Groundwater is an essential for living human and other creatures,lots of anthropogenic activity like drinking, irrigation and industrial activity depends on it. It has been well known that heavy metal leads to cancer. Several heavy metals like Lead, Arsenic, cadmium, etc. enters into the human body through daily water consumption.Arsenic (As) is carcinogenic toxic heavy metalloid, exists in four oxidation states out of four, As (III) is usually more toxic than As (V). Arsenic contamination in environment by natural process (rockweathering) and anthropogenic activity(insecticides and herbicides, synthetic organic compounds Open mining, cosmetics, deep water irrigation etc.). Due to serious water scarcity and increasing demand of water for agricultural crops, industrial practices and urban consumption, deep water boring are being preferred. These wrong practices increase sedimental inorganic As contamination in water as well as in our food chain because this contaminated water are being used forirrigation of crops, vegetables etc. and making food stuffs in industries. IARC (International Agency for Research on Cancer recognize Arsenic as a group-I carcinogenic and EU (European Union) directive declared Arsenic as Toxic and dangerous for the environment.  Arsenic leads in human chronic arsenic poisoning (arsenicosis).Initiation and progression of disease depends on incubation period of the compound inside body and extent of exposure. Long term exposure to arsenic in drinking waterincreases risks for epithelial cancer, lung, bladder and kidney cancer, as well as other skin deformity such as hyperkeratosis and pigmentation change increased risks of lung and bladder cancer.

Permissible limit

World Health Organization (WHO) set a permissible limit to 10ppb (parts per billion) for drinking water purpose. In India, Department of Drinking Water Supply Ministry of Rural Development set a permissible limit to 50ppb for drinking purposes.

Distribution

Inorganic arsenic is naturally present at higher levels in the groundwater of a number of countries, uch as Argentina, Chile, China, India, Mexico, the United States of America, and Bangladesh etc.More than twenty Countries, including India, are in the midst of a large scale thread cause by chronic mass toxicity through arsenic contamination.Ganga–Meghna–Brahmaputra (GMB) plain highly Arsenic contaminated. In Indian Scenario Arsenic affected states are West Bengal, Bihar, Uttar Pradesh, Assam, Chhattisgarh,and Manipur. Table 1 summarizes the affected state and districts of India.

Table 1: Arsenic contaminated water affected state and districts of India

Sources of Arsenic Contamination in Ground Water

Source of arsenic contamination in groundwater is both natural and anthropogenic activities.In Natural aquifer of   the Ganga–Brahmaputra plains mainly the contaminated by a release of As from Holocene sediments. In parts of the Bengal Delta Plains (BDP), West Bengal and Gangetic plains of Bihar As contamination released from Gondwana coal strata in Rajmahal basin, Bihar mica-belt, pyrite-shale from the Proterozoic Vindhyan range, and Darjeeling Himalayas belt. The contaminated aquifers are of Quaternary age and comprise micaceous sand, silt and clay derived from the Himalayas and basement complexes of eastern India. Anthropogenic activities like deep water exploitation of groundwater, excess use offertilizers, insecticide, coal burning and coal-ash tailings.

Health problems: Challenges

Arsenical compounds interfere in biochemical physiology of thebody, experimental evidences suggest that As inhibit a number of important metabolic enzymes in both animals and humans.Phenylarsine oxide (PAO) blocks glucose transport by inhibiting insulin activation, when it extensively accumulated in the liver then it inhibits NAD-linked oxidation of pyruvate or α-ketoglutarate. Arsenic decreases the production of succinyl coenzyme A and subsequently decrease in ATP production. As (III) inhibits the reduction of nicotinamide adenine dinucleotide by deactivating critical enzymes of thetricarbonylic acid cycle, and As (V), uncouples oxidative phosphorylation by arsenolysis in mitochondria.Short duration exposure to Arsenic contamination, absorption of arsenic are by ingestion or inhalation it causes acute gastrointestinal irritation, muscular pain, weakness with flusking skin. Severe nausea and vomiting, colicky abdominal pain, and profuse diarrhoea with rice-water stools. Sometimes Capillary damage leads to generalized vasodilation, transudation of plasma, and vasagenice shock. Arsenic affects mucosal vascular supply, muscle cramps, numbness in hands and feet, reddish rashes in the body.  Whereas chronic exposure to contaminated Arsenic through water or food leads Carcinogenic effect. The pre-cancerous dermal keratosis, skin epidermoid carcinoma and lung cancer and exposure of humans to water-soluble inorganic arsenic through arsenic contamination. Skin cancers are mostly monocentric but sometimes multicentric cases are also found. In arsenicosis many neoplastic changes of the skin, including, Bowen's disease and basal cell carcinoma located on the trunk. Respiratory cancer has been observed among workers of pesticides and mining industries etc. exposed to inorganic arsenic.Humans are more sensitive to arsenic than animals and weak and malnutritious people can be easily affected byit.

Remediation strategy-

However Arsenic present in nature but the problem arises  with an excessive anthropogenic activity which accelerate its adverse effect  at carcinogenic level now it become a threat to the peoples of affected areas.At the present time many remediation technologies developed to remediate arsenic from water through Physical, chemical and biological methods.Activated alumina /Granulated ferric hydrated oxide or precipitation and coagulation,Ion exchange,Iron coated sand,Low pressure Nano filtration,Oxidation-reduction, Reverse Osmosis and electrolysistechnique generally apply to remediate Arsenic contaminated water. Physical and chemical remediation technologies more suitable for treatment of contaminated water, whereas biological remediation more suitable for treatment of contaminated soils, industrial waste treatment. Biological methods are less costly, sustainable to the environment in comparison to others.In biological remediation many bioagent like bacteria, fungi, algae, Plants, etc. are applied, which performs biosorption, bioaccumulation, microbes mediated oxidation-reduction, methylation-demethylation, biostimulation, biovoltlization, biomineralization, biofilm formation and plants remediation known as phytoremediation.

Future perspectives:

Rainwater harvesting and solar oxidation may provide eco-friendly approachesto remediate arsenic. The Separate Department should be constituted in the District hospital for treating arsenicosis in highly affected areas.Medical person and easy health diagnostic kit should be available free in affected states. Call center and mass awareness programsshould be accelerated in affected and less affected areas. Cancer hospital and curing medicines are easily available and tax free.