50% Of Human Sewage Produced

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50% Of Human Sewage Produced

Yearly Is Spread On Cropland

By Mulvihill

7-12-1

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. 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 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 100.

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 land.

The total concentration of BDEs in the biosolids 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 BDEs, ``rivaling the highest fillet burdens

reported in the world so far,'' the report indicates.

``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 mimic 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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