Health Risk from Consuming POC-Contaminated Fish: Part I. Tolerance Levels and Consumption Patterns Michael H. Dong, MP

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

2. taken at the Epcot Center, Orlando, Florida, USA

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

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

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

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

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

21. 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.

22. 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.

23. 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 142.4 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.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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.

30. 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.