Arsenic

Arsenic occupies an unusual place among toxic elements. It’s naturally present in the Earth’s crust and leaches into groundwater in many regions worldwide. It’s found in foods — particularly rice, which absorbs arsenic from soil more efficiently than other grains. And it has a long history of deliberate poisoning, earning its nickname “inheritance powder” in medieval times. Today, chronic low-level arsenic exposure affects hundreds of millions of people globally and represents one of the most significant environmental health challenges.

Understanding arsenic requires distinguishing between its forms. Inorganic arsenic — found in contaminated water and to a lesser extent in rice and some other foods — is the dangerous form. It’s a known human carcinogen linked to cancers of the skin, lung, bladder, and other organs. Organic arsenic — primarily arsenobetaine found in seafood — is much less toxic and is rapidly excreted. This distinction is crucial for interpreting test results: someone who ate shrimp yesterday may have high total arsenic that’s almost entirely harmless organic forms.

The health effects of chronic inorganic arsenic exposure are serious and wide-ranging: increased cancer risk, cardiovascular disease, diabetes, skin changes, and neurological effects. Perhaps most concerning, these effects develop gradually with chronic exposure and may not become apparent for years or decades. Testing identifies elevated exposure before these consequences manifest, allowing intervention through source identification and exposure reduction.

Order Your Arsenic Test

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Key Benefits of Testing

Arsenic testing reveals exposure that would otherwise go undetected. You can’t taste, smell, or see arsenic in water or food. Symptoms of chronic low-level exposure are nonspecific or absent until damage accumulates. Without testing, you won’t know if your well water, your rice-heavy diet, or your workplace is exposing you to harmful levels.

For people using private well water, testing is particularly important. Unlike municipal water supplies, which are regulated and monitored for arsenic, private wells are the owner’s responsibility. Arsenic contamination of groundwater is common in many regions, and the only way to know your well’s arsenic level is to test it — or to test yourself for arsenic exposure.

For those with high rice consumption, testing can reveal whether dietary arsenic is accumulating to concerning levels. This is especially relevant for people following gluten-free diets (which often substitute rice for wheat), those eating rice as a staple food, infants fed rice cereal, and people consuming rice-based products like rice milk or rice protein.

For occupational exposure — workers in smelting, glass manufacturing, semiconductor production, wood preservation, and pesticide application — testing monitors whether workplace protections are adequate. Biological monitoring is more meaningful than air sampling alone because it captures all exposure routes and individual variation in absorption.

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What Does Arsenic Testing Measure?

Arsenic can be measured in urine, blood, hair, or nails. Each provides different information, and the choice depends on what question you’re trying to answer.

Urine Arsenic

Urine is the preferred specimen for assessing recent arsenic exposure because most absorbed arsenic is excreted in urine within a few days. Urine testing can measure either total arsenic or speciated arsenic (separated into different forms).

Total urine arsenic: Measures all arsenic forms combined. Simple and inexpensive but can be misleading — elevated total arsenic after eating seafood reflects harmless organic arsenobetaine, not toxic inorganic exposure.

Speciated urine arsenic: Separates arsenic into its various forms: inorganic arsenic (toxic), and its metabolites (monomethylarsonic acid and dimethylarsinic acid, which indicate inorganic arsenic exposure), plus organic forms like arsenobetaine (from seafood, non-toxic). This distinction is essential for meaningful interpretation.

Recommendation: If total arsenic is elevated, speciation is needed to determine whether it represents concerning inorganic exposure or benign seafood-related organic arsenic. Many experts recommend speciated testing as the initial test to avoid confusion.

Blood Arsenic

Blood arsenic has a short half-life (hours) and reflects only very recent exposure or ongoing high-level exposure. It’s less useful than urine for most situations because arsenic is rapidly cleared from blood to tissues and urine.

Best for: Acute high-dose poisoning (where blood levels may be very high); assessing very recent exposure.

Limitations: Not useful for chronic low-level exposure assessment; will miss exposure that occurred more than a day or two ago.

Hair and Nail Arsenic

Arsenic accumulates in keratin-rich tissues (hair and nails) over time, providing a record of exposure over weeks to months. These specimens can assess historical exposure that urine would miss.

Best for: Documenting chronic exposure; forensic or historical exposure assessment; situations where recent exposure has stopped but past exposure is suspected.

Limitations: Can be contaminated by external arsenic (arsenic in dust or water contacting hair/nails); requires careful collection and interpretation; less standardized than urine testing.

Water Testing

If groundwater exposure is suspected, testing the water itself is complementary to biological testing. Private well water should be tested for arsenic (and other contaminants). Water arsenic levels directly inform whether treatment systems or alternative water sources are needed.

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Why Arsenic Testing Matters

The Global Groundwater Crisis

Arsenic contamination of groundwater is a massive global health issue. The WHO estimates that over 200 million people worldwide drink water with arsenic above safe limits. The worst-affected regions include Bangladesh, West Bengal (India), parts of Southeast Asia, and areas of the Americas — but arsenic-contaminated groundwater exists on every continent, including significant portions of the United States.

In the US, private wells are most commonly affected because they’re not subject to EPA drinking water standards. The USGS estimates that millions of Americans drink well water with arsenic above the EPA limit. Testing is the only way to identify exposure if you rely on well water.

The Rice Problem

Rice has emerged as a significant arsenic source in recent years. Rice plants are uniquely efficient at absorbing arsenic from soil — about ten times more than other grains. Rice paddies flooded with arsenic-contaminated water, or grown in soil with legacy arsenic from pesticides, accumulate arsenic in the grain.

For most people eating rice occasionally, this isn’t a significant concern. But for those with high rice consumption — many Asian populations, people on gluten-free diets, infants fed rice cereal, consumers of rice milk or rice-based products — dietary arsenic can accumulate to meaningful levels. Testing reveals whether your rice consumption is elevating arsenic exposure.

Cancer Prevention

Inorganic arsenic is a known human carcinogen (IARC Group 1). Chronic exposure increases risk of:

Skin cancer: Multiple types including squamous cell carcinoma and Bowen’s disease, often preceded by characteristic skin changes.

Lung cancer: Risk increases with both ingestion and inhalation exposure.

Bladder cancer: Well-established association with chronic arsenic in drinking water.

Kidney cancer: Elevated risk with chronic exposure.

Liver cancer: Associated with high-level chronic exposure.

Identifying and reducing arsenic exposure before these cancers develop is the goal. Testing enables this by revealing elevated exposure.

Cardiovascular and Metabolic Effects

Beyond cancer, chronic arsenic exposure is associated with:

Cardiovascular disease: Increased risk of heart disease, stroke, and peripheral vascular disease.

Diabetes: Some evidence links arsenic exposure to diabetes risk.

Hypertension: Association with elevated blood pressure.

These effects occur at exposure levels lower than those causing cancer, making them relevant for populations with moderate contamination.

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What Can Affect Arsenic Levels?

Sources of Arsenic Exposure

Drinking water: The most significant source for heavily exposed populations. Arsenic occurs naturally in groundwater in many regions. Private wells are unregulated and may contain high arsenic. Even some municipal supplies have detectable arsenic, though regulated below EPA limits.

Rice and rice products: Rice accumulates arsenic from soil and water. Products made from rice — rice cereal, rice milk, rice flour, rice syrup, rice protein — concentrate this exposure. Brown rice typically contains more arsenic than white rice because arsenic concentrates in the bran layer.

Other foods: Apple juice (from arsenic-based pesticide legacy in orchards), some wines, certain vegetables (particularly those grown in contaminated soil), and chicken (historically, arsenic compounds were used in poultry feed — now mostly banned) can contribute to exposure.

Seafood: Fish and shellfish contain primarily organic arsenobetaine, which is non-toxic. However, some seafood (especially seaweed, mussels, and certain fish) can contain inorganic arsenic or other organic forms that metabolize to compounds measured as arsenic. Seafood consumption before testing can dramatically elevate total arsenic while posing little health risk.

Occupational exposure: Smelting, glass manufacturing, semiconductor production, wood preservation (CCA-treated lumber), pesticide manufacturing and application, and mining involve potential arsenic exposure.

Pressure-treated wood: Wood treated with chromated copper arsenate (CCA) for decay resistance was widely used until 2003 for residential purposes. Old decks, playgrounds, and fences made from CCA wood can release arsenic, particularly when weathered.

Traditional medicines: Some traditional Chinese, Indian, and other cultural medicines contain arsenic compounds deliberately.

Factors Affecting Arsenic Metabolism

Genetics: Genetic variations in arsenic-metabolizing enzymes (particularly AS3MT) affect how efficiently individuals methylate and excrete arsenic. “Poor methylators” retain arsenic longer and may be more susceptible to toxicity.

Nutritional status: Folate and other B vitamins are required for arsenic methylation. Deficiency impairs arsenic metabolism and excretion. Adequate nutrition provides some protection.

Protein intake: Amino acids (particularly methionine and cysteine) support arsenic excretion. Low protein intake may impair arsenic elimination.

Why Levels May Be Elevated Without Toxic Exposure

Recent seafood consumption: The most common cause of elevated total arsenic in people without toxic exposure. Organic arsenobetaine from fish and shellfish is rapidly excreted in urine but will spike total arsenic measurements. Speciated testing distinguishes this from dangerous inorganic exposure.

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Understanding Your Results

Interpreting Urine Arsenic

Interpretation depends critically on whether the test is total arsenic or speciated arsenic.

Total urine arsenic: Elevated results require follow-up speciation to determine the source. High total arsenic after seafood consumption is usually benign arsenobetaine. High total arsenic without recent seafood suggests inorganic exposure requiring attention.

Speciated urine arsenic: The key values are inorganic arsenic plus its metabolites (MMA and DMA). This sum reflects toxic inorganic arsenic exposure. Elevated levels warrant source investigation (water, diet, occupation) and exposure reduction. Arsenobetaine (seafood-derived) is reported separately and is not a health concern.

Timing considerations: Arsenic is rapidly excreted — urine reflects exposure over the preceding 2-4 days. A single normal result doesn’t exclude intermittent exposure. A single elevated result could reflect transient exposure. Multiple specimens or 24-hour collection improves accuracy.

What Elevated Results Mean

Elevated inorganic arsenic or its metabolites indicates exposure that should be investigated and reduced:

Identify the source: Test well water if using private well. Review dietary patterns (rice consumption, apple juice, other sources). Consider occupational exposure. Think about traditional medicines or supplements.

Reduce exposure: Install water treatment if water is contaminated (reverse osmosis and certain other systems remove arsenic). Reduce rice consumption or choose lower-arsenic varieties/preparation methods. Address occupational or other identified sources.

Follow-up testing: Retest after exposure reduction to confirm levels have declined.

Medical evaluation: Significantly elevated levels warrant medical assessment for signs of arsenic toxicity and monitoring of potentially affected systems.

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Health Connections

Cancer

Skin cancer: Chronic arsenic exposure causes characteristic skin changes (hyperpigmentation, keratoses) that can progress to squamous cell carcinoma.

Lung cancer: Arsenic is a known lung carcinogen whether inhaled or ingested. Risk adds to that from smoking.

Bladder cancer: Strong association with arsenic in drinking water. One of the most consistently observed arsenic-cancer relationships.

Cardiovascular Disease

Heart disease and stroke: Chronic arsenic exposure is associated with increased cardiovascular mortality, including coronary heart disease and stroke. Mechanisms may include oxidative stress, inflammation, and effects on vascular function.

Peripheral vascular disease: “Blackfoot disease” — severe peripheral vascular disease causing gangrene — was described in highly arsenic-exposed populations in Taiwan.

Diabetes and Metabolic Effects

Diabetes risk: Epidemiological studies link arsenic exposure to increased diabetes risk, potentially through effects on insulin signaling and pancreatic beta cells.

Neurological Effects

Peripheral neuropathy: Arsenic causes peripheral nerve damage with numbness, tingling, and weakness, particularly with higher-level exposure.

Cognitive effects: Children exposed to arsenic may show cognitive deficits. Adult neurological effects at lower exposures are less well characterized.

Skin Changes

Arsenical keratoses: Characteristic rough, scaly patches on palms and soles that are a hallmark of chronic arsenic exposure and can be precursors to skin cancer.

Hyperpigmentation: “Raindrop” pigmentation pattern is another characteristic skin finding.

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Why Regular Testing Matters

Routine arsenic screening isn’t needed for most people. However, specific situations warrant testing:

Private well users: If you drink water from a private well, especially in areas with known groundwater arsenic, testing yourself (or your water) is prudent. This is particularly important if the well has never been tested for arsenic.

High rice consumers: Those eating rice as a staple food, following strict gluten-free diets, or consuming significant rice-based products may benefit from testing to assess cumulative exposure.

Occupationally exposed workers: Biological monitoring as part of workplace health programs.

People with suggestive symptoms: Unexplained peripheral neuropathy, characteristic skin changes, or other symptoms consistent with arsenic exposure warrant testing.

Residents of high-arsenic areas: People living in regions with known elevated environmental arsenic may benefit from periodic assessment.

After elevated levels found: Follow-up testing confirms that exposure reduction efforts have successfully lowered arsenic levels.

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Related Biomarkers Often Tested Together

Lead — Another toxic heavy metal often evaluated when environmental contamination is a concern. Different sources but sometimes co-occurring.

Mercury — A toxic metal with different primary sources (fish for methylmercury). Often included in heavy metal panels.

Cadmium — Toxic metal from smoking and certain occupational/environmental exposures. May be included in comprehensive panels.

Creatinine — Used to adjust urine arsenic results for urine concentration. Spot urine arsenic is typically reported both as concentration and per gram creatinine.

Complete Blood Count — Arsenic can cause bone marrow suppression with cytopenias. CBC assesses for these effects with significant exposure.

Liver Function Tests — The liver is involved in arsenic metabolism and can be affected by toxicity.

Note: Information provided in this article is for educational purposes and doesn’t replace personalized medical advice.