Arsenic
The bad news is that arsenic is really highly toxic even in small doses. The good news is that it does not accumulate within the body and is excreted within 10 hours. Even with such a brief window of activity is can cause cell disruption, damage and death.
Ways Arsenic Is Absorbed by the Human Body
- Ingestion: The primary route for arsenic absorption is through ingestion, especially from contaminated food (such as rice, grains, and seafood) and drinking water. Soluble arsenic compounds are rapidly and extensively absorbed from the gastrointestinal tract—up to 95% of ingested soluble trivalent arsenic is absorbed
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- Inhalation: Arsenic can be absorbed through the lungs when inhaled as dust or fumes, particularly in occupational settings. The extent of absorption depends on particle size and solubility in lung fluids
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- Dermal (skin) absorption: Absorption through the skin can occur, but it is not a major route compared to ingestion and inhalation
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Toxicity and Mechanisms
- Oxidative stress: Arsenic generates reactive oxygen species, leading to cellular damage.
- Disruption of cellular metabolism: Interferes with energy production by uncoupling oxidative phosphorylation and inhibiting enzymes.
- DNA damage and epigenetic changes: Causes DNA strand breaks, mutations, and alters gene expression through methylation.
- Impaired glucose metabolism: Affects insulin secretion and glucose uptake, contributing to diabetes risk
- Interference with cell signaling: Disrupts pathways involved in cell growth and apoptosis.
Accumulation and Elimination
- Arsenic does not accumulate significantly in most tissues for long periods. The half-life of inorganic arsenic in humans is about 10 hours, and most (about 70%) is excreted in urine within a few days after exposure
- Some arsenic may persist longer in hair and nails, which can serve as biomarkers of past exposure
- Arsenic undergoes methylation in the liver, producing metabolites that are excreted in urine
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Diseases and Health Effects
- Skin lesions: Hyperpigmentation, keratosis, and skin cancers.
- Cancer: Increased risk of skin, lung, bladder, and kidney cancers.
- Cardiovascular disease: Hypertension, atherosclerosis, and heart disease.
- Neurological effects: Peripheral neuropathy, cognitive deficits (especially in children).
- Diabetes: Impaired glucose metabolism and increased risk of type 2 diabetes
- Liver and kidney damage: Hepatotoxicity and nephrotoxicity.
Safe Levels
- Drinking water: The World Health Organization (WHO) guideline is 10 μg/L for arsenic in drinking water.
- Dietary exposure: There is no universally accepted “safe” level, but regulatory agencies monitor and set limits based on risk assessment.
- Biomarkers: Urinary arsenic is the best indicator of recent exposure. Blood arsenic is only useful for acute or recent high-level exposures
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Summary Table
| Pathway | Absorption Rate/Notes | Main Accumulation Sites | Key Health Effects |
|---|---|---|---|
| Ingestion | Up to 95% (soluble forms) | Liver (metabolism) | Cancer, skin, diabetes |
| Inhalation | Depends on particle/solubility | Lungs, liver | Lung disease, cancer |
| Dermal | Minor | Local, rare | Rare, local irritation |
Arsenic is a significant toxicant, with ingestion and inhalation being the main routes of exposure. While it is rapidly excreted, chronic exposure can lead to serious health effects, especially cancer and metabolic disorders. There is no completely safe level, but regulatory limits aim to minimize risk
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