February 24, 2005 (ENS): In a new study of
breast milk and milk purchased in stores across the
United States, scientists at Texas Tech University found
perchlorate in every sample but one. The results suggest
that the chemical may be more widespread than previously
The chemical can interfere with iodide uptake in the
thyroid gland, disrupting adult metabolism and childhood
Perchlorate is a waterborne contaminant left over from
propellants and rocket fuels. There are about 12,000
Department of Defense sites in the United States that
have been used for training with live explosives.
Led by Professor Purnendu Dasgupta, Ph.D. of the university's
department of chemistry and biochemistry, the researchers
analyzed 47 dairy milk samples purchased randomly from
grocery stores in 11 states, and 36 breast milk samples
from women recruited at random in 18 states.
Every sample of breast milk contained perchlorate,
and only one sample of dairy milk contained no detectable
levels, researchers found.
The average perchlorate concentration in breast milk
was 10.5 micrograms per liter; the dairy milk average
was 2.0 micrograms per liter.
No definitive national standard exists for permissible
levels of the chemical in milk, although the U.S. Environmental
Protection Agency has suggested a limit of 1.0 micrograms
per liter in drinking water.
The researchers also found that high levels of perchlorate
correlated with low levels of iodide in breast milk,
which can inhibit thyroid function in nursing women,
an essential component for proper neural development
of the fetus.
Although the data are limited, the levels of iodide
in this study are sufficiently low to be of concern,
according to the researchers. They suggest that the
recommended daily intake of iodine for pregnant and
nursing women may need to be revised upwards.
In March 2003, the Texas Tech University Institute
of Environmental and Human Health received a $2 million
research award from the Department of Defense Strategic
Environmental Research and Development Program to research
the effects the residues from explosives have on the
environment and how to clean up any contamination.
The program's principal investigator Ronald Kendall,
Ph.D said, "This work will be implemented to assist
the Department of Defense in developing risk assessments
on explosives and breakdown products of these compounds,
and to assist in the establishment of safe limits and
in remediation," he said.
"The consequences of having explosives and their
breakdown products in the environment are not well understood,"
The report was published February 22 on the website
of "Environmental Science & Technology,"
a peer-reviewed journal of the American Chemical Society,
the world's largest scientific society.