PUBLIC HEALTH ASSESSMENT
CITY OF NOME/ALASKA GOLD COMPANY SITE
The City of Nome/Alaska Gold Company Site was evaluated for the potential health threat to area residents from contamination of groundwater, surface water, air, soil, and sediments. Levels of arsenic, primarily in the form of arsenopyrite, and mercury, primarily elemental, may pose a health threat to area residents. High levels of arsenic and mercury are found in mine tailings which are widely used for building foundations, fill, and roadways. Arsenic and mercury contamination is widespread throughout the Nome, Alaska area, and available for human exposure through groundwater, surface water, soil, sediments, air, and bioaccumulation in food species.
The Agency for Toxic Substances and DiseaseRegistry (ATSDR) has been requested by the FederalEnvironmental Protection Agency (EPA), Region XOffice, to evaluate the public health impactsattributable to contamination of the Alaska GoldSite.
An EPA Technical Assistance Team (TAT) conductedair, water, soil, and sediment sampling duringOctober 1986 to define the lateral extent ofarsenic and mercury contamination in the Nomevicinity and to evaluate the risks posed to publichealth as a result of contamination. Samplingresults are presented in the Priliminary SiteAssessment (PSA) which was used in evaluating thepublic health impact of Alaska Gold Site contaminants.
Gold placer deposits have been mined around Nome,Alaska since 1899. The placer separation processconcentrates arsenic bearing minerals and generatesarsenic and mercury containing dredge tailings. These tailings have been commonly used asfoundation and fill for numerous constructionprojects throughout the Nome area.
Operations from mining and gold extraction in and around Nome, Alaska, may have caused potential health risks to area residents. Preliminary sampling indicate arsenic and mercury contamination of water, sediment, and soil is directly attributable to gold extraction activities.
"Nome Arsenic and Mercury Health Hazard and RiskAssessment, October - December, 1986," Middaugh,John, et al., State of Alaska, Department of Healthand Social Services, Division of Public Health,December 15, 1986.
"TAT Activities Report, Preliminary SiteAssessment, City of Nome/Alaska Gold Company, Nome,Alaska, October 27 to November 1, 1986," TechnicalAssistance Team TDD #10-8701-01, EnvironmentalProtection Agency Region 10, January 1987.
Memorandum from Acting Chief, Epidemiology and Medicine Branch, OHA, Subject: Health COnsultation, Steadman Field Site, Nome, Alaska, June 3, 1987.
|Contaminant||Maximum Reported Concentration|
|Mercury (Vapor)||0.026 mg/m3|
|Mercury (Particulate)||0.245 ug/m3|
*Contaminant levels are results from the 1985Alaska Gold Company Site Assessment sampling program.
Identified environmental pathways for sitecontaminants include surface water, groundwater,air, soil, and sediments. Bioaccumulation ofcontaminants in water, soil, and sediments can leadto increased human exposure to contaminants.
Potential exposure routes for arsenic and mercurycontaminants associated with the Alaska Gold Sitefor area residents include:
- Ingestion of contaminanted groundwater, sediments, soil, and surface water.
- Direct contact with contaminated sediments, soil, groundwater, and surface water.
- Ingestion of contaminated fish, aquatic food species, and game which can bioaccumulate contaminants from surface water, soils, and sediments.
- Inhalation of contaminant vapors and fugative dusts.
Analysis of surface water, groundwater, soil,sediment, and air samples collected at the AlaskaGold Site revealed a wide range of arsenic andmercury contaminant levels throughout the Nome,Alaska, area. Sampling results implicate goldmining and extraction operations as the primarysource for arsenic and mercury contaminants. Useof contaminant containing mine tailings asconstruction fill for roads, parks, and buildingshas resulted in widespead contaminant distribution.
Steadman Field, a recreational facility locatedwithin a residential area, was constructed on theformer site of a commercially operated goldextraction facility. This facility is used for anumber of recreational purposes, such as teamsports, and also includes an all-terrain vehiclecourse. Analysis of soil samples collected fromSteadman Field revealed soil arsenic levels as highas 10,000 ppm and mercury levels up to 85 ppm. Results of soil sampling conducted at other localplaygrounds and school facilities revealed arseniccontaminant levels ranging from 20 - 110 ppm andmercury levels from 0.01 - 0.05 ppm.
Soil contaminant levels at the Steadman FieldRecreational area are sufficently high to pose apublic health risk to those using this facility. Potential health risks are associated with theingestion of contaminated soils and the inhalationof fugitive dusts. (See Health Consultation,Steadman Filed Site, Nome, Alaska, (SI-87-080C)
Sediment and mine tailing wastes samples from active and inactive mining and retort operations revealed high levels of mercury contamination. Mercury levels in waste tailings were as high as 144 ppm, while sediment samples collected below the retort operation outfall had mercury contaminant levels up to 484,600 ppm. Sediment, fresh water, and salt water contaminants could be bioaccumulated by aquatic food species and expose those consuming affected organisms. The Alaska Gold Site area supports a considerable amount of subsistance and commercial fishing operations which increases the significance of this exposure route. Preliminary sampling of fish and crustaceans revealed contaminant levels below Food and Drug Administration guidelines, however, tested species did not include bottom feeding - fresh water species. Due to incomplete data, ATSDR has not been able to evaluate this pathway in detail.
Air sampling conducted during the site assessmentmonitored levels of arsenic and mercurycontaminants at a number of locations within theAlaska Gold Site. Samples detected no arseniccontamination and low mercury levels ranging from0.025 - 0.245 ug/m3. Mercury monitoring was notconducted at the active gold retort site whereamalgam processing could serve as a source ofmercury vapor contamination.
Air monitoring was conducted at ambient airtemperatures of 20-31ºF and during a period ofpartial ice and snow ground coverage. Theseconditions may have caused sampling results to beunrepresentative of airborne contaminant levelsfound in warm, dry, or windy conditions. Particulate and mercury vapor levels are likely tobe higher during the warm weather months, not onlybecause of favorable climatic conditions, but alsodue to increased dust generating activities such asconstruction and road grading.
Local groundwater supplies serve as a source forpotable water to Nome, Alaska, municipal system andresidents on private wells. Groundwater samplingand analysis showed Moonlight Springs, the Nomemunicipal water source, to contain a maximumarsenic level of 6 ppb with mercury levels belowthe 0.2 ppb detection limit. Results of domesticwell samples taken at three different Nome, Alaskalocations revealed a maximum arsenic level of 24ppb and mercury levels 0.2 ppb or less. Mercuryand arsenic levels are below the U.S. EnvironmentalProtection Agency (EPA) Maximum Contaminant Level(MCL) for drinking water contaminants.
Results of the EPA TAT sampling program revealed maximum surface water levels of arsenic at 220 ppb and mercury levels below 2 ppb. A site assessment performed in October, 1985 by an Alaska Department of Environmental Conservation (ADEC) contractor revealed mercury concentrations up to 195 ppb in active Alaska Gold Company dredge effluent. Analysis of ADEC contractor collected samples from the present Alaska Gold retort site near Dry Creek revealed mercury concentrations in soil of up to 484,600 ppm with mercury levels ranging from 1.4 to 6.6 ppm in surface water. Dry Creek sediment samples collected both upstream and downstream of the gold house discharge had mercury levels ranging from 0.09 to 308 ppm.
Since preliminary studies indicate that arsenic and mercury levels in private and municipal potable water sources below Maximum Contaminant Levels (MCL), it appears that the present impact on public health from drinking water contamination is minimal. Characteristics of groundwater flow and recharge are inconclusive at this time and further studies may be necessary to document a flow pattern and assess the possibility of groundwater contamination by Alaska Gold Site contaminants.
Soil samples indicate high levels of arsenic and mercury in a number of locations. Contaminated soils in residential areas, most notably recreational areas such as Steadman Field, may be ingested by small children and also serve as sources of contaminated windblown dusts. Although local climatic conditions limit contact with contaminated soils during most of the year, they do not eliminate associated health risks.
Sediment samples taken from local mining and retortoperations exhibited extremely high levels ofmercury. Area streams which support sport andsubsistance fishing were also contaminated withmercury and arsenic. Although the PremiliminarySite Assessment included sampling of beach and marine sediments, collected samples consistedprimarily of sand. Arsenic and mercury contaminantsare more likely associated with fine silt andsediments and would therefore be found at lowlevels in samples consisting primarily of sand.
Air monitoring was performed during the Alaska Gold Site assessment to evaluate contaminant levels and the likelihood of human exposure through this pathway. The air sampling program was conducted under climatic conditions which included low ambient temperatures, less than 30º F, partial ground coverage with ice and snow, and winds less than 2 miles per hour. These conditions may have served to suppress levels of mercury vapor and particulates. Mercury vapors were detected in only one location at a level half the established TLV level. Subsequent sampling at this location had negative results. The mercury vapor monitoring program did not include the active gold retort operation where amalgum heat processing could serve as a major source of mercury vapors.
Particulate sampling results where negative for arsenic contaminants but revealed mercury levels as high as 0.245 ug/m3, and may pose a threat to the public health of local residents. As mentioned above, the air sampling program was conducted during conditions which would suppress contaminant levels, therefore, air monitoring results are inconclusive at this time.
- Conduct analysis of local groundwater flow and recharge patterns, and use this data to determine the likelihood of contamination by site contaminants.
- Continue to monitor municipal and private water sources to ensure sufficient water quality.
- Restrict public access to contaminated soils and sediments such as those found in the Steadman Field Recreational area and around gold retort operations.
- Sample freshwater and marine aquatic and game food species from areas in and around surface waters impacted by Alaska Gold Site to determine levels of bioaccumulated contaminants. Provide results of sample analysis to ATSDR for review.
- Monitor air contaminant levels around active gold retort operations and residential areas during summer months and under conditions more conducive to elevated contaminant vapor and particulate levels.
Sittig, Marshall, "Handbook of Toxic and Hazardous Chemicals and Carcinogens," 2nd Edition, Noyes Publications, 1985.
"Drinking Water and Health," Volume 3, National Research Council, National Academy Press, 3rd Edition, November 1986.
"Draft Health Advisories," U.S. Environmental Protection Agency, Office of Drinking Water, Washington D.C., 1985.
"Monographs on the Evaluation of the Carcinogenic Risks of Chemicals to Humans, Some Metals and Metallic Compounds," Volume 23, WHO International Agency for Research on Cancer, 1980.