NEW YORK (Reuters Health) - Biosolids, the treated sewage sludge that is spread on cropland as a fertilizer, contain 'high concentrations of an environmentally persistent class of organic pollutants" called brominated diphenyl ethers (BDEs), study results indicate.
And the researchers report that they found BDEs in 87% of fish sampled from Virginia waters, with one fish close to setting a world record for contaminant levels,
"THIs finding 'indicates that significant environmental release of these pollutants is occurring in the United States and that humans may be exposed to them through their diet," according to Dr. Robert C. Hale and colleagues from the Virginia Institute of Marine Science in Gloucester Point.
BDEs are added to polyurethane, the synthetic foam used to make seat cushions and many other materials, as a fire retardant. The European Commission (news - @web sites) plans to ban BDEs due to mounting concerns about their potential health risks and a recent study that found
concentrations of BDEs on the rise in human breast milk-, Hale explained in an interview with Reuters Health.
"What's new here is the fact that BDEs are a persistent pollutant--meaning that it does not
readily break down 'in the environment--and they have not been well studied," Hale told Reuters Health.
Notably, Hale pointed out that concentrations in US biosolids exceed those typically found in European biosolids by a factor of 10 to I 00.
In the study, published in the July 12th issue of the journal Nature, the researchers analyzed 11 samples of treated biosolids from California, New York, Virginia and Maryland.
The total concentration of BDEs in the blosolids was 1,100 to 2,290 micrograms per kilogram of dry weight, "suggesting that input was high and consistent, regardless of the region of origin and irrespective of pre-application treatment," the authors write.
The researchers found BDEs in 87% of 334 fish from Virginia waters that they tested In fact, a carp from one stream in Virginia contained 47,900 micrograms per kilogram of total BIA's, - rivaling the highest fillet burdens reported in the world so far,' the report indicate.
"The jury is still out about how toxic BDEs are, but the fact remains--they do bio-accumulate and they are persistent,' Hale said.
Hale also noted that BDEs are "quite similar in structure to the drug thyroxine" and said that the chemicals may mimc the drug's activity in humans.
Thyroxine is used In the treatment of thyroid disorders and helps regulate growth and cell metabolism.
Over half the sewage sludge produced annually in the United States is applied to land, amounting to roughly 4 million tons in 1998, the authors note.
SOURCE: Nature 2001,412:140-141.
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