Environmental impact of nuclear power materials decay, they release particles that can damage the body and lead to cancer, particularly cesium-137 and iodine-131. In the Chernobyl disaster, releases of cesium-137 contaminated land. Some communities, including the entire city of Pripyat, were abandoned permanently. One news source reported that thousands of people who drank milk contaminated with radioactive iodine developed thyroid cancer. The exclusion zone (approx. 30 km radius around Chernobyl) may have significantly elevated levels of radiation, which is now predominantly due to the decay of cesium-137, for around 10 half-lives of that isotope, which is approximately for 300 years. Due to the bioaccumulation of
Caesium-137 forest site 50 km from the stricken plant, Cs-137 concentrations were high in leaf litter, fungi and detritivores, but low in herbivores. By the end of 2014, "Fukushima-derived radiocesium had spread into the whole western North Pacific Ocean", transported by the North Pacific current from Japan to the Gulf of Alaska. It has been measured in the surface layer down to 200 meters and south of the current area down to 400 meters. Caesium-137 is reported to be the major health concern in Fukushima. The government is under pressure to clean up radioactivity from Fukushima from as much land as