Lake Coeur d’Alene study seems just ‘a little fishy’ — Part 1

Editor’s note:  This op-ed — which is part one of two parts — was published July 20th, 2003 in the Coeur d’Alene Press.  (Part two, here.)

woodcut fish

(PHOTO CREDIT:  Wikimedia Commons)

In May, the EPA published a study of fish in Lake Coeur d’Alene.  Soon afterward, the Coeur d’Alene Tribe and the Idaho Department of Health and Welfare jointly published a fish consumption advisory for the Lake.  Word has it, moreover, that the Lake will soon be posted for that advisory.

There was something — dare we say it! — a little fishy about the publication of this study at so late a date, we thought.

A long and expensive program of contract research led up to the publication of the EPA’s Record of Decision or ROD for the Coeur d’Alene Basin in September, 2002.  The human health element of that research — a considerable enterprise in its own right — was published in its final version more than a year earlier, in June, 2001.

Why then, some eight months after the ROD’s publication and almost two years after the human health study’s publication, comes EPA’s publication of a special study on human health risk associated with Lake Coeur d’Alene fish?

Did the fish study speak to some important gap in the EPA’s Human Health Risk Assessment (HHRA)?  Did the Lake’s fish pose a looming danger to local anglers or others?    

Common sense suggests that lake-caught fish would be an unlikely source of significant environmental risk for humans.  For starters, what EPA terms a toxic chemical’s “reference dose” — which is to say, the maximum level of daily, long-term intake of a substance that does not augur harm for humans — is built on an assumption of persisting toxic exposure and a resulting daily intake.

EPA’s definition of a “reference dose” is “an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.”

Yet fishing — at least for most of us — is an inherently sporadic activity.  A number of factors limit caught-it-myself fish consumption in lakes.  Fishing season restricts the practice of fishing to only a fraction of the year.  Most of us neither can nor wish to go fishing every day of fishing season.  Not every fishing experience results in actually catching fish — some experiences generate little more than bundles of snarled line and lost lures.  Some sportsmen don’t eat what they catch and an increasing fraction do catch-and-release, which reduces the risks of fishing to, say, being pierced by fin spines or, perhaps, falling overboard.

Short of radioactive fish that glow in the dark, all these factors would seem to render fishing and the consumption of lake-caught-fish an unlikely source of significant contamination for the lakeside populations.  Held up against the daily and lifelong imagery of EPA’s reference dose language, lake fishing may be one of the last places to look for tangible human health threats.

EPA’s new fish study examined fish only.  Limiting the study’s focus to fish alone shades from view the importance of the frequency of fishing and fish-eating in lakeside populations.  Indeed, a more direct approach to the risks posed by lake fish to human health might have assessed (1) whether human populations around the lake registered unacceptable bodily contamination levels and, in turn, (2) whether the practice of fishing and eating the catch was correlated with elevated human contamination levels.

In fact, the Agency of Toxic Substances and Disease Registry (ATSDR) conducted just such a study in the Coeur d’Alene Basin, published in 1989.  The ATSDR study asked, to quote its report, whether “…the consumption of fish captured in Lake Coeur d’Alene..and the Coeur d’Alene River, as well as the adjacent Chain Lakes could significantly increase lead and cadmium levels in human blood and urine.”

One of the study’s interesting findings was that most Coeur d’Alene Tribe respondents — over three-quarters of those sampled — did not serve fish at all in an average week.  About 90% of the tribal sample ate two servings per week or fewer (including, as already noted, no fish at all).  In the tribal sample average fish consumption amounted to only about one-half serving per person per week.  Moreover, this figure represented fish consumption during the time of year most favorable for fishing.

Though hampered by attrition from its human samples, the study concluded that there were no statistically significant relationships between fish consumption and human lead and cadmium levels.  The study authors concluded:  “…we do not recommend the curtailment of fish or waterfowl consumption.”

A second ATSDR analysis, this one published in 1998, assessed the safety of consuming fish caught in the lateral chain lakes — that is, Killarney, Medicine, and Thompson Lakes.  This report characterized these water bodies as “…three of the most metal contaminated lakes among the Coeur d’Alene Basin’s lateral chain lakes” (ATSDR, 1998, p. 2).

So low were the frequencies of fish consumption by the Tribe that the 1998 ATSDR study applied fish consumption estimates drawn from an earlier 1994 EPA study of fish consumption in four Native American tribes in the Columbia River Basin — the Umatilla, Nez Perce, Yakima, and Warm Springs tribes — as stand-ins for Coeur d’Alene Tribe consumption estimates.

By our own calculation, these “stand-in” consumption figures were from 5 to 11 times greater than actual mean consumption of Coeur d’Alene Tribe members, though of course the rare heavier consumer of fish might come closer to the 1994 EPA study’s Columbia River Basin estimates.

Still, however, the 1998 ATSDR study concluded that no fish advisories were necessary.

The 1989 and 1998 ATSDR studies provide the proximate background for the new EPA study published in May, 2003.

— SNRC Science Committee

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One Response to Lake Coeur d’Alene study seems just ‘a little fishy’ — Part 1

  1. Pingback: Lake Coeur d’Alene study seems just ‘a little fishy’ — Part 2 | Disputing EPA Science in North Idaho's Silver Valley

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