Health Risk from Consuming POC-Contaminated Fish: Part I. Tolerance Levels and Consumption Patterns Michael H. Dong, MPH, DrPA, PhD October, 2007 Readings

taken at the Epcot Center, Orlando, Florida, USA

Lecture Objectives  Learn about fish’s nutritional values.  Learn about the toxicities of POCs.  Learn about the tolerance levels, the maximum residue limits, and similar limits set for POCs in fish.  Learn about the fish consumption rates (patterns) in some of the regions.

Performance Objectives  Students are expected to know that fish is a global commodity of great nutritional values to mankind. .. to know that many fish and shellfish are contaminated with POCs. .. to know what the POC tolerance levels and fish consumption patterns are like for people worldwide.

Fish’s Nutritional Values  Fish has little bad fats which otherwise are commonly found in red meat.  It contains high quantities of complete protein, good (polyunsaturated) fats, and other quality nutrients.  The good fats abundant in fish are largely Omega-3 fatty acids, which are essential nutrients to humans.

POC Contamination of Fish  Many fish are contaminated with very toxic agents at some level.  One major group of these toxic fish contaminants is the highly persistent organochlorine compounds (POCs).  Fish and shellfish are contaminated with POCs primarily through their pollution to the aquatic systems.

Aquatic Accumulation of POCs  Bottom-dwelling organisms will feed on POC-contaminated particles that are suspended in the aquatic systems.  The contaminated microbes in turn will serve as food for aquatic biota.  Fish consumers can then be exposed to POCs present in these aquatic systems through the biota-human food chain.

Organochlorine Compounds (OCs) (aka: Chlorinated Organic Compounds; Organic Compounds of Chlorine) Chlorine-carbon bond are chemically very strong and stable. Most OCs are persistent, toxic, lipophilic, and bioaccumulative. DDT Lindane Mirex PCB 103 Dioxin Carbon Tetrachloride

Toxicities of POCs (I)  Many POCs are found toxic to humans.  The toxicological properties for some of these chemicals have been assessed by the U.S. ATSDR (and WHO).  These assessment documents are each prepared and published by the agency as separate toxicological profiles for the individual chemicals.

Toxicities of POCs (II)  Most POCs assessed are classified as at least a possible human carcinogen.  They induce toxic effects on several body systems (liver, kidneys, immune, endocrine, reproductive, and nervous).  PCBs were by far the subgroup most often linked to children’s health by a fair amount of epidemiological data.

Tolerances for POCs in Fish  Some health regulatory authorities have set forth health advisories or tolerance limits (ppm) for certain POCs in fish.  These tolerances are largely on wet weight basis, and are > the outdated legal limits set for trade purposes.  Different countries have interpreted or used these tolerance limits differently.

Action Levels in the U.S.  Tolerances for pesticide residues in fisheries products are referred to and enforced by U.S. FDA as action levels.  They can use these levels to legally remove the product from the market.  Local authorities and other countries often rely on these action levels to set their own fish advisories.

Tolerances in European Union  The European Union has not yet set any tolerances for POC residues in fish.  Instead, they have developed residue limits similar to those by Codex (i.e., on fat basis for meat other than marine).  These residue limits are now coined with the term maximum residue levels (or limits), or MRLs for short.

The MRLs Used by Codex  A Codex MRL is the maximum level of (pesticide) residues intended to be legally permitted in/on animal feeds and food commodities.  As OCPs tend to concentrate and stay in fatty tissues, these MRLs may also be used (but with caution) to set health advisories or even legal actions.

Tolerances in Asia/Pacific  Australia’s tolerance levels for pesticide residues (in fish) are commonly referred to as extraneous residue limits.  Japan’s residue tolerances currently are available as provisional maximum residue limits, which took into account Codex’s standards first but ended up relying on U.S. FDA’s action levels.

Derivation of MRLs/Residue Tolerance Limits (I) (Food Concentration) x (Food Consumption) ______________________________________________________ (Body Weight) = (Intake Dosage) Equation I

Derivation of MRLs/ Residue Tolerance Limits (II) (Food Concentration) = (Intake Dosage) x (Body Weight) ________________________________________ (Food Consumption) Equation II

Derivation of MRLs/Residue Tolerance Limits (III)  Where intake dosage in Equation II (in the last slide) = ADI or RfD, then food concentration = tolerance limit or a similar residue limit (e.g., MRL).  Therefore, tolerance limits/MRLs are affected by the consumption rates or ADI/RfD used.

Fish Consumption Rates (I)  Often times, the consumption rate used for tolerance derivation is insufficient for at least some localities or countries.  For example, average fish consumption in Finland is 15 g/day per capita, whereas in Kiribati is up to 567 g/day.  The actual rates for fish consumers are higher than those based on per capita.

Fish Consumption Rates (II)  A per capita rate of 6.5 g/day was used by U.S. EPA to guide the earlier version of action levels set by U.S. FDA.  U.S. EPA currently uses g/day for subsistence fishers.  U.S. EPA is also aware that the daily consumption could be up to 600 g per consumer for certain American tribes.

Consumption-Related Issues (I)  Complicating the consumption issue further is the potential for misuse of the fat-based Codex MRLs.  For OCPs in meat other than marine mammals, Codex sets the MRLs on fat basis by adopting a daily fat intake of 50 g from their standard diet assumed for meat eaters.

Consumption-Related Issues (II)  Fish and shellfish on average contain 5% of fat by weight, suggesting that the daily fish diet assumed by U.S. EPA for subsistence fishers contains 7 g of fat.  It in turn implies that the daily intake of fat from the subsistence fisher diet alone is about 7 times less than that getting from the Codex standard meat diet.

MRLs vs. U.S. EPA’s Estimates  The fat-based MRLs derived by Codex thus should be about 7 times lower than that estimated by U.S. EPA.  Such a reduction is appropriate in that the higher fat intake assumed in the Codex diet should be accounted for.  The difference would be greater if U.S. EPA used a lower consumption rate.

Issues on Fat Content in Fish  Another issue with tolerance/MRL derivation is the use of 5% by weight as the default fat content in fish.  Certain fish species have much more (or much less) than 5% of fat in their body.  How one should equate the MRLs from two agencies thus would also depend on what fish species are actually consumed.

Issues on Fat-Based MRLs  POC residues expressed on the basis of wet weight fish flesh differ empirically from those expressed on fat basis, even after fat or tissue normalization.  Procedures for residue levels measured on fat basis require lipid extraction from meat samples, for which the analytical techniques are far from perfect.

Issues on ADIs and RfDs  The ADIs and RfDs used for tolerance derivation are only as meaningful as the toxicity data used which are insufficient.  They also may not have incorporated an adequate safety factor for the higher risk groups (e.g., infants and children).  Nor have they accounted for the potential for synergism or additivity of toxicity.

Use of Screening Values  For the prominent POCs, U.S. EPA has updated their screening values intended as threshold levels for provoking more intensive specific-site monitoring.  Values of this type can also be used to provide a rough health risk analysis for consumption of POC-contaminated fish, as illustrated and discussed in Part II.