Evidence is sufficient to conclude that there is a positive association. That is, a positive association has been observed between an exposure to a specific agent and a health outcome in human studies in which chance, bias, and confounding could be ruled out with reasonable confidence.

• Pyridostigmine bromide and transient acute cholinergic effects in doses normally used in treatment and for diagnostic purposes.

• Anthrax vaccination and transient acute local and systemic effects.

• Botulinum toxoid vaccination and transient acute local and systemic effects.

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.

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.

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.