<unk> <unk>  contamination areas<unk>  is a form of<unk>  pollution which is often due to naturally occurring high concentrations of<unk>  in deeper levels of<unk> . It is a high-profile problem due to the use of deep tube wells for water supply in the Ganges Delta, causing serious<unk>  poisoning to large numbers of people. A 2007 study found that over 137 million people in more than 70 countries are probably affected by<unk>  poisoning of drinking water. The problem became serious health concern after mass poisoning of water in Bangladesh.<unk>  is found in many countries throughout the world, including the US. The World Health Organization recommends limiting<unk>  concentrations in water to 10 μg/L, although this is often an unattainable goal for many problem areas due to the difficult nature of removing<unk>  from water sources. Approximately 20 major incidents of<unk> <unk>  contamination have been reported. Of these, four major incidents occurred in Asia- in Thailand, Taiwan, and Mainland China. Locations of potentially hazardous wells have been mapped in China.
Arsenic contamination of groundwater
Infection in childcare
Intentional contagion of infection
Pesticide toxicity to bees
Antibiotic use in livestock
Vaccine contamination with SV40
Latent iron deficiency
Illness and injuries during spaceflight