Toxins may pass down generations

Chemicals can change the way genes work
Toxic chemicals that poisoned your great-grandparents may also damage
your health, research suggests.
A team from Washington State University has produced evidence that some
inherited diseases may be caused by poisons polluting the womb.

Research on rats suggests man-made environmental toxins may alter
genetic activity, giving rise to diseases that pass down at least four
generations.

The research is published in the journal Science.

It is a new way to think about disease

Dr Michael Skinner

The scientists exposed pregnant rats to two agricultural chemicals
during the period that the sex of their offspring was being determined.

The compounds were vinclozolin, a fungicide commonly used in vineyards,
and the pesticide methoxychlor.

Both are known as endocrine disruptors - chemicals that interfere with
the normal functioning of reproductive hormones.

Rats exposed to the compounds produced male offspring with low sperm
counts and poor fertility

They were still able to produce young, however. When these rats were
then mated with females that had not been exposed to the toxins, their
male offspring had the same problems.

The effect persisted through at least four generations, impairing the
fertility of more than 90% of male offspring in each generation.

The researchers found the damage was not caused by alterations in the
DNA code, but changes in the way the genes work.

These 'epigenetic' changes are caused by small chemicals that become
attached to the DNA, modifying its activity.

Epigenetic changes have been observed before - but were not previously
known to pass onto later generations.

Cancer clue

Lead researcher Dr Michael Skinner believes they may contribute to
diseases such as breast cancer and prostate cancer.

 We need to find out whether this trans-generational effect is
translated to much lower doses

Professor Alan Boobis

Both diseases are becoming more common, and Dr Skinner says that cannot
be down to genetic mutations alone.

The researchers believe their findings suggest exposure to
environmental toxins may play a key role in the evolutionary process.

Evolution may not be driven entirely by genetic mutations, as commonly
thought.

Dr Skinner said: "It is a new way to think about disease.

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

However, Dr Skinner stressed more work was needed to corroborate the
findings.

The levels of chemicals the rats were exposed to were very high - much
higher than people normally ever encounter.

Professor Alan Boobis, a toxicologist at Imperial College London, told
the BBC News website the findings were interesting, but he said there
was no need for people to be alarmed.

"This effect is likely to be concentration dependent, and these animals
were exposed to very high levels of chemicals," he said.

"We need to find out whether this trans-generational effect is
translated to much lower doses."