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HEALTH CONSULTATION

EXPOSURE INVESTIGATION

LYNX CREEK PRIVATE DRINKING WATER WELLS
(a/k/a HASSAYAMPA/LYNX CREEK ABANDONED MINES)
PRESCOTT, YAVAPAI COUNTY, ARIZONA


PURPOSE

In September 1999, the United States Environmental Protection Agency(USEPA) Region 9 contacted the Arizona Department of Health Services(ADHS), Office of Environmental Health, concerning potentialcontamination of private drinking water wells in the Walker, Arizona miningdistrict. Historical mining activities in the area may have resulted incontamination of groundwater by acid mine run-off as well as metals fromextraction processes. The USEPA and ADHS determined that the historicalmining activity had caused environmental damage and the potential foradverse human health impacts.

ADHS initiated a private well sampling program to determine if the miningactivity has had an adverse impact on the quality of water from these wells. Several area residents have expressed concerns about their water quality.

The objective of this public health consultation is to evaluate the potentialfor health effects from exposure to contaminants in private drinking waterwells in the Walker, Arizona area.


BACKGROUND

The Walker area is located approximately 10 miles southeast of Prescott,Arizona in the Bradshaw Mountains. The area is within the unincorporatedboundaries of Yavapai County, and consists of a mixture of Private andFederally owned land. The Prescott National Forest surrounds the area,and the private properties are located on Patented Mining Claims within thePrescott National Forest boundaries (Prescott National Forest, 1999).

The Walker Mining District was established in the 1860's after the discoveryof gold and silver in the region. The area was heavily prospected with severallarger mines and hundreds of smaller mines being worked since that time. Thelargest mine in the area, the Sheldon Mine, removed several hundred thousandtons of ore for processing over the course of its lifetime. Other smaller minesremoved lesser amounts of materials. The overburden materials were oftenpiled directly upon the properties or deposited in the most convenient place.Because of the topography, which consists of steep canyons with both annualand perennial streams at their bases, the mine wastes often ended up in thesestreams. Mine adits (horizontal shafts dug into the side of a hill) were oftendug adjacent to these waters, with the waste rock ending up in the water(Prescott National Forest, 1999). Figure 1 displays the location of theselandmarks and the approximate location of mining claim properties with privatewells.

Because the homes built in the area are located on these mining claims,they are often built either upon or adjacent to both the mining ore and theprocessed waste materials. Due to the nature of the ore bodies in theDistrict, other metals are often found. Metals such as arsenic, mercury,cadmium, antimony, and selenium are common metals within these types ofore bodies (California Environmental Protection Agency, 1996).

Approximately 300 properties and mining claims are present in the WalkerMining District area. Most of the properties contain residences that consistof homes and/or mobile homes. A visual inspection of the area found that theoccupied properties generally have private drinking water well sources. Thereare a few properties that appear to share private drinking water sources.There are no water systems in the area that have enough service connectionsto constitute a regulated drinking water system.


METHODS

Prior to sampling the water of the residents in the area, the ADHS, UnitedStates Environmental Protection Agency (USEPA), Arizona Department ofEnvironmental Quality (ADEQ), and the United States Forest Service (USFS)formulated a plan on how to proceed with the various soil and water sampling.This plan called for a two-tiered approach, using human health and ecosystemdamage as the criteria for further investigations. Since human health was of themost importance, the group suggested that the ADHS assume the lead in thisarea.

ADHS staff conducted several site visits to determine the extent of communityinterest in a water quality investigation. Site visits included meetings with theWalker Fire Board, the primary community group for the area. At the meetingsseveral area residents expressed an interest in having their water sampled andanalyzed. Serious health concerns regarding water quality were never expressedduring the meetings.

The ADHS offered free water testing to the area residents for priority metals andsulfates because of the close proximity of the residences to known mine sites, andthe possibility of shared groundwater sources. Because the properties useindividual sewage disposal systems (septic tanks and leach fields) biologicaltesting for fecal contamination was considered an important component of thesampling program.

ADEQ water quality specialists collected the water samples from the wells. TheADHS State Laboratory analyzed the samples for priority metals and sulfate.Analyses for coliform bacteria were conducted to determine if levels of diseasecausing bacteria were present in quantities that would warrant further analysis.

May 2000 Sampling Program
ADHS posted a notification at the Walker Fire District bulletin board in December 2000 offering free water testing for area residents with private drinking water wells. Residents of 25 of the approximately 300 properties responded to the request and asked for their water source to be tested.

The ADEQ collected water samples from 20 private drinking water wellsthroughout the Walker area in May 2000. Several samples indicatedcontaminant concentrations in excess of USEPA drinking water standards.

April 2001 Sampling Program
Based upon the list of residents who expressed interest in having their water sampled, ADHS attempted to contact those residents in February 2001. A total of 10 wells were sampled during the April 2001 sampling event. Analytical results were similar to the May 2000 results. Several samples contained chemicals in excess of USEPA drinking water standards.

In July 2000, ADHS met with the local Fire District Board in order todistribute the sampling results. The ADHS also mailed each well owner acopy of their analytical results and an explanation of the results.


RESULTS

A total of 30 wells were sampled in the Walker area. One well wassampled during both sampling events, resulting in a total of 31 samples.

Contaminants were selected for further toxicological evaluation if theconstituent was found in at least one well in excess of the ATSDR ChronicExposure Comparison Value for Children. ATSDR Chronic ExposureComparison Values are screening values used to determine whether furtherinvestigation of a contaminant is warranted. Concentrations ofcontaminants less than the Comparison value are unlikely to pose a healththreat.

The following table summarizes the analytical results. The contaminantsselected for further evaluation are arsenic, cadmium, selenium, and sulfate.

Private Well Sampling Results, Walker Arizona

Contaminant

ATSDR Child Comparison Value
(mg/L)

Frequency of Detection

Range
(mg/L)

Frequency of Detection Above Comparison Value

Contaminant of Concern?

Metals          
Antimony

0.015*

3/31

ND-0.006

0/31

No
Arsenic

0.003

6/31

ND-0.058

6/31

Yes

Barium

0.7

5/31

ND-0.15

0/31

No

Beryllium

0.01

2/31

ND-0.0009

0/31

No

Cadmium

0.002

14/31

ND-0.13

13/31

Yes
Mercury

0.002

0/21

ND

0/21

No

Nickel

0.2

0/31

ND

0/31

No

Selenium

0.05

6/31

ND-0.089

1/31

Yes
Thallium

0.0005

0/31

ND

0/31

No

           
Non metals          
Cyanide

0.2

0/31

ND

0/21

No

Sulfate

250#

31/31

16-900

8/31

Yes

* USEPA Region 9 Preliminary Remediation Goal. No ATSDR Comparison Value Available.
# Secondary Maximum Contaminant Level. No ATSDR Comparison Value Available.

Overall, 17 of the 30 drinking water sources contained no contaminants of concern. Thirteenof the wells contained at least 1 contaminant in excess of ATSDR Chronic ExposureComparison Value for Children. Two (2) of the 21 samples taken in May 2000 were positivefor total coliform bacteria, but not fecal coliform bacteria.


DISCUSSION

Exposure Quantification
The ADHS has made several assumptions regarding dose intake and assumptions used to quantify exposures. Professional judgment was used in estimating many of the variables using observations made at the site, using conversations with residents and members of the community, and with staff from the ADEQ.

Adults residing in the area are assumed to drink 2 liters of water per day for 30years from their private wells. Children are assumed to drink 1 liter of water perday from the well throughout childhood, defined as 0-6 years of age. The dosecalculations assume an adult body weight of 70 kilograms (kg) and a childbodyweight of 15 kg. The equations used to determine exposure can be foundin the Appendix.

Exposure Analysis
ATSDR has developed a Minimal Risk Level (MRL) for common contaminants to evaluate health effects from exposure to contaminants in water. The MRL is an estimate of daily human exposure to a contaminant below which non-cancer, adverse health effects are unlikely to occur. MRLs are not used to determine the specific adverse health effects from exposure, rather they are used to determine if there is the need for a more thorough, contaminant specific investigation. MRLs are developed for acute (less than 14 days), intermediate (14 to 365 days), and chronic (greater than 365 days) exposure.

A common misconception is that health guidance values such as MRLs represent a level above whichtoxicity is likely to occur. The MRL is neither a threshold for toxicity nor a level beyond whichtoxicity is likely to occur. MRLs are established solely as screening tools to use to determine whetherfurther evaluation of the contaminant is warranted. This information is contained in documentsknown as toxicological profiles published by ATSDR. These chemical-specific profiles provideinformation on health effects, environmental transport, human exposure, and regulatory status.

Additional evaluation is necessary to determine whether a health hazard exists when exposureestimates exceed MRLs. Literature sources are reviewed to determine what exposure doses aredocumented to actually cause a health problem. The No Observed Adverse Effect Level (NOAEL)is the exposure dose at which no effect was observed on the animal or human population in the study. The Lowest Observed Adverse Effect Level (LOAEL) for a contaminant is the lowest exposure doseobserved that results in a measurable adverse health effect in the animal or human population in thestudy. Whenever possible, NOAELs and LOAELs from studies in humans are reviewed whenevaluating possible health effects as a result of exposure to the contaminant. However, if no humanstudies exist, studies on laboratory animals are reviewed, and the health assessor might include safetyfactors to address human differences when evaluating whether health effects might be possible.

The Appendix displays childhood dose estimates. Exposure doses thatexceed an MRL, NOAEL, or LOAEL are indicated in the last 3 columns.Remember that only a dose (not a chemical concentration) can exceed anMRL, NOAEL, or LOAEL.

Private Well Health Hazard Analysis
ADHS calculated the estimated doses for each of the contaminants found in the wells that exceeded the ATSDR Chronic Childhood Comparison Values. Overall, 21 of the private wells contained no chemicals at a level of concern. Thirteen of the wells contained at least one contaminant in excess of the Child Comparison Value. Only 2 of the wells contained total coliform bacteria (Well 14 and 18). None of the wells contained fecal coliform bacteria, suggesting that bacterial water quality is generally good with no indications that pathogenic bacteria are present in any of the wells.

Estimated exposure doses to contaminants were compared to the chronicMRL, NOAEL, and LOAEL to evaluate the potential for adverse healtheffects for each contaminant. Each of the contaminants of concern wereevaluated for their carcinogenic potential. Overall 10 of the wellscontained at least 1 contaminant at a concentration that may cause anadverse health effect. The following table displays these wells andcontaminants:

Wells and Contaminants of Health Concern
Well NumberContaminants present thatcould harm childrenContaminants present thatcould harm adults
2SulfateSulfate
8 Cadmium
Sulfate
Sulfate
13ArsenicArsenic
20SeleniumSelenium
21 Arsenic
Cadmium
Sulfate
Arsenic
Cadmium
Sulfate
23 Cadmium
Sulfate
Cadmium
Sulfate
24 Arsenic
Sulfate
Arsenic
Sulfate
26ArsenicArsenic
27 Arsenic
Sulfate
Arsenic
Sulfate
30CadmiumCadmium

The following paragraphs discuss the contaminant levels for each of thewells that had at least 1 contaminant of concern

Well 2
This well contained concentrations of cadmium and sulfate in excess of the ATSDR Comparison Values. The estimated doses for both contaminants exceeded the MRLs.

Estimated cadmium exposure doses for children are above the MRL, butmore than 10 times lower than the NOAEL for humans, suggesting thatcadmium levels in this well do not pose a health threat (ATSDR, 1999).

Estimated daily doses of sulfate in children and adults exceed the NOAELand LOAEL. Based upon the levels of sulfates in this well, infants whoseformula was prepared using the water might experience somegastrointestinal upset and diarrhea. Other persons, including adults thatare sensitive to sulfates may also experience gastrointestinal upset anddiarrhea (USEPA, 1999)

No other contaminants were detected that represent a health threat. Noneof the contaminants detected are thought to cause cancer.

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofsulfate. Other residential uses of water from this well pose no apparenthealth hazard.

Well 8
This well contained concentrations of cadmium and sulfates in excess of the ATSDR Comparison Values. Child exposure doses for both cadmium and sulfate exceed the MRLs.

Estimated cadmium exposure doses for children are very close to theNOAEL, suggesting that cadmium may have the potential to pose anoncancer health hazard in sensitive persons if exposure continues over 20to 30 years (ATSDR, 1999). Potential health effects may include subtlechanges in kidney cells without affecting kidney function. Cadmium indrinking water has not been associated with the development of cancer.

Exposure doses based upon the estimated child dose to sulfates exceeded the NOAEL andLOAEL. Based upon the levels of sulfates in this well, infants whose formula was preparedusing the water might experience some gastrointestinal upset and diarrhea. Adult estimateddoses are greater than the NOAEL and equal to the LOAEL, suggesting that adults that aresensitive to sulfates may also experience gastrointestinal upset and diarrhea (USEPA, 1999).

No other contaminants were detected that represent a health threat. Noneof the contaminants detected are thought to cause cancer from exposure inwater.

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofsulfate and cadmium. Other residential uses of water from this well poseno apparent health hazard.

Well 12
This well contained concentrations of cadmium in excess of the ATSDR Comparison Values. Exposure doses based upon the estimated daily dose for children and adults for cadmium were slightly lower than the MRLs. Estimated doses are more than 10 times lower than the NOAEL for humans, suggesting that cadmium levels in this well do not pose a health threat. Cadmium in drinking water has not been associated with the development of cancer (ATSDR, 1999).

No other contaminants were detected that represent a health threat. Noneof the contaminants detected are thought to cause cancer from exposure inwater. Using this well for drinking water and other residential uses posesno apparent health hazard.

Well 13
This well contained concentrations of arsenic and cadmium in excess of the ATSDR Comparison Values. Exposure doses based upon the estimated daily dose for children to both contaminants exceeded the MRLs.

Childhood estimates of exposure to arsenic at 0.0038 mg/kg/day exceedthe NOAELrange of 0.0004 to 0.0009mg/kg/day. The estimated dose isthe same order of magnitude and is approximately the same as the LOAELof 0.005 mg/kg/day. This suggests that exposure to arsenic present in thiswell may represent a health hazard for children such as changes in skinpigmentation. The adult estimated dose for arsenic of 0.001 is close tothe LOAEL but greater than the NOAEL, suggesting that arsenic in thiswell may also represent a health hazard for adults such as changes in skinpigmentation (ATSDR, 2000).

Exposure to arsenic in drinking water has been reported to increase therisk of skin, liver, bladder, and kidney cancer. Studies suggest that thesecancer effects may occur following long-term exposure. The concentrationof arsenic in Well 13 was 58 ug/L, which is higher than the currentdrinking water standard of 50 ug/L and the 2006 standard of 10 ug/L. Lifetime exposure of arsenic at 58 ug/L in water would pose a cancer riskof less than one-in-one-thousand.

Estimated cadmium exposure doses are 10 times lower than the NOAEL,suggesting that exposure to the contaminant does not pose a health hazard. Cadmium in drinking water has not been associated with the developmentof cancer (ATSDR, 1999).

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofarsenic. Other residential uses of water from this well pose no apparenthealth hazard.

Well 14
This well contained concentrations of cadmium in excess of the ATSDR Comparison Value. The exposure dose estimate for cadmium exceeds the MRL. However, estimated cadmium exposure doses are 10 times lower than the NOAEL, suggesting that exposure to cadmium present in this well do not pose a non-cancer health hazard. Cadmium in drinking water has not been associated with the development of cancer (ATSDR, 1999).

No other contaminants were detected that represent a health threat. Noneof the contaminants detected are thought to cause cancer from exposure inwater.

Using this well for drinking water or other residential uses poses noapparent health hazard.

Well 15
This well contained concentrations of cadmium in excess of the ATSDR Comparison Values. Exposure doses based upon the estimated daily dose for children and adults for cadmium were slightly lower than the MRLs. Estimated doses are more than 10 times lower than the NOAEL for humans, suggesting that cadmium levels in this well do not pose a health threat. Cadmium in drinking water has not been associated with the development of cancer (ATSDR, 1999).

No other contaminants were detected that represent a health threat. Noneof the contaminants detected are thought to cause cancer from exposure inwater. Using this well for drinking water and other residential uses posesno apparent health hazard.

Well 18
This spring-type well contained total coliform bacteria suggesting that there may be bacterial contamination in the water. However, the water did not contain any fecal coliform bacteria. Total coliform tests are used as a general indicator of bacterial water quality, while fecal coliform test determine whether human pathogens may be present in the water.

Well 20
This well contained concentrations of arsenic, cadmium, and selenium in excess of the ATSDR Comparison Value. Concentrations of arsenic, cadmium, and selenium also exceeded the MRLs for these contaminants.

The childhood estimated exposure dose for arsenic of 0.0007 mg/kg/dayis at the middle of the NOAELrange of 0.0004 to 0.0009mg/kg/day. Estimated adult exposures are below the NOAEL range. A child'sestimated dose of 0.0007 mg/kg/day is less than 10 times lower than theLOAEL of 0.005 mg/kg/day suggesting that exposure to arsenic in thiswell does not pose a non-cancer health hazard (ATSDR, 2000).

This well contained concentrations of cadmium in excess of the ATSDRComparison Values. Exposure doses based upon the estimated daily dosefor children and adults for cadmium were slightly lower than the MRLs. Estimated doses are more than 10 times lower than the NOAEL forhumans, suggesting that cadmium levels in this well do not pose a healththreat. Cadmium in drinking water has not been associated with thedevelopment of cancer (ATSDR, 1999).

The exposure dose estimate for selenium exceeds the MRL. Theestimated selenium exposure dose of 0.0059 mg/kg/day is close to theNOAEL of 0.015 mg/kg/day, suggesting that selenium may pose a non-cancer health hazard. Health effects from selenium in drinking water caninclude brittle hair and deformed nails (ATSDR, 1996).

No other contaminants were detected that represent a health threat. Noneof the contaminants detected are thought to cause cancer from exposure inwater.

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofselenium. Other residential uses of water from this well pose no apparenthealth hazard.

Well 21
This well contained arsenic, cadmium and sulfates in excess of their ATSDR Comparison Values. Estimated exposure doses to antimony, arsenic, cadmium, and sulfate exceed MRLs.

The childhood estimated exposure dose for arsenic of 0.0009 mg/kg/day is at the maximum of the NOAELrange of 0.0004 to 0.0009 mg/kg/day. Estimated adult exposures are below the NOAEL range. A child's estimated dose of 0.0009 mg/kg/day is less than 10 times lower than the LOAEL of 0.005 mg/kg/day suggesting that exposure to arsenic in this well does not pose a non-cancer health hazard (ATSDR, 2000).

Exposure to arsenic in drinking water has been reported to increase therisk of skin, liver, bladder, and kidney cancer. Studies suggest that thesecancer effects may occur following long-term exposure. The concentrationof arsenic in Well 21 was 13 ug/L, which is lower than the currentdrinking water standard of 50 ug/L, but higher than the 2006 standard of10 ug/L. Lifetime exposure of arsenic at 13 ug/L in water would pose acancer risk of less than one-in-five-thousand.

The child estimated exposure dose of 0.009mg/kg/day cadmium exceedsthe LOAEL of 0.008 mg/kg/day. The LOAEL was established based on astudy that found renal tubule interstitial lesions in humans exposed tocadmium in drinking water at a dose of 0.008 mg/kg/day after 25 yearsof exposure. The adult estimated exposure dose to cadmium, 0.004mg/kg/day, is approximately at the LOAEL of 0.008 mg/kg/day(ATSDR, 1999).

Potential health effects may include subtle changes in kidney cells withoutaffecting kidney function. Exposure to cadmium in drinking water has notbeen associated with the development of cancer.

Estimated sulfate exposure doses for adults and children exceed theLOAEL. Based upon the levels of sulfates in this well, infants whoseformula was prepared using the water might experience somegastrointestinal upset including diarrhea. Other persons, including adultsthat are sensitive to sulfates may also experience gastrointestinal upset anddiarrhea. Sulfate has not been associated with the development of cancer(USEPA, 1999).

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofsulfate, arsenic, and cadmium. Other residential uses of water from thiswell pose no apparent health hazard.

Well 23
This well contained concentrations of cadmium and sulfates in excess of the ATSDR Comparison Values. Exposure doses based upon the estimated daily dose for children and adults to both contaminants exceeded the MRLs.

Estimated cadmium exposure doses for children are very close to theNOAEL, suggesting that cadmium may have the potential to pose a non-cancer health hazard in sensitive persons if exposure continues over 20 to30 years. Potential health effects may include subtle changes in kidneycells without affecting kidney function. Cadmium in drinking water has notbeen associated with the development of cancer (ATSDR, 1999).

Children and adult estimated exposure doses to sulfates exceed theNOAEL and LOAEL. Based upon the levels of sulfates in this well, infantswhose formula was prepared using the water might experience somegastrointestinal upset and diarrhea. Other persons, including adults thatare sensitive to sulfates, may also experience gastrointestinal upsetincluding diarrhea. Sulfate has not been associated with the developmentof cancer (USEPA, 1999).

No other contaminants were detected that represent a health threat. Noneof the contaminants detected are thought to cause cancer from exposure inwater.

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofcadmium and sulfate. Other residential uses of water from this well poseno apparent health hazard.

Well 24
This well contained concentrations of arsenic, cadmium, and sulfate in excess of the ATSDR Comparison Value. Concentrations of sulfate, arsenic, and cadmium also exceeded the MRLs for these contaminants.

A child's estimate exposure dose to arsenic of 0.002 mg/kg/day is approximately at theLOAEL of 0.005 mg/kg/day. That suggests that a child's exposure to arsenic in this wellmay pose a non-cancer health hazard such as changes in skin pigmentation. The adultestimated dose for arsenic of 0.0008 is less than the LOAEL but is greater than the NOAEL,suggesting that arsenic in this well may also pose a non-cancer health hazard for adults suchas changes in skin pigmentation (ATSDR, 2000).

Exposure to arsenic in drinking water has been reported to increase therisk of skin, liver, bladder, and kidney cancer. Studies suggest that thesecancer effects may occur following long-term exposure. The concentrationof arsenic in Well 24 was 28 ug/L, which is lower than the currentdrinking water standard of 50 ug/L, but higher than the 2006 standard of10 ug/L. Lifetime exposure of arsenic at 28 ug/L in water would pose acancer risk of less than one-in-three-thousand.

This well contained concentrations of cadmium in excess of the ATSDRComparison Values. Exposure doses based upon the estimated daily dosefor children and adults for cadmium were slightly lower than the MRLs. Estimated doses are more than 10 times lower than the NOAEL forhumans, suggesting that cadmium levels in this well do not pose a healththreat. Cadmium in drinking water has not been associated with thedevelopment of cancer (ATSDR, 1999).

Exposure dose estimates for sulfate exceed the LOAEL. Based upon thelevels of sulfates in this well, infants whose formula was prepared using thewater might experience some gastrointestinal upset and diarrhea.Estimated adult exposure doses are less than the NOAEL, suggesting thatsulfate does not pose a non-cancer health hazard to adults in this well. Sulfate has not been associated with the development of cancer (USEPA,1999).

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofsulfate and arsenic. Other residential uses of water from this well pose noapparent health hazard.

Well 26
This well contained arsenic in excess of their ATSDR Comparison Values. Estimated exposure doses to arsenic exceed MRLs.

Exposure to arsenic in drinking water has been reported to increase therisk of skin, liver, bladder, and kidney cancer. Studies suggest that thesecancer effects may occur following long-term exposure. The concentrationof arsenic in Well 26 was 19 ug/L, which is lower than the currentdrinking water standard of 50 ug/L, but higher than the 2006 standard of10 ug/L. Lifetime exposure of arsenic at 19 ug/L in water would pose acancer risk of less than one-in-three-thousand (USEPA, 2000).

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofarsenic. Other residential uses of water from this well pose no apparenthealth hazard.

Well 27
This well contained concentrations of arsenic and sulfate in excess of the ATSDR Comparison Value. Estimated exposure doses to both contaminants also exceeded the MRLs.

A child's estimated exposure dose of arsenic is approximately that of theLOAEL of 0.005 mg/kg/day. However, the estimated exposure dose issufficiently close to the LOAEL to suggest that a child exposed to arsenicin this well may represent a health hazard for children such as changes inskin pigmentation. The adult estimated dose for arsenic of 0.001 is closeto the LOAEL but greater than the NOAEL, suggesting that arsenic in thiswell may also represent a health hazard for adults such as changes in skinpigmentation (ATSDR, 2000).

Exposure to arsenic in drinking water has been reported to increase therisk of skin, liver, bladder, and kidney cancer. Studies suggest that thesecancer effects may occur following long-term exposure. The concentrationof arsenic in Well 27 was 58 ug/L, which is higher than the currentdrinking water standard of 50 ug/L and the 2006 standard of 10 ug/L. Lifetime exposure of arsenic at 58 ug/L in water would pose a cancer riskof less than one-in-one-thousand.

This well contained concentrations of sulfate in excess of the ComparisonValue. Exposure dose estimates based upon the estimated child dose alsoexceed the LOAEL. Based upon the levels of sulfates in this well, infantswhose formula was prepared using the water might experience somegastrointestinal upset and diarrhea. Estimated adult exposure doses areless than the NOAEL, suggesting that sulfate in this well does not pose anon-cancer health hazard to adults. Exposure to sulfate has not beenassociated with the development of cancer (USEPA, 1999).

This well contained concentrations of cadmium in excess of the ATSDRComparison Values. Exposure doses based upon the estimated daily dosefor children and adults for cadmium were slightly lower than the MRLs. Estimated doses are more than 10 times lower than the NOAEL forhumans, suggesting that cadmium levels in this well do not pose a healththreat. Cadmium in drinking water has not been associated with thedevelopment of cancer (ATSDR, 1999).

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofsulfate and arsenic. Other residential uses of water from this well pose noapparent health hazard.

Well 30
This well contained concentrations of cadmium in excess of the ATSDR Comparison Value. Cadmium exposure dose estimates exceed the MRL.

The estimated cadmium exposure dose for children of 0.002 mg/kg/day isapproximately equal to the LOAEL of 0.008 mg/kg/day. These exposureestimates suggest that this well may present a noncancer health hazard tochildren due to elevated cadmium levels. Potential health effects mayinclude subtle changes in kidney cells without affecting kidney function.Exposure to cadmium in drinking water has not been associated with thedevelopment of cancer. Adult exposure estimates are less than half of theNOAEL, suggesting that cadmium does not pose a non-cancer healthhazard to adults (ATSDR, 1999).

No other contaminants were detected that represent a health threat. Noneof the contaminants detected are thought to cause cancer from exposure inwater.

The ADHS recommends that this well not be used for drinking water orpreparing beverages including infant formula due to elevated levels ofcadmium. Other residential uses of water from this well pose no apparenthealth hazard.


CHILD HEALTH INITIATIVE

All exposure dose estimates were calculated assuming childhood exposure,which incorporates exposure assumptions that reflect children's greaterintake of water relative to body weight. All conclusions in this report arebased on these childhood exposure assumptions. Infants that may drinkwater containing elevated levels of sulfate are the most sensitive populationin this study. All conclusions and recommendations about using waterfrom wells were based on this most sensitive population.


CONCLUSIONS

Ten of the 30 wells tested in 2000 and 2001 pose a health hazard because contaminants are presentin the wells at levels that could cause adverse health effects. The wells that should not be used fora drinking water supply are Well Number 2, 8, 13, 20, 21, 23, 24, 26, 27, and 30. Other residentialuses of water from these wells pose no apparent health hazard.

Twenty of the 30 wells pose no apparent health hazard from the contaminants for which analyses were conducted.

Other private wells are present in the area that were not tested. Some of thesewells could contain contaminants at levels that could cause adverse health effects.


RECOMMENDATIONS

Residents of homes supplied drinking water from wells 2, 8, 13, 20, 21, 23, 24, 26,27, and 30 should find an alternative source of drinking water.

All residents in the Walker area that use well water for drinking or beverage preparation should test their well water for sulfate, arsenic, and cadmium.


PUBLIC HEALTH ACTION PLAN

The ADHS has previously notified well owners whose wells were above theMCL's for the metals and sulfates, as well as the bacteriological agents.

The ADHS presented the general findings of the sampling program to theWalker Fire Board.

The ADHS will notify the owners of all the wells that have been determined tobe a health hazard in this report.

The ADHS will place an advisory notice in the Walker Fire Board Newsletter,with information on the findings of the investigation, along with recommendationsto residents to have their well water analyzed for the contaminants found atconcentrations above the MCL's. ADHS will also advise that wells be tested atleast once per year for the bacteriological agents.

The ADHS will coordinate with the University Of Arizona Cooperative ExtensionService to promote the water testing program for rural counties in the Walkerarea.

ADHS staff will attend 4 Walker Community Fire Board meetings during2002 to communicate the results of this Consultation and to answer anyadditional questions that community members have.


PREPARERS OF REPORT

Arizona Department of Health Services, Office of Environmental Health

Brian Hasty, ADHS Office of Environmental Health
Will Humble, Chief, Office of Environmental Health, Principal Investigator

ATSDR Regional Representative

William Nelson
Office of Regional Operations, Region IX
Office of the Assistant Administrator

ATSDR Technical Project Officer

Gail Godfrey
Division of Health Assessment and Consultation
Superfund Site Assessment Branch
State Programs Section


REFERENCES

ATSDR 1992. U.S. Public Health Service, Agency for Toxic Substances and DiseaseRegistry. Toxicological Profile for Antimony. Division of Toxicology. September 1992.

ATSDR 1996. U.S. Public Health Service, Agency for Toxic Substances and DiseaseRegistry. Toxicological Profile for Selenium. Division of Toxicology. August 1996.

ATSDR 1999. U.S. Public Health Service, Agency for Toxic Substances and DiseaseRegistry. Toxicological Profile for Cadmium. Division of Toxicology. July 1999.

ATSDR 2000. U.S. Public Health Service, Agency for Toxic Substances and DiseaseRegistry. Toxicological Profile for Arsenic. Division of Toxicology. September 1996.

California Environmental Protection Agency 1996. Abandoned Mines andMining Waste. Department of Toxic Substances Control. August 1996.

Prescott National Forest 1999. Personal Communication with BeverlyEverson, Staff Geologist, Prescott National Forest Bradshaw RangerStation. July 1999.

USEPA 1999. Health Effects from Exposure to High Levels of Sulfate in Drinking WaterStudy. Office of Water. EPA 815-R-99-001. January 1999.


EXPOSURE DOSE EQUATIONS

The ADHS used the ATSDR exposure assessment documents to calculate anexposure dose for persons living in the Walker area. The doses were calculatedusing the following equations:

Ingestion of chemicals in water:

CDI= CW x IR x EF x ED
           BW x AT

CDI: chronic daily intake (ug/l/day)
CW: concentration in water (ug/L)
IR: intake rate (l/day)
EF: exposure frequency (days/yr)
ED: exposure duration (yrs)
BW: body weight (kg)
AT: Averaging time (days)
------------------------------------------------------------------

Variable Assumptions
Variable Assumptions Adults Children
IR(ingestion, water): 2 1
EF: 350 350
ED: 30 6
BW: 70 15
AT: 10950 2190

Well Dose Estimates and Comparison Values*

Well I.D. & Contaminant of Concern Child's Estimated Daily Dose (mg/kg/day) Child Dose Exceeds MRL? Child Dose Exceeds NOAEL? Child Dose Exceeds LOAEL?
Well 2        
Sulfate 51 Yes Yes Yes
Cadmium 0.0009 Yes Yes Yes
         
Well 8        
Sulfate 40 Yes Yes Yes
Cadmium 0.0016 Yes Yes Yes
         
Well 12        
Cadmium 0.0002 No No No
         
Well 13        
Arsenic 0.0038 Yes Yes Yes
Cadmium 0.00287 Yes Yes Yes
         
Well 14        
Cadmium 0.000433 Yes No No
         
Well 15        
Cadmium 0.000147 No No No
         
Well 20        
Arsenic 0.000667 Yes No No
Cadmium 0.000167 No No No
Selenium 0.000593 Yes No No
         
Well 21        
Arsenic 0.000867 Yes Yes No
Cadmium 0.008667 Yes Yes Yes
Sulfate 60 Yes Yes Yes
         
Well 23        
Cadmium 0.001333 Yes Yes No
Sulfate 18.666 Yes Yes Yes
Well 24        
Arsenic 0.001867 Yes Yes Yes
Cadmium 0.00014 No No No
Sulfate 19.333 Yes Yes Yes
         
Well 26        
Arsenic 0.001267 Yes Yes Yes
         
Well 27        
Arsenic 0.0003867 Yes Yes Yes
Cadmium 0.000147 No No No
Sulfate 24 Yes Yes Yes
         
Well 30        
Cadmium 0.002267 Yes Yes Yes

Well Location Map
Figure 1. Well Location Map


CERTIFICATION

This Exposure Investigation of Private Drinking Water Wells Health Consultation was prepared by the Arizona Department of Health Services under cooperative agreement with the Agency for Toxic Substances and Disease Registry. It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.

Gail D. Godfrey
Technical Project Officer, SPS, SSAB, DHAC


The Division of Health Assessment and Consultation, ATSDR has reviewed this health consultation and concurs with the findings.

Roberta Erlwein
Chief, SSAB, DHAC


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