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Arsenic in Livestock Well Water on the Din é Reservation. Clarita Lefthand, Ph.D. Student University of Washington Som e Data presented here was obtained from the Navajo EPA . Prevalence of Arsenic and Some Background. Naturally occurring element in bedrock
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Arsenic in Livestock Well Water onthe Diné Reservation Clarita Lefthand, Ph.D. Student University of Washington Some Data presented here was obtained from the Navajo EPA
Naturally occurring element in bedrock • Have no smell and no taste. • Difficult to tell if arsenic is present in food, water, or air
Anthropogenic Sources • Smelting of metals • Pharmaceutical industry (medicines) • Pesticide manufacture (very limited) • Wood preservative • Cattle and sheep dips • Petroleum, coal, and wood burning • Waste incineration
Counties with arsenic concentrations exceeding MCL in 10% or more groundwater samples.
Some Current Sampling Data • Of 199 sources tested for inorganic compounds: • 44 (22%) exceeded one or more of the primary drinking water standards • The most frequent exceedance was arsenic (24 [12%] sources) followed by uranium (9 [5%] sources). The highest arsenic level was 190ug/L • Of 188 water sources tested for bacteria: • 40 (21%) were positive for E. coli and • 144 (77%) were positive for total coliforms
Livestock Well 30% Did Not Specify 37% Livestock Well Chapter House Natural Spring Did Not Specify or “Other” Chapter House Natural Spring 22% 11% Hauled Drinking Water Sources • Nresponses= 94 (Ntotal=296) • Multiple sources could be used by same individual
Organic Arsenic • Less toxic than inorganic As • Produced bybiomethylation • Microorganisms in soil and water • Humans detoxify organic As
Mode of Action • Cancer: • The most accepted explanation of the mode of action for Ar carcinogenicity is that it induces chromosomal abnormalities without interacting directly with DNA • Non-cancer: • Ar has inhibitory effects cellular respiration at the level of the mitochondrion. • Oxidative stress might also have an important role in both cancer and non-cancer effects
Absorption • Absorption • Soluble forms are well absorbed in the GIT by humans • 60%-90% • Animals – 50% • Insoluble forms • Limited absorption
Distribution • After absorption Ar initially accumulates in the • Nails • Hair • Bone • Kidney, liver, lung • Binds to sulfhydryl containing proteins - concentrates in the hair and fingernails
Metabolism of Inorganic Arsenic Ar undergoes methylation to less toxic metabolites As5+ (Arsenate) As3+ (Arsenite) Methylarsenite(liver) Dimethylarsenite (readily eliminated – urine)
Excretion • Half-life= 3-5 days • Primarily via urine
Health Effects of Chronic Ingestion Cancers: Bladder, kidney, liver and skin cancers: drinking water Lung cancer caused from inhalation Non-Cancer Endpoints: Blackfoot disease Increases a person’s risk of vascular and heart disease, type 2 diabetes, reproductive and developmental disorders, low birth weights in babies, neurological problems and lower IQ’s in children. neurological, renal, cardiovascular, hematological, and testicular effects.
Epidemiology Studies • Taiwan: The most studied area • Chile: • Argentina: • In these studies chronic exposure was determined to cause bladder, lung and skin cancer • [Ar] were several hundred micrograms per liter • EPA cancer risk assessment has used the cancer data from SW Taiwan (primarily bladder cancer cases in the Blackfoot-Disease endemic area) to predict the cancer risk from arsenic in drinking water in the USA
Routes of Exposure • Ingestion – The most important route of exposure because it does the most damage • Skin Contact – Also a very important route of exposure • Inhalation– A minor pathway of exposure
Exposureamong Diné Communities • In this assessment we are primarily concerned with ingestion of Ar • Current data suggest that exposure occurs mainly from the ingestion of arsenic through contaminated livestock well water • Adverse health effects depend on dose, duration of exposure, and the nutritional state of exposed populations • In the case of the Diné community, chronic exposure is of concern
Exposure Assessment • Ingestion (mg/kg/day) =(C*IR*ED*EF) BW*AT • C: Concentration = 0.17 mg/L • IR: Ingestion Rate =0.927L/day • ED:Exposure Duration = 75 yr • EF: Exposure Frequency= 365 days/yr • BW: Body Weight= 70 kg • AT:Averaging time= 75 yr*365 day=27,375 d
Exposure Assessment • Ingestion =0.17 mg/L*0.927L/day = 70 kg • Ingestion= 0.0023 mg/kg/day • EPA RfD=0.3 ug/kg/day=0.0003 mg/kg/day • The average adult person’s exposure is 8 times higher than the EPA’s RfD
Exposure Assessment Limitations • Other exposure questions that must be address include: • Is exposure from food ingestion possible? • Arsenic may also be released into the atmosphere from coal-fired power plants and incinerators because coal and waste products often contain some arsenic • Soil consumption by children • Moreover what about children’s or pregnant mother’s Dose?
Precautionary Assessment • Community/Social Issues • Exposure Issues • Hazard/Toxicity
Precautionary AssessmentCommunity/Social Issues A score of 13 suggests that at present there is very little support for health or community Note: Please see end of presentation for more detailed information about Evaluation Scores
Precautionary AssessmentExposure Issues A score of 16 suggests that there is an exposure problem that presents concerns to the community Note: Please see end of presentation for more detailed information about Evaluation Scores
Precautionary AssessmentHazard/Toxicity A score of 27 suggest that there is a significant hazard that present a serious concern Note: Please see end of presentation for more detailed information about Evaluation Scores
Conclusions • Exposure Assessment • Ingestion= 0.0023 mg/kg/day • EPA RfD=0.0003 mg/kg/day • The average adult person’s exposure is 8 times higher than the EPA’s RfD. • Precautionary Assessment • Community and Social Issues: 13/15 • Exposure Issues: 16/20 • Hazard and Toxicity: 27/30 • In essence the [Ar] present in well water on the Diné do not strongly promote human health, a sustainable environment, and poorly ensures that future generations of all species have an opportunity to thrive
Risk Management • Continue to monitor and sample for all the livestock wells • It would be useful to have a better understanding about other exposures: • i.e., Sheep meat, soil ingestion, and air contamination • Consider how the nutritional state of the exposed Diné population might impact individual health • Determine long-term strategies for for drinking water issues including those that extend beyond arsenic contamination • For example: fecal coliform and uranium; and lack of drinking water for future
Risk Management • Remediation • Point of use: daily consumption of water • Would need to be modified for water haulers!
Risk Management • Remediation • Point of use: daily consumption of water • Would need to be modified for water haulers!
Risk Management • Need plans that will extend water lines to Diné homes • Need to establish a safe water hauling point • Ask Community what they believe is the best approach to remediating water • If the community is not involved, funds may be used to create a solution that is not culturally viable
Risk Communication • Help educate the community who are directly impacted by contaminated water about their potential exposure to Arsenic and the adverse health risks • Arsenic in water is invisible, does not smell, and has no taste • Inform the community in a culturally appropriate way • Continue and encourage community involvement in the decision making process to clean up the well water or to find alternative water sources that are viable for the community
References • NRDC • http://www.nrdc.org/water/drinking/qarsenic.asp • EPA • http://www.epa.gov/safewater/arsenic/index.html • Toxmetal • http://www.dartmouth.edu/~toxmetal/research/projects/Arsenic.html
