Dairy cow. Click the image
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Perchlorate in Milk Examined
By Kim Kaplan
October 31, 2005
A dairy cow's rumen can act as a biological filter, breaking down most
perchlorate in feed, according to an Agricultural Research Service (ARS) study published this week in the Proceedings of the National Academy of
The research was done by animal physiologist
V. Capuco and a team of scientists from the ARS
Functional Genomics Laboratory, and by chemist
Rice and a team from the ARS
Quality Laboratory. Both labs are part of the ARS
A. Wallace Beltsville (Md.) Agricultural Research Center. The scientists
found that up to 83 percent of perchlorate fed to cows is metabolized by the
Public concern about perchlorate, an industrially used oxidant as well
as a naturally occurring compound, has increased in recent years, especially
after very low levels of perchlorate were found in milk.
Capuco and his colleagues found that while perchlorate levels in the
milk of cows fed various levels of perchlorate did increase slightly as
consumption increased, the levels did not rise in direct proportion to the
increased consumption. Similar trends were noted in urine, feces and blood.
Previous work had shown that perchlorate did not accumulate in the
cows' tissues, and the researchers found no deleterious health effects in the
cows, even at the highest level of perchlorate fed--40 mg/day--in the study. No
changes were found in the cows' blood chemistry, blood differential counts,
incidence of mastitis, body temperature or thyroid hormone concentrations, or
in indirect measures of health such as feed intake and milk production.
This study helps assess environmental influences on milk perchlorate
levels and provides a context for assessing the potential for impact on human
ARS is the U.S. Department of
Agriculture's chief in-house scientific research agency.