1. Arsenic in Livestock Well Water on the Diné Reservation
Clarita Lefthand, Ph.D. Student University of Washington
Some Data presented here was obtained from the Navajo EPA

2. Prevalence of Arsenic and Some Background

3. Naturally occurring element in bedrock Have no smell and no taste.
Difficult to tell if arsenic is present in food, water, or air

4. 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

5. Counties with arsenic concentrations exceeding MCL in 10% or more groundwater samples.

6. 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

7. Hauled Drinking Water Sources
Livestock Well
30%
Chapter House
22%
Natural Spring
11%
Did Not Specify
37%
or “Other”
Nresponses= 94 (Ntotal=296)
Multiple sources could be used by same individual

9. Assessment of arsenic in Unregulated Drinking Water Sources

10. Hazard Identification

11. Water Soluble Arsenic Species
Arsenate: As (III) and Arsenite: As (V)
are the dominant species in water.

12. Organic Arsenic Less toxic than inorganic As
April 19, 2017
Organic Arsenic
Less toxic than inorganic As
Produced by biomethylation
Microorganisms in soil and water
Humans detoxify organic As
A Small Dose of Toxicology - Overview

13. Mode of Action Cancer: Non-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

14. Toxicokinetics

15. Absorption Absorption
Soluble forms are well absorbed in the GIT by humans
60%-90%
Animals – 50%
Insoluble forms
Limited absorption

16. 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

17. Metabolism of Inorganic Arsenic
April 19, 2017
Metabolism of Inorganic Arsenic
Ar undergoes methylation to less toxic metabolites
As5+ (Arsenate)
As3+ (Arsenite)
Methylarsenite (liver)
Dimethylarsenite
(readily eliminated – urine)
A Small Dose of Toxicology - Overview

18. Excretion
Half-life= 3-5 days
Primarily via urine

19. 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.
Skin, bladder cancer and possibly lung cancer
Birth defects and reproductive problems
Hyperpigmentation

20. 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

21. Exposure Assessment

22. 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

23. Exposure among 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

24. Ar Concentrations Measured in Diné Communities
Community
Concentration of Arsenic (mg/L)
Sweetwater (09T-592)
0.026
Red Mesa (9T-538)
0.05
Lower Greasewood
0.17
A lot of communities
~0.02

25. Standards for Arsenic in Drinking Water
Agency
Level
Comments
World Health Organization (WHO)
0.01mg/L is the allowable concentration
Inorganic arsenic is a documented human carcinogen.
Environmental Protection Agency
(EPA)
mg/ml is the maximum contaminant level
-- zero mg/ml is the MCLG
-- RfD=0.3 ug/kg/day
EPA’s 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

26. 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

27. Exposure Assessment Ingestion =0.17 mg/L*0.927L/day = 70 kg
Ingestion= mg/kg/day
EPA RfD=0.3 ug/kg/day= mg/kg/day
The average adult person’s exposure is 8 times higher than the EPA’s RfD

28. 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?

30. Precautionary Assessment
Community/Social Issues
Exposure Issues
Hazard/Toxicity

31. Precautionary Assessment Community/Social Issues
A score of 13 suggests that at present there is very little support for health or community
Parameter
Score
Goal 2
Need 3
Future Generations
Democratic Community Based Process
Alternatives
Total
13/15
Note: Please see end of presentation for more detailed information about Evaluation Scores

32. Precautionary Assessment Exposure Issues
A score of 16 suggests that there is an exposure problem that presents concerns to the community
Parameter
Score
Exposure 3
Multiple Exposures
Children Exposed 5
Consumer Products (Sheep Meat) 2
Occupational Exposure 1
Food Exposure
Total
16/20
Note: Please see end of presentation for more detailed information about Evaluation Scores

33. Precautionary Assessment Hazard/Toxicity
A score of 27 suggest that there is a significant hazard that present a serious concern
Parameters
Score
Hazard 10
Individual Sensitivity 3
Ecological Hazard 2
Volume 5
Persistent
Bioaccumulate 1
Uncertainty
Total
27/30
Note: Please see end of presentation for more detailed information about Evaluation Scores

34. Conclusions Exposure Assessment
Ingestion= mg/kg/day
EPA RfD= 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

35. 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

36. Risk Management Remediation Point of use: daily consumption of water
Would need to be modified for water haulers!

37. Risk Management Remediation Point of use: daily consumption of water
Would need to be modified for water haulers!

38. 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

39. 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

40. References NRDC EPA Toxmetal
EPA
Toxmetal

41. Precautionary Assessment Community / Social Issues
April 19, 2017
Precautionary Assessment Community / Social Issues
Community / Social Issues
 Score
Evaluate effects on the community and related social issues.
Goal
1-3
1-a lot, 2-some, 3-little. Does this move forward the goal of human and environmental health?
Need
1-a lot, 2-some, 3-little or not sure. Ask the question: Is it necessary? Do we really need this?
Future Generations
1-little, 2-some, 3-high impact. Is there a potential impact on future generations of humans and other species?
Democratic, community based process
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.
Alternatives
1-alternatives were carefully considered, 2-some consideration, 3-no consideration. Where alternatives considered?
Total
5-15
5-good, supportive of health and community 15-poor, not supportive of health or community
A Small Dose of Toxicology - Overview

42. Precautionary Assessment Exposure
April 19, 2017
Precautionary Assessment Exposure
Exposure Issues
Score 
Evaluate Potential Exposure Issues
Exposure
0-3
0-none, 1-little, 2-some, 3-high. Do we have control over the exposure?
Multiple exposures
0-none, 1-little, 2-some, 3-high. Is there exposure to other chemicals with similar hazard?
Children exposed
0,3,5
0-none, 3-little, 5-some or high or don't know. Children are often more vulnerable. Are children being exposed.
Consumer products
0-not in consumer products, 1-little, 2-some, 3- a lot or do not know. Is this compound in consumer products?
Occupational exposure
0-no occupational exposure, 1-little, 2-some, 3- a lot or do not know. Is there occupational exposure?
Food exposure
0-not in food supply, 1-little, 2-some, 3- a lot or do not know. Is the compound present in the food supply.
Total
0-20
0-no exposure, no problems 20-significant exposure, serious concern
A Small Dose of Toxicology - Overview

43. Precautionary Assessment
April 19, 2017
Precautionary Assessment
Hazard / Toxicity
 Score
Evaluate Potential Hazards
Hazard
1,5,10
1-low, 5-some, 10-high. Follow classical hazard evaluation, pick endpoint, exam relevant quality studies (cancer, reproductive, neurotoxicity, irreversible)
Individual Sensitivity
1-3
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 hazard
1-little 2-some, 3-a lot. Is it a hazard to other species or the environment?
Volume
1-5
how much is produced (1=research only, 2=<1000 lbs, 3=<10,000, 4=<100,000, 5=>100,000 or do not know)
Persistent
1-little persistence 2-some, 3-a lot of persistence or do not know. Is the compound persistent in the environment?
Bioaccumulate
1-little 2-some, 3-a lot. Does it bioaccumulative in humans or animals or move up the food chain?
Uncertainty
1-little 2-some, 3-a lot. How certain is the information?
Total
7-30
7-low hazard 30-significant hazards or unknowns, serious concern
A Small Dose of Toxicology - Overview