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

Prevalence of Arsenic and Some Background

• Naturally occurring element in bedrock• They have no smell, and most have 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 188 water sources tested for bacteria:– 40 (21%) were positive for E. coli and – 144 (77%) were positive for total coliforms.

• 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

Hauled Drinking Water Sources

• Nresponses= 94 (Ntotal=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 HouseNatural SpringDid Not Specifyor “Other”

Hazard Identification

Water Soluble Arsenic Species

Organic Arsenic

• Less toxic than inorganic As• Produced by biomethylation

• Organisms 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.

• Noncancer:• Ar has inhibitory effects cellular respiration at the level

of the mitochondrion. • Oxidative stress might also have an important role in

both cancer and noncancer effects.

Toxicokinetics

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

As5+ (Arsenate)

As3+ (Arsenite)

Methylarsenite (liver)

Dimethylarsenite (readily eliminated – urine)

Metabolism of Inorganic ArsenicAr undergoes methylation to less toxic metabolites

Excretion

• Half-life= 3-5 days • Primarily via urine

– 60% - 95% in 5 days

Health Effects of Chronic IngestionCancers:

• 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.

Exposure Assessment

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

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.

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

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)

-- 0.01 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

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?

• Adverse health effects depend on dose, duration of

exposure, and the nutritional state of exposed populations.

Precautionary Assessment

• Community/Social Issues• Exposure Issues• Hazard/Toxicity

Precautionary AssessmentCommunity/Social Issues

Parameter Score

Goal 2

Need 3

Future Generations 3

Democratic Community Based Process 2

Alternatives 3

Total 13/15

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

Precautionary AssessmentExposure Issues

Parameter Score

Exposure 3

Multiple Exposures 3

Children Exposed 5

Consumer Products (Sheep Meat) 2

Occupational Exposure 1

Food Exposure 2

Total 16/20

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

Precautionary AssessmentHazard/Toxicity

Parameters Score

Hazard 10

Individual Sensitivity 3

Ecological Hazard 2

Volume 5

Persistent 3

Bioaccumulate 1

Uncertainty 3

Total 27/30

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

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

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

• 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– Whole house: 200 gallons water/day– Point of use: daily consumption of water

Risk Communication• Help educate the community who are directly impacted

by contaminated water about their potential exposure to Arsenic

• 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/p

rojects/Arsenic.html

Precautionary AssessmentCommunity / Social Issues

Community / Social Issues Score

Evaluate effects on the community and related social issues.

Goal 1-31-a lot, 2-some, 3-little. Does this move forward the goal of human and environmental health?

Need 1-31-a lot, 2-some, 3-little or not sure. Ask the question: Is it necessary? Do we really need this?

Future Generations 1-3

1-little, 2-some, 3-high impact. Is there a potential impact on future generations of humans and other species?

Democratic, community based process 1-3

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.

Alternatives 1-3

1-alternatives were carefully considered, 2-some consideration, 3-no consideration. Where alternatives considered?

Total 5-155-good, supportive of health and community15-poor, not supportive of health or community

Precautionary AssessmentExposure

Exposure Issues Score Evaluate Potential Exposure Issues

Exposure 0-30-none, 1-little, 2-some, 3-high. Do we have control over the exposure?

Multiple exposures 0-3

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 0-3

0-not in consumer products, 1-little, 2-some, 3- a lot or do not know. Is this compound in consumer products?

Occupational exposure 0-3

0-no occupational exposure, 1-little, 2-some, 3- a lot or do not know. Is there occupational exposure?

Food exposure 0-3

0-not in food supply, 1-little, 2-some, 3- a lot or do not know. Is the compound present in the food supply.

Total 0-200-no exposure, no problems20-significant exposure, serious concern

Precautionary AssessmentHazard / 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 1-3

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 1-31-little persistence 2-some, 3-a lot of persistence or do not know. Is the compound persistent in the environment?

Bioaccumulate 1-31-little 2-some, 3-a lot. Does it bioaccumulative in humans or animals or move up the food chain?

Uncertainty 1-3 1-little 2-some, 3-a lot. How certain is the information?

Total 7-307-low hazard30-significant hazards or unknowns, serious concern