All weapons of war are destructive of human life, but chemical and bacteriological (biological) weapons stand in a class of their own as armaments which exercise their effects solely on living matter. The fact that certain chemical and biological agents are potentially unlimited in their effects, both in distance and durability, and that their large-scale use could have irreversible effects on the balance of nature adds to the sense of insecurity and tension which the existence of this class of weapons engenders.
Chemical and biological weapons pose a special threat to civilians because the high concentrations in which they would be used in military operations could lead to significant unintended involvement of the civilian population within the target area and for considerable distances downwind. Protection can be afforded by masks, filter canisters, impermeable clothing, reduction of psychological stress (thermal stress) by use of "permeable" protective clothing (permeable to air and water vapour but not to toxic chemicals), detection and contamination of toxic chemicals, medical antidotes and medical treatment, and collective physical protection in shelters. However, the large-scale or, with some agents, even limited use of chemical and biological weapons where no protective measures exist, could cause illness to a degree that would overwhelm existing health resources and facilities.
Large-scale use of chemical and biological weapons could also cause lasting changes of an unpredictable nature in man's environment. The possible effects of chemical and biological weapons are subject to a high degree of uncertainty and unpredictability, owing to the involvement of complex and extremely variable meteorological, physiological, epidemiological, ecological and other factors. Although advanced delivery systems are required for the employment of chemical and biological agents on a militarily significant scale against large civilian targets, isolated and sabotage attacks requiring only simple delivery could be very destructive in certain circumstances with some of these agents.
The potential for developing an armoury of chemical and biological weapons has grown considerably in recent years, not only in terms of the number of agents but in their toxicity and in the diversity of their effects. Possible long-term effects of such warfare include: chronic illness caused by exposure to chemical and biological agents; delayed effects in persons directly exposed (causation of cancer, severe damage to the human foetus, and detrimental alterations in the human gene); organic, particularly nervous, damage which lasts throughout life, even though the person is not killed. Biological agents spreading from person to person can give rise to waves of secondary attack which, in diseases like plague, may continue for months or years after the event. Decontamination of persons and equipment could be required for persistent chemical and biological agents.
Concerns have been expressed that massive attacks may alter the ecological relationship between man and lower animal and insect vectors of diseases previously latent. Because most biological and chemical warfare agents are specific in action (against humans), broad-scale environmental impact is unlikely. In certain cases, biological warfare aimed at animals (in order to disrupt meat, poultry and dairy production) could have important ecological consequences. However, the large-scale use of herbicides as a method of warfare could have devastating effects of the environment.