title: An assessment of radiation doses at an educational institution 57.8 km away from the Fukushima Daiichi nuclear power plant 1 month after the nuclear accident.
abstract: OBJECTIVE
  On 11 March 2011, the Great East Japan Earthquake occurred. Due to this earthquake and subsequent tsunami, malfunctions occurred at the Fukushima Daiichi nuclear power plant. Radioactive material even reached the investigated educational institution despite being 57.8 km away from the power station. With the goal of ensuring the safety of our students, we decided to carry out a risk assessment of the premises of this educational institution by measuring radiation doses at certain locations, making it possible to calculate estimated radiation accumulation.
  
  
  METHODS
  Systematic sampling was carried out at measurement points spaced at regular intervals for a total of 24 indoor and outdoor areas, with 137 measurements at heights of 1 cm and 100 cm above the ground surface. Radiation survey meters were used to measure environmental radiation doses.
  
  
  RESULTS
  Radiation dose rates and count rates were higher outdoors than indoors, and higher 1 cm above the ground surface than at 100 cm. Radiation doses 1 cm above the ground surface were higher on grass and moss than on asphalt and soil. The estimated radiation exposure for a student spending an average of 11 h on site at this educational institution was 9.80 μSv.
  
  
  CONCLUSIONS
  Environmental radiation doses at our educational institution 57.8 km away from the Fukushima Daiichi nuclear power plant 1 month after the accident were lower than the national regulation dose for schools (3.8 μSv/h) at most points. Differences in radiation doses depending on outdoor surface properties are important to note for risk reduction.
authors.affiliation: Department of Hygiene and Preventive Medicine, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima 960-1295, Japan. tsuji@fmu.ac.jp
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Tsuji
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Kanda
authors.forename: Takeyasu
authors.initials: T
authors.lastname: Kakamu
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kobayashi
authors.forename: Masao
authors.initials: M
authors.lastname: Miyake
authors.forename: Takehito
authors.initials: T
authors.lastname: Hayakawa
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Mori
authors.forename: Toshiyasu
authors.initials: T
authors.lastname: Okochi
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hazama
authors.forename: Tetsuhito
authors.initials: T
authors.lastname: Fukushima
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis; D000398:Air Pollution, Radioactive / Q000032:analysis*; D002947:Cities; D004190:Disasters; D055866:Earthquakes; D004781:Environmental Exposure / Q000032:analysis*; D007564:Japan; D055848:Nuclear Power Plants; D011847:Radioactive Fallout / Q000032:analysis*; D018788:Radioactive Hazard Release; D013997:Time Factors
chemical_list: D011847:Radioactive Fallout