Cows that consume feed, grass or water contaminated with radioactive iodine-131 can concentrate the element in their milk. Peter Elvidge/iStockphoto.com hide caption

itoggle caption Peter Elvidge/iStockphoto.com

The facilities at the Fukushima Dai-ichi nuclear power plant were designed to withstand strong earthquakes and tsunamis, but not to the strength and size experienced on March 11. Air Photo Service/AP hide caption

itoggle caption Air Photo Service/AP

Firefighters use heavy equipment to tear apart a collapsed 300-year-old house while searching for the dead in the rubble of Rikuzentakata, Japan. John Burnett/NPR hide caption

itoggle caption John Burnett/NPR

The facilities at the Fukushima Dai-ichi nuclear power plant were designed to withstand strong earthquakes and tsunamis, but not to the strength and size experienced on March 11. Air Photo Service/AP hide caption

itoggle caption Air Photo Service/AP

Japanese Self-Defense Force soldiers walked in a line after finding the body of a boy in the rubble in Higashimatsushima, Miyagi prefecture earlier today (March 31, 2011). Yasuyoshi Chiba/AFP/Getty Images hide caption

itoggle caption Yasuyoshi Chiba/AFP/Getty Images

One of the soggy wallets that have been brought into the Kamaishi police department following the tsunami. John Burnett/NPR hide caption

itoggle caption John Burnett/NPR

Tokyo Electric Power Co. Chairman Tsunehisa Katsumata (second from right) and other executives bow prior to a press conference at the company's headquarters in Tokyo on Wednesday. Kazuhiro Nogi/AFP/Getty Images hide caption

itoggle caption Kazuhiro Nogi/AFP/Getty Images