slide1
Download
Skip this Video
Download Presentation
The Importance of Selenium/Mercury Research in Seafood and Health Factors

Loading in 2 Seconds...

play fullscreen
1 / 24

History - PowerPoint PPT Presentation


  • 217 Views
  • Uploaded on

The Importance of Selenium/Mercury Research in Seafood and Health Factors. Laura Raymond Energy & Environmental Research Center Grand Forks, ND March 28, 2007. History. Minimata Bay, Japan 1950’s

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'History' - Roberta


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

The Importance of Selenium/Mercury Research in Seafood and Health Factors

Laura Raymond

Energy & Environmental Research Center

Grand Forks, ND

March 28, 2007

history
History
  • Minimata Bay, Japan 1950’s
    • From 1932 to 1968, Chisso Corporation, dumped an estimated 27 tons of mercury compounds into Minamata Bay.
    • Hundreds of people died.
    • Over 3,000 victims have been recognized as having "Minamata Disease".
  • Iraq 1971-1972
    • Grain treated with mercury containing fungicide
    • 459 people died
    • Hospitalization of over 6,000
    • Hair Hg levels up to 674 ppm (today <1.4 ppm)
the great debate
The Great Debate
  • Faroe Island study
    • Neurological defects in children neonatally exposed to Hg from fish and whale consumption:
  • Seychelles Island study
    • No adverse effects in children born to mothers exposed to eating fish:
    • Fish consumption levels are 10-20X higher than common U.S. consumption.
reference dose 0 1 g kg bw day
Reference dose 0.1g/kg bw/day
  • Based on Faroe Island study
  • Benchmark Dose Lower Limit (BMDL)
    • U.S. has the lowest BMDL
      • World health organization, British Food Standards Agency, United Kingdom, Canadian government
  • Centers for Disease Control and Prevention indicate that no one in the U.S. tests anywhere near the BMDL.
  • Add an “uncertainty factor” of 10
  • Reference Dose value 0.1g/kg bw/day
methylmercury concentrations
Methylmercury concentrations

Reference dose 0.1g/kg bw/day

135-lb. woman: 1.5oz. Swordfish or 7 oz. tuna/week

50-lb. child: 0.5oz. Swordfish or 2.6 oz. tuna/week

  • Freshwater fish 0.1-0.4 ppm
  • Ocean fish 0.6-0.8 ppm
  • Predator fish > 1.0ppm
  • Fish in “polluted” water > 10ppm
  • Fish from Minamata Bay ~ 50ppm
  • Whale meat ~4ppm
  • Whale liver >1000ppm
reference dose 0 1 g kg bw day6
Reference Dose 0.1g/kg bw/day
  • The 2000 National Research Council Report stated that 60,000 newborns annually are born at risk due to methylmercury.
    • Assuming that women eating the most fish (the top 5%) are risking their babies health.
  • 2002 government hearing - this number was assumed to be increased to 400,000 pregnancies per year.
  • July 2006 national survey conducted by Opinion Research Corporation found that 40% of Americans believe at least 10,000 childhood cases of mercury poisoning are documented by scientists each year.
  • There are NO documented cases of mercury poisoning from fish consumption.
third study united kingdom study
Third Study United Kingdom Study
  • Increased risks for neurodevelopmental defects with decreased fish consumption:
    • Maternal compliance with the EPA RfD increased risks of their children scoring in the lowest quartile for verbal IQ, and increased risks for pathological scores in fine motor, communication and social skills compared to mothers exceeding the RfD recommendation.

Huh?????

Neurological defects - Faroe Island study

No adverse effects - Seychelles Island study

Increased riskswith decreased fish consumption -UK Study

selenium
Selenium?
  • “Protective effect” of selenium
  • Numerous reports indicating selenium supplementation counteracts the negative impacts of exposure to mercury.
    • Neurotoxicity
    • Fetotoxicity
    • Developmental toxicity
  • Protective effects of selenium against Hg toxicity has been shown in all investigated species of mammals, birds, and fish.
selenium physiology 21 st amino acid selenocysteine
Selenium Physiology21st amino acid – Selenocysteine
  • Development
  • Thyroid homeostasis
  • HIV and other viruses
  • Cancer
  • Immune system
  • Cardiovascular disease
  • Reproduction
  • Mood
  • Disease links
    • Congenital muscular dystrophy
    • Autism
    • Alzheimer\'s, Downs syndrome
    • Brain tumors
    • Diabetes
    • Liver diseases
    • Any condition associated with increased oxidative stress or inflammation (rheumatoid arthritis, pancreatitis, asthma, obesity, septic diseases)
protective effect of selenium
Protective effect of Selenium

Se binds to mercury, so mercury is unavailable to cause harm.

H2Se

+

MeHg

Se-Hg

Binding Affinity ~1045

Extremely low solubility ~10-58 to 10-65

or is it the thieving effect of mercury
Or is it theThieving effect of Mercury?

Hg is binding to selenium, so selenium is unavailable for it’s needed roles

MeHg

+

H2Se

Hg-Se

Binding Affinity ~1045

Extremely low solubility ~10-58 to 10-65

significance to mercury toxicity
Significance to mercury toxicity
  • During Se depletion, there is retention and redistribution of Se to the brain, endocrine organs and reproductive organs.
  • Mercury has the ability to cross the placental and blood-brain barriers and diminish Selenoenzyme activities!
research focus
Research Focus
  • Investigating the role of Se in Hg bioaccumulation, toxicity and retirement from the environment.
    • Molecular
    • Cellular
    • Tissue
    • Animal
    • Population
    • Environmental
effects of mehg in rats fed low normal and selenium rich diets
Effects of MeHg in rats fed low, normal, and selenium-rich diets

Objective: To investigate the effect of dietary mercury on selenium distributions and selenoenzyme activities in rats fed varying concentrations of mercury and selenium.

effects of mehg in rats fed low adequate and selenium rich diets
Effects of MeHg in Rats Fed Low, Adequate, and Selenium-rich Diets

All of these rats were fed diets prepared with 10 ppm methylmercury added. The rat on the left has been fed a selenium deficient diet, the center rat was fed a selenium adequate diet and the rat on the right was fed a selenium rich diet.

effects of mehg on neurobehavior
Effects of MeHg on Neurobehavior

This rat, fed a selenium-deficient diet with

10 ppm methylmercury, showed significant signs of neurotoxicity.

(hind limb crossing, uneven gait, poor motor coordination and loss of balance).

This rat, fed a selenium-rich diet with 10 ppm methylmercury, showed no signs of neurotoxicity.

selenium s therapeutic effect
SELENIUM’S THERAPEUTIC EFFECT
  • To exam potential therapeutic effects of selenium, at week 11 the toxicity group was further divided into three groups
    • No change in diet
    • Same amount of Hg with added Se
    • No Hg with added Se
results show
Results show…
  • Hair and blood Hg levels accurately reflect exposure BUT not risk.
    • Increased Hg in hair, blood and brain was associated with decreased toxicity.
    • The lowest Hg concentrations in hair, blood and brain were associated with the highest toxicity.
    • It was the molar ratios of Hg to Se that determined toxicity.
  • MeHg toxicity was only apparent with Se-deficient diets.
    • The increased molar excess of Hg:Se indicated toxicity.
  • Se-therapy effects were nearly identical in treatment groups regardless of whether MeHg exposure was discontinued or not.
why is this important
Why is this important?
  • Fish are among the richest sources of nutritional selenium in the American diet.
  • Out of 1100 foods commonly consumed in the United States, 16 of the top 25 sources of dietary selenium are from fish.

Fish data depicted from Hall et al. (1978); pilot whale from Julshamn et al.(1987)

and swordfish from Friedman et al. (1978).

selenium levels
Selenium Levels
  • Worldwide area with Low Selenium
    • Northern Europe
    • Finland
    • Sweden
    • New Zealand
    • Parts of China
    • Africa
can selenium explain the great debate
Can selenium explain “The Great Debate”?
  • Faroe Island study
    • Neurological defects in children neonatally exposed to Hg from fish and whale consumption
  • Seychelles Island study
    • No adverse effects in children born to mothers exposed to eating fish:
    • Fish consumption levels are 10-20X higher than common U.S. consumption.
  • United Kingdom Study
    • Increased risks for neurodevelopmental defects with decreased fish consumption
    • Maternal compliance with the EPA RfD increased risks of their children scoring in the lowest quartile for verbal IQ, and increased risks for pathological scores in fine motor, communication and social skills compared to mothers exceeding the RfD recommendation.
fda and epa message
FDA and EPA Message
  • The reference dose is based on mercury levels only
  • “Avoidshark, swordfish, golden bass, and king mackerel. Limit your fish intake to two meals per week and choose low mercury containing fish.”
  • 74% of women of childbearing age and 85% of pregnant women consume <6 oz/wk.
  • By focusing only on MeHg exposure without consideration and measurements of additional nutrients in fish, these warning statements are inadequate, inaccurate, misleading and potentially dangerous.
ad