Transcript of Arsenic in Livestock Well Water on the Diné Reservation Clarita Lefthand, Ph.D. Student University...
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- Arsenic in Livestock Well Water on the Din Reservation Clarita
Lefthand, Ph.D. Student University of Washington Some Data
presented here was obtained from the Navajo EPA
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- Prevalence of Arsenic and Some Background
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- Naturally occurring element in bedrock Have no smell and no
taste. Difficult to tell if arsenic is present in food, water, or
air
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- 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
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- Counties with arsenic concentrations exceeding MCL in 10% or
more groundwater samples.
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- 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
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- Hauled Drinking Water Sources N responses = 94 (N total =296)
Multiple sources could be used by same individual Livestock Well
30% Chapter House 22% Natural Spring 11% Did Not Specify 37%
Livestock Well Chapter House Natural Spring Did Not Specify or
Other
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- Hazard Identification
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- Water Soluble Arsenic Species
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- Organic Arsenic Less toxic than inorganic As Produced by
biomethylation Microorganisms in soil and water Humans detoxify
organic As
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- 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
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- Toxicokinetics
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- Absorption Soluble forms are well absorbed in the GIT by humans
60%-90% Animals 50% Insoluble forms Limited absorption
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- 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
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- As 5+ (Arsenate) As 3+ (Arsenite) Methylarsenite (liver)
Dimethylarsenite (readily eliminated urine) Metabolism of Inorganic
Arsenic Ar undergoes methylation to less toxic metabolites
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- Excretion Half-life= 3-5 days Primarily via urine
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- 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
persons risk of vascular and heart disease, type 2 diabetes,
reproductive and developmental disorders, low birth weights in
babies, neurological problems and lower IQs in children.
neurological, renal, cardiovascular, hematological, and testicular
effects.
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- 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
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- Exposure Assessment
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- 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
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- Exposure among Din 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 Din community, chronic exposure is
of concern
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- Ar Concentrations Measured in Din Communities
CommunityConcentration of Arsenic (mg/L) Sweetwater (09T-592)0.026
Red Mesa (9T-538)0.05 Lower Greasewood0.17 A lot of
communities~0.02
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- Standards for Arsenic in Drinking Water AgencyLevelComments
World Health Organization (WHO) 0.01mg/L is the allowable
concentration Inorganic arsenic is a documented human carcinogen.
Environmental Protection Agency (EPA) -- 0.01 mg/ml is the maximum
contaminant level -- zero mg/ml is the MCLG -- RfD=0.3 ug/kg/day
EPAs stated policy in setting MCLs for known human carcinogens has
the goal of ensuring that the MCL falls within the 1: 10,000 to 1:
million range
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- 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
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- 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 persons exposure is 8 times higher than the EPAs
RfD
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- 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 childrens or pregnant mothers Dose?
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- Precautionary Assessment Community/Social Issues Exposure
Issues Hazard/Toxicity
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- Precautionary Assessment Community/Social Issues ParameterScore
Goal2 Need3 Future Generations3 Democratic Community Based Process2
Alternatives3 Total13/15 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
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- Precautionary Assessment Exposure Issues ParameterScore
Exposure3 Multiple Exposures3 Children Exposed5 Consumer Products
(Sheep Meat)2 Occupational Exposure1 Food Exposure2 Total16/20
Note: Please see end of presentation for more detailed information
about Evaluation Scores A score of 16 suggests that there is an
exposure problem that presents concerns to the community
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- Precautionary Assessment Hazard/Toxicity ParametersScore
Hazard10 Individual Sensitivity3 Ecological Hazard2 Volume5
Persistent3 Bioaccumulate1 Uncertainty3 Total27/30 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
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- Conclusions Exposure Assessment Ingestion= 0.0023 mg/kg/day EPA
RfD=0.0003 mg/kg/day The average adult persons exposure is 8 times
higher than the EPAs 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 Din do not
strongly promote human health, a sustainable environment, and
poorly ensures that future generations of all species have an
opportunity to thrive
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- 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 Din
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
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- Risk Management Remediation Point of use: daily consumption of
water Would need to be modified for water haulers!
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- Risk Management Remediation Point of use: daily consumption of
water Would need to be modified for water haulers!
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- Risk Management Need plans that will extend water lines to Din
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
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- 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
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- References NRDC http://www.nrdc.org/water/drinking/qarsenic.asp
http://www.nrdc.org/water/drinking/qarsenic.asp EPA
http://www.epa.gov/safewater/arsenic/index.htm l
http://www.epa.gov/safewater/arsenic/index.htm l Toxmetal
http://www.dartmouth.edu/~toxmetal/research/ projects/Arsenic.html
http://www.dartmouth.edu/~toxmetal/research/
projects/Arsenic.html
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- Precautionary Assessment Community / Social Issues Community /
Social Issues Score Evaluate effects on the community and related
social issues. Goal1-3 1-a lot, 2-some, 3-little. Does this move
forward the goal of human and environmental health? Need1-3 1-a
lot, 2-some, 3-little or not sure. Ask the question: Is it
necessary? Do we really need this? Future Generations1-3 1-little,
2-some, 3-high impact. Is there a potential impact on future
generations of humans and other species? Democratic, community
based process1-3 1-a lot of community involvement and consultation,
2-some, 3-little. Was the community consulted early and often in
the process? Was the process democratic and inclusive.
Alternatives1-3 1-alternatives were carefully considered, 2-some
consideration, 3-no consideration. Where alternatives considered?
Total5-15 5-good, supportive of health and community 15-poor, not
supportive of health or community
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- Precautionary Assessment Exposure Exposure IssuesScore Evaluate
Potential Exposure Issues Exposure0-3 0-none, 1-little, 2-some,
3-high. Do we have control over the exposure? Multiple exposures0-3
0-none, 1-little, 2-some, 3-high. Is there exposure to other
chemicals with similar hazard? Children exposed0,3,5 0-none,
3-little, 5-some or high or don't know. Children are often more
vulnerable. Are children being exposed. Consumer products0-3 0-not
in consumer products, 1-little, 2-some, 3- a lot or do not know. Is
this compound in consumer products? Occupational exposure0-3 0-no
occupational exposure, 1-little, 2-some, 3- a lot or do not know.
Is there occupational exposure? Food exposure0-3 0-not in food
supply, 1-little, 2-some, 3- a lot or do not know. Is the compound
present in the food supply. Total0-20 0-no exposure, no problems
20-significant exposure, serious concern
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- Precautionary Assessment Hazard / Toxicity ScoreEvaluate
Potential Hazards Hazard1,5,10 1-low, 5-some, 10-high. Follow
classical hazard evaluation, pick endpoint, exam relevant quality
studies (cancer, reproductive, neurotoxicity, irreversible)
Individual Sensitivity1-3 1-little 2-some, 3-a lot. Determine if
any individuals are more sensitive than health adult such as the
very young or old. Ecological hazard1-3 1-little 2-some, 3-a lot.
Is it a hazard to other species or the environment? Volume1-5 how
much is produced (1=research only, 2= 100,000 or do not know)
Persistent1-3 1-little persistence 2-some, 3-a lot of persistence
or do not know. Is the compound persistent in the environment?
Bioaccumulate1-3 1-little 2-some, 3-a lot. Does it bioaccumulative
in humans or animals or move up the food chain?
Uncertainty1-31-little 2-some, 3-a lot. How certain is the
information? Total7-30 7-low hazard 30-significant hazards or
unknowns, serious concern
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