14.2 Health Effects of Water Pollutants

Waterborne Diseases from Poor Sanitation

Contaminated water and poor sanitation directly transmit numerous infectious diseases. When water sources are not adequately protected or treated, they become breeding grounds for pathogens.

Common Waterborne Diseases:

Absent, inadequate, or inappropriately managed water and sanitation services expose individuals to preventable health risks, leading to widespread illness and mortality, especially in developing regions.

Heavy Metal Contamination

Industrial and agricultural runoff can introduce toxic heavy metals into the water supply. These metals are persistent and can accumulate in the environment and in living organisms.

Key Heavy Metal Pollutants and Their Health Effects:

Health Impacts of Heavy Metals

Heavy metals can have detrimental effects on human health, even at low concentrations.

Neurotoxicity: Damage to the brain or peripheral nervous system, causing mental and neurological issues. Mercury ($Hg$) and Lead ($Pb$) are primary neurotoxicants. Mercury causes Minamata disease; Lead impairs cognitive development in children.

Nephrotoxicity: Damage to the kidneys, potentially leading to kidney failure. Cadmium ($Cd$) is particularly known for accumulating in the kidneys and causing Itai-Itai disease.

Bioaccumulation and Biomagnification:

• Bioaccumulation: The gradual buildup of non-biodegradable toxic substances (e.g., heavy metals, DDT) in the tissues of a single organism over time.
• Biomagnification: The progressive increase in concentration of these substances as they move up successive trophic levels in the food chain. Top predators accumulate the highest concentrations.

As these metals move up the food chain, their concentration increases, leading to severe health problems such as cancer and various syndromes in humans and wildlife.

Other Chemical Pollutants

In addition to heavy metals, other ions can cause significant health issues:

Nitrates ($N{O}_3^{-}$): High levels in drinking water can cause methemoglobinemia (Blue Baby Syndrome) in infants. Nitrates are reduced to nitrites in the infant digestive system; nitrites react with haemoglobin to form methemoglobin, which cannot carry oxygen.

Fluoride ($F^{-}$): While small amounts (0.5–1 ppm) prevent tooth decay, excessive fluoride leads to fluorosis:

• Dental fluorosis: mottled and discoloured tooth enamel
• Skeletal fluorosis: brittle and deformed bones