Data regarding the 131I content in these 28 women and relevant information released by the citizens group on April 21 and May 18 were obtained from their website (‘Radioactivity in breast milk’, cited September 15, 2011; available from URL: http://bonyuutyousa.net/). Air pollution with radioactive materials occurred over a geographically wide area within 300 to 400 km of the FNP in the morning of March 15, 2011 (Fig. 2). Although the air radiation

dose rate was <0.07 µGy/h before the FNP accident in the areas shown in Figure 1, it increased sharply to 19 µGy/h in Fukushima city on March 15, then decreased to 1.6 µGy/h by the end of May. In Tokyo, located 230 km south of the FNP, the highest radiation dose rate of 0.81 µGy/h on March 15 decreased to <0.07 µGy/h by mid-April. The amount Cyclopamine chemical structure of 131I radioactivity in fallout per day reached a peak level of 93 000 MBq/km2 in Hitachinaka

city, located 130 km south of the FNP, on March 20, while it reached a peak level of 38 000 MBq/km2 in Tokyo on March 22 (Fig. 3). Consequently, vegetables such as spinach, cows milk and chicken eggs were also contaminated with 131I (Fig. 4). The highest content of 131I was 24 000 Bq/kg, found in spinach on March 18 in Kitaibaraki city, located 75 km south of the FNP. The 131I content in spinach decreased over time; for example, a level of 3500 Bq/kg was recorded in Utsunomiya city on March 19, decreasing to 480 Bq/kg on April 13, 120 Bq/kg on April 20, 12 Bq/kg on April 26, and became undetectable on May 3 (Fig. 4). Among the three foods, see more the 131I content was lowest in chicken eggs. It rained on March 20 and 21 in these areas, and the rain accelerated the pollution of water with 131I (Fig. 5). In Tokyo, 131I radioactivity in tap water from the Kanamachi water

purification plant reached a peak level of 210 Bq/kg on March 22. The content of 131I in the tap water decreased and became undetectable in many cities by mid-April (Fig. 5). Seven of 23 women (30.4%) who were tested in April secreted a detectable level of 131I in their breast milk (Table 1). The concentrations ranged from 2.2 to 8.0 Bq/kg and appeared to be higher than those in tap water Bcl-w available for these seven women at the same time points. As expected from the data on 131I radioactivity in the fallout, vegetables and water (Figs 3 to 5), the radioactivity of 131I in the breast milk became undetectable by May 15 in these seven women (Table 1). None of the remaining 96 women tested in May exhibited a detectable amount of 131I in their breast milk samples with detection limits of 1.6 ± 0.3 Bq/kg (data not shown). The present study demonstrated that environmental pollution with 131I causes the contamination of breast milk with 131I.