Special Topics

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Special Topics I. Selenium Ecotoxicology II. Arsenic in Drinking Water Principles of Environmental Toxicology Instructor: Gregory Möller, Ph.D. University of Idaho. Examine the chemistry of selenium in inorganic and organic molecules. Understand the role of seleno-amino acids in the expression of selenium toxicity in plant and animal systems. Examine chronic selenium toxicosis (selenosis). Understand the role of selenium in reproductive failure.

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Principles of Environmental Toxicology Learning Objectives • Examine the chemistry of selenium in inorganic and organic molecules. Special Topics • Understand the role of seleno-amino acids in the I. Selenium Ecotoxicology expression of selenium toxicity in plant and animal II. Arsenic in Drinking Water systems. • Examine chronic selenium toxicosis (selenosis). Principles of Environmental Toxicology • Understand the role of Instructor: Gregory Möller, Ph.D. selenium in reproductive University of Idaho failure. Principles of Environmental Toxicology Principles of Environmental Toxicology Learning Objectives Environmental Selenium • Sulfur analogue. • Describe the biogeochemical cycle of selenium. – sulfate/selenate. • Analyze environmental Se case studies. – sulfite/selenite. • Examine the regulatory and scientific issues involved in Se risk assessment. – sulfide/selenide. • Explore the occurrence of Arsenic in drinking water. – S(0)/Se(0). • Describe the US As regulatory changes – organic compounds. • Describe the clinical pathology of arsenicosis. • Essential trace element, toxic at • Examine the arsenic in drinking higher water public health emergency concentrations. in Bangladesh. Principles of Environmental Toxicology Principles of Environmental Toxicology Forms of Selenium Forms of Selenium, 2 Elemental Se0 Stable reducing Selenides (-II) Se2- Reducing environments. Selenium (0) environments; very Forms metal complexes; slow oxidation and highly immobile reduction Dimethylselenide (CH3)2Se Volatilization from soil bacteria and fungi Dimethyldiselenide (CH3)2Se2 Volatilization from plants Dimethylselenone (CH3)2SeO2 Volatile metabolite Hydrogen selenide H2Se Unstable moist air; decomposes to Se0 in water Seleno-amino acids Selenomethionine, Se-cysteine, Se- methyl-selenocysteine, Se-cystathionone Red Se(0) in a Se reducing bacteria culture. 1
Principles of Environmental Toxicology Principles of Environmental Toxicology Forms of Selenium, 3 Forms of Selenium, 4 Selenite (+IV) SeO32- Soluble form Selenate (+VI) SeO42- Se(VI) is stable in well-oxidized environments and very mobile in soils Trimethylselenomium (CH3)3Se+ Important urinary metabolite Selenic acid H2SeO4- Common in soils Selenous acid H2SeO3- Common in soils HSeO4- HSeO3- Selenium dioxide SeO2 Formed as a product of fossil fuel combustion Principles of Environmental Toxicology Principles of Environmental Toxicology Global Selenium Mobilization Distribution of Se (mg/kg) • Atmosphere. Terrestrial – Deposition to marine system; deposition to terrestrial Earth’s crust 0.09 system. Limestone 0.1 - 14.0 • Marine. – Volatilization; sea salt suspension; marine biota uptake; Shales and phosphate rk < 1 - 55 sediment deposition to land. Crude oil 0.06 - 0.39 • Terrestrial. Coal 0.5 - 11.0 – Volatilization; dust particles; river dissolved and particulates. Soils: • Anthropogenic Nonseleniferous < 0.1 - 2.0 – Mining; petroleum; irrigation. Seleniferous 2 - 200 Principles of Environmental Toxicology Principles of Environmental Toxicology Distribution of Se (mg/L) Distribution of Se (mg/kg) Aquatic Anthropogenic -4 -3 Ocean water 10 - 4x10 Petroleum products 0.15 - 1.65 -4 -4 River water 10 - 4x10 Fly ash 1.2 - 16.5 Aquatic plants 0.02 - 0.14 Sewage sludge 1.8 - 4.8 Plankton 1.1 - 2.4 Paper products 1.6 - 19.0 Fish 0.5 - 6.5 Aquatic Biota Criteria: 0.005 mg/L Drinking Water MCL: 0.050 mg/L 2
Principles of Environmental Toxicology Principles of Environmental Toxicology Se Cycling in Soils The Selenium Conundrum • Essential trace element for aerobes. Well aerated, alkaline Acid, poorly aerated – GSH-px (antioxidant); immune function. slow slow slow • Poor control response. Heavy metal Elemental Se Selenites Selenates selenides – Deficiency ↔ normal ↔ toxic ranges closer and less slow slow Se0 SeO32- SeO42- Se2- “controlled” than other essential trace elements. • Can do sulfur chemistry in biosynthesis. Organo-Se – Results in seleno-amino acids. Fe(OH)SeO3 – Disulfide bridges in protein Insoluble Insoluble complexes Plants tertiary structure now changed. (Insoluble) • Toxic at high enough levels. Leaching • Lentic vs. lotic aquatic systems. Microbial Interactions: Sulfate Reducing Bacteria • Species sensitivity variations. Principles of Environmental Toxicology Principles of Environmental Toxicology The Selenium Debates Receptors • Selenium is not usually essential to • Disagreement on impacts in different environmental plants but is for animals. systems. • Can substitute for sulfur in biochemical systems. – Lentic (ponds, lakes); lotic (streams, rivers) • Incorporated into amino acids and therefore can • Extrapolation of observations to low levels. form selenoproteins. • Interplay of required vs. toxic exposures. – Basis of plant and animal toxicity. • Precaution or overly conservative? • 1930s: Se levels in plants of interest because of grazing deaths in sheep and cattle. • Food chain bioconcentration observed. Principles of Environmental Toxicology Principles of Environmental Toxicology Se - Normal Plants Se - Adapted Plants Grown in the presence of Se Grown in the presence of Se Harborne Harborne S and Se separated No separation of S from Se Se S O Biosynthesis of Synthesis of non-protein S OH O O amino acid analogues NH2 Se O HSe OH OH Methionine NH2 NH2 Se OH O Selenomethionine + Selenocysteine NH2 Se-methylselenocysteine HS OH 1. Incorportation into protein NH2 O 2. Se — Se bridges less stable Cysteine HSe OH than S — S bridges NH2 Normal protein 3. Enzymes lose activity Selenohomocysteine synthesis 4. Death of plant No toxic side effects 3
Principles of Environmental Toxicology Principles of Environmental Toxicology Case Study: Belews Lake, NC Belews Lake Observations • Man-made reservoir; coal-fired • Elevated rates of fish terata (10-70%). power plant. • Some reaches w/ 95% of California wetlands have disappeared in the last century. in aquatic birds and ducks – Monitored for biological caused great public outcry. productivity; chemical contamination. – “The Poisoning of the West” • Observation of reproductive failure in aquatic birds and ducks. Principles of Environmental Toxicology Principles of Environmental Toxicology Kesterson Observations, 1 Kesterson Observations, 2 Stilts Coot Ohlendorf Ohlendorf 4
Principles of Environmental Toxicology Principles of Environmental Toxicology Kesterson Observations, 3 Kesterson Observations, 4 Mallard Coot Ohlendorf Ohlendorf Principles of Environmental Toxicology Principles of Environmental Toxicology Case Study: Selenium and Phosphate Mining Phosphate Mining in Idaho USGS • Considered, a clean strip mining operation where phosphoria layers are removed and overburden waste rock and soil is replaced. Principles of Environmental Toxicology Principles of Environmental Toxicology Chronic Selenosis Geochemistry • Waste rock contains Chert, Limestone and Siltstone (Shale) • Se primarily associated with the siltstone • Pyrite micro grains ~0.1-6% Se 5
Principles of Environmental Toxicology Principles of Environmental Toxicology Arsenic in Drinking Water Mining Challenges • Control of Se release. • Animal management. • Control at historical mining sites. • Monitoring of impact. Principles of Environmental Toxicology Principles of Environmental Toxicology Natural Occurrence of As Anthropogenic Sources • In rock: especially iron ores and • In soil and water: sources include pesticides and magmatic sulfides. wood preservatives. • In sediments, soils and water: • Anthropogenic activities can speed dissolution results from mineral dissolution. from parent rock and introduction to water • Anionic in solution: As(V) As(III) Principles of Environmental Toxicology Principles of Environmental Toxicology Health Effects, Chronic Health Effects - Acute • 50 to 300 mg of inorganic As fatal to • As builds up in tissues - humans. skin, hair • Gastrointestinal injuries, kidney damage. • Melanosis, keratosis, • Circulatory collapse, respiratory failure. unusual pigmentation • Lesions, vascular system • Industrial exposures damage – mining, agriculture • Skin, lung, bladder, lymph • Environmental exposures – water, diet, treated wood, glands, kidney, prostate, Paris Green and liver cancers • Intentional exposures – arsenical drugs Evidence for damage to central nervous system 6
Principles of Environmental Toxicology Principles of Environmental Toxicology As en México y América del Sur Arsenic: Common Drinking Water Contaminant • US, Taiwan, Chile, Mexico, Argentina, • Mucha gente ha Bangladesh, India… sufrido en el mundo latino también. • WHO drinking water standard 10 ug/L • Especialmente en • Many countries, especially the less México Chile, donde el agua industrialized, maintain a 50 ug/L standard contiene una parte por • US standard: 50 ug/L millón. changing to • La mayoría de lugares 10 ug/L Chile ahora tienen (compliance by 2006). tratamiento para arsénico. Argentina Principles of Environmental Toxicology Principles of Environmental Toxicology U.S. Arsenic Regulation (past) US Arsenic Regulation (present) • EPA’s new MCL was 10 µg/L • As is a Class A, known human carcinogen. (Jan. 22, 2001) – 1-2 in 1000 risk (1 in 100?) at 50 ug/L. – Same level specified by WHO – As was listed before 1987, and had no BAT. – Below this food becomes the predominant • As MCL was 50 µg/L. source – BAT’s were named • Bush administration suspends new rule (March, 2001) • New rule promulgated October 2001 Principles of Environmental Toxicology Principles of Environmental Toxicology As in the United States US Public Water Systems (PWSs) As level Large Small As µg/L % PWSs exceeded PWSs PWSs 1 36 50 µg/L 58 200 2 25 10 µg/L 508 1542 5 14 10 8 Large PWSs: >1000 people 20 3 Small PWSs:
Principles of Environmental Toxicology Principles of Environmental Toxicology Bangladesh Scope of the Bangladesh Problem An Arsenic in drinking water public health emergency. “With more than an estimated 20 million of its 126 million people assumed to be drinking contaminated water and another 70 million potentially at risk, Bangladesh is facing what has been described as perhaps the largest mass poisoning in history.” (World Bank) "Bangladesh makes the Chernobyl disaster look like a Sunday-school picnic." (R. Wilson, Harvard U.) Encarta Principles of Environmental Toxicology Principles of Environmental Toxicology Bangladesh – Public Health Concerns History of the Bangladesh Problem World Bank • In the early 1970s, most of Bangladesh's rural “The story beggars belief. In the 1970s, international population got its drinking water from surface ponds agencies headed by the United Nations Children’s Fund (UNICEF) began pumping millions of dollars of and nearly a quarter of a million children died each aid money into Bangladesh for tubewells to provide year from water-borne diseases. “clean” drinking water. According to the World Health – The provision of tubewell water for 97 percent of Organization, the rural population has been credited with bringing the direct result has been down the high incidence of the biggest outbreak of diarrheal diseases and mass poisoning in history. contributing to a halving of Up to half the country’s the infant mortality rate. tubewells, now estimated to number 10 million, are • Paradoxically, the same wells poisoned. Tens, perhaps that saved so many lives now hundreds of thousands will die.” pose a threat due to the (F. Pearce, UNESCO) unforeseen hazard of arsenic. Principles of Environmental Toxicology Principles of Environmental Toxicology Arsenic Water Contamination Levels Arsenic Lesions R. Wilson 8
Principles of Environmental Toxicology Principles of Environmental Toxicology Arsenic Lesions, Extreme Arsenic Lesions, Cancer R. Wilson R. Wilson Principles of Environmental Toxicology Principles of Environmental Toxicology Keratosis, Palm of a Patient Arsenic Lesions, Chest & Arms R. Wilson R. Wilson Principles of Environmental Toxicology Principles of Environmental Toxicology Arsenic Lesions on Feet, Cancer Gangrene Caused by Arsenic Poisoning R. Wilson R. Wilson 9
Principles of Environmental Toxicology Principles of Environmental Toxicology Portrait of Pinjira Begum and Her Daughter Bangladesh – Cultural/Social Factors • “The social consequences of the arsenic crisis are far- • Both died of arsenic W orld Bank reaching and tragic. related causes. – Because of illiteracy and lack of information, many confuse the skin lesions caused by arsenicosis with leprosy. • The most hard-hit villages where health problems have gripped a large population are treated much like isolated leper colonies. Within the community, arsenic-affected people are barred from social activities and often face rejection, even by immediate family members. – Women are unable to get married, and wives have been abandoned by their husbands. – Children with symptoms are not sent to school in an effort to hide the problem.” World Bank Principles of Environmental Toxicology Principles of Environmental Toxicology Collection and Testing of Tubewell Water Coloring Tubewells After Testing • Green-safe, red-unsafe Principles of Environmental Toxicology Principles of Environmental Toxicology Home Water Treatment Chemical Treatment to Remove Arsenic 10
Principles of Environmental Toxicology Principles of Environmental Toxicology Harvesting Rainwater Governmental and Agency Control Measures • Immediate detection of the arsenicoses patients and ensure their treatment. • Find alternate sources of safe drinking water. • Find reasons of arsenic contamination in soil water. • Conduct health education campaigns encouraging people to avoid arsenic contaminated drinking water. • Training for health personnel. 11