To a much lesser extent, particles may adhere to an individual or his clothing. The effective area covered varies with many factors, including wind speed, humidity, and sunlight. In the absence of direct evidence of an attack, the first clue would be mass casualties fitting a clinical pattern compatible with one of the biological agents. This may occur hours or days after the attack. Toxins may cause direct pulmonary toxicity or be absorbed and cause systemic toxicity.
Toxins are frequently as potent or more potent by inhalation than by any other route.
Mucous membranes, including conjunctivae, are also vulnerable to many biological warfare agents.