By Taiwan News

A recent study by the Environmental Protection Administration has found that fish in Taiwan's rivers generally contain high levels of flame-retardant toxic chemicals in their tissues.

The chemicals, polybrominated diphenyl ethers, or PBDEs, are widely used as an inexpensive flame retardant in consumer goods such as furniture, building materials, plastic products, and electronic devices.

Medical researchers have found that an excessive accumulation of PBDEs over time could cause swelling of the thyroid gland and possibly lead to thyroid cancer.

In the EPA study, conducted this March and August, various types of freshwater fish were captured from nine rivers midstream and three river mouths, and 60 samples were analyzed.

The tested waterways were Yilan's Lanyang River, Miaoli's Houlong River, Taichung's Dajia River, Changhua's Wu River, Jiayi's Bajang River and Kaohsiung's Fengshan River. The river mouths were at Hsiangshan, Lukang and Erren rivers.

The fish caught from Erren River, a natural border separating Tainan and Kaohsiung counties, had the highest level of PBDEs.

The average concentration of PBDEs in these samples was higher those in northern Europe, but lower than those in the Great Lakes in the United States.

The EPA assured the public that market fish are usually farm-raised or caught in the ocean and are relatively safe to eat, but officials are urging freshwater fishermen not to eat any fish they catch.

Certain forms of PBDE's have also been found in soil sediments, on computer and desk surfaces, on the insides of residential windows, and in meat and dairy products.

While there are currently no standards for PBDE levels in food, the European Union banned several types of PBDE's last year.

The EPA also plans to restrict the use of two forms of PBDEs soon. In 1999, it restricted the use of a deca-PBDE but did not ban it.

PBDEs came into use in the 1970s, as manufacturers, responding to strong consumer-protection laws, placed brominated flame-retardants in household products, particularly plastic ones.

Fire department officials say that these have saved hundred of lives from fires as well as prevented the release of incineration byproducts like dioxin.

Products are coated in PBDEs to become flame-retardant, but the chemical is not molecularly bound to anything. Therefore, when the product is disposed of as waste, the PBDEs disengage and attach themselves to dust particles, thus entering the food chain.

As a class of so-called organic compounds, PBDEs have been found to build up inside organisms due to their fat solubility. Other PBDEs properties include semi-volatilization and difficulty in degradation.

Humans, at the top of the food chain, are more likely to ingest more concentrated chemicals, and fat-soluble toxins, which is why health professionals have become deeply concerned about the effects of PBDEs in humans -- particularly in breast milk.

Toxins have tainted breast milk since 1951 with the highest concentrated toxins being being DDT and PCB. This issue has troubled doctors and mothers alike because PBDEs may remain in human tissue for several months to several years and endanger the immune systems of future generations.