Limited/Suggestive Evidence of an Association

Evidence is suggestive of an association between exposure to a specific agent and a health outcome in humans, but is limited because chance, bias, and confounding could not be ruled out with confidence.

  • Exposure to sarin at doses sufficient to cause acute cholinergic signs and symptoms and subsequent long-term health effects.

Inadequate/Insufficient Evidence to Determine Whether an Association Does or Does Not Exist

The available studies are of insufficient quality, consistency, or statistical power to permit a conclusion regarding the presence or absence of an association between an exposure to a specific agent and a health outcome in humans.

  • Exposure to uranium and lung cancer at higher levels of cumulative exposure (>200 mSv or 25 cGy).

  • Exposure to uranium and lymphatic cancer; bone cancer; nervous system disease; nonmalignant respiratory disease; or other health outcomes (gastrointestinal disease, immune-mediated disease, effects on hematological parameters, reproductive or developmental dysfunction, genotoxic effects, cardiovascular effects, hepatic disease, dermal effects, ocular effects, or musculoskeletal effects).

  • Pyridostigmine bromide and long-term adverse health effects.

  • Exposure to sarin at low doses insufficient to cause acute cholinergic signs and symptoms and subsequent long-term adverse health effects.

  • Anthrax vaccination and long-term adverse health effects.

  • Botulinum toxoid vaccination and long-term adverse health effects.

  • Multiple vaccinations and long-term adverse health effects.

Limited/Suggestive Evidence of No Association

There are several adequate studies covering the full range of levels of exposure that humans are known to encounter, that are mutually consistent in not showing a positive association between exposure to a specific agent and a health outcome at any level of exposure. A conclusion of no association is inevitably limited to the conditions, levels of exposure, and length of observation covered by the available studies. In addition, the possibility of a very small elevation in risk at the levels of exposure studied can never be excluded.

  • Exposure to uranium and lung cancer at cumulative internal dose levels lower than 200 mSv or 25 cGy.

  • Exposure to uranium and clinically significant renal dysfunction.



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