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Key Facts

Scientists know that:

  • I-131 breaks down rapidly in the atmosphere and environment
  • Exposure was highest in the first few days after each nuclear test explosion
  • Most exposure occurred through drinking fresh milk
  • People received little exposure from eating fruits and leafy vegetables as compared to drinking fresh milk because although I-131 was deposited on fruits and leafy vegetables, the I-131 in fallout was deposited only on the surface; people generally wash or peel fruits and leafy vegetables
  • Thyroid cancer is uncommon, usually curable, and approximately 2 to 3 times more common in women

Reliable information about I-131's impact on human health has been difficult to collect, but scientists think that:

  • Risk for thyroid cancer increases with exposure, but even among people exposed to I-131, few develop this cancer
  • People exposed as children have a higher risk than people exposed as adults