Fukushima 2011 Iodine-131 sampling

The following is archived information that was originally published on this website in 2011.

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 sample measurements
(testing for Iodine-131)
Date Iodine 131
(in pCi/m³*)
5/9/2011 0.0000
5/2/2011 0.0000
4/24/2011 0.0110
4/23/2011 0.0000
4/22/2011 0.0150
4/21/2011 0.0000
4/20/2011 0.0240
4/19/2011 0.0000
4/18/2011 0.0110
4/17/2011 0.0220**
4/16/2011 0.0150
4/15/2011 0.0340
4/14/2011 0.0000
4/13/2011 0.0170
4/12/2011 0.0150
4/11/2011 0.0221
4/10/2011 0.0210
4/9/2011 0.0265
4/8/2011 0.0205
4/7/2011 0.0468
4/06/2011 0.0590
4/05/2011 0.0400
4/04/2011 0.1160
4/03/2011 0.1390
4/02/2011 0.0723
4/01/2011 0.0500
3/31/2011 0.0540
3/30/2011 0.1453
3/29/2011 0.2091
3/28/2011 0.2817
3/27/2011 0.3460
3/26/2011 0.4900
3/25/2011 0.5300
3/24/2011 0.5890
3/23/2011 0.2780
3/22/2011 0.4677
3/21/2011 1.0090
3/20/2011 1.8490
3/19/2011 0.3140

Measuring iodine in air samples

The Washington State Department of Health is monitoring air in the Seattle area for radioactive iodine (I-131) associated with the nuclear power plant emergency in Japan. Samples are collected and analyzed regularly. As expected, analysis showed low, but measureable amounts of radioactive iodine in the air.

The level of iodine is far below any public health concern. Iodine levels in the samples have dropped sharply since March 20. They might fluctuate slightly with changes in the air movement coming in from the Pacific, but iodine levels are expected to remain very low and are likely to drop below our detection level very soon. The state health department will continue to analyze air samples until it is no longer possible to detect iodine 131. The daily air monitoring is in addition to routine air monitoring around the state for normal background radiation found in the environment.

* Measures are in picocuries per cubic meter (pCi/m³).

**Number revised from previous sample posted.

Air samples collected in the Seattle area.