Arsenic is a naturally occurring element found in the Earth’s crust, widely distributed in our environment – air, water, and land. It’s crucial to understand that in its inorganic form, arsenic is highly toxic and poses a significant threat to public health worldwide. Exposure to elevated levels of inorganic arsenic can occur through various pathways, most notably via contaminated drinking water, the use of contaminated water in food preparation and crop irrigation, industrial processes, dietary intake of contaminated food, and even smoking tobacco.
Chronic arsenic poisoning, resulting from long-term exposure, primarily through drinking water and food, is a serious concern. The most visible and characteristic effects of such prolonged exposure are skin lesions and the development of skin cancer. Understanding “What Is Arsenic” and its pathways into our lives is the first step in mitigating its harmful effects.
Sources of Arsenic Exposure
To effectively address arsenic exposure, it’s vital to pinpoint the sources through which humans are exposed to this toxic element. These sources are diverse, ranging from natural contamination of water sources to industrial and lifestyle factors.
Drinking-water and Food: A Major Pathway
The most significant threat to public health related to arsenic originates from contaminated groundwater. Inorganic arsenic is naturally present at elevated levels in groundwater across numerous countries globally, including regions in Argentina, Bangladesh, Cambodia, Chile, China, India, Mexico, Pakistan, the United States, and Viet Nam. Consequently, drinking water sourced from these contaminated wells becomes a primary source of exposure. Furthermore, crops irrigated with arsenic-laden water and food prepared using contaminated water also contribute to dietary arsenic intake.
While drinking water is the primary concern, other dietary sources can contribute to arsenic exposure. Fish, shellfish, meat, poultry, dairy products, and cereals can contain arsenic. However, generally, the level of exposure from these food sources is considerably lower compared to contaminated groundwater. It’s also important to note that arsenic in seafood is predominantly in its organic form, which is considered less toxic than inorganic arsenic.
Industrial Processes: Occupational and Environmental Risks
Arsenic plays a role in various industrial applications. It is utilized as an alloying agent and in the manufacturing processes of glass, pigments, textiles, paper, metal adhesives, wood preservatives, and even ammunition. The hide tanning industry also uses arsenic, and to a lesser extent, it finds application in pesticides, feed additives, and pharmaceuticals.
These industrial uses create potential pathways for both occupational and environmental arsenic exposure. Workers in these industries may face direct exposure, while environmental contamination can occur through industrial discharge and waste, potentially affecting surrounding communities and ecosystems.
Tobacco: An Often Overlooked Source
Smoking tobacco is another route of arsenic exposure that is often underestimated. Tobacco plants can naturally absorb inorganic arsenic present in the soil as they grow. Therefore, individuals who smoke tobacco are exposed to the naturally occurring arsenic content within the tobacco leaves. Historically, the risk of arsenic exposure from tobacco was even higher when lead arsenate insecticides were commonly used on tobacco plants. While regulations have reduced the use of such insecticides, the natural presence of arsenic in soil remains a contributing factor for smokers.
Health Effects of Arsenic: Acute and Long-Term Consequences
Inorganic arsenic is a well-established human carcinogen and recognized as the most significant chemical contaminant in drinking water on a global scale. While arsenic can exist in both inorganic and organic forms, it’s crucial to differentiate their toxicity. Inorganic arsenic compounds, typically found in contaminated water, are highly toxic. In contrast, organic arsenic compounds, prevalent in seafood, are considerably less harmful to human health.
Acute Effects: Immediate Reactions to Arsenic Poisoning
Acute arsenic poisoning, occurring from a sudden high dose exposure, manifests with immediate and severe symptoms. These initial symptoms include vomiting, intense abdominal pain, and diarrhea. As the poisoning progresses, individuals may experience numbness and tingling sensations in their extremities, muscle cramping, and in severe, untreated cases, arsenic poisoning can lead to death.
Long-Term Effects: Chronic Health Problems from Prolonged Exposure
The effects of long-term exposure to even low levels of inorganic arsenic are insidious and can lead to a range of chronic health problems. The earliest and most visible signs of chronic arsenic exposure typically appear on the skin. These include changes in skin pigmentation, the development of various skin lesions, and the formation of hard patches on the palms of the hands and soles of the feet, a condition known as hyperkeratosis. These skin manifestations usually emerge after at least five years of exposure and are considered potential precursors to skin cancer.
Beyond skin cancer, prolonged arsenic exposure is linked to an increased risk of cancers in other internal organs, specifically the bladder and lungs. The International Agency for Research on Cancer (IARC) has classified arsenic and arsenic compounds unequivocally as carcinogenic to humans, emphasizing that arsenic in drinking water is also carcinogenic.
Furthermore, long-term ingestion of inorganic arsenic is associated with a broader spectrum of adverse health effects, including developmental problems, diabetes, pulmonary diseases, and cardiovascular diseases. Arsenic-induced myocardial infarction (heart attack), in particular, is a significant contributor to excess mortality in arsenic-exposed populations.
Arsenic exposure is also linked to negative pregnancy outcomes and increased infant mortality. Studies indicate that arsenic exposure during prenatal and early childhood stages can have long-lasting consequences, increasing the risk of mortality in young adults due to various cancers, lung disease, heart attacks, and kidney failure. Moreover, numerous studies have demonstrated the detrimental impacts of arsenic exposure on cognitive development, intelligence, and memory function in children.
Magnitude of the Arsenic Problem: A Global Health Crisis
Arsenic contamination of groundwater is a widespread and extensive issue, affecting numerous regions around the world. Many areas face significant arsenic contamination in their drinking water sources, creating a global health crisis. Estimates suggest that approximately 140 million people across at least 70 countries are currently drinking water with arsenic levels exceeding the World Health Organization (WHO) provisional guideline value of 10 μg/L. Recent statistical modeling further emphasizes the scale of the problem, indicating that between 94 and 220 million people are at risk of exposure to elevated arsenic concentrations in groundwater.
It’s important to recognize that the symptoms and signs of long-term arsenic exposure can vary significantly among individuals, population groups, and geographical locations. This variability means there is no universally accepted definition of arsenic-related disease, complicating the assessment of the overall health burden attributable to arsenic exposure.
Similarly, distinguishing between cancers caused by arsenic and those induced by other factors is currently impossible. This lack of specific diagnostic methods hinders the ability to obtain a reliable estimate of the true magnitude of the arsenic problem worldwide in terms of cancer incidence and mortality.
In 2010, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) conducted a re-evaluation of arsenic’s health effects, incorporating new scientific data. JECFA concluded that in regions with inorganic arsenic concentrations in drinking water exceeding 50–100 μg/L, there is clear evidence of adverse health effects. In areas with moderately elevated arsenic levels (10–50 μg/L), JECFA acknowledged the possibility of adverse effects, but noted that these would likely occur at a low incidence, making them difficult to detect in typical epidemiological studies.
Prevention and Control Strategies: Protecting Public Health
The most critical step in mitigating arsenic’s harmful effects in affected communities is preventing further exposure. This is primarily achieved by providing access to a safe water supply for drinking, food preparation, and irrigation of food crops. Several effective strategies can be implemented to reduce arsenic levels in drinking water and minimize exposure.
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Substitute High-Arsenic Sources: Replacing high-arsenic sources, particularly groundwater, with low-arsenic, microbiologically safe alternatives is a fundamental solution. This can involve utilizing rainwater harvesting or treating surface water sources. Prioritizing low-arsenic water for drinking, cooking, and irrigation, while reserving high-arsenic water for non-consumption purposes like bathing and washing clothes, can significantly reduce exposure.
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Discriminate Between Water Sources: Implementing methods to differentiate between high-arsenic and low-arsenic water sources is crucial. Testing water sources for arsenic levels and using visual cues, such as painting tube wells or hand pumps in different colors to indicate arsenic levels, can be a cost-effective and rapid way to reduce exposure, especially when combined with effective public education campaigns.
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Water Blending: Mixing low-arsenic water with higher-arsenic water sources to achieve an acceptable arsenic concentration level is another viable approach, particularly in areas where completely switching water sources is not immediately feasible.
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Arsenic Removal Systems: Installing arsenic removal systems, either at a centralized community level or at the household level, offers a direct solution. These systems utilize various technologies, including oxidation, coagulation-precipitation, absorption, ion exchange, and membrane filtration, to effectively remove arsenic from water. While effective and low-cost household removal options are becoming increasingly available, ensuring their sustained and effective use over time remains a challenge. Proper disposal of the removed arsenic is also a critical consideration.
Beyond water-related interventions, long-term actions are needed to minimize occupational arsenic exposure in industrial settings. Implementing stricter workplace safety regulations and employing arsenic-free alternatives where possible are essential steps.
Crucially, education and community engagement are vital for the success of any arsenic mitigation efforts. Community members need to understand the risks associated with high arsenic exposure, the various sources of exposure, including the uptake of arsenic by crops like rice from contaminated irrigation water and the transfer of arsenic into food from cooking water. Empowering communities with knowledge enables them to make informed decisions and actively participate in prevention strategies.
Furthermore, high-risk populations, particularly those in known arsenic-contaminated areas, should be regularly monitored for early signs of arsenic poisoning, with skin problems being the most readily detectable initial indicators. Early detection allows for timely intervention and management of health effects.
WHO Response: Global Leadership in Arsenic Mitigation
Arsenic is recognized by the WHO as one of the top 10 chemicals of major public health concern globally. The WHO plays a leading role in reducing arsenic exposure through various initiatives, including establishing guideline values, conducting evidence reviews, and providing risk management recommendations to countries worldwide. The WHO publishes a guideline value for arsenic in its comprehensive “Guidelines for drinking-water quality,” which serves as a crucial reference point for regulation and standard setting globally.
The current WHO recommended limit for arsenic in drinking water is 10 μg/L. However, this guideline value is designated as provisional due to the practical challenges associated with completely removing arsenic from drinking water in many settings. Despite this, the WHO emphasizes that every effort should be made to keep arsenic concentrations as low as reasonably possible and ideally below the guideline value, especially when resources are available.
Recognizing the reality that millions of people globally are exposed to arsenic concentrations far exceeding the guideline value (100 μg/L or even higher), the WHO prioritizes reducing exposure for these most highly affected populations. In situations where achieving the 10 μg/L guideline value is immediately challenging, the WHO advises Member States to set higher interim limits or values as part of a phased strategy to progressively reduce risks. These interim measures should be tailored to local circumstances, available resources, and the potential risks associated with switching to alternative water sources that may be microbiologically contaminated, even if they have lower arsenic levels.
The WHO/UNICEF Joint Monitoring Programme for Water Supply, Sanitation and Hygiene (JMP) actively monitors global progress towards achieving safe drinking water targets. Within the framework of the 2030 Agenda for Sustainable Development, the indicator of “safely managed drinking water services” includes tracking the population’s access to drinking water that is free from both faecal contamination and priority chemical contaminants, including arsenic. This global monitoring effort underscores the commitment to addressing arsenic contamination as a critical component of ensuring safe and sustainable water access for all.
References
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(3) The developmental neurotoxicity of arsenic: cognitive and behavioral consequences of early life exposure.Tolins M, Ruchirawat M, Landrigan P. Ann Glob Health. 2014;80(4):303-14.
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