"Sanitation" refers to all conditions that affect health, especially with regard to dirt and infection and specifically to the drainage and disposal of sewage and refuse from houses (The Concise Oxford Dictionary). At its first meeting in 1950, the WHO Expert Committee on Environmental Sanitation defined environmental sanitation as including the control of community water supplies, excreta and wastewater disposal, refuse disposal, vectors of disease, housing conditions, food supplies and handling, atmospheric conditions, and the safety of the working environment. Environmental problems have since grown in complexity, especially with the advent of radiation and chemical hazards. Meanwhile, the world's needs for basic sanitation services (i.e., drinking-water supply, excreta and wastewater disposal) have greatly increased as a result of rapid population growth and higher expectations. This led to the designation by the United Nations of the International Drinking Water Supply and Sanitation Decade (1981-1990).
There has been considerable awareness of community water supply needs, but the problems of excreta and wastewater disposal have received less attention. In order to focus attention on these problems, "sanitation" became used and understood by people worldwide to refer only to excreta and wastewater disposal. A WHO Study Group in 1986 formally adopted this meaning by defining sanitation as "the means of collecting and disposing of excreta and community liquid wastes in a hygienic way so as not to endanger the health of individuals and the community as a whole" (WHO, 1987a). Hygienic disposal that does not endanger health should be the underlying objective of all sanitation programmes.
The cost of a sewerage system (which is usually more than four times that of on-site alternatives) and its requirement of a piped water supply preclude its adoption in the many communities in developing countries that lack adequate sanitation. On-site disposal, dealing with excreta where it is deposited, can provide a hygienic and satisfactory solution for such communities.
Safe disposal of excreta is of paramount importance for health and welfare and also for the social and environmental effects it may have in the communities involved. Its provision was listed by the WHO Expert Committee on Environmental Sanitation in 1954 among the first basic steps that should be taken towards ensuring a safe environment (WHO, 1954). More recently a WHO Expert Committee on the Prevention and Control of Parasitic Infections (WHO, 1987b) stressed that "the provision of sanitary facilities for excreta disposal and their proper use are necessary components of any programme aimed at controlling intestinal parasites. In many areas, sanitation is the most urgent health need and those concerned with the control of intestinal parasitic infections are urged to promote intersectoral collaboration between health care authorities and those responsible for the provision of sanitation facilities and water supply at the community level."