To a much lesser extent, particles may adhere to an individual or his clothing, thus the need for individual decontamination. The effective area covered varies with many factors, including wind speed, humidity, and sunlight. In the absence of an effective real-time alarm system or direct observation 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. Other routes for delivery of biological agents are thought to be less important than inhalation, but are nonetheless potentially significant. Contamination of food and water supplies, either purposefully or incidentally after an aerosol biological warfare attack, represents a hazard for infection or intoxication by ingestion. Assurance that food and water supplies are free from contamination should be provided by appropriate preventive medicine authorities in the event of an attack. Intact skin provides an excellent barrier for most biological agents.