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Arsenic in the Environment: Health Effects and Risk Assessment

Arsenic in the Environment: Health Effects and Risk Assessment. Charles O. Abernathy, Ph.D. Toxicologist, Office of Water US EPA Washington, DC. Characteristics Sources Uses. Arsenic Characteristics. Most natural waters contain inorganic species

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Arsenic in the Environment: Health Effects and Risk Assessment

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  1. Arsenic in the Environment: Health Effects and Risk Assessment Charles O. Abernathy, Ph.D. Toxicologist, Office of Water US EPA Washington, DC

  2. Characteristics Sources Uses

  3. Arsenic Characteristics • Most natural waters contain inorganic species • As (III) or arsenite predominant in ground waters H3AsO3 • As (V) or arsenate in surface waters H2AsO4 & HAsO4-2

  4. Crystalline Rock Soil Ground Water Surface Water Avg. 2 ppm 1-40 ppm 0.01 – 800 ppb As high as 40,000 in hot springs 2.38 – 65 ppb As high as 22,000 in river water Natural Arsenic Levels

  5. Some Arsenic Uses/Anthropogenic Sources • Smelting of metals • Pharmaceutical industry (medicines) • Pesticide manufacture (very limited) • Wood preservative – CCA [in phase out] • Cattle and sheep dips • Feed additives • Dye stuffs • Petroleum, coal, and wood burning • Semiconductor manufacture • Waste incineration

  6. Toxicokinetics

  7. Toxicokinetics • Absorption • Soluble forms • Humans – 40 % to complete absorption • Animals – 50% to complete absorption • Insoluble forms • Limited absorption

  8. Toxicokinetics cont. • Distribution • Found in all humans – Blood conc. (1-5 ppb) • Smokers (2 – 10 ppb) • Occupational exposure (10 ppb) • Taiwan (20 – 60 ppb) • Poisonings (1,000 – 2,000 ppb)

  9. Distribution • Highest levels (ppb) • Nails (0.89) • Hair (0.18) • Bone (0.07 – 0.12) • Heart, kidney, liver, lung (0.03 – 0.05)

  10. SAM SAH SAM SAH SAM SAH Metabolism of Inorganic Arsenic iAs5 Reduction Methylation iAs3 MAs5 MAs3 DMAs5 DMAs3 TMAs5 TMAs3

  11. Excretion • Primarily via urine • 60% - 95% in 5 days • Fecal excretion low

  12. Adverse Health Effects Non-Cancer

  13. Animal Rats Mice Guinea pigs Humans LD50 (mg/kg) 15 - 293 26 - 43 9 1 - 4 (approx) Acute Toxicity

  14. Acute Effects – Humans(est. LD50  1-4 mg/kg) • Peripheral neuropathy • Anemia • Renal and liver dysfunction • Skin pigmentation • EKG abnormalities • Severe GI effects

  15. Chronic Toxicity: HumansVascular • Taiwan • Blackfoot disease • Poland • Vintners • 6 cases of gangrene • Chile • Raynaud’s disease

  16. Chronic Toxicity: Humans • Nervous system • Peripheral neuropathy – legs and arms • Cranial nerves • Loss of hearing in Japanese infants

  17. Adverse Health Effects Cancer

  18. Countries Reporting Tumors After Arsenic Exposure • Taiwan • Mexico • Argentina • Chile • China • Mongolia • Japan

  19. Cancers Associated with Exposure to Arsenic in Drinking Water • Skin • Bladder • Lung • Kidney • Liver • Prostate

  20. MCL LED01 ED01 50 300 - - Margin of Exposure - - (MOE) Lifetime Risk of Cancer (per 1000) ED01 = Effective dose (central estimate) at which 1% of population is affected by the contaminant LED01 = Lower limit of range with 95% certainty of being the effective dose for 1% MOE = Ratio of LED01 divided by MCL option (300/50) = 6 Point of Departure (PoD)

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