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Health Effects of Methylmercury and North Carolinas Advice on Eating Fish Luanne K. Williams, Pharm.D. Toxicologist NC Department of Health and Human Services.

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Presentation on theme: "Health Effects of Methylmercury and North Carolinas Advice on Eating Fish Luanne K. Williams, Pharm.D. Toxicologist NC Department of Health and Human Services."— Presentation transcript:

1 Health Effects of Methylmercury and North Carolinas Advice on Eating Fish Luanne K. Williams, Pharm.D. Toxicologist NC Department of Health and Human Services

2 Objectives Accumulation of methylmercury in fish Health effects in children and adults Health benefits of eating fish Issuance of NC and US fish advisories NCs advice on eating fish Basis for issuance of fish advisories

3 Accumulation of Methylmercury in Fish Mercury methylmercury invertebrates fish Deposited in water from air and biotransformed by bacteria Invertebrates consume methylmercury Small fish consume invertebrates Large fish consume small fish Builds up to high levels in predatory fish Methylmercury binds to protein or meat of fish and cannot be removed by cooking or cleaning

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5 Fish High in Methylmercury Levels higher in long-lived predator fish Regional environmental pollution and conditions influence levels in fish Fish high in methylmercury 0.4 ppm and greater – ocean fish like shark, swordfish, king mackerel, and tilefish – freshwater fish like blackfish (bowfin), largemouth bass, and jack fish (chain pickerel)

6 Health Effects Methylmercury well absorbed Measured in blood and hair Half-life 2 to 3 months Developing fetus 3 times more sensitive than adults- affects the way they think, learn, and problem solve

7 Health Effects on Adults Significantly less sensitive than children Numbness of lips, tongue, fingers, and toes Blurred vision

8 Issuance of Fish Advisories 45 states issued fish advisories due to high levels of methylmercury in some fish NC statewide advisory consistent with US EPA and FDA national advisories NC recommends avoiding or limiting consumption of 7 fish with high methylmercury levels Positive message as well - recommends consumption of fish with low methylmercury levels

9 N.C. Advice N.C. Advice Sensitive populations 0 meals/week fish high mercury 2 meals a week fish low mercury General public 1 meal a week fish high mercury 4 meals a week fish low mercury

10 Ocean Fish High in MethylMercury shark swordfish King mackerel tilefish

11 NC Freshwater Fish High in Methylmercury South and East of I-85 Bowfin or blackfish Largemouth bass Chain pickerel or jack

12 Fish Low In Methylmercury farm-raised fish canned fish including tuna, fish sticks shrimp, crab, lobster, clams, oysters, scallops spot, croaker, king fish (sea mullet), speckled trout (spotted trout), flounder, mahi mahi, salmon, cod, whitefish, pollock, ocean perch, halibut, haddock, herring trout, crappie, sunfish, perch, bream

13 Health Benefits of Eating Fish Low-fat, high-protein food Reduces risk of coronary heart disease Reduces cholesterol and triglyceride levels Inhibits platelet aggregation May reduce blood pressure Omega-3 fatty acids important for optimal brain and nervous system development in developing fetuses and infants

14 Fish - Good for Brain and Nervous system Development and Heart Women of childbearing age and children could consume 2 meals a week of fish low in methylmercury (<<0.4 mg/kg) General public could consume 4 meals a week of fish low in methylmercury

15 Studies in 50s, 60s and 70s Human Health Effects Studies in 50s, 60s and 70s Human Health Effects High dose seafood poisonings in Japan in 50s and 60s and high dose bread poisoning in Iraq in 70s Health effects on developing neurological system of greatest concern Children born with mental retardation, cerebral palsy, deafness, and blindness Adults with numbness and tingling lips, tongue, fingers, toes Led to studies of methylmercury effects on developing children after prenatal exposure

16 Two Large Epidemiology Fishing Village Studies 1980s -1990s Evaluated child neurodevelopment from to birth to several years old Children from mothers who consumed fish or whale meat on a routine basis during pregnancy Seychelles Islands, Indian Ocean near Africa Faroes Islands, North Atlantic between Scotland and Iceland

17 Seychelles Islands Univ Rochester School of Medicine and Dentistry mother-infant pairs 12 meals/wk of fish low levels avg <0.3 ppm Less than NCs 7 advisory fish 1 ppm Mercury levels mothers hair during pregnancy Avg hair levels 6.8 ppm ( ppm) Children broad range of cognitive-behavioral tests approx 6 months, 1 1/2 yrs, 2 1/2 yrs, 5 1/2 yrs and 9 years and NO EFFECTS

18 Faroes Islands Harvard School of Public Health mother-infant pairs meals/wk of fish low levels avg < 0.3 ppm 1 meal/mo pilot whale high levels avg 1 ppm and > similar to NCs 7 advisory fish 1 ppm Mercury levels mothers hair during pregnancy and cord blood Avg hair levels 4.3 ppm ( ppm) similar to Seychelles Maternal hair 10 ppm and cord blood 58 ppb 10% risk dysfunction in language, attention, and memory when children evaluated at 7 years

19 Differences in Results Faroes - weekly consumption of fish with low levels but monthly consumption pilot whale meat high levels > 1 ppm resulted in a high peak or bolus dose Seychelles - weekly consumption of fish with low levels and no monthly consumption of fish with high levels American Academy of Pediatrics monthly bolus doses Faroes children received during critical developing periods may be more likely to cause neurodevelopmental damage than the same doses given cumulatively over several months

20 US EPA and National Academy of Sciences Reviewed the studies Faroe Islands study - study of choice to assess risk from consumption of fish containing methylmercury A dose of 1.0 microgram per kilogram per day maternal consumption = 10% risk to child having abnormal neuropsychological test scores A safety factor of 10 applied to account for variability in susceptibility and uncertainty in long-term effects later on in life Derived health-protective dose of 0.1 microgram per kilogram per day for fish consumption

21 Risks to Developing Child Following Prenatal Exposure from Maternal Consumption of Fish Maternal consumption of 5 meals a week of fish Containing 0.4 mg/kg (our action level) Corresponds to a 10% risk to child Neurological effects Child may have problems with the way they think, learn, and problem solve later on in life Minimize risks to developing child, NC recommends WCB and children under 15 yrs avoid fish with high mercury - shark, swordfish, king mackerel, tilefish, and largemouth bass, bowfin and chain pickerel caught S and E I-85

22 Summary Summary High methylmercury levels in some fish Concern largely for developing child Health risks for developing child following prenatal exposure from maternal consumption of fish high in methylmercury as supported by Faroes Islands Study Women of childbearing age and children avoid fish high in methylmercury Benefits of eating fish - brain and nervous system development and heart Maternal consumption of fish low in methylmercury is safe as supported by the Seychelles Islands Study

23 Faroes Islands Sunset


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