Radiation from Japanese reactors found in SJC rainwater – not enough to be dangerous

San Juan County Health Officer, Frank James, M.D., reports that measurable amounts of radiation from Japan have been found in rainwater in San Juan County, but not enough to raise health concerns.

In statewide tests, the measurable amount of radioactive iodine in the air peaked in tests conducted in Olympia on March 20 and in rainwater about a week later.

Results of tests on samples taken from a rainwater catchment system in San Juan County on April 1 found a level of iodine 131 at only 10 percent of the level, which would normally trigger re-testing, and a fraction of a percentage point of the level at which it would be a public health concern for “a single point in time exposure.”

James notes that the level is slightly above the drinking water standard; however he said, “That standard considers that the risk of drinking 2 liters of contaminated water daily for 70 years would increase the risk of cancer by one person in one million.”

James said that because the half-life of radioactive iodine is only eight days, the amount of radiation in the water should drop below detectable levels in approximately 80 days. A second test may be performed here next week to confirm that radiation levels here are falling, as expected.

The vast majority of San Juan County residents get their drinking water from wells, community or municipal water systems, which have not been affected by the release of radiation in Japan.

The radioactive iodine contamination is related to a single "venting" of the pressurized containment vessels that occurred on March 12, 2011 at a Japanese electrical plant. No other releases are believed to have occurred that would lead to additional contamination reaching the US.

For further information see the Washington Department of  Health “Frequently Asked Questions” at

Paul Kamin, General Manager of Eastsound Waters Users Association, released the following statement.

"I want to emphasis that this finding is specific to ONE domestic rainwater catchment system. It is the Health Department’s radiation specialist’s conclusion that this finding should have no impact on either groundwater or surface water systems. EWUA uses both groundwater and surface water supplies, but NOT rain catchment. It takes many months for rainwater to migrate through the soils into the groundwater, and often years to migrate through the aquifer to a well’s point of withdrawal.

"Similarly, rainwater recharging Purdue Lake is significantly diluted prior to entering the water treatment process. EWUA is using about 10 percent of Purdue Lake’s holding capacity each month, and at this time of year much more water is actually overflowing the lake than we are treating for use."

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