By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - Toxic chemicals that poisoned your grandparents,
or even great-grandparents, may also affect your health, U.S.
researchers suggested on Thursday.

A study in rats shows the effects of certain toxic chemicals were
passed on for four generations of males.

The finding, published in the journal Science, suggests that toxins may
play a role in inherited diseases now blamed on genetic mutations.

"It's a new way to think about disease," said Michael Skinner, director
of the Center for Reproductive Biology at Washington State University
in Pullman.

"We believe this phenomenon will be widespread and be a major factor in
understanding how disease develops."

For their study, Skinner and colleagues injected pregnant rats with
vinclozolin, a fungicide commonly used in vineyards, and methoxychlor,
a pesticide that replaced DDT.

Both are endocrine disrupters -- synthetic chemicals that interfere
with the normal functioning of reproductive hormones, notably
testosterone and estrogen. Animal studies have shown they can affect
fertility and the development of genitals, for example.

Scientists knew that treating pregnant rats with high doses of
vinclozolin every day produces sterile male pups.

Skinner's team injected vinclozolin into pregnant rats during a
specific time during gestation when the developing embryos take on
sexual characteristics. "It is when either an ovary or testes develop,"
Skinner said in a telephone interview.

The time was comparable to mid-gestation in humans.

Male rat pups born to these mothers had a 20 percent lower than normal
sperm count, their sperm were less motile, meaning they did not swim as
well, and they were less fertile.