Health Hazards of Arsenic in Drinking Water

Arsenic is one of the most dangerous naturally occurring contaminants found in groundwater worldwide. Unlike many pollutants that can be easily detected, arsenic in drinking water is tasteless, odorless, and invisible – making it a silent threat. The World Health Organization (WHO) lists arsenic among its ten chemicals of major public health concern, and for good reason. Prolonged exposure through contaminated drinking water has been linked to a wide range of health problems, from skin diseases to multiple types of cancer. In this post, we’ll break down exactly how arsenic in drinking water harms human health, what happens with long-term exposure, and which regions of the world are most severely affected.

How arsenic enters drinking water 🔗

Arsenic is a natural element found in the Earth’s crust. It gets into groundwater when certain geological conditions cause it to leach from rocks and sediments into aquifers. This is the primary route of human exposure – people drinking water pumped from underground wells. In addition to direct consumption, arsenic-contaminated water used for cooking and irrigating food crops (especially rice) creates secondary pathways of exposure.

The WHO has set a provisional guideline value of 10 micrograms per liter (µg/L) for arsenic in drinking water. However, many countries, particularly in South and Southeast Asia, still follow the older standard of 50 µg/L established in 1963. A 2024 study from the University of Sheffield found that roughly 32 percent of the world’s population lives in countries that have not adopted the current WHO-recommended safe limit, putting millions at risk – especially in low- and middle-income nations.

Health implications of arsenic exposure 🔗

The health consequences of arsenic exposure range from mild skin changes to life-threatening conditions. The type and severity of effects depend on the concentration of arsenic, the duration of exposure, and individual factors such as nutritional status and genetics.

Skin conditions: the earliest warning signs 🔗

Skin changes are typically the first and most recognizable signs of chronic arsenic exposure. These include melanosis (dark patches of pigmentation on the chest, back, and limbs), keratosis (thickened, rough patches on the palms and soles), and leucomelanosis (white spots interspersed with dark areas). According to the Agency for Toxic Substances and Disease Registry (ATSDR), this pattern of skin changes is the single most characteristic effect of long-term oral arsenic exposure. In severe cases, these skin lesions can progress to skin cancer, including both basal cell carcinoma and squamous cell carcinoma.

In affected communities in Bangladesh and West Bengal, India, people suffering from visible arsenicosis often face social stigma. The skin deformities can resemble leprosy, leading to social isolation and discrimination – compounding the physical harm with psychological and social damage.

Cancer risks 🔗

Arsenic is classified as a Group 1 carcinogen (carcinogenic to humans) by the International Agency for Research on Cancer (IARC). Beyond skin cancer, chronic ingestion of arsenic through drinking water has been strongly linked to cancers of the bladder, lungs, liver, and kidneys.

Research conducted in southwestern Taiwan, where populations were historically exposed to high arsenic levels through artesian well water, demonstrated clear dose-response relationships. A study reviewed by the National Research Council found that individuals exposed to arsenic concentrations of 0.71 mg/L or more had over three times the risk of developing bladder cancer compared to those with lower exposure levels.

What makes arsenic-related cancer particularly insidious is its long latency period. Cancers can take decades to appear after the initial exposure. This means that communities consuming contaminated water today may not see the full burden of cancer cases for many years.

Neurological effects 🔗

Arsenic doesn’t spare the nervous system. Both the peripheral and central nervous systems can be affected. Common neurological complaints include tingling and numbness in the hands and feet (peripheral neuropathy), weakness, confusion, and impaired memory. A study on chronic arsenic toxicity in Bangladesh and West Bengal found evidence of arsenic-related neuropathy in over 37 percent of cases examined in one group, with predominantly sensory nerve damage.

Multiple studies have also demonstrated that arsenic exposure, particularly during early life, negatively affects cognitive development, intelligence, and memory in children. This developmental neurotoxicity is a major concern because it can limit educational outcomes and lifelong potential for affected populations.

Long-term effects of chronic arsenic exposure 🔗

While the acute effects of very high arsenic doses (such as nausea, vomiting, and diarrhea) are well known, it is the chronic, low-level exposure that presents the biggest public health challenge. People drinking mildly to moderately contaminated water over years or decades can develop a range of serious conditions.

Cardiovascular disease 🔗

A growing body of evidence links prolonged arsenic exposure to increased cardiovascular morbidity and mortality. A systematic review published in the journal Current Atherosclerosis Reports concluded that the evidence is sufficient to infer a causal relationship between high chronic arsenic exposure and cardiovascular disease. The specific cardiovascular conditions associated with arsenic include hypertension, coronary heart disease, myocardial infarction (heart attacks), and stroke.

The mechanisms involved include oxidative stress, chronic inflammation, and damage to the endothelial cells lining blood vessels. Arsenic-induced heart attacks have been identified as a significant contributor to excess mortality in heavily affected regions. In Chile, for example, increased mortality from acute myocardial infarction was documented during a period when drinking water arsenic concentrations ranged from 90 to 870 µg/L.

Even low-to-moderate arsenic exposure levels (below 100 µg/L) have shown associations with elevated blood pressure and increased risk of ischemic heart disease, according to the HEALS study in Bangladesh.

Diabetes 🔗

Several epidemiological studies have found a connection between chronic arsenic exposure and type 2 diabetes. Arsenic appears to act as an endocrine disruptor, interfering with insulin signaling and glucose metabolism. This effect has been observed in populations across multiple countries, including Taiwan, Bangladesh, and the United States. Arsenic-exposed individuals with pre-existing diabetes may also face amplified cardiovascular risks.

Respiratory disease 🔗

Chronic arsenic ingestion has been linked to pulmonary problems, including chronic cough, bronchiectasis, and restrictive lung disease. Studies from West Bengal found that chronic arsenic poisoning patients frequently presented with non-productive cough and significant restrictive changes in lung function tests. Long-term exposure also increases the risk of lung cancer independently of smoking.

Reproductive and developmental health 🔗

Arsenic can cross the placenta, directly exposing the developing fetus. Pregnant women chronically exposed to arsenic-contaminated water face higher risks of spontaneous abortion, stillbirth, preterm birth, and low birth weight. A study in Bangladesh found that women consuming water with arsenic levels of 100 µg/L or higher had a 2.5 times greater risk of stillbirth compared to those with lower exposure.

The consequences extend beyond pregnancy. Exposure during in utero development and early childhood has been linked to increased mortality in young adults from cancers, lung disease, heart attacks, and kidney failure. These findings suggest that arsenic programs the body for disease long before symptoms ever appear.

Case studies and global statistics 🔗

The scale of arsenic contamination in drinking water is staggering. According to the WHO, an estimated 140 million people in at least 70 countries consume water with arsenic levels exceeding the 10 µg/L guideline. More recent statistical modelling suggests that between 94 and 220 million people are at risk globally.

Bangladesh: the world’s largest mass poisoning 🔗

Bangladesh represents the most devastating case of arsenic contamination anywhere in the world. An estimated 50 million people in the country are at risk of exposure through groundwater. Ironically, this crisis originated from well-intentioned efforts. In the 1970s, international agencies including UNICEF helped install millions of tubewells to provide clean drinking water and reduce waterborne diseases. No one tested for arsenic at the time. By the 1990s, widespread arsenic contamination was discovered, but millions had already been drinking poisoned water for years.

By 2012, the Directorate General of Health Services of Bangladesh had identified nearly 66,000 confirmed arsenicosis cases. However, experts believe the actual number of affected individuals is far higher due to under-reporting and the long latency period of arsenic-related diseases. A collaborative study between the University of Chicago and Columbia University found that arsenic exposure may account for one in five deaths in the study area of Araihazar.

West Bengal, India 🔗

Right across the border from Bangladesh, West Bengal faces a similar crisis. Arsenic contamination was first identified in the state in 1983 in the lower Ganga plain. It is estimated that roughly 6 million people in West Bengal are exposed to arsenic-contaminated groundwater. Nine districts in the state have reported arsenic levels above the WHO’s 50 µg/L threshold. Affected districts include Murshidabad, Nadia, North and South 24 Parganas, and others along the Ganga-Brahmaputra floodplain.

Clinical studies from the Institute of Postgraduate Medical Education and Research (IPGMER) in Kolkata found that patients in the region had mean water arsenic levels of 0.25 mg/L – 25 times the WHO guideline. Skin and mucosal lesions, liver enlargement, and restrictive lung changes were the most common clinical findings.

Other affected regions 🔗

While South Asia dominates headlines, arsenic contamination is a global issue. Significant contamination has been reported in Argentina, Chile, China, Mexico, Taiwan, Cambodia, Vietnam, Myanmar, Nepal, Pakistan, and parts of the United States. In the United States, the Environmental Working Group notes that even at the current legal limit of 10 µg/L, up to 600 per million people could potentially develop cancer from a lifetime of exposure. The western and north-central regions of the U.S. have the highest groundwater arsenic concentrations.

In Chile’s Antofagasta region, populations were exposed to dramatically elevated arsenic levels (up to 870 µg/L) from the late 1950s to the 1970s. Decades later, researchers documented increased rates of bladder cancer, lung cancer, and cardiovascular mortality in those who were children during the exposure period – providing some of the clearest evidence for the long-latency effects of early-life arsenic exposure.

Why arsenic remains a persistent challenge 🔗

Several factors make arsenic in drinking water a uniquely difficult problem to solve. First, the contamination is natural and geological, meaning it cannot be eliminated at the source. Second, arsenic-affected regions are often among the world’s poorest, with limited resources for large-scale water treatment infrastructure. Third, the health effects develop slowly over years and decades, which reduces the sense of urgency among policymakers.

Treatment technologies like reverse osmosis, iron-based adsorption, and coagulation-filtration do exist and can effectively reduce arsenic levels. But the challenge lies in deploying and maintaining these systems at scale, particularly in rural and resource-limited settings. As the PLOS One analysis of global arsenic regulations noted, having legal standards does not guarantee that those standards will be implemented – especially in regions where government capacity and resources are limited.

Public awareness, community education, regular water testing, and improved nutrition (particularly folate and selenium intake, which can modify susceptibility to arsenic) are all important components of a comprehensive response.

The bigger picture 🔗

Arsenic contamination in drinking water is not just a water quality issue – it is a public health emergency affecting hundreds of millions of people. Its effects span nearly every organ system in the body, and the most vulnerable populations – low-income communities, pregnant women, and young children – bear the heaviest burden. The health toll includes skin diseases, multiple cancers, heart disease, diabetes, neurological damage, and reproductive harm. Many of these effects are irreversible, and some don’t manifest until decades after exposure begins.

Addressing this crisis requires a coordinated effort that combines safer water supply systems, stronger and enforced regulatory standards, targeted health surveillance, and community-level education. The evidence is clear and overwhelming – the question is whether the global response will match the scale of the problem.

What do you think? Given that affordable arsenic-removal technologies already exist, what do you believe are the main barriers preventing their widespread adoption in affected regions? And how should governments balance the cost of water treatment infrastructure against the long-term healthcare burden of arsenic-related diseases?

References

1. https://www.who.int/news-room/fact-sheets/detail/arsenic
2. https://www.sciencedaily.com/releases/2024/03/240321001152.htm
3. https://wwwn.cdc.gov/tsp/PHS/PHS.aspx?phsid=18&toxid=3
4. https://www.ncbi.nlm.nih.gov/books/NBK230891/
5. https://pubmed.ncbi.nlm.nih.gov/11778666/
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC3483370/
7. https://pubmed.ncbi.nlm.nih.gov/19371619/
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC6281155/
9. https://www.sciencedirect.com/science/article/pii/S1607551X11001124
10. https://www.ewg.org/tapwater/reviewed-arsenic.php
11. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0263505