PCB's (polychlorinated biphenyls)
Organochlorine Pesticides, PCBs Found To
Accumulate in Snow on Mountains.
A team of Canadian researchers has discovered that mountains in the temperate zone are susceptible to accumulation of snow that is contaminated by organochlorine pesticides and polychlorinated biphenyls (PCBs). Scientists have been aware that snow fall in the poles can be contaminated with these substances, but this is the first study to show that contamination increases with altitude in the temperate zone.
Organochlorines are produced at low latitudes and become airborne in warm areas. The chemicals are then carried to the poles, where they condense and fall with snow in cold areas, a process known as cold condensation. This study shows that a similar process occurs at high altitudes in the temperate zone.
The findings "demonstrate that temperate-zone mountain regions, which tend to receive high levels of precipitation while being close to pollutant sources, are particularly susceptible to the accumulation of semivolatile organochlorine compounds," said the report.
Analysis of the snow took place in the Rocky Mountains in southwestern Canada. The study shows that concentrations of the chemicals increases gradually with altitude at first, but then rise steeply at altitudes higher than 6,600 feet. The chemicals that were found were chlordane, dieldrin, endosulfan, heptachlor epoxide, hexachlorocyclohexane, and both bichlorinated biphenyls and trichlorinated biphenyls.
The results of the study are published in the Oct. 8 issue of the journal _Nature_.
MODEST EXPOSURE TO PCBs LOWER IQ, STUDY
Pennsylvania Dept. of Environmental protection's UPDATE (source: The Washington Post 9/12/96)
A new study on PCBs published in the Sept. 12 issue of the New England Journal of Medicine found children exposed to moderate levels of the pollutant scored lower on intelligence tests.
Over 200 Michigan children, all age 11, were given a battery of intelligence tests. Children with higher than average prenatal exposures to PCBs were three times more likely to have IQ scores in the lowest portion of the IQ range. they were also twice as likely to be two years behind in reading comprehension.
Previous studies on prenatal PCBs do not disappear as the children grow older.
Some were skeptical of the study's findings. "I don't think this paper proves anything," said Renate Kimbrough, a senior medical associate at the Institute for Evaluating Health Risks, who is reviewing the quality of research on pollutants under a grant from the Chemical Manufacturers Association.