Arsenic

Arsenic is a natural component of the earth’s crust and is widely distributed throughout the environment in the air, water and land. It is highly toxic in its inorganic form and considered a carcinogenic heavy metal.

People are exposed to elevated levels of inorganic arsenic through:

• drinking contaminated water
• using contaminated water in food preparation
• irrigation of food crops
• industrial processes
• eating contaminated food
• smoking tobacco

Long-term exposure to inorganic arsenic, mainly through drinking-waterand food, can lead to chronic arsenic poisoning. Skin lesions and skin cancer are the most characteristic effects.

Other specific sources:

• Rice (Rice accumulates ten times more arsenic than other grains)
• Rat poisons
• Automobile exhaust
• Household detergents
• Wood preservatives
• Insecticide residues on fruits and vegetables
• Wine (if arsenic in pesticides used)
• Colored chalk
• Wallpaper dye and plaster
• Drinking water
• seawater
• well water
• Sewage disposal
• Seafood (source of nontoxic arsenic)
• Chicken

Symptoms & effects:

Exposure to arsenic-laden drinking water can induce symptoms of gastroenteritis and lead to cancer, diabetes, and neurological and vascular dysfunction. Long-term arsenic exposure in drinking water shows a dose-response relationship to carotid atherosclerosis. The mechanism involves the induction of expression of genes coding inflammatory mediators.

Arsenic has also been linked to dermatosis and cancers of the skin, bladder, and lung.

Clinical symptoms:

Arsenic exposure is associated with the following clinical symptoms:

• Neurological: Central depression with visual effects, headache and high fever
• Hematological: Abnormal RBC counts, increased megalocytes and microcytes
• GI tract: Increased peristalsis with “rice water” stools
• Skin: “Milk and roses” complexion from vasodilation, darkening and degeneration

Toxic versus non-toxic and seafood:

Laboratory values of arsenic represent both the toxic form of arsenic and the non-toxic form of arsenic. Because seafood is rich in the non-toxic form of arsenic, the clinician should rule out ingestion of seafood in cases of borderline or moderate arsenic elevation before implementing aggressive therapy.

Urinary arsenic:

Urinary arsenic is most commonly measured to screen for arsenic exposure. Urine reflects arsenic exposure in the few days prior to specimen collection. To eliminate the contribution of seafood to total arsenic levels, avoid seafood 72 hours before test.

Hair, nail and urinary arsenic levels have been shown to be comparable.

Hair/nail arsenic:

Hair or nail arsenic represents several months of exposure prior to taking the specimen. Hair arsenic greater than 1 μg/g dry weight has been taken to indicate excessive exposure.

Serum arsenic:

Since elevated arsenic in the serum drops within 6 to 10 hours, serum is not the best specimen for determining chronic arsenic exposure. Whole blood is suitable for identifying acute exposure to arsenic, and high levels should be addressed immediately.

References:

• https://www.who.int/news-room/fact-sheets/detail/arsenic
• https://emedicine.medscape.com/article/812953-overview
• https://www.atsdr.cdc.gov/csem/csem.asp?csem=1&po=11
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1742758/
• https://www.sciencedirect.com/science/article/pii/B978012418688000006X
• https://www.ncbi.nlm.nih.gov/pubmed/20056736
• https://www.ncbi.nlm.nih.gov/pubmed/21332098
• https://www.ncbi.nlm.nih.gov/pubmed/26025251
• https://www.ncbi.nlm.nih.gov/pubmed/26766512
• https://www.ncbi.nlm.nih.gov/pubmed/28233618