Source: Environmental Health Perspectives (NIEHS)
Released: Thu 02-Dec-2004, 10:40 ET

Organochlorines Reduce Bone Density in Polar Bears

Exposure to organochlorine chemicals is linked to reduced bone mineral density among polar bears from East Greenland, according to a study published today in the December issue of
the peer-reviewed journal Environmental Health Perspectives (EHP). In
the study of 139 polar bear skulls, researchers compared 41 samples
collected between 1892 and 1932 with 98 samples collected between 1961
and 2002. Bone mineral density in the skulls collected before
1932 (considered "pre-pollution" by the researchers) was
significantly higher than that in skulls sampled in the "post-pollution" period
after 1961, when scientists first began seeing organochlorines and
other persistent organic pollutants (POPs) in the fat of polar bears.

The researchers also analyzed a subset of 58 skulls collected between
1999 and 2002 to examine the organochlorine body burden in relation to
bone mineral density. In this group, exposure to PCB compounds and to
chlordane (a now-banned insecticide) both correlated with low bone
mineral density among younger bears. In adult males, concentrations of
dieldrin (another banned insecticide) and total DDT residues also
correlated with low density.

POPs resist breakdown, store easily in fat, and bioaccumulate through
the food chain. Once widely used in agriculture and industry, several
types have been classified as probably or possibly carcinogenic to
humans, and there are now restrictions or bans related to their
application. However, these highly toxic chemicals are very stable
over time, and they remain widely present in the environment, where
they still pose a serious health threat. "Polar bears from East Greenland, Svalbard, and the
Kara Sea carry higher loads of organochlorines than do polar bears
elsewhere in the Arctic due to the different atmospheric transport
routes," the study, authors write. "The strong correlative relationships [between bone
mineral density and exposure] suggest that disruption of the bone
mineral composition in East Greenland polar bears may have been caused
by organochlorine exposure."

Given the results of previous studies on organochlorines, the findings
are not surprising, according to Dr. Jim Burkhart, science editor for
EHP. "Previous research suggests DDT and PCBs reduce bone density in
humans and in Baltic grey seals. Now they appear to have a similar
impact on polar bears," he said.

The lead author of this study was Christian Sonne of the National
Environmental Research Institute in Roskilde, Denmark. Other authors
included Rune Dietz, Erik W. Born, Frank F. Riget, Maja Kirkegaard,
Lars Hyldstrup, Robert J. Letcher, and Derek C.G. Muir. The article is
available free of charge at
http://ehp.niehs.nih.gov/members/2004/7293/7293.html.

EHP is published by the National Institute of Environmental Health
Sciences, part of the U.S. Department of Health and Human Services.
EHP is an Open Access journal. More information is available online at
http://www.ehponline.org/.

=====
"Even the mighty oak was once just a nut who stood its ground."

Asked what he thought about Western Civilization, Gandhi replied that he thought it would be a good idea.

A new civilization is being built, and we now know it must rest on all four directions.

CompostCycleStudyPlay
earth foundations let us lay

______________________________________________________________________