plastic lining inside tinned foods, on thermal till receipts and in consumer electronics such as mobile phones and televisions, while phthalates are present in vinyl flooring, shower curtains and children's toys.
CHEM Trust (Chemicals Health & Environment Monitoring Trust), the British pressure group which commissioned the research, urged the UK Government and the EU to press industry to find safer alternatives. Six out of 10 adults in England are overweight or obese and diabetes has more than doubled since 1996 to 2.9 million people in the UK.