Over withdrawals of groundwater in West Bengal and Bihar has increased the concentration of arsenic.

Explanation:

Groundwater is a vital source of drinking water for millions of people in West Bengal and Bihar, two states in India. However, due to excessive withdrawals for various purposes such as irrigation and domestic use, the groundwater levels have been significantly depleted. This depletion has led to a phenomenon known as groundwater arsenic contamination.

1. Groundwater Arsenic Contamination:
- Over the years, the excessive pumping of groundwater has created a negative pressure in the aquifers, causing the infiltration of contaminated water from adjacent layers into the depleted aquifers.
- The underlying geological formations in West Bengal and Bihar contain high levels of naturally occurring arsenic.
- As the groundwater level drops, the water from these arsenic-rich layers seeps into the depleted aquifers, leading to an increase in the concentration of arsenic in the groundwater.

2. Health Implications:
- Arsenic is a highly toxic element and long-term exposure through drinking water can lead to severe health issues.
- Chronic arsenic exposure can cause various health problems such as skin lesions, cancers (skin, bladder, lung), cardiovascular diseases, and developmental effects in children.
- The World Health Organization (WHO) has set a maximum acceptable limit of 10 micrograms per liter (µg/L) for arsenic in drinking water.

3. Impact on the Population:
- The contaminated groundwater is used for drinking, cooking, and irrigation purposes by the population in affected areas.
- As a result, the people consuming this arsenic-contaminated water are at a high risk of developing arsenic-related health issues.
- The problem is particularly severe in rural areas where access to alternative sources of safe drinking water is limited.

4. Mitigation Measures:
- It is crucial to address this issue to ensure the provision of safe drinking water to the affected population.
- Some mitigation measures include the installation of arsenic removal filters in households, the promotion of rainwater harvesting, and the development of alternative water sources.
- Government initiatives, NGO interventions, and community awareness programs are essential for tackling this problem effectively.

In conclusion, the over withdrawals of groundwater in West Bengal and Bihar have led to the increased concentration of arsenic in the groundwater. This contamination poses significant health risks to the population, emphasizing the need for immediate measures to provide safe drinking water to the affected areas.