MISHIMA, Japan, Dec. 1 -- Two Japanese researchers say it is "plausible and provocative" to associate the obesity epidemic with chemical triggers present in the modern environment.

Taisen Iguchi and Yoshinao Katsu of the Graduate University for Advanced Studies in Japan say the rise in obesity in humans over the past 40 years parallels the increased use of industrial chemicals during the same period.

The researchers note the chemical Tributyltin is used as a wood and textile preservative in paints for boats, as a pesticide on high-value food crops and many other applications.

Tributyltin affects sensitive receptors in the cells of animals, from water fleas to humans, at very low concentrations -- one-thousandth that of other pollutants known to interfere with sexual development of wildlife species.

The study, published in the journal BioScience, finds the harmful effects of the chemical on the liver and the nervous and immune systems in mammals are well known, but its powerful effects on the cellular components known as retinoid X receptors in a range of species are a recent discovery.

When activated, retinoid X receptors can migrate into the nuclei of cells and switch on genes that cause the growth of fat storage cells and regulate whole body metabolism, the researchers say. (UPI)