HEALTH CONSULTATION
Selenium in Fish Streams of the Upper Blackfoot River Watershed
SOUTHEAST IDAHO SELENIUM PROJECT
SODA SPRINGS, CARIBOU COUNTY, IDAHO
BACKGROUND AND STATEMENT OF ISSUE
The Bureau of Environmental Health and Safety (BEHS), Division of Health, Idaho Department of Health and Welfare has a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR) to conduct public health assessments and consultations for hazardous waste sites in Idaho. As part of the cooperative agreement, BEHS prepared this health consultation for the Southeast Idaho Phosphate Resource Area (SEIPRA) to evaluate selenium in fish in streams of the upper Blackfoot River watershed. This Health Consultation addresses the following question: Are people in the SEIPRA being exposed to selenium through fish in streams of the upper Blackfoot River watershed at levels that may cause harm?
This health consultation only addresses the public health significance of exposure to selenium from fish in streams of the upper Blackfoot River watershed. Consumption of wild game and livestock was addressed in a previous health consultation, "Evaluation of Selenium in Beef, Elk, Sheep, and Fish in the Southeast Idaho Phosphate Resource Area" (BEHS 2001). BEHS and ATSDR will collaboratively address specific concerns for Native Americans in a separate health consultation.
The Blackfoot River watershed has several active and inactive phosphate mines that potentially could adversely affect aquatic resources in several tributaries of the Blackfoot River (Appendix A). Phosphate has been mined from the area since 1919. Some of the ore is seleniferous, containing selenium levels that are much higher than background levels. In the late 1990s, several horses and sheep pastured around mines were diagnosed with chronic selenosis. Hunters from the area reported dead cattle and sheep near mines, and were concerned about potential selenium exposure from the environment. Idaho Department of Environmental Quality (IDEQ) reported finding about 200 dead sheep around the Conda Mine in the Spring 2001. In 1997, the Idaho Mining Association (IMA) formed a Selenium Area Wide Advisory Committee (SeAWAC) to address this issue and BEHS became involved in 1999. Recent concerns about the potential impact on aquatic and terrestrial ecosystems from phosphate mining activities have been the subject of several reports (MW 1998, 1999abc, 2000, 2001). Elevated concentrations of selenium have been reported in limited samples of fish fillets and aquatic invertebrates (MW 1999c).
Since 2000, Tetra Tech EMI, an environmental contractor for IDEQ, conducted a Selenium Area Wide Investigation and reviewed studies conducted by Montgomery Watson. In the study, they found the selenium concentrations in some fish were above 2 micrograms per gram (mg/kg) or parts per million (ppm) wet weight. The IDEQ Area Wide Risk Assessment report cited that consumption advisories to protect human health were issued in California when selenium concentrations in edible tissues exceeded 2 ppm (wet weight), while health professionals advised against any human consumption when selenium concentrations in edible tissues exceeded 5 ppm. Because some of the levels of selenium in fish were above 2 ppm, IDEQ, requested that BEHS review the data to determine if a fish advisory should be issued for fish consumed from streams of the upper Blackfoot River watershed.
Since 1997, SEAWAC investigated the occurrence and potential release of metals associated with phosphate mining activities in the Southeast Idaho Phosphate Resource Area. Fish from the streams in the upper Blackfoot River watershed in southeast Idaho were collected by the mining companies' contractor, Montgomery Watson, in September 1998, September 1999 and May 2000. Fish samples were analyzed for selenium concentrations in the skin-on fillets. The edible fish tissue samples were collected only for harvest fish exceeding 4 inches in length. The summary analytical data are presented in Appendix B. The focus area is about 600 square miles of the watershed above but not including the Blackfoot Reservoir (Appendix A). The upper Blackfoot River and its tributaries provide regional sport fisheries primarily for Cutthroat Trout, but also other cold water species. There are some "catch and release" provisions for Yellowstone Cutthroat Trout in the area based on size limitations. To date the site studies have been focused on the regional impacts of selenium releases from historic phosphate mining activities.
The U.S. Environmental Protection Agency (EPA) has developed reference doses (RfD) and recommended screening values (SV) for target contaminants (EPA 1995). The RfD is defined as an estimate of the daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime (EPA 2000). The RfD of 0.005 milligram per kilogram per day (mg/kg/day) was derived for clinical selenosis using a No-Observed-Adverse-Effect Level (NOAEL) of 0.015 mg/kg/day. The RfD was based on a human epidemiological study published by Yang et al. (1989a). A NOAEL is the highest dose of a chemical where no observed adverse health effects are seen. An uncertainty factor of 3 was applied to the NOAEL to account for sensitive individuals. A full factor of 10 was not deemed necessary because similar NOAELs were identified in two moderately sized human cohorts exposed to selenium in excess of the National Research Council's Recommended Dietary Allowances (RDA) throughout a lifetime without apparent clinical signs of selenosis (EPA 2000). The RDA is 0.070 mg/day for males and 0.055 mg/day for females for vitamin supplements.
ATSDR defines a Minimal Risk Level (MRL) as an estimate of daily human exposure to a substance that is likely to be without appreciable risk of adverse, non-carcinogenic effects over a specified duration of exposure. The chronic oral MRL derived by ATSDR for selenium is 0.005 mg/kg/day, which is the same as EPA's RfD value. This is based on a NOAEL of 0.015 mg/kg/day for dermal effects (nail disease) identified in chronically exposed people in China as reported by Yang et al. (1989a, 1989b), and divided by an uncertainty factor of 3 to account for sensitive individuals. ATSDR (2001) believes its MRL is consistent with NOAELs observed by Longnecker et al. (1991).
Screening values are target chemical concentrations in fish tissue that are of potential public health concern and are used as standards against which levels of contaminants in similar tissue collected from the ambient environment can be compared. Exceeding the screening values indicated that more intensive site-specific monitoring and/or evaluation of human health risk should be conducted (EPA 1995). The SVs are equal to the exposure levels at the RfD for non-carcinogens, given average ingestion rates (IR) of 6.5 grams per day (g/d) and body weights (BW) of 70 kg, for the general adult population. The EPA's SV for selenium in fish is 50 ppm. On the basis of a SV of 50 ppm, no fish advisory for general adult population would be warranted for fish consumed from streams of the upper Blackfoot River watershed.
Several states, including California, use a SV of 2 ppm. The California Environmental Protection Agency (CEPA) has questioned the use of the 6.5 g/d default ingestion rate that was used to calculate the SV of 50 ppm (Gassel 1997). CEPA's recommended default ingestion rate for sport fishing populations in California is 21 g/d for the median value, 50 g/d for the mean, 107 g/d for the 90th percentile, and 161 g/d for the 95th percentile rate when estimating consumption of both marine and freshwater sources of sport fish and shellfish in California. This may explain the low 2 ppm health advisory level for some states, including California, as cited in the IDEQ Area Wide Risk Assessment report. However, the California fish IRs, which include marine sources, are not considered representative of fish consumption rates that would be expected from the focus area of the streams of the upper Blackfoot River watershed (freshwater).
BEHS adopts the standard risk assessment procedures developed by EPA with minor exposure assumption adjustment to best fit Idahoan's needs. The risk assessment assumptions are listed in Table 1. BEHS considers the "no consumption restriction" category when consumption of more than two 8 ounce fish meals per week is considered safe. Two 8 ounce meals per week yield an average of 65 g/day that is protective for 95% of the general population and reasonably represents the consumption rate of Native Americans.
Table 1. General risk assessment assumptions and action levels for selenium in fish
| Population | General Population | Pregnant Womena | Childrenb |
| Body Weight (kg)c | 80 | 70 | 20 |
| Meal Size Uncooked (oz)d | 8 | 8 | 4 |
| Screening Values of Selenium in Fish (mg/kg)e | 6.2 | 5.4 | 3.1 |
a: pregnant women, women may become pregnant, and nursing mothers
b: children less than 7 years old
c: adjusted from Idaho Behavioral Risk Factors (BVRHS, 2001)
d: 1 oz = 0.0283 kg; 8 oz = 0.2268 kg
e: Reference dose of selenium is 0.005 mg/kg/day (EPA)
Calculation for Screening Values
Where,
SV: Screening Value (mg/kg)
RfD: Reference Dose (mg/kg/day) (0.005 mg/kg/day for Selenium)
BW: Body weight (kg)
EF: Exposure Frequency (104 days/year)
MS: Meal Size Uncooked (kg)
The calculated screening values for selenium in fish (Table 1) are 6.2, 5.4, and 3.1 mg/kg respectively for the general population, pregnant women and children less than 7 years old. For the general population and pregnant women, the average fish tissue selenium concentrations (Appendix B) of different fish species at all the locations are lower than their screening values, while the screening values are also 3 times lower than the maximum selenium concentrations (Appendix B) (BEHS 2002). Thus, there is no consumption of fish restriction for the general population and pregnant women (BEHS 2002).
With the exception of Yellowstone Cutthroat and Brook Trout from the East Mill Creek (Appendix B), all other average fish tissue selenium concentrations are lower than the screening value for children, while the screening values are also 3 times lower than the maximum selenium concentrations (Appendix B) (BEHS 2002). Therefore, Yellowstone Cutthroat and Brook Trout from the East Mill Creek are the only fish species contributing to an advisory for children (BEHS 2002).
For the Yellowstone Cutthroat and Brook Trout from the East Mill creek, we further calculated the limited meals for children by the following equation.
Where,
RfD: Reference Dose (mg/kg-day) (0.005 mg/kg/day for selenium)
BW: Body weight (kg)
Conc: Fish tissue concentration (mg/kg)
days/mo: Days per month
MS: Meal Size Uncooked (kg)
Consumption of Yellowstone Cutthroat and Brook Trout from the East Mill Creek for children should be limited to five (4 oz) meals per month.
Temporary Selenium Fish Advisory
The goal of the Idaho Fish Consumption Advisory Program (IFCAP) is to protect the public from adverse health risks associated with consuming contaminated fish from Idaho's waters. In accordance to the IFCAP's categories (BEHS 2002), consumption of Yellowstone Cutthroat and Brook Trout from the East Mill Creek for children should be adjusted to four (4 oz) meals per month. Because of the small sample number (less than 10), only a temporary selenium fish advisory has been issued (Table 2).
Table 2. Temporary selenium fish advisory for streams of the upper Blackfoot River watershed
| Species | Locations | Selenium Concentration (mg/kg) |
Consumption Advisory | |||
| Mean | Range | General Population | Pregnant Women | Children | ||
| Rainbow Trout | All the locationsa | 0.72 | 0.13-1.4 | No fish consumption restriction b | No fish consumption restriction b | No fish consumption restriction c |
| Yellowstone Cutthroat and Brook Trout | East Mill Creek | 4.8 | 1.7-7.9 | No fish consumption restriction b | No fish consumption restriction b | Four meals (4 oz.) per month c |
| Locations except of East Mill Creek | 0.85 | 0.1-2.5 | No fish consumption restriction b | No fish consumption restriction b | No fish consumption restriction c | |
a Locations including the Upper Segment and Lower Segment of Blackfoot
Reservoir, Blackfoot River, Angus Creek, Spring Creek, East Mill Creek, Timber
Creek, and Stewart Creek
b More than two 8 oz. fish meals per week for general population
and pregnant women
c More than two 4 oz. fish meals per week for children
CONCLUSIONS AND RECOMMENDATIONS
Children under the age of seven should not eat more than four (4 oz meal) meals per month of Yellowstone Cutthroat and Brook Trout from the East Mill Creek. There is no consumption restriction of Rainbow Trout nor are Yellowstone Cutthroat and Brook Trout restricted at other locations for children under the age of seven.
There is no fish consumption restriction for the general public and pregnant women at any location.
BEHS suggests sampling more Yellowstone Cutthroat and Brook Trout from the East Mill Creek to confirm that the Yellowstone Cutthroat and Brook Trout continue to pose a public health hazard. Issuance of a formal selenium fish advisory by IFCAP will be made after sufficient sampling is conducted to fulfill the IFCAP protocol requirements. Future sampling for other areas of the Blackfoot Reservoir and the streams is recommended only when future resources are available.
Issuance of the temporary fish consumption advisory for the East Mill Creek is a precautionary action. Idaho fishing regulations designate the Upper Blackfoot River watershed as "catch and release". Keeping Yellowstone Cutthroat Trout from the river is illegal. Fish from the East Mill Creek are very limited. Subsistence use of this area is considered highly unlikely.
The following actions and activities are in progress:
ATSDR 2001. Toxicological Profile for Selenium. Agency for Toxic Substances and Disease Registry. September.
BEHS 2001. Health Consultation. Evaluation of Selenium in Beef, Elk, Sheep, and Fish in the Southeast Idaho Phosphate Resource Area. Bureau of Environmental Health and Safety, Division of Health, Idaho Department of Health and Welfare. June.
BEHS 2002. Idaho Fish Consumption Advisory Program Protocol. Bureau of Environmental Health and Safety, Division of Health, Idaho Department of Health and Welfare.
BVRHS 2001. Idaho Behavioral Risk Factors. Bureau of Vital Records and Health Statistics, Division of Health, Idaho Department of Health and Welfare. Boise, ID
EPA 1995. Guidance for Assessing Chemical Contaminant Data for Use in Fish Advisories: Volume 1, Fish Sampling and Analysis, Second edition. Office of water, Washington, DC. EPA 823-R-95-007.
EPA. 2000. Integrated Risk Information System (IRIS) Database. United States Environmental Protection Agency. May.
Gassel 1997. Chemicals in Fish Report No. 1: Consumption of Fish and Shellfish in California and the United States. Final Draft Report. Pesticide and Environmental Toxicology Section. Office of Environmental Health Hazard Assessment. California Environmental Protection Agency. Berkeley, CA.
Longnecker, M.P., P.R. Taylor, O.A. Levander et. al.. 1991. Selenium in diet, blood, and toenails in relation to human health in a seleniferous area. American Journal of Clinical Nutrition 53: 1288-1294.
MW 1998. Draft 1998 Regional Investigation Report - Southeast Idaho Phosphate Resource Area Selenium Project. Prepared for the Idaho Mining Association's Selenium Subcommittee. Steamboat Springs, Colorado. Montgomery Watson. June.
MW 1999a. Responses to Comments on the Draft 1998 Regional Investigation Report - Southeast Idaho Phosphate Resource Area Selenium Project. Bureau of Land Management (BLM) comments; K. Ford, BLM-DEN[Memo to P. Oberlandacher, BLM-BOI]. June and Idaho Department of Environmental Quality (IDEQ) Comments. August. and US Forest Service (USFS) Comments; A. Lemly, USFS-Blacksburg, Virginia to J Jones, USFS-Soda Springs, Idaho. Montgomery Watson. July.
MW 1999b. 1999-2000 Remedial Investigation Field Sampling Plan. Part 1 - Field Sampling Plan. Prepared for the Idaho Mining Association's Selenium Subcommittee. Montgomery Watson. August.
MW 1999c. Final 1998 Regional Investigation Report - Southeast Idaho Phosphate Resource Area Selenium Project. Prepared for the Idaho Mining Association's Selenium Subcommittee. Steamboat Springs, Colorado. Montgomery Watson. December.
MW 2000. DRAFT Interim Investigation Data Report for the Southeast Idaho Phosphate Resource Area Selenium Project. Prepared for the Idaho Mining Association's Selenium Subcommittee. Steamboat Springs, Colorado. Montgomery Watson. April.
MW 2001. DRAFT 1999-2000 Regional Investigation Data Report for Surface Water, Sediment and Aquatic Biota Sampling Activities, September 1999, Southeast Idaho Phosphate Resource Area Selenium Project. Prepared for the Idaho Mining Association's Selenium Subcommittee. Steamboat Springs, Colorado. Montgomery Watson. April.
Yang, G., R. Zhou and S. Yin. 1989a. Studies of Safe Maximal Daily Dietary Selenium Intake in Seleniferous Area of China, Part I: Selenium Intake and Tissue Selenium Levels in the Inhabitants. Journal of Trace Elements and Electrolytes Heath Disease 3:77. In Talcott et. al.. 2000.
Yang, G., S. Yin, R. Zhou, et al. 1989b. Studies of Safe Maximal Daily Dietary Selinium Intake in a Seleniferous Area in China. II. Relation Between Selenium Intake and the Manifestation of Clinical Signs and Certain Biochemical Alterations in Blood and Urine. Journal of Trace Elements and Electrolytes Health Disease 3(2): 123-130. In EPA's IRIS Database.
Preparers of Report:
Lijun Jin
Public Health Assessor/Toxicologist
Bureau of Environmental Health and Safety
Division of Health
Idaho Department of Health and Welfare
Reviewers
Aaron Scheff, Health Education Specialist
Elke D. Shaw-Tulloch, Bureau Chief
Bureau of Environmental Health and Safety
Division of Health
Idaho Department of Health and Welfare
Allen Robison
ATSDR
ATSDR Technical Project Officer:
Gregory V. Ulirsch
Environmental Health Engineer
Superfund Site Assessment Branch
Division of Health Assessment and Consultation
ATSDR Regional Representatives
Karen L. Larson, Ph.D., Regional Representative
Office of Regional Operations, Region X
Agency for Toxic Substances and Disease Registry
1200 Sixth Avenue, Room 1930 (ATS-197)
Seattle, WA 98101
The Idaho Bureau of Environmental Health and Safety prepared this Health Consultation under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was initiated.
Gregory V. Ulirsch
Technical Project Officer, SPS, SSAB, DHAC
The Superfund Site Assessment Branch (SSAB), Division of Health Assessment and Consultation (DHAC), ATSDR has reviewed this health consultation and concurs with its findings.
Sven E. Rodenbeck
for Roberta Erlwien
Chief, SSAB, DHAC, ATSDR
APPENDIX A: STREAMS OF THE UPPER BLACKFOOT WATERSHED
Figure A-1. Streams of the Upper Blackfoot Watershed
APPENDIX B: FISH SELENIUM CONCENTRATION DATA (1998, 1999 AND 2000) IN THE STREAMS OF THE UPPER BLACKFOOT RIVER WATERSHED
Table B-1. Fish Selenium Concentration Data (1998, 1999 and 2000) in the Streams of the Upper Blackfoot River Watershed
| Station ID | Station Description | Fish Species | Concentration (mg/kg - wet weight) |
# Fish | |
| Range | Mean | ||||
| Blackfoot Reservoir | |||||
| RV001 | Upper segment | Rainbow Trout | 0.13-0.22 | 0.18 | 2 |
| Yellowstone Cutthroat | 0.19-0.71 | 0.45 | 2 | ||
| RV002 | Upper segment | Yellowstone Cutthroat | 0.59-0.80 | 0.7 | 6 |
| RV003 | Upper segment | Yellowstone Cutthroat | 0.19-0.78 | 0.51 | 8 |
| RV004 | Upper segment | Yellowstone Cutthroat | 0.65-0.79 | 0.72 | 2 |
| RV005 | Upper segment | Yellowstone Cutthroat | 0.68-0.75 | 0.72 | 2 |
| RV008 | Lower segment | Rainbow Trout | 0.69 | 1 | |
| Streams | |||||
| ST019 | Blackfoot River, downstream of Ballard Creek | Yellowstone Cutthroat | 0.17-2.2 | 1.1 | 6 |
| ST021 | Blackfoot River, downstream of Trail Creek | Yellowstone Cutthroat | 0.65-1.5 | 1 | 6 |
| ST023 | Blackfoot River, downstream of Dry Valley Creek | Yellowstone Cutthroat | 0.1-1.6 | 0.7 | 6 |
| ST026 | Blackfoot River, downstream of The Narrows | Yellowstone Cutthroat | 0.52-2.5 | 1.55 | 9 |
| ST029 | Blackfoot River, upstream of Spring Creek | Yellowstone Cutthroat | 0.66-2.4 | 1.14 | 6 |
| ST129 | Angus Creek, downstream of Wooley Valley Mine | Yellowstone Cutthroat | 0.20-0.41 | 0.28 | 3 |
| ST145 | Spring creek, downstream of East Mill Creek | Brook Trout | 0.37-0.93 | 0.65 | 2 |
| Yellowstone Cutthroat | 0.36-0.89 | 0.61 | 4 | ||
| ST148 | Spring Creek, upstream of East Mill Creek | Brook Trout | 0.47-1.1 | 0.89 | 3 |
| Yellowstone Cutthroat | 0.15-0.19 | 0.17 | 2 | ||
| ST227
(1999, 2000 data) |
East Mill Creek | Brook Trout | 3.2-6.6 | 4.9 | 2 |
| Yellowstone Cutthroat | 1.7-4.1 | 2.9 | 2 | ||
| ST227 (1998 Data) | East Mill Creek | Yellowstone Cutthroat | Maximum: 7.9 Average: 6.0 (for these three fish) |
2 | |
| Brook Trout | 1 | ||||
| ST229 | Blackfoot River, downstream of Spring Creek | Brook Trout | 0.41-0.91 | 0.66 | 2 |
| Rainbow Trout | 1.1 | 1 | |||
| Yellowstone Cutthroat | 0.21-1.9 | 1 | 5 | ||
| ST232 | Blackfoot River, upstream of Blackfoot Reservoir | Rainbow Trout | 0.91-1.4 | 1.2 | 2 |
| Yellowstone Cutthroat | 0.28-1.6 | 0.95 | 4 | ||
| ST236 | Timber Creek | Rainbow Trout | 0.59 | 1 | |
| Yellowstone Cutthroat | 0.19-1 | 0.66 | 5 | ||
| ST237 | Stewart creek | Yellowstone Cutthroat | 0.7-1.4 | 0.94 | 6 |
