Water pollution and cancer

The water bodies (lakes, rivers and oceans) which are necessary for human and aquatic life are adversely affected by industrialization, agricultural production and urban life. Across the Globe, approximately 80% of industrial and municipal wastewater is discharged untreated which can affect humans and ecosystems. Untreated pollutants from industries include toxic chemicals, organic and inorganic substances, toxic solvents and volatile organic chemicals. Some of these harmful pollutants include compounds such as arsenic, cadmium and chromium. 

The agricultural sector as a result of run-off, also contributes through pesticides, nitrogen fertilizers and organic farm wastes. Other water pollutants from agricultural activities include nitrates, phosphorous, pesticides, soil sediments, salts and pathogens. The other main cause of drinking water pollution includes the deteriorating network of drinking water pipelines. The site of contamination whether at the source or end-user determines the type and amount of carcinogen present in drinking water. Some of the pollutants causing cancer include arsenic, nitrate, chromium, phosphorous etc. 

Listed are the compounds which at a higher concentration are associated with respective cancers:

i) Arsenic in drinking water is associated with skin, kidney and bladder cancer,

ii) Nitrates are associated with colorectal cancer,

iii) Hexavalent chromium has the potential to cause cancers of the respiratory and gastric system, 

iv) Trihalomethane (THM) is associated with brain, bladder cancers among both sexes, and non-hodgkin’s lymphoma, kidney cancer among men,

v) Chlorinated by-products are associated with bladder and rectal cancers,

Radionuclides such as radon are implicated in the causation of lung cancer, however their concentration in drinking water does not contribute to the risk of cancer. The associated risk is because of airborne radon released from water in dishes, tubs, and while cleaning/bathing. As per the Bureau of Indian Standards IS-10500-2012, water is defined as unfit for drinking if it is bacteriologically contaminated with E-coli, viruses etc, or if chemical contamination exceeds the following maximum permissible limits: fluoride (>1.5 mg/l), Total dissolved solids (>2000 mg/l), Iron (>0.3 mg/l), manganese (>0.3 mg/l), arsenic (>0.05mg/l), nitrates (>45 mg/l) etc. 

The physic-chemical analysis of water is done by the multi-parameter water quality field test kit, which offers both quantitative and semi-quantitative results. The quantitative test includes total hardness, total alkalinity and chloride tests. Semi-quantitative tests are done for the remaining parameters using color comparison charts: turbidity, pH, total hardness, total alkalinity, chloride, ammonia, phosphate, residual chlorine, iron, nitrate, sulphate and fluoride. A separate kit is available for testing arsenic, which is used in locations where arsenic is detected in sources of drinking water.