Human Health Effects of Mercury

1. Human Health Effects of Mercury Monica Vohmann, MD Assistant Clinical Professor, Family Medicine, UW Madison Member, BOD Physicians for Social Responsibility

2. Objectives • Discuss mercury as a substance • Discuss human health effects of mercury and particularly vulnerable populations • Public Health Applications • Clinical Applications

3. Mercury Exposures • All forms of mercury are poisonous • > 90% of US adults have measurable mercury in their blood • 7.8% of US population has blood mercury level >5.8 ppb, considered unsafe • 3-600,000 US babies born yearly at risk from Hg • Effect of exposure depends on • type of mercury, • amount of mercury, • timing and frequency of exposure.

4. Forms of Mercury • Vapors (readily absorbed via lung to blood) • production, processing, industrial • Amalgam dental fillings • Elemental Hg (inorganic Mercury salts) • Thermometers, BP manometers, lab chemicals, thermostats, fluorescent light bulbs, button batteries, amalgam dental fillings, cleaners and degreasers, folk remedies, old light-up toys. • Ethylmercury • Thimerisol vaccines, removal since 1999, all available without, preservative for contact lens solutions and nasal sprays.

5. Forms of Mercury - II • Methylmercury • biotransformed from elemental Hg released into air • bioaccumulative in food chain • biopersistant – only leaves body very slowly • lipophilic, crosses placenta, concentrates in CNS • FISH, FISH and FISH, FISHOIL CAPSULES • Large, long lived, predator fish such as shark, king mackerel, swordfish, tilefish • Also high are fresh tuna, salmon, sardines, herring, bluefish, albacore canned tuna (“white tuna”)

6. Do No Harm • Thimerisol and childhood vaccines • no clear evidence, • potential for harm present, especially multiple injections at once, • Used to have 25 micrograms per vaccine, now nanograms left over from production process • Influenza vaccine still contains 25mcg/full dose • Fish consumption and its health effect • Fish oil capsules and their health effects • Medical Waste Incineration amounts to 10% of total mercury emissions (www.noharm.org)

7. Health Impacts Adults • Direct effects only at high levels of exposure • Occupational/industrial • Daily high risk fish intake • Vapor can cause bronchitis and respiratory failure • Paresthesias, ataxia, generalized weakness, decreased vision/hearing • ? Increased CAD risk, obliterates health effects of omega-3 (increased bp, heart rate changes) • Indirect effect on unborn fetus for adult females

8. Health Impacts Children • More susceptible • Acute toxicity: rash, swollen and painful extremities, peripheral neuropathy, HTN, renal tubular dysfunction • High dose fetal exposures: low birth weight, small head circumference, mental retardation, cerebral palsy, deafness, blindness, seizures (Minamata Bay, Iraq)

9. How Children, Fetuses Differ Other Factors Contributing to Child (Fetal) Vulnerability Immature defenses • Immature blood-brain barrier • Immature detoxification systems Different Intestinal absorption Unique environments (womb, school) Unique diets Unique behaviors • hand-to-mouth • life at ground level

10. Health Impact Fetus • 1.16 million US women eat sufficient amounts of mercury contaminated fish to pose a risk to future children • Small doses cause subtle but permanent impairments of • Language • Attention and Memory • Fine Motor • Visual Spatial Skills

11. Health Impacts Fetus continued • Studies done and their results • New Zealand study showed that IQ lowered by 3 points if women had child born and their hair mercury levels > 6 ppm • Seychelle study showed no real evidence of harm except in one test which is the least dependent on translation, had small numbers of study participants

12. 6.0 million "gifted" 80 40 60 100 120 140 160 70 130 Effects of Low-Level Lead Exposure:IQ Distribution In Population Of 260 Million mean = 100 6.0 million "mentally retarded" I.Q. Adapted from Weiss 1997

13. 57% INCREASE IN "Mentally Retarded” Population 2.4 million "gifted" 9.4 million "mentally retarded" 40 80 100 120 140 160 60 70 130 Population Impact of Low-Level Pb Exposure: 5 Point Decrease in Mean IQ New Mean IQ = 95 I.Q. Adapted from Weiss 1997

14. Health Impact on Fetus continued • Faroe Island Study • Now studying children 14 years out after fetal exposures • Effects shown over a wide range of exposures and dose related deficits in memory, attention, language and visual-spatial • Also showed decreased hr variability (parasympathetic/sympathetic NS) • Found to be most credible study by National Academy of Science

15. Babies at Risk • 7.8% of US population has blood Hg level > 5.8 ppb, considered unsafe • 15.7% of US women of childbearing age have blood mercury concentrations >3.5mcg/L • 316-637,000 children each year have cord blood mercury levels of > 5.8 mcg/L (level at which Faroe Study found effects on neurodevelopment) • Of women who eat any fish at all, 50% consume more than safe levels

16. Mercury Measurements • EPA “safe intake” level is considered 0.1 mcg/kg body weight/day (for a 132 lb person this would equal 7 oz canned tuna/week, for a child 2.5x safe intake if ate same amount). • FDA Fish Levels 1ppm mercury (found mostly in muscle, not fatty parts, thus can’t cut off), now 0.5 ppm considered by many fish advisories

17. Mercury Measurements II • Cord Blood Methylmercury levels are most sensitive biomarker of in utero exposures and while the EPA has set a benchmark cord blood level of 58 mcg/L, the Faroe and New Zealand studies showed conclusive developmental effects at 5.8 mcg/L • Cord blood Hg levels are by 30-70% higher than maternal blood levels

18. Precautionary Principle At first sign of danger of a toxic substance stop or curb exposures and study further rather than pollute and expose while neurodevelopmental and other toxic effects on humans are unknown.

19. The Scientific Background • With increased scientific understanding toxic thresholds tend to fall • Small individual effects may cause profound population effects • Additive or Synergistic Effects – knowing the effect of one toxin at a time is not good enough (mercury and PCBs worse together than either alone)

20. 100 10 1 0.1 0.01 1970 1980 1990 2000 MercuryDeclining Threshold of Harm Level associated with Iraq34 µg/kg/d harmful effect Regulatory standard (maximum safe exposure or high end exposure from allowed fish contamination) (micrograms/kg/day Hg) DAILY INTAKE Faroe Islands<0.85 µg/kg/d FDA WHO ATSDR EPA RfD: 0.1 µg/kg/d YEAR

21. The Scientific Background II • Latency between exposure and effect • Animal studies consistently underestimate human neurodevelopmental toxicity • Windows of vulnerability in human development, especially neurologically • Emerging research on genetic susceptibility of subpopulations

22. Public Health Paradigms • Avoid exposures rather than expose to unknown • Prove no harm prior to large scale exposures • Protect those in particular need: • Reproductive years, pregnancy, early childhood • Underpriviledged and overexposed • Highly genetically susceptible (emerging) (Not those who profit from the hazard production and distribution)

23. Mercury Contamination of Environment • Seafood contamination of mercury 70% from anthropogenic sources, 30% from natural sources • Anthropogenic sources: • Coal-fired power plants (41%) • Municipal Waste Incineration (19%) • Industrial Boilers (18%) • Medical Waste Incineration (10%)

24. Mercury Contamination Regulations • Clean Air Act developed during 1990s and currently in effect would cut mercury emissions from power plants from 48 tons/year in 1999 to 5 tons/year in 2008 • Clear Skies Act would relax controls and permit 26 tons/year to be released through 2010. • EPA Utility Mercury Reduction Rule (passed 3/15/05, 38 tons/year until 2010, 15 tons/year until 2018)

25. Economic Cost of Mercury Pollution • “Public Health and Economic Consequences of Methylmercury Toxicity to the Developing Brain” Study • Loss of IQ secondary to mercury in 10-15% of the 4 million children born in US each year • $ 8.7 billion lost in earnings annually, coal-fired power plant emissions cause $1.3 billion of this economic loss

26. Clinical Application • Legitimize patient concerns • Answer your clinical questions • Individual patient education • Using media for patient education • Legislative work to protect your patients • Tracking Systems – document and find connections

27. What to Tell Patients • Children and all women of childbearing age should be cautioned re: mercury intake (especially King Mackerel, Swordfish, Shark, Tilefish) • When discussing benefits of fish in diet and fish oil capsules, caution re: mercury contents • Distribute practical advice cards and other patient education materials (such as from www.mercuryaction.org) • Advise people to check local fish advisories before eating any fish they caught themselves.

28. Websites to Find Mercury Info • www.mercuryaction.org • www.epa.gov/waterscience/fish • www.noharm.org • www.psr.org • www.dnr.wi.gov • Public Health and Economic Consequences of Methylmercury Toxicity to the Developing Brain article: http://dx.doi.org/