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North Morrow and Northwestern Umatilla Perchlorate Area

EHAP was asked by the Agency for Toxic Substances and Disease Registry (ATSDR) to address the public health effects of exposure to water and food contaminated with perchlorate in North Morrow and Northwestern Umatilla counties.

In 2003, perchlorate was detected at low levels by the Oregon Department of Environmental Quality (DEQ) and the federal Environmental Protection Agency (EPA) in drinking and irrigation groundwater wells in this area. Additional groundwater sampling conducted in 2003 and 2004 also found low levels.

Perchlorate exposure is of particular concern for infants, small children, and women of childbearing age. It is particularly concerning for women who are pregnant or nursing, because it can affect iodide and thryoid hormone levels that are essential for proper physical and mental development. Also of concern are people with severe iodine deficiency or hypothyroidism.


EHAP conducted an initial investigation and completed a Health Consultation (HC) in 2006, which concludes that perchlorate contamination at this site poses an indeterminate public health hazard.

Although perchlorate concentrations in the area's drinking water have not been detected at levels of concern, EHAP concluded that there was not enough information about exposure concentrations from sources other than drinking water, such as produce and milk available to area residents. Once data from other sources are available, the exposure of sensitive populations that currently have contaminated drinking water can be assessed.

As a follow-up to the initial investigation, EHAP conducted an Exposure Investigation (pdf). Samples of milk and produce (corn, tomatoes, and watermelon) available to area residents were collected and analyzed. Based on an evaluation of these data, EHAP concluded that exposure to perchlorate is not a health threat for residents of this area.  

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