PUBLIC HEALTH ASSESSMENT
CITY OF NOME/ALASKA GOLD COMPANY SITE
NOME, ALASKA
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 Disease Registry (ATSDR) has been requested by the Federal Environmental Protection Agency (EPA), Region X Office, to evaluate the public health impacts attributable to contamination of the Alaska Gold Site.
An EPA Technical Assistance Team (TAT) conducted air, water, soil, and sediment sampling during October 1986 to define the lateral extent of arsenic and mercury contamination in the Nome vicinity and to evaluate the risks posed to public health as a result of contamination. Sampling results are presented in the Priliminary Site Assessment (PSA) which was used in evaluating the public health impact of Alaska Gold Site contaminants.
Gold placer deposits have been mined around Nome, Alaska since 1899. The placer separation process concentrates arsenic bearing minerals and generates arsenic and mercury containing dredge tailings. These tailings have been commonly used as foundation and fill for numerous construction projects 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 Risk Assessment, October - December, 1986," Middaugh, John, et al., State of Alaska, Department of Health and Social Services, Division of Public Health, December 15, 1986.
"TAT Activities Report, Preliminary Site Assessment, City of Nome/Alaska Gold Company, Nome, Alaska, October 27 to November 1, 1986," Technical Assistance Team TDD #10-8701-01, Environmental Protection 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.
LIST OF PRINCIPAL CONTAMINANTS
The highest detected levels of contaminants for surface water, groundwater,
soil, and sediment samples taken in the Alaska Gold Site area are shown below.
| Contaminant | Maximum Reported Concentration |
|
AIR |
|
| Mercury (Vapor) | 0.026 mg/m3 |
| Mercury (Particulate) | 0.245 ug/m3 |
| SOIL | |
| Arsenic | 10,000 ppm |
| Mercury | 85 ppm |
| Mercury* | 484,600 ppm |
| SURFACE WATER | |
|
Arsenic |
220 ppb |
| Mercury* | 6.6 ppm |
| GROUNDWATER | |
| Arsenic | 24 ppb |
| Mercury | 0.2 ppb |
| SEDIMENT | |
| Arsenic | 120 ppm |
| Mercury | 50 ppb |
| Mercury* | 308 ppm |
*Contaminant levels are results from the 1985 Alaska Gold Company Site Assessment sampling program.
Identified environmental pathways for site contaminants include surface water, groundwater, air, soil, and sediments. Bioaccumulation of contaminants in water, soil, and sediments can lead to increased human exposure to contaminants.
Potential exposure routes for arsenic and mercury contaminants associated with the Alaska Gold Site for area residents include:
Analysis of surface water, groundwater, soil, sediment, and air samples collected at the Alaska Gold Site revealed a wide range of arsenic and mercury contaminant levels throughout the Nome, Alaska, area. Sampling results implicate gold mining and extraction operations as the primary source for arsenic and mercury contaminants. Use of contaminant containing mine tailings as construction fill for roads, parks, and buildings has resulted in widespead contaminant distribution.
Steadman Field, a recreational facility located within a residential area, was constructed on the former site of a commercially operated gold extraction facility. This facility is used for a number of recreational purposes, such as team sports, and also includes an all-terrain vehicle course. Analysis of soil samples collected from Steadman Field revealed soil arsenic levels as high as 10,000 ppm and mercury levels up to 85 ppm. Results of soil sampling conducted at other local playgrounds and school facilities revealed arsenic contaminant levels ranging from 20 - 110 ppm and mercury levels from 0.01 - 0.05 ppm.
Soil contaminant levels at the Steadman Field Recreational area are sufficently high to pose a public health risk to those using this facility. Potential health risks are associated with the ingestion of contaminated soils and the inhalation of 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 assessment monitored levels of arsenic and mercury contaminants at a number of locations within the Alaska Gold Site. Samples detected no arsenic contamination and low mercury levels ranging from 0.025 - 0.245 ug/m3. Mercury monitoring was not conducted at the active gold retort site where amalgam processing could serve as a source of mercury vapor contamination.
Air monitoring was conducted at ambient air temperatures of 20-31ºF and during a period of partial ice and snow ground coverage. These conditions may have caused sampling results to be unrepresentative of airborne contaminant levels found in warm, dry, or windy conditions. Particulate and mercury vapor levels are likely to be higher during the warm weather months, not only because of favorable climatic conditions, but also due to increased dust generating activities such as construction and road grading.
Local groundwater supplies serve as a source for potable water to Nome, Alaska, municipal system and residents on private wells. Groundwater sampling and analysis showed Moonlight Springs, the Nome municipal water source, to contain a maximum arsenic level of 6 ppb with mercury levels below the 0.2 ppb detection limit. Results of domestic well samples taken at three different Nome, Alaska locations revealed a maximum arsenic level of 24 ppb and mercury levels 0.2 ppb or less. Mercury and arsenic levels are below the U.S. Environmental Protection 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 retort operations exhibited extremely high levels of mercury. Area streams which support sport and subsistance fishing were also contaminated with mercury and arsenic. Although the Premiliminary Site Assessment included sampling of beach and marine sediments, collected samples consisted primarily of sand. Arsenic and mercury contaminants are more likely associated with fine silt and sediments and would therefore be found at low levels 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.
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.
