Health Effects of Methylmercury andHealth Effects of Methylmercury andNorth Carolina’s Advice on Eating FishNorth Carolina’s Advice on Eating Fish

Luanne K. Williams, Pharm.D.

Toxicologist

NC Department of Health and Human Services

ObjectivesObjectives

Accumulation of methylmercury in fishHealth effects in children and adultsHealth benefits of eating fishIssuance of NC and US fish advisories NC’s advice on eating fish Basis for issuance of fish advisories

Accumulation ofAccumulation ofMethylmercury in FishMethylmercury 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

Fish High in Fish High in Methylmercury Methylmercury

Levels higher in long-lived predator fishRegional environmental pollution and

conditions influence levels in fishFish 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)

Health EffectsHealth Effects

Methylmercury well absorbed Measured in blood and hairHalf-life 2 to 3 monthsDeveloping fetus 3 times more sensitive

than adults- affects the way they think, learn, and problem solve

Health Effects Health Effects on Adultson Adults

Significantly less sensitive than childrenNumbness of lips, tongue, fingers, and toesBlurred vision

Issuance of Fish AdvisoriesIssuance of Fish Advisories45 states issued fish advisories due to high levels of

methylmercury in some fishNC statewide advisory consistent with US EPA and

FDA national advisoriesNC recommends avoiding or limiting consumption

of 7 fish with high methylmercury levels Positive message as well - recommends

consumption of fish with low methylmercury levels

N.C. AdviceN.C. AdviceSensitive 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 http://www.epi.state.nc.us/epi/fish

Ocean Fish High in MethylMercuryOcean Fish High in MethylMercury

shark

swordfish

King mackerel

tilefish

NC Freshwater Fish High in Methylmercury South and East of I-85

Bowfin or blackfish

Largemouth bass

Chain pickerel or jack

Fish Low In Methylmercury Fish Low In Methylmercury farm-raised fishcanned fish including tuna, fish sticksshrimp, crab, lobster, clams, oysters, scallopsspot, 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

Health Benefits of Health Benefits of Eating FishEating Fish

Low-fat, high-protein foodReduces risk of coronary heart diseaseReduces cholesterol and triglyceride levelsInhibits platelet aggregationMay reduce blood pressureOmega-3 fatty acids important for optimal

brain and nervous system development in developing fetuses and infants

Fish - Good for BrainFish - Good for Brainand Nervous systemand Nervous systemDevelopment and Development and HeartHeart

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

Studies in 50s, 60s and 70s Studies in 50s, 60s and 70s Human Health EffectsHuman 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

Two Large Epidemiology Two Large Epidemiology Fishing Village StudiesFishing Village Studies

1980s1980s - -1990s1990s

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

Seychelles IslandsSeychelles IslandsUniv RochesterUniv Rochester

School of Medicine andSchool of Medicine and Dentistry Dentistry

1989 - 740 mother-infant pairs 12 meals/wk of fish low levels avg <0.3 ppm Less than NC’s 7 advisory fish 1 ppm Mercury levels mothers’ hair during pregnancy Avg hair levels 6.8 ppm (0.5 - 27 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

Faroes Islands Faroes Islands Harvard School Harvard School of Public Healthof Public Health

1986 - 700 mother-infant pairs 1 - 3 meals/wk of fish low levels avg < 0.3 ppm 1 meal/mo pilot whale high levels avg 1 ppm and > similar to NC’s 7

advisory fish 1 ppm Mercury levels mothers’ hair during pregnancy and cord blood Avg hair levels 4.3 ppm (0.2 - 39 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

Differences in ResultsDifferences in ResultsFaroes - 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

US EPA and US EPA and National Academy of SciencesNational 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

Risks to Developing Child Risks to Developing Child Following Prenatal Exposure Following Prenatal Exposure

from Maternal Consumption of Fishfrom 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

SummarySummary

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

Faroes Islands Sunset Faroes Islands Sunset