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Evaluation of Metals in Bullhead, Bass, and Kokanee from Lake Coeur D'Alene



Arsenic (As)--Noncancer

Inorganic arsenic is the primary concern in fish and shellfish. Most arsenic in fish and shellfish is in an organic formand is considerably less toxic. The arsenic data provided by USEPA (2003) are total amounts and do not distinguishbetween inorganic and organic forms. Thus, we do not have a direct measure of the more toxic inorganic form ofarsenic. In the human health risk assessment for the Bunker Hill Site, USEPA assumed that 10 % of total arsenic infish was the inorganic form (TerraGraphics 2000, 2001). IDOH typically also assumes that 10% of total arsenic isinorganic. Studies of arsenic in shellfish indicate that between 3% and 20 % of total arsenic is present in the form ofinorganic arsenic (ATSDR 2000). We conservatively assumed that 20% of total arsenic was inorganic (the moretoxic form).

The highest average total arsenic value reported by USEPA (2003) was 0.218 mg/kg in bullhead gutted carcasssamples from the center sampling area (Table 2). A 70 kg adult consuming 540g of fish daily (traditional subsistenceconsumer) with an average total arsenic concentration of 0.218 mg/kg (20% of which is inorganic arsenic) wouldhave an estimated exposure dose of 0.00034 mg/kg/day. This is only slightly above the chronic minimal risk level(MRL) of 0.0003 mg/kg/day established by ATSDR (ATSDR 2000). This is the same level as the Reference Dose(RfD) established by USEPA. MRLs and RfDs are daily human exposure estimates considered to have noappreciable risk of adverse non-cancer health effects over a specified length of exposure. Conservative approachesare used in developing MRLs and RfDs. They are often 3-100 times below levels shown to be non-toxic. MRLs areused by ATSDR health assessors to identify contaminants that may be of concern(

Arsenic concentrations in bass and kokanee gutted carcass samples were on average about 1.5 times below the centerlake bullhead gutted carcass sample. Arsenic concentrations in bullhead gutted carcass samples from the north andsouth lake sampling areas were about 3.5 times less than those from the center lake sampling area. Arsenicconcentrations in fillets were typically about one-half of those found in gutted carcass samples (Table 2). Thisindicates that people consuming fish meals prepared from fillets and gutted carcass portions of a variety of fishspecies would have exposures lower than our worst case exposure dose. Exposure to arsenic from meals preparedusing bullhead gutted carcass portions can be reduced by (1) avoiding bullheads from the center lake sampling areaand by (2) using bullhead, bass or kokanee fillets.

Exposure scenarios with a lower consumption rate (170 g/day for contemporary subsistence fish consumer) and lessfrequent fish consumption (104 days per year for non-residents), result in exposure dose estimates ( 0.0001mg/kg/day) that are well below the MRL or RfD for arsenic. Actual exposures are expected to be less because totalintake of fish typically consists of meals prepared with a variety of fish species, not just bullheads. Traditionalsubsistence consumers eating 540 g or more of fish per day who are concerned about exposure to arsenic couldgreatly reduce their exposure by switching from gutted carcass portions to fillet portions.

Exposure potential for children was evaluated using the highest average arsenic level (0.218 mg/kg), 20% inorganicarsenic, an ingestion rate of 65 g/day, an AEF of 1 (365 days per year) and a body weight of 10 kg (children 1YOA). This resulted in an estimated exposure dose of 0.00028 mg/kg/day, which is at about the same level as thechronic oral MRL and the RfD. Other child exposures were estimated using a (1) a body weight of 16 kg (children 2-6 YOA) with an ingestion rate of 65 g/day and (2) a body weight of 35 kg (children 7-14 YOA) with an ingestionrate of 170 g/day. The resulting worst case exposure estimates were 0.00018 mg/kg/day and 0.00021 mg/kg/day,respectively; both of which are below the MRL and the RfD. All other realistic exposure estimates for children werealso below the MRL and the RfD.

USEPA (2000) has published adult non-cancer consumption limits for arsenic in fish. These are based on 8 oz. fish portions, a 70 kg body weight, and the RfD (0.0003 mg/kg/d). For levels up to 0.088 mg/kg, there is no limit on fish consumption; between 0.088 and 0.180 mg/kg, the limit is 16 eight-oz. fish meals/month; and between 0.180 and 0.230 mg/kg, the consumption limit drops to 12 meals/month. All but one fillet arsenic concentration (Table 2) were in USEPA's unlimited consumption category. Arsenic in the bullhead gutted carcass sample from the center lake area (0.218 mg/kg) fell into the 12 meals/month category. Not everyone eats 8 oz. portions, but these USEPA limits provide another way to help us evaluate the Lake Coeur d'Alene fish data reported by USEPA (2003). It also supports the importance of people knowing about their personal fish consumption habits to make better evaluations about health concerns.

Our exposure scenario used to evaluate arsenic assumes that the highest average concentration will be in every fishconsumed. While this is not likely to occur, some people may be still be concerned about arsenic accumulation infish. Fish can absorb inorganic arsenic from water and sediment and rapidly convert most of it to organic arsenic.Common forms of organic arsenic include arsenobetaine, monomethyl arsenic and dimethyl arsenic. This is a naturalprocess and many fish, especially saltwater fish, have high levels of organic arsenic. Organic arsenic is not harmfulto people because it is easily and quickly eliminated from the body in urine.

It is important to note the conservative nature of our assumption that 20% of total arsenic is inorganic. The State ofIdaho assumes 10% inorganic arsenic for their fish advisory protocol. USEPA (2002c) described the inorganicarsenic content of fish and summarized data that revealed average inorganic arsenic concentrations of 1% and 9% inanadromous and resident species, respectively, collected from the lower Columbia and Willamette rivers. Reducingthe amount of inorganic arsenic used in our non-cancer calculations to 10% reduces our worst case exposureestimate by half, which is clearly below the MRL and the RfD.

A person's diet is likely to consist of fillets and gutted carcass portions from a variety of fish species from differentparts of the lake. Given all the considerations discussed previously, it is unlikely that non cancer adverse healtheffects would be expected (for anyone regardless of how much they eat) from exposure to arsenic in bullheads, bassor kokanee from Lake Coeur d'Alene based on the contaminant concentrations reported by USEPA (2003).

Arsenic (As) - Cancer

Using the maximum estimated exposure dose for arsenic calculated previously from gutted carcass data (0.00034mg/kg/day) and a cancer slope factor of 1.5 (ATSDR 2000), an additional lifetime cancer risk of 510-4 wascalculated. This is a 95% upper confidence limit that five additional cancers could occur over a 70 year lifetime if (1)10,000 people (2) consumed 540 grams of fish every day that (3) contained a total arsenic concentration of 0.218mg/kg with (4) 20% inorganic arsenic. We are using this as a worst case exposure evaluation.

About one out of every four people (25%) in the U.S develops some type of cancer during their lifetime. Thus, forevery 10,000 people about 2,500 would be expected to develop some type of cancer during their lifetime. Themaximum arsenic exposure scenario evaluated for consumption of Lake Coeur d'Alene fish in this consultationcould increase the number of expected cancer cases from 2,500 to 2,505 over a lifetime. This represents a 95% upperconfidence limit that five additional cancer cases could develop if 10,000 people ate 540 grams of fish per day withan arsenic concentration of 0.218 mg/kg over a lifetime. Actual exposures would be expected to be less becausepeople's total intake of dietary fish would consist of a variety of fish species and not just meals prepared with guttedbass carcasses. In addition, the cancer rate is a theoretical estimate of maximum risk and individual risk is likely less,and could be zero.

Two exposure periods shorter than 70 years were considered: 30 years (maximum time at one residence) and 9 years(median time at one residence). These exposure scenarios resulted in excess cancer risks of 210-4 and 710-5 for 30years and 9 years, respectively, using the maximum exposure dose previously calculated (0.00034 mg/kg/day).

Maximum exposure conditions for contemporary subsistence fish consumers (170 g/day) and recreational fish consumers (65 g/day) resulted in excess cancer risk estimates of 2x10-4 and 610-5, respectively. For a non-resident recreational fish consumer (65 g/day, 104 days per year), an excess cancer risk of 210-5 was calculated. This represents a 95% upper confidence limit that two additional cancers could be expected over a lifetime if 100,000 people consumed fish with an As level of 0.218 mg/kg (with 20% inorganic arsenic) at a rate of 65 g/day for 104 days/year. This risk would increase the number of expected cancer cases from 25,000 to 25,002.

The highest arsenic value in fillet samples (0.116 mg/kg) was about one-half of the highest gutted carcass mean.This translates to lower estimated exposure doses of 0.00018, 0.00006, and 0.00002 mg/kg/day for traditionalsubsistence (540 g/day), contemporary subsistence (170 g/day) and resident recreational fish consumers (65 g/day),respectively. The additional cancer risks associated with these exposure scenarios were 310-4, 810-5, and 310-5,respectively. For non-resident recreational/sport fish consumers (65 g/day, 104 days/yr), a maximum exposure doseof 0.000006 mg/kg/day was estimated for arsenic in fillets. The associated increased cancer risk for this exposurescenario is 910-6. Upper limit cancer risk estimates for exposures to arsenic in Lake Coeur d'Alene fish arecompared in Table 6. The highest mean arsenic level for each species (Table 2) was used.

Cancer risks from potential exposure to carcinogens are estimated by using mathematical models to estimatemaximum likely additional cancer risks. Estimated additional cancer risks for specific exposures may often be statedas 110-6, or one in one million. This means that in a population of one million people exposed to a carcinogen overa lifetime, one additional case of cancer (beyond the 25,000 that would be expected) may occur. This represents a95% upper confidence limit estimate of additional cancer risk. The true risk is not known, but will likely be lower.

It is important to note again that additional cancer risk means above and beyond what is considered background ornormal. Based on health statistics for the United States, one out of four people (25 %) develop some type of cancerin their lifetime, which is generally assumed to be 70 years. This is typically considered as the background cancerrate in the United States. Thus, for every one million people living in the United States, about 250,000 would beexpected to develop some type of cancer over their lifetime. If we calculate an excess risk of one in a million (110-6) for a specific chemical exposure, and one million people are exposed over an entire lifetime, then one additionalcancer case would be expected (or 250,001 cases). If 10,000 people are exposed at a 110-6 risk level, it is not verylikely than an increase of cancer in the population could be measured. If several million people were exposed, thenone might be able to measure an increase in cancer. Calculations of excess cancer risk apply only to populations, notto individuals. The excess cancer risk estimates do not predict the actual risk of any individual person developingcancer.

Table 6.

Upper limit excess cancer risk estimates for arsenic in Lake Coeur d'Alene fish.
  Gutted Carcass Fillet Risk Category Summary
Fish Consumer Exposure Period Bullheads Gutted Carcass/Fillet
Traditional Subsistence 70 yrs 5 x 10 -4 3 x 10 -4 Increased
Traditional Subsistence 30 yrs 2 x 10 -4 1 x 10 -4 Increased
Traditional Subsistence 9 yrs 7 x 10 -5 3 x 10 -5 Moderate
Contemporary Subsistence 70 yrs 2 x 10 -4 8 x 10 -5 Increased
Contemporary Subsistence 30 yrs 7 x 10 -5 4 x 10 -5 Moderate
Contemporary Subsistence 9 yrs 2 x 10 -5 1 x 10 -5 Moderate
Recreational, Resident 70 yrs 6 x 10 -5 3 x 10 -5 Moderate
Recreational, Non-resident 70 yrs 2 x 10 -5 9 x 10 -6 Moderate
Traditional Subsistence 70 yrs 3 x 10 -4 1 x 10 -4 Increased
Traditional Subsistence 30 yrs 1 x 10 -4 6 x 10 -5 Increased
Traditional Subsistence 9 yrs 4 x 10 -5 2 x 10 -5 Moderate
Contemporary Subsistence 70 yrs 1 x 10 -4 5 x 10 -5 Increased/Moderate
Contemporary Subsistence 30 yrs 5 x 10 -5 2 x 10 -5 Moderate
Contemporary Subsistence 9 yrs 1 x 10 -5 6 x 10 -6 Moderate
Recreational, Resident 70 yrs 4 x 10 -5 2 x 10 -5 Moderate
Recreational, Non-resident 70 yrs 1 x 10 -5 5 x 10 -6 Moderate/Low
Traditional Subsistence 70 yrs 3 x 10 -4 2 x 10 -4 Increased
Traditional Subsistence 30 yrs 1 x 10 -4 8 x 10 -5 Increased
Traditional Subsistence 9 yrs 4 x 10 -5 2 x 10 -5 Moderate
Contemporary Subsistence 70 yrs 1 x 10 -4 6 x 10 -5 Increased
Contemporary Subsistence 30 yrs 5 x 10 -5 3 x 10 -5 Moderate
Contemporary Subsistence 9 yrs 1 x 10 -5 8 x 10 -6 Moderate
Recreational, Resident 70 yrs 1 x 10 -5 2 x 10 -5 Moderate
Recreational, Non-resident 70 yrs 1 x 10 -5 6 x 10 -6 Moderate/Low

In this consultation, ATSDR staff determined that the maximum estimated exposure dose for arsenic could result in an excess cancer risk is 510-4, or 5 in 10,000. This says that if 10,000 people eat 540 grams of fish with 0.218 mg/kg arsenic every day for seventy years, the expected number of cancer cased could increase by five and go from 2,500 to 2,505.

Conservative estimates for additional cancer risks for arsenic were in the 10-5 to 10-6 range for (1) resident and non-resident recreational/sport fish consumers; (2) contemporary subsistence consumers of fillets; and (3) for some less than lifetime exposures for traditional subsistence consumers (Table 6). Lifetime (70 yrs) exposure estimates for traditional subsistence fish consumers were in the 10-4 range. Switching to fillets could appreciably reduce risks (from 10-4 to 10-5 or from 10-5 to 10-6) in some cases, as could lower overall consumption rates.

Cadmium (Cd)

The maximum average cadmium concentration reported by USEPA (2003) was 0.139 mg/kg found in the kokanee gutted carcass sample (Appendix B). Using this along with our highest ingestion rate (540 g/day for traditional subsistence consumer), an annual exposure factor of 1 (person exposed 365 days per year) and an absorption factor of 1 (all the cadmium measured in fish is bioavailable to human consumer), yields a worst case estimated exposure dose of 0.0011 mg/kg/day. This is about five times higher than the chronic oral MRL for cadmium (0.0002 mg/ kg/day). USEPA has established an oral RfD of 0.001 mg/kg/day for cadmium. Actual exposures are expected to be less because people likely consume fish meals prepared from fillets and gutted carcass portions of a variety of fish species. Also, people eating lower amounts of fish or consuming fish less frequently would have lower exposures.

In bass and bullhead gutted carcass samples, average cadmium values were 2-17 times lower than in the kokanee gutted carcass sample. Average cadmium concentrations in fillet samples from all three species were from 8-28 times lower than in the kokanee gutted carcass sample (Table 2). This indicates that people eating meals prepared from fillets and gutted carcass portions of these fish species would have exposures much lower than our worst case estimated dose. Exposure to cadmium from consuming kokanee gutted carcass portions can be reduced by eating (1) kokanee fillets and (2) bass or bullhead gutted carcasses or fillets.

For non-resident adult recreational consumers (65 g/day, 104 days/yr) and contemporary subsistence consumers (170 g/day, 365 days/yr), estimated exposures to cadmium were 0.000036 and 0.00034 mg/kg/day, respectively. Resident adult recreational fish consumers were estimated to have a maximum exposure dose of 0.00013 mg/kg/day. These exposures are below, or well within the same concentration range as, the MRL. None of these exposure estimates exceed the RfD. Overall, if people consume a variety of fish species from Lake CDA, cadmium exposures are expected to be about 2-28 times lower than our worst case estimate.

The maximum exposure dose for children 7-14 years old was estimated using the highest average cadmium concentration (0.139 mg/kg), an ingestion rate of 65 g/day, an annual exposure factor of 1 (exposed 365 days per year), an absorption factor of 1 (100% absorbed), and a body weight of 35 kg. Using these components, a maximum exposure dose of 0.00026 mg/kg/day was calculated. This does not exceed the RfD, and is in the same range as the MRL. Actual exposures would be expected to be less if a variety of fish species are eaten. We do not think that young children are likely to consume more than 65 grams of fish per day on an annual basis.

Conservative aspects of our exposure estimates include using the highest average level reported by USEPA (2003). People's diets are likely to consist of fillets and gutted carcass portions of several fish species from different parts of the lake. Based on cadmium concentrations provided by USEPA (2003), lake averages for bullhead and bass gutted carcass samples were about 3-9 times lower, respectively, than in the kokanee gutted carcass specimens. Lake averages for bass and bullhead fillets were about 9 to 15 times, respectively, lower than the kokanee gutted carcass value used in our exposure dose estimate. The overall average for cadmium in fillet samples was about 3 times lower than in gutted carcass samples (Table 2).

USEPA (2000) has published consumption limits for cadmium in fish. These are based on 8 oz. fish portions, a 70 kg body weight, and the RfD (0.001 mg/kg/d). For cadmium levels up to 0.088 mg/kg, there is no limit on consumption. Between 0.088 and 0.180 mg/kg, the limit on consumption is 16 eight-ounce fish meals per month. At cadmium levels between 0.180 and 0.230 mg/kg, the consumption limit drops to 12 meals per month. While not everyone may eat 8 oz. portions, the USEPA limits provide another way to help evaluate the fish data reported in the Coeur d'Alene Fish Investigation (USEPA 2003). This also helps to show how important information on personal fish consumption habits is when making evaluations on health impacts. Given our assumptions, adverse health effects associated with realistic adult or child exposures to cadmium in bullheads, bass or kokanee from Lake Coeur d'Alene are not considered likely.

While cadmium can be carcinogenic when inhaled, human or animal studies have not provided sufficient evidence to show that cadmium is a carcinogen by oral routes of exposure (ATSDR 1999b). Thus, cancer evaluations for cadmium were not done as part of this consultation.

Lead (Pb)

Average lead concentrations reported for gutted carcass samples in the Coeur d'Alene Lake Fish Investigation were highest (3.85 mg/kg) in bullheads from the center lake sampling area. Average lead levels were 113 times lower (0.034 mg/kg) in bass from the southern sampling area (Table 2). Lake averages for bass (0.129 mg/kg) and kokanee (0.115 mg/kg) gutted carcass samples were 15-16 times below the average for bullhead gutted carcass samples (1.92 mg/kg).

Mean lead levels in fillet samples varied from 0.232 mg/kg in bullheads from the center lake sampling area to 0.020 mg/kg in bass and kokanee (Table 2). For the three species collected, average lead levels in fillets were 6-20 times lower as compared to gutted carcass samples of the same species. The overall average lead concentration in fillets (0.065 mg/kg) was about 14 times lower than the overall average calculated for gutted carcass samples (0.893 mg/kg). Lead is known to accumulate in bones, likely accounting for higher levels in gutted carcass samples.

Maximum estimated exposure doses calculated ranged from 0.001 mg/kg/day for a recreational, non-resident fish consumer (65 g/day, 104 days/year) to 0.030 mg/kg/day for a traditional subsistence fish consumer (540 g/day; 365 days/year). There is currently no MRL or RfD available for lead to allow direct comparison to these estimated exposure doses. Lead exposures are evaluated further in the following sections with regard to increases in blood lead levels.

Increases in Blood Lead (Pb) Concentrations

The approach described by ATSDR (1999b, Appendix D) was used to estimate blood lead increases that could result from exposures to lead in Lake Coeur d'Alene fish. Daily lead intakes from fish, a component of exposure dose calculations, were converted to micrograms (µg) and used to estimate lead (µg Pb) ingested per day. Estimated lead intakes were multiplied by diet slope factors, which have units of g of Pb/dL of blood per ug Pb ingested/day, resulting in estimated blood lead increases in units of µg/dL. Diet slope factors of 0.034 and 0.027 µg/dL per µg Pb ingested/day were used for adult females and males, respectively. A diet slope factor of 0.24 µg/dL per µg Pb ingested/day was used for children. Using average lead levels in fish (Table 2), estimated blood lead increases were calculated for subsistence and recreational consumption scenarios for both sample types and all three species (Table 7).

Adult traditional (540 g/day) and contemporary (170 g/day) subsistence consumers of bullhead gutted carcass portions could exceed the 10 µg/dL blood lead level used as a benchmark by the Centers for Disease Control and Prevention (CDC). Adult resident sport/recreational fish consumers with elevated blood lead levels could exceed 10 µg/dL if they eat 65 g/day or more of bullhead gutted carcass portions (Table 7). Adult non-resident consumers (65 g/day; 104 days/yr) would not be expected to have elevated blood lead levels from eating the fish species and portion types which we evaluated. Adult resident consumers would not be expected to have elevated blood lead levels from eating bass or kokanee gutted carcass or fillet portions, or bullhead fillets.

CDC (2003) reported blood lead levels for four age groups (Table 7). Children who eat 65 g/day or more of bullhead gutted carcass portions could reach or exceed the 10 µg/dL CDC benchmark (Table 8). Children 1-5 YOA with blood lead levels at the 95th percentile level reported by CDC (2003) could exceed the CDC benchmark if they eat as little as 6.5 g/day of bullhead gutted carcass portions (Tables 8, 9). Children could eat more bass or kokanee gutted carcass portions, or bullhead fillets before reaching a 10 µg/dL blood lead level. Eating fish fillets results in lower lead exposures for all fish consumers (Table 8).

Table 7.

Blood lead levels (µg/dL) reported by CDC (2003).
Age Groups (years of age, YOA) Geometric Mean 95th Percentile
1-5 2.23 (1.99-2.49) 7.00 (5.20-9.90)
6-11 1.51 (1.35-1.69) 4.50 (3.30-6.30)
12-19 1.10 (1.03-1.18) 2.80 (2.50-3.00)
20 + 1.75 (1.67-1.83) 5.20 (4.70-5.70)

* 95% confidence intervals shown in parentheses.

Assumptions for the estimated blood lead increases shown in Table 8 are very conservative. People likely eat avariety of fish species, portion types, and amounts (Table 3) from different locations. Daily exposures to high leadlevels are not expected. Our approach helps us to evaluate worst case exposures, target concerns, and to guide peoplein determining where their individual exposures may fall. Additional discussion of lead exposures in children is provided in the later section on Children's Health Considerations.

Table 8.

Estimated blood lead increases (µg/dL) for adults and children.
Fish Species Sample Type Average Lead Value (mg/kg) Fish Ingestion Rate (g/day) Annual Exposure Factor Lead Ingested Per Day (µg) Blood Lead Increases
Adults (F) Adults (M) Children
Bullhead Gutted Carcass 1.92 540 1


35.251 27.994  
1.92 170 1


11.098 8.813 78.336
1.92 65 1


4.243 3.370 29.952
1.92 65 0.28


1.188 0.943 8.378
1.92 6.5 1


0.424 0.337 2.995
Bass " 0.129 540 1


2.368 1.881  
0.129 170 1


0.746 0.592 5.263
0.129 65 1


0.285 0.226 2.012
0.129 65 0.28


0.080 0.063 0.563
0.129 6.5 1


0.028 0.023 0.201
Kokanee " 0.115 540 1


2.111 1.677  
0.115 170 1


0.665 0.528 4.692
0.115 65 1


0.254 0.202 1.794
0.115 65 0.28


0.071 0.057 0.502
0.115 6.5 1


0.025 0.020 0.179
Bullhead Fillet 0.096 540 1


1.763 1.400  
0.096 170 1


0.555 0.441 3.917
0.096 65 1


0.212 0.168 1.498
0.096 65 0.28


0.059 0.047 0.419
0.096 6.5 1


0.021 0.017 0.150
Kokanee and Bass " 0.020 540 1


0.367 0.292  
0.020 170 1


0.116 0.092 0.816
0.020 65 1


0.044 0.035 0.312
0.020 65 0.28


0.012 0.010 0.087
0.020 6.5 1


0.0044 0.0035 0.031

Note: Traditional and contemporary subsistence, and resident recreational fish consumers are represented by fish ingestion rates of 540, 170 and 65 g/day, respectively, and an annual exposure of 1 (365 days/yr). Non-resident recreational fish consumers are indicated by the annual exposure factor of 0.28 (104 days/yr). Average lead (Pb) concentrations are lake averages from Table 2. F indicates females and M indicates males.

Mercury (Hg)

The highest mean mercury level reported by USEPA (2003) was 0.188 mg/kg in bass fillets from the center of Lake CDA. Mercury levels in bass fillet and gutted carcass samples were 2-4 times greater than those in bullhead or kokanee, likely because bass are top predators. The mercury levels reported by USEPA (2003) were assumed to be methyl mercury, the more toxic form.

Adult non-resident recreational fish consumer (65 g/day,104 days/yr) exposure estimates were below the ATSDR MRL (0.0003 mg/kg/day) and the EPA RfD (0.0001 mg/kg/day). For adult resident recreational fish consumers (65 g/day, 365 days/year), exposure estimates were less than the MRL and the RfD for all samples except bass fillets (Table 9). Adult contemporary subsistence consumer exposure estimates were above the MRL for bass, above the RfD for kokanee, and below the RfD for bullheads. For traditional subsistence adults, exposure estimates exceeded the MRL for all three species. Both the MRL and the RfD are for methyl mercury.

Using a fish ingestion rate of 6.5 g/day resulted in child exposure doses below the RfD for children 2-6 YOA and 7-14 YOA (Table 9). For children 1 YOA, the 6.5 g/day rate resulted in doses below the RfD in all cases except bass fillets. A fish ingestion rate of 65 g/day yielded exposure estimates above the RfD in all cases, and many times above the MRL, for 1 year old children and 2-6 year old children. It is not considered very likely that 1 year old children will consume 65 g of fish each day. For the 7-14 year old group, using 65 g/day indicated exposures below the RfD in bullheads and in kokanee gutted carcass portions; other exposures fell between the RfD and the MRL. Children 7-14 YOA eating fish at 170 g/day could exceed the MRL for bass and kokanee, and the RfD for bullheads. Avoiding bass fillets would reduce exposures.

ATSDR's MRL is based on the Seychelles Child Development Study of over 700 mother-infant pairs in the Seychelles Islands. This population eats a large quantity and variety of fish, with 12 fish meals/week being typical. This is likely as much, or more, than people using Lake CDA for their source of dietary fish. Mercury levels in 350 fish (25 species) ranged from 0.5-0.75 ppm, which is higher than in the Lake CDA fish sampled. Developing fetuses were exposed in utero through maternal fish ingestion during pregnancy. Newborn children continued to be exposed during breast feeding and after their shift to a fish diet (ATSDR 1999a). In the 66-month evaluation period of the Seychelles study, multiple developmental domains were assessed with six tests. None of these indicated adverse effects of methyl mercury exposure. The study also mentioned positive benefits of the fish diet. ATSDR derived a no observed adverse effect level (NOAEL) of 0.0013 mg/kg/day from the highest exposure group in this study. The MRL was derived by applying an uncertainty factor of 3 for human variability and a modifying factor of 1.5 to account for domain specific findings in the Faroe Islands study (ATSDR 1999a).

IDOH uses the RfD for methyl mercury for fish consumption advisories. The RfD is based on a benchmark dose analysis of developmental and neurological impairment. The RfD and the MRL differ by a factor of three, but they are in the same concentration range. Although derived by different methods, the RfD and the MRL are both relevant to Lake Coeur d'Alene, especially given concerns about preventing adverse fetal and infant exposures to methyl mercury.

Table 9.

Estimated exposure doses for mercury.
Fish Species Sample Type Mercury Level (mg/kg) Ingestion Rate (g/day) Annual Exposure Factor Adult Exposure Dose Above RfD/MRL Child
(7-14 YOA) Exposure Dose
Above RfD/MRL Child
(2-6 YOA) Exposure Dose
Above RfD/MRL Child
(1 YOA) Exposure Dose
Above RfD/MRL


Bass Fillet 0.188 540 1


0.188 170 1




0.188 65 1




Yes/No 0.000764 Yes 0.001222 Yes
0.188 65 0.28




No 0.000214 Yes/No 0.000342 Yes
0.188 6.5 1




No 0.000076 No 0.000122 Yes/No
0.188 6.5 0.28




No 0.000021 No 0.000034 No


Bass Gutted Carcass 0.152 540 1


0.152 170 1




0.152 65 1




Yes/No 0.000618 Yes 0.000988 Yes
0.152 65 0.28




No 0.000173 Yes/No 0.000277 Yes/No
0.152 6.5 1




No 0.000062 No 0.000099 No
0.152 6.5 0.28




No 0.000017 No 0.000028 No


Kokanee Fillet 0.092 540 1


0.092 170 1




0.092 65 1




Yes/No 0.000374 Yes 0.000598 Yes
0.092 65 0.28




No 0.000105 No 0.000167 Yes/No
0.092 6.5 1




No 0.000037 No 0.000060 No
0.092 6.5 0.28




No 0.000010 No 0.000017 No


Kokanee Gutted Carcass 0.075 540 1


0.075 170 1




0.075 65 1




Yes/No 0.000305 Yes/No 0.000488 Yes
0.075 65 0.28




No 0.000085 No 0.000137 Yes/No
0.075 6.5 1




No 0.000030 No 0.000049 No
0.075 6.5 0.28




No 0.000009 No 0.000014 No


Bullhead Fillet 0.055 540 1


0.055 170 1




0.055 65 1




No 0.000223 Yes/No 0.000358 Yes
0.055 65 0.28




No 0.000063 No 0.000100 No
0.055 6.5 1




No 0.000022 No 0.000036 No
0.055 6.5 0.28




No 0.000006 No 0.000010 No


Bullhead Gutted Carcass 0.042 540 1


0.042 170 1




0.042 65 1




No 0.000171 Yes/No 0.000273 Yes/No
0.042 65 0.28




No 0.000048 No 0.000076 No
0.042 6.5 1




No 0.000017 No 0.000027 No
0.042 6.5 0.28




No 0.000005 No 0.00008 No

Note: A single yes indicates that the respective estimated exposure dose was above the MRL and the RfD. A single no indicates that the respective estimated exposure dose was below the RfD and the MRL. Yes/no indicates exposure doses falling above the RfD and below the MRL. A 35 kg body weight was used for children 7- 14 years of age (YOA), 16 kg for children 2-6 YOA, and 10 kg for 1 year old children.

Our conservative exposure scenarios indicate that adverse health effects could result from fetal or infant exposures tomercury in fish from Lake Coeur d'Alene, especially bass fillets. Mercury levels in bullhead and kokanee were 2-4times below that in bass. Pregnant women, women of child-bearing age, and young children could reduce mercuryexposures by not eating bass.

Arsenic, Cadmium, Lead and Mercury Concentrations in Lake Coeur d'Alene Fish

Overall average cadmium, lead and mercury concentrations were higher in the Lake Coeur d'Alene samplescollected in 2002 (Tables 2, 11) than in samples from the lateral lakes (Table 11) previously evaluated by ATSDR(1998). The different species, sample types and specimen sizes collected in these studies allow only generalcomparisons.

Data reported from other investigations of contaminant residues in fish can help provide some perspective on theoccurrence of metals in fish in Lake Coeur d'Alene. Comparison of data reported by USEPA (2003) with resultsreported by other investigators must be done cautiously. Different species, sample types, and specimen sizes areimportant factors to consider when comparing different studies on metals in fish.

Schmitt and Brumbaugh (1990) evaluated seven metals in whole-body fish samples from a variety of speciescollected nationwide from 1976-1984. These data provide a robust comparison base for arsenic, cadmium, mercuryand lead levels for the gutted carcass samples (Tables 2, 11) reported by USEPA (2003). Metal levels in guttedcarcass samples should usually be lower than in whole-body samples. A basic comparison (Table 12) indicates thisis the case for the Coeur d'Alene samples, except for mercury in bass, cadmium in kokanee, and lead in bullheads.

More recently USGS (2002) reported that arsenic was found in 28% of fish samples from the Mississippi River Basin, cadmium in 49%, lead in 87%, and mercury in 97% (Table 13). Highest levels of As (0.3-0.56 µg/g) were almost always found in largemouth bass. Arsenic tends to accumulate more in planktivorous fish species, which are often prey for bass (USGS 2002).

Average arsenic, cadmium and mercury levels in bass and bullhead gutted carcass samples from Lake Coeurd'Alene (USEPA 2003) were below, or about the same as, the whole-body samples from the USGS (2002) referencesite. Average lead in bass and bullhead gutted carcass samples from Lake Coeur d'Alene were usually higher thanthe reference site and the maximum sub-basin or station mean reported by USGS (2002). Average lead levels inbullhead gutted carcass samples from the north and center Lake Coeur d'Alene sampling areas were higher than themaximum whole body lead value (Table 13) reported by USGS (2002).

Eight fish-related food items (Table 14) in the Food and Drug Administrative (FDA) Total Diet Studies Databasewere compared to fish samples from Lake Coeur d'Alene. Preferences for these foods in the Lake Coeur d'Alenearea are unknown. Mean arsenic levels in the Lake Coeur d'Alene samples were lower than the FDA food itemswhile average cadmium levels were about the same. Lead and mercury concentrations in the 2002 Lake Coeurd'Alene fish samples, and in the lateral lakes samples evaluated by ATSDR (1998), were higher than in fish-relatedFDA Total Diet food items (Table 14). Over 250 food items are contained in the FDA Total Diet Studies database (Pennington 1992).

Table 10.

Overall lake averages (mg/kg, wet weight) for arsenic, cadmium, lead and mercury reported by USEPA (2003).
Species and Sample Type Arsenic
Bass, gutted carcass 0.129 0.015 0.129 0.152
Bass, fillet 0.064 0.015 0.020 0.188
Kokanee, gutted carcass 0.145 0.139 0.115 0.075
Kokanee, fillet 0.083 0.018 0.020 0.092
Bullhead, gutted carcass 0.113 0.044 1.92 0.042
Bullhead, fillet 0.056 0.009 0.096 0.055
Overall Average 0.098 0.040 0.383 0.101

Table 11.

Summary of results (mg/kg) from health consultation on lateral lakes (ATSDR 1998).
Metal Overall Average Maximum Average Lake Species
Cadmium 0.015 0.042 Medicine Lake Yellow perch
Lead 0.209 0.115 Medicine Lake Yellow perch
Mercury 0.08 0.495 Killarney Lake Northern pike

Table 12.

Comparison of As, Cd, Pb, and Hg in samples collected nation-wide with Lake Coeur d' Alene fish samples.
Schmitt et al 1990 2002 Lake Coeur d'Alene Samples
Metal Range of Means
Bass Kokanee Bullhead
Arsenic (As) 0.14-0.27 Below/within range Below/within range Below/within range
Cadmium (Cd) 0.03-0.07 Below/within range Above range Below/within range
Lead (Pb) 0.11-0.28 Below/within range Below/within range Above range
Mercury (Hg) 0.10-0.12 Above range Below/within range Below/within range

Note: 1976-1984 data is for whole-body fish samples; concentrations reported as µg/g, wet weight (equivalent to mg/kg); means reported as geometric.

Table 13.

Metal concentrations in bass and carp samples from the Mississippi River Basin (USGS 2002).
USGS Status and Trends Data Arsenic
Frequency of Detection in Fish Samples 28% 49% 87% 97 %
Frequency of Detection at Sampling Sites 48% 91% 100% 100 %
Maximum Metal Concentration 0.56 0.51 0.69 0.45
Sub-basin Average Concentration Range, Bass 0.07-0.24* 0.018-0.162* 0.01-0.04 0.14-0.33
Reference Site Concentration, Bass <0.12 <0.02-0.03 0.01 0.22
Sub-basin Average Concentration Range, Carp 0.07-0.24* 0.018-0.162* 0.06-0.14 0.09-0.17
Reference Site Concentration, Carp <0.12 <0.02-0.03 0.11 0.04

Notes: Samples were whole-body fish. Concentrations reported as µg/g, wet weight (equivalent to mg/kg concentrations used elsewhere in this consultation). Asterisk (*) denotes that the ranges shown for As and Cd are approximate station averages across species, not sub-basin averages.

Table 14.

Average As, Cd, Pb and Hg concentrations (mg/kg, wet weight) for eight fish-related items in the FDA market basket database.
FDA Market Basket Food Item FDA Food Item No. Arsenic
Tuna, canned in oil 32 0.88 0.020 0.001 0.165
Fish sticks, frozen 34 0.92 0.010 0.001 0.005
Haddock, pan cooked 243 5.5 0.002 0.003 0.070
Shrimp, boiled 244 0.80 0.015 0.032 0.027
Tuna noodle casserole 272 0.107 0.016 0.003 0.023
Fish sandwich, fast food 276 0.54 0.012 0.005 0.002
New England clam chowder, canned 285 0.137 0.014 0.008 ND*
Salmon steaks/filets (fresh or frozen), baked 318 0.38 0.002 (max) ND* 0.029
Overall Average --- 1.158 0.011 0.007 0.029

Note: ND = not detected. Average metal concentrations obtained from Total Diet Study Statistics on Element Results, U.S. Food and Drug Administration (2001), Washington, DC. Available from the internet site: . Some additional information on total diet studies is provided by Pennington (1992).



Children are more sensitive to elevated blood lead levels because their brain, nervous system and other organsystems are still developing. Incomplete development of the blood-brain barrier in fetuses and young children (up to3 years of age) increases the risk of lead entering the nervous system. This can result in prolonged or permanentneurobehavioral disorders. Renal, endocrine, and hematic systems may also be adversely affected. As more sensitivestudies and measures are developed, threshold exposure levels for many of these effects are being reviseddownward.

Blood lead readily crosses the placenta, putting the developing fetus at risk. This is especially important in theneurological development of the fetus because there is no blood-brain barrier. The mother's blood lead level is animportant indication of risk to the fetus. In addition, mothers who had previous elevated exposure to lead may storeit in their bones, from which it could be released during times of calcium stress, such as pregnancy and lactation.

ATSDR recognizes that children can be more sensitive to chemical exposures than adults. The ATSDR public healthassessment for the Coeur d'Alene site includes children's exposures to metals in soil, dust and other media, and thepotential health effects of these exposures.

Children exposed to lead residentially and from recreational activities may have an increased risk of developingneurological problems. These children may have elevated blood lead levels and be especially susceptible toadditional exposures to lead from eating locally caught fish. This is especially true for gutted carcass fish portionsbecause lead tends to accumulate more in the non-fillet portions of fish than in the fillet. Consuming contaminatedfish in great quantity, coupled with residential and possibly recreational exposures, could result in various adversehealth effects. Pregnant and nursing women should also limit the amount of locally caught fish that they consume inorder to decrease the chance of contaminants being transferred to the fetus/infant.

Inside the Box

The population living in the 21 square mile Bunker Hill Superfund Site (often referred to as "the Box") has been thefocus of several lead health studies since 1974. Soil and house dust with high lead levels have been identified asprimary causes of elevated blood lead levels for these people. Typical lead concentrations in wastes and soils withinthe Bunker Hill smelter complex reach or exceed 10% (100,000 ppm). In the early 1980s, soils in residential yards"in the Box" averaged 2,500-5,000 ppm while house dust lead levels averaged 2,000-4,000 ppm. The 1983 LeadHealth Study revealed that about 80% of a child's lead intake was from incidental ingestion of soil and dust. About40% of this intake appeared to come from indoor house dusts, 30% from home yard soils, and 30% fromneighborhood or community-wide sources.

Since 1974, over 6,000 blood lead screens have been performed for children living in the Bunker Hill site. Up to 75% of preschool children tested during the 1970s had elevated blood lead levels. During that time, mean blood lead levels for preschool children living within one mile of the Bunker Hill Complex were almost 70 µg/dL. Since 1974, the Panhandle Health District (PHD) has implemented effective public health education interventions to combat elevated blood lead levels in these children. The PHD has received help from IDOH, Bureau of Environmental Health and Safety (BEHS, now the Bureau of Community and Environmental Health), CDC and ATSDR. A steady decline in blood lead levels has been observed in children living "in the Box." In 1988, 46% of children screened "in the Box" had a blood lead level 10 µg/dL compared to 3% in 2001. Children participating in these screenings were 6 months to 9 years old. During the summer of 2002, 259 children through 6 years of age were tested. Of these, only six children (2%) had blood lead levels 10 µg/dL. The mean blood lead level was 2.8 µg/dL.

Outside the Box

In 1996, BEHS and PHD conducted the Coeur d'Alene River Basin Environmental Health Exposure Assessment incommunities located "outside the Box." The assessment showed that exposure pathways identified for residentsliving "in the Box" also exist for individuals living "outside the Box." Tailings in the river's floodplain in this areaaverage 2% lead. In soil near the river, lead typically ranges from 2,000-12,000 ppm in the Lower Basin (westernhalf of the site "outside the Box") and from 500-25,000 ppm in the Upper Basin (eastern half of the site "out-side theBox"). Lead in soil samples typically averages 2,500 - 2,800 ppm in this area.

In the early 1970s, children tested who lived "outside the Box" often had blood lead levels of 40-50 µg/dL. No regular child blood lead screening occurred in this area from 1975-1996. In 1996, blood lead screening was offered to children 6 months - 9 years old as part of the Coeur d'Alene River Basin Environmental Health Exposure Assessment. Of the children tested in 1996, 13.7% had elevated blood lead (10 µg/dL). Since 1996, screenings "outside the Box" have been done annually. In 2000, 8.93% of the children (6 months - 9 years old) screened had elevated blood lead levels. The mean blood level for the 117 children (6 months - 6 years) screened in 2001 was 3.7 µg/dL, and 6% had elevated blood levels. Children 7-9 years old "outside the Box" were not screened in 2001 due to funding decreases. For the 103 children screened in 2002, the mean blood lead value was 3.2 µg/dL, and four (4%) had elevated blood lead levels.

Mean blood levels for children living inside and outside the Box are similar to mean levels reported by CDC (2003). Children with mean blood lead levels could eat 65 g/day of fish fillets (bullhead, kokanee or bass) or gutted carcass portions (kokanee or bass) and be expected to have blood lead levels of 5 µg/dL or less. Children who eat 65 g/day of bullhead gutted carcass portions would likely exceed the 10 µg/L benchmark. Children 1-5 YOA with blood lead levels similar to the 95th percentile value reported by CDC (2003) could exceed 10 µg/dL by eating as little as 6.5 g/day of gutted bullhead carcass portions (Tables 8, 9).


Infants and children can be much more sensitive to methyl mercury induced neurotoxicity than adults. Criticalperiods of neonatal development and the early months after birth are times that are particularly sensitive to theharmful effects of methyl mercury on the nervous system. Exposure to methyl mercury is more dangerous for youngchildren than for adults because methyl mercury more easily passes into the developing brain of young children andmay interfere with developmental processes. Methyl mercury can accumulate in fetal blood to concentrations higherthan in the mother. Abnormal heart rhythms have been seen in children who ate grains contaminated with very highlevels of methyl mercury. Methyl mercury that enters the body can be converted to inorganic mercury and result inkidney damage.

Additional information on arsenic, cadmium, lead and mercury is provided in Appendix D.


It is important to consider the benefits of eating fish as part of a balanced diet of traditional and contemporary foods.Fish are an excellent protein source and are associated with reduced risk of coronary heart disease. The benefits ofeating fish have been associated with low levels of unsaturated fats (e.g., omega-3 polyunsaturated fatty acids)which are essential nutrients. Saturated fats are linked with increased cholesterol levels and risks of heart disease.Fish also provide a good source of some vitamins and minerals. The American Heart Association recommends twoservings of fish per week as part of a healthy diet.

The health benefits of eating fish deserve particular consideration when dealing with subsistence consumerpopulations. Removing fish from these diets can have serious health, social and economic consequences. Providingaccurate, balanced information is very important to help people make informed decisions about the risks and benefitsof personal fish consumption. Benefits of traditional foods in healthy diets are receiving more attention as tribesfocus more attention on contaminant impacts to their trust resources (ADPH 1998).

Fish can be a source of essential trace elements required by the body in small amounts to function normally. Severalof the metals determined not to be contaminants of concern in Lake Coeur d'Alene fish are essential trace elements. Table 15 shows tolerable upper intake levels for seven such metals found in Lake Coeur d'Alene fish. Maximumestimated adult daily intakes were generally within the levels established. Average exposure conditions by age groupwould also likely be well within these limits. This helps to illustrate the balance needed in weighing the risks versusbenefits when making decisions about fish consumption.

Table 15.

Tolerable upper intake levels (ULs) by life stage group.
Life Stage Group Copper
0-6 months ND ND ND ND 45 ND 4
7-12 months ND ND ND ND 60 ND 5
1-3 yrs 1,000 2 300 0.2 90 ND 7
4-8 yrs 3,000 3 600 0.3 150 ND 12
9-13 yrs 5,000 6 1,100 0.6 280 ND 23
14-18 yrs 8,000 9 1,700 1 400 ND 34
19-50 yrs 10,000 11 2,000 1 400 1.8 40
> 50 yrs 10,000 11 2,000 1 400 1.8 40
Pregnant: < 8 yrs 8,000 9 1,700 1 400 ND 34
Pregnant: 19-50 yrs 10,000 11 2,000 1 400 ND 40
Lactation: < 18 yrs 8,000 9 1,700 1 400 ND 34
Lactation: 19-50 yrs 10,000 11 2,000 1 400 ND 40
Lactation: 19-50 yrs 10,000 11 2,000 1 400 ND 40
Max. Daily Intake from Lake Coeur d'Alene Fish 1,080 µg/d 9.7 82 1.88 404 0.111 19.4

Table Notes:

These tolerable upper intake levels (ULs) are part of the new Dietary Reference Intake (DRI) values thatare replacing the old Recommended Daily Allowance (RDA) values.

Tolerable Upper Intake Level (UL) is defined as the highest level of daily nutrient intake that is likely topose no risks of adverse health effects to almost all individuals in the general population. As intakeincreases above the UL, the risk of adverse effects increases. Unless specified otherwise, the ULrepresents total nutrient intake from food, water, and supplements.

Information extracted from three books by the Food and Nutrition Board of the Institute of Medicine(view or order books from ):

Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese,Molybdenum, Nickel, Silicon, Vanadium, and Zinc. (2001, 650 p).

Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. (1999, 448 p).

Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. (2000, 529 p).

Vanadium in food has not been shown to cause adverse effects in humans. The UL is based on adverse effects inlaboratory animals. These data were used to set UL for adults, but not children or adolescents. There is no knownreason to add vanadium to food. Vanadium supplements should be used with caution.

ND = Not determinable due to lack of data on adverse effects in this age group and concern about lack of ability tohandle excess amounts. Source should be food only to prevent high levels of intake.

Maximum daily intakes calculated in manner similar to estimated exposure doses in Appendix C (used the maximummetal concentration maximum ingestion rate).

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