The ingestion of contaminated water, either direct or through food and the use of contaminated water for purpose of personal hygiene and recreation leads to water borne diseases. Developing countries carry a heavy burden of water-related diseases major ones being the diarrhoeal diseases. Water-related diseases may be classified as follows:
- Biological water borne diseases
- Chemical related water borne diseases
Biological water borne diseases:
Those caused by the presence of an infective agent
- Viral – hepatitis A, hepatitis E, poliomyelitis, viral diarrhea in infants
- Bacterial – typhoid, paratyphoid, bacillary dysentery, E. coli dysentery, cholera
- Protozoal – amoebiosis,
- Helmenthic – roundworm, hookworm, tapeworm
Those caused by the presence of an aquatic host
- Snail –
- Cyclops – guineaworm, fish tape worm
Chemical related water borne diseases:
Chemical pollutants are derived from industrial and agricultural wastes. These pollutants include
- detergent solvents
- heavy metals
- minerals and organic acids
- nitrogenous substances
- bleaching agents
- sulphides, ammonia
- toxic and biocidal organic compounds
Chemical pollutants may affect man's health directly or indirectly by accumulating in aquatic life (e.g. fish used as human food). In addition to the acute toxic effects on human health, chemical pollutants also have an effect on long term effects at low level exposure which are non-specific and difficult to detect. Further, some of the pollutants cannot be removed easily from water source by conventional water treatment or purification methods.
Other water borne diseases:
- Dental health – fluoride offers protection against caries
- Cardiovascular diseases – hardness of water might protect against cardiovascular diseases
- Diseases occurring due to inadequate use of water – shigellosis, trachoma conjunctivitis etc.
- Diseases due to insects breeding in water – malaria, filarial, dengue etc.
While pollution seems to be an inevitable consequence of modern industrial technology, it is now essential to determine the level of pollution that permits economic and social development without causing hazards to health. The evaluation of the health effects of environmental pollutants is currently being carried out as part of the WHO Environmental Health Criteria Programme.