Chemical incidents, especially acts of terrorism, may also cause fear and anxiety in populations, as well as injury from fire, explosion or toxicity. Depending on the chemical exposure, symptoms may present themselves differently. In general, the adverse health outcomes to toxic chemical exposure may be:

- effects that are local or arise at the site of contact with the chemical, such as bronchoconstriction from respiratory irritants, or irritation of the skin and eyes by gases, liquids and solids;

- effects that are systemic or affect organ systems remote from the site of absorption, such as depression of the central nervous system from inhalation of solvents, or necrosis of the liver from the inhalation of carbon tetrachloride; and

- effects on mental health arising from real or perceived releases, which depend on the psychosocial stress associated with an incident.

PRECA project is aimed to guarding against chemical threats to Mass Gatherings by developing Poison Information Centres.