Reiko Nakamura, a 37-year-old mother of three children, said she has been checking radiation levels outside her house in Meguro Ward, Tokyo, every day since she bought a dosimeter in May.
Based on her readings, she decides whether to open the windows or leave them shut tight.
Trying to protect her children from radioactive materials spewing from the Fukushima No. 1 nuclear power plant, Nakamura has been buying produce grown in west Japan since mid-March.