Estimation of radiation dose for recreational activities along river banks

• Estimates were made supposing that a child often plays at rivers and lakes over summer vacastion (Lower Figure)
• Even when the concentration of radioactive cesium at the river botto and air dose rates were assumed to be high (conservative assumption), radiation doses by water-based recreational activities was 0.031 mSv for rivers 0.030 mSv for lakes.

Table 1　Estimated exposure doses from water-based recreation (Ministry of the Environment, 2015, partially modified)

	River		Lake
Assumed condition※	Averaged condition	Conservative condition	Averaged condition	Conservative condition
Concentration of radioactive cesium at the bottom (Bq/kg)	200	2,000	500	5,000
Air dose rate in peripheral environment (µSv/h)	0.3	0.6	0.2	0.5
Estimated radiation dose (mSv)	0.013	0.031	0.0086	0.030

※ Concerning the concentration of radioactive cesium in bottom sediment and air dose rates in peripheral environment, both averaged condition and conservative condition are assumed on the basis of the mean values and 90% percentile values in Fukushima Prefecture (except for evacuation order district).

Reference: Documents 5 used in the 13th Meeting on Environmental Recovery, Ministry of Environment “Outline of Radiation Exposure Estimation by Recreation Activities at Waterside”）

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Reference

1. 環境省, “水辺のレクリエーション活動における被ばく線量の試算について（概要）”, 環境回復検討会（第13回）, 2015-01, 2p.