Magnification of arsenic poisoning factors along the length of river
Previous studies have not explored the link between the downstream distance of rivers and increased incidence of arsenic toxicity. We find that in South Asia almost all the sites of arsenic toxicity are close to a river and are furthest from the source of river. The 3 factors that we posit are contributing to this distribution but have not been studied are: 1. deforestation, 2. misguided commercial forestation and 3. runoff and magnification in rivers. Deforestation and misguided commercial forestation of plants that results in reduced biodiversity and soil holding capacity contribute to erosion and leaching of arsenic. Massive commercial forestation in Northern Himalayas and expansion of agriculture in North Indian plains in the last few centuries have drastically altered the previous equilibrium of the system. Runoff in river can influence increased arsenic toxicity in 3 ways: 1. direct runoff of pesticides and other compounds containing arsenic, 2. industrial, agricultural and domestic-use compounds that increase arsenic mobilization and 3. decreased pH that increases arsenic mobilization. In the coming years, we expect additional factors of ground water cycling and other anthropogenic factors to alter this distribution and worsen the situation of arsenic toxicity.