Chemical pollution may have harmed the brains of millions of children around the world in what scientists are calling a "silent pandemic".

The world is bathed in a soup of industrial chemicals which are damaging the intellectual potential of the next generation and may increase the incidence of conditions such as Parkinson's disease, they say.

One in every six children has a developmental disability, such as autism, attention deficit disorder or cerebral palsy, the effects of which may be life-long.

The role of low-level pollutants, such as lead and mercury, on the growing brain has been recognised for decades and measures taken to reduce exposure to a minimum. But scientists from the Harvard School of Public Health, in Boston, say at least 202 chemicals are known to have the capacity to damage the brain and their effects at low levels of exposure are unknown. They say limits for exposure to chemicals should be set for pregnant women and young children, recognising the unique sensitivity of the developing brain, which is much more susceptible to the toxic effects of chemicals.

Philippe Grandjean, visiting professor at Harvard and lead author of the review, published in the online Lancet, said: "The human brain is a precious and vulnerable organ. Even limited damage may have serious consequences. It probably is going to be difficult [to set exposure limits] but this is a classical case where there really is a lot at stake. We are talking about the brain development of future generations. There will be an enormous cost of not regulating exposure."

Critics accused the scientists of scaremongering and said their claim of a silent pandemic was a "gross overstatement".

The 202 chemicals listed by the authors have been shown to cause serious accidents when ingested, or have been used in suicide attempts. They include chemicals used in household products, such as aluminium in saucepans and soft-drink cans, and acetone in nail-polish remover. The main exposure to the pollutants is through contamination of the environment during manufacture, when the chemicals seep into ground water, are carried in air or contaminate food.

Commenting on the review, Professor Nigel Brown, dean of medicine at St George's School of Medicine, University of London, said: "This is a campaigning article. In their enthusiasm, the authors verge on scaremongering.

"[Their claim] of a silent pandemic is a gross overstatement. It is possible that there is a problem, we should be aware of this and we should study it but there is currently not a shred of evidence of a pandemic."

What chemical pollution can do

Acrylamide

Used in adhesives, printing ink and agricultural sprays. Can cause drowsiness and hallucinations.

Cyclohexane

Used to make nylon, paint and resin removers, and fungicides. Can cause headaches and convulsions.

Acetone

Used in nail-polish remover and to make plastics, fibres and drugs. Breathing it over long periods can cause light-headedness and confusion.

Methanol

Used as a petrol additive and in spray paints. Can cause an effect similar to drunkenness followed by severe stomach, leg and back pain.

Trichloroethylene

Used in dry cleaning. Breathing it for long periods may cause dizziness, poor co-ordination and difficulty concentrating.

Aniline

Used to make pesticides, dyes and rubber. Breathing in small amounts over several years may cause cancer.

Styrene

Used in making plastics. Breathing small amounts over long periods causes alterations in vision, hearing loss and slower reaction times.

© 2006 Independent News and Media Limited

###