Scientists in Sweden are becoming increasingly concerned about chemical pollutants that pose a serious risk to unborn babies. The chemicals, known as PBDEs, are a by-product of high tech industry. They appear to be passing into the environment in rapidly increasing amounts.

Fish in the Baltic Sea are becoming contaminated, and when they are eaten by humans the toxins are being passed on.

It is feared that unborn babies whose mothers eat the contaminated fish are most at risk.

The chemicals, which can be passed on in breast milk, are thought to affect brain development and hormonal balance.

Scientists at Sweden's Karolinska Institute have been monitoring the situation.

Dr Koidu Noren said the amount of PBDEs detected has been doubling every five years. She said: "The children get these compounds in a very sensitive period of development. It has been shown to be a toxic compound, so it should not be there."

Research has shown that very low doses of PBDE given to baby mice, led to irreparable brain damage, causing reduced learning capacity and hyperactive behavior.

Dr Michael Warhurst, a safer chemicals campaigner for the charity Friends of the Earth, said that BBC News Online that women should not be put off breastfeeding, as it was the most effective way to provide babies with the nutrients they need.

He said little was yet known about the exact effect of PBDEs on human health. But he said: "These chemicals are clearly accumulating both in the environment and in our bodies. We believe any chemical that does this should be phased out as a precautionary measure."

Dr Warhurst said safer alternatives were available.

The Swedish government has issued a health warning alerting people to the dangers of eating fish.

PBDEs, or polybrominated diphenyl ethers, are a by-product of a flame retardant chemical used in electronic appliances. They collect in the fatty tissue of the fish.