Perchlorate in Eastern Oregon | Region 10 | US EPA

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Perchlorate in Eastern Oregon

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We are working with a number of state, local and federal stakeholders to learn more about the presence of perchlorate in the local environment, to assess the potential for health concerns and find potential ways to reduce exposure to perchlorate. Perchlorate can inhibit the uptake of iodide by the thyroid and prolonged exposure to perchlorate may lead to hypothyroidism which impact growth and development in the fetus, infant and child as well as metabolism in all people.

Perchlorate was found in over half of the wells sampled in the Lower Umatilla Basin (LUB) in 2003, 2004 and 2005. EPA has also taken a preliminary look at locally available milk and produce to see if there is a concern about total dietary exposure to perchlorate.

Perchlorate is a manufactured salt that is found in rocket fuels, explosives, flares, fireworks, some bleach products, and some herbicides. It also occurs naturally in arid environments and has been found in natural fertilizers imported from Chile.

What has been done so far?

In 2008, EPA collected pasteurized milk samples from grocery stores in northern Morrow and northwestern Umatilla Counties to learn more about dietary exposure from perchlorate. Results from the data collection and analysis are now available. The levels of perchlorate found in the milk Region 10 purchased in the LUB are similar to those found in FDA’s national studies. The mean perchlorate concentration in milk collected by EPA Region 10 in the LUB is 4.8 ug/l, while the mean perchlorate concentrations in milk collected during FDA’s 2004-2005 Exploratory Survey and FDA’s 2005-2006 Total Diet Study were 5.8 ug/l and 7.0 ug/l, respectively.

Summary of Perchlorate mean levels detected in milk available for retail purchase and consumption in the Lower Umatilla Basin
Milk Grade and TypeWhole2%1%Fat Free
Grade A pasteurized Regular (non organic) (μg/L)4.9
n = 8
Range (3.2 – 8.5)
n = 5
Range (4.3 -6.8)
n = 4
Range (2.7 - 5.6)
n = 4
Range (3.7 - 5.6)
Grade A pasteurized
Organic μg/L
n = 3
Range (2.0 - 5.8)
n = 2
Range (3.2 -4.8)
n = 2
Range (5.9 -7.0)
n = 4
Range (2.8 – 7.4)
Overall mean = 4.8 μg/L
n = number of samples collected
Range = lowest and highest levels detected
μg/L = micrograms per liter

In 2006, watermelons were sampled at several locations in northern Morrow and northwestern Umatilla Counties.

What is the next step?

EPA Region 10 is continuing work to understand risks that may be presented from dietary exposure to perchlorate in combination with exposure from drinking water sources. A Perchlorate Exposure Analysis Report for the LUB has been developed, but is currently undergoing agency review. It will be made available to the public once the review is completed.

Learn about perchlorate and its health effects Documents and Fact Sheets Additonal Information Contacts
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