DISEASE TRANSMISSION BY CONTAMINATED WATER - Environmental Engineering: Prevention and Response to Water-,Food-,Soil-,And Air-Borne Disease and Illness - page 4

Source (agent factors-physical, chemical biologic): food and infected or infested animals; poisonous plants and animals;
parasites; toxic solid, liquid, and gaseous substances and natural deposits; genetic and inherited materials; ionizing and
nonionizing radiations; noise.
Mode of transmission or contributing factors (environmental factors): environmental pollutants; contact; animals; personal
behavior; level of hygiene, sanitation, standard of living; work, recreation, travel,home, climate.
Susceptibility (host factors): all animals or susceptibles, resulting in acute, chronic, or delayed effects, depending on portal of
entry, dose, and virulence or toxicity of the agent; natural and acquired resistance of the host, and lifestyle.
Animals include humans and arthropods. Arthropods include insects, arachnids, crustaceans, and myriapods. Environmental
pollutants may be transmitted by air, water, food, or contact. Personal behavior may involve cigarette smoking, drug use,
poor nutrition, stress, lack of exercise, cultural habits, and obesity. Physical agents may be heat, cold, precipitation, and
causes of accidents. Biologic agents include arthropods, helminthes, protozoa, fungi, bacteria, rickettsiae, and viruses.
Chemical agents include inorganic and organic chemicals.

FIGURE 1.1 Spread of communicable and noninfectious diseases.

does not guarantee that the disease may be expressed. There is ample evidence
that individuals may be carriers of a pathogenic agent (necessary factor) but not
become clinically ill. The kinds of factors proposed by Gerstman are addressed
elsewhere in the chapter. Elimination or control of the source and environmental
exposure to disease agents or vectors is a primary step to be carried out to the
extent feasible. Individuals frequently are not aware that they are being exposed
to a potential source of disease, particularly when it is a minute, insidious, and
cumulative substance, such as certain chemicals in the air, water, and food. An
additional complication arises on the biological front when the disease agent is
transmissible by more than one route. For example, many of the viral and bacterial
agents of disease can be transmitted through both contaminated food and water.
In many instances, control at the source is not only possible but also practical.
Measures that might be taken to reduce or eliminate the appearance of toxic
substances in waters are:

1. Change the raw material or industrial process to eliminate or adequately
minimize the offending substance. For example, terminate the production