Important information about this page.

The Department of Health posted daily results of environmental monitoring in March and April 2011 in response to the nuclear events following the earthquake and tsunami in Japan. All detections of radioactive material were far below any public health risk. The data posted online included monitoring conducted by the state health department in addition to the federal monitoring that is always taking place. In May, when amounts of radioactive material were lower than detection levels with standard monitoring, the additional state sampling and daily data posting were stopped. Daily federal monitoring has concluded, but the historical data for that period is available on the Environmental Protection Agency’s RadNet website.

Air monitoring stations

Daily measurements

Radiation from the damaged nuclear reactors in Japan is not a health risk in Washington. The Department of Health takes hourly measurements from monitors in four locations throughout the state — Richland, Seattle, Spokane, and Tumwater.

This page will be updated weekdays at about three o’clock with the most current measurements. (Weekend information will be posted to the data archive page on Mondays by 3 p.m. unless otherwise noted.)

The chart shows radiation measures known as “gross beta,” a term that refers to all radioactive materials that emit beta radiation. Gross beta measurements are used because they give us the fastest indication of any change in radiation levels. They’re measured in “counts per minute.”

All monitoring stations have continually shown normal background levels of radiation since the March 11 earthquake and tsunami in Japan. The annual average measurement at our Tumwater air monitor for 2010 was 25 counts per minute. The levels would have to be at least hundreds of thousands of times higher than these readings before state health officials would recommend protective actions.

We don’t expect to see significant increases in gross beta as a result of the disaster in Japan. If that did happen, we would measure specific isotopes in order to determine if steps are needed to protect public health.

*Historical data will be published soon.

Data archive since, March 3, 2011

For more information,  read our frequently asked questions or send e-mail to prepare@doh.wa.gov