Mercury Levels in Farm Raised Trout

1
Mercury Levels in Farm Raised Trout

• Gary Fornshell University of Idaho
• Jeffrey M. Hinshaw
• North Carolina State

2
Acknowledgements

• Nelson Sons, Inc.
• USTFA
• Environmental Quality Institute UNCA
• Processors and growers from Idaho, Michigan,
  North Carolina, and Pennsylvania
  

3
Why Mercury, and Why Now?

• Clean Air Mercury Rule
• 2004 FDA/EPA Joint Mercury Advisory on Seafood
• EPA Administrator Mike Leavitt Its about
  trout, not tuna. (Published comments by the
  Associated Press, 2004)

4
How Does Mercury Get Into Fish?

• Where does it originate?
• 60 from anthropogenic air emissions, of which
  coal fired utilities contribute 43
  
• 40 from natural sources
• Released primarily as elemental mercury via gases
  and particulates into the atmosphere
  
• Bacteria in aquatic environments convert
  elemental Hg into methylmercury, most toxic form
  for humans
  
• Bioaccumulation in fish results in increasing
  concentration with size, age, and tropic level
  
• Relatively few species have been tested

5
What Are the Health Risks?

• Effects depend on dose, age of person, duration
  of exposure, route of exposure and health of
  person exposed
  
• At high levels can harm brain, heart, kidneys,
  lungs, and immune system
  
• Nervous system damage (crosses blood-brain
  barrier placenta)
  
• Learning impairment, developmental delays
• Numbness or tingling in hands or feet, around the
  mouth problems with vision and hearing

6
How Much is TOO Much?

• Toxic effects of high MeHg exposures are well
  established in humans and animals
  
• Implications of low MeHg exposure remain
  controversial due to contrasting results observed
  in studies done in the Faroes and in the
  Seychelles
• Seleniums protective effect against MeHg
  toxicity has been demonstrated in all species
  studied
  

7
Documented cases of Prenatal MeHg Poisoning

• Contaminated grain
• Sweden 1954 (exposure unknown)
• Iraq 1972-3 exposure 100 ppm
• New Mexico 1971 (exposure unknown)
• Contaminated fish
• Minamata, Japan 1950s (exposure unknown)
• Niigata, Japan 1960s exposure 293 ppm

8
The Two Studies

• Seychelles
• Began in 1983
• High fish consumption 12 meals per week
• Prenatal exposure measured in maternal hair
  segments growing during pregnancy
  
• Exposure averaged 6.9 ppm range
• 4 MeHg associations
• Two beneficial one adverse one unclassified

9
The Two Studies

• Faroes
• Began in 1986
• High fish/pilot whale consumption (avg. daily
  adult consumption fish 72 grams whale meat 12
  grams whale fat 7 grams)
  
• Exposure measured in cord blood and hair
• MeHg associations language, attention, memory,
  visual spatial, motor
  
• Study complicated by PCBs and other toxins in
  whale meat/fat
  

10
Biomarkers Hair Cord Blood

• Hair
• Can recapitulate entire pregnancy
• Hg stable once deposited
• Known correlation with brain levels

• Cord blood
• Measures exposure near delivery
• Hg stable only in red blood cells and volume
  varies
  
• No data available correlating relation to brain
  concentrations

11
Conclusions Gary Myers, MDUniversity of
Rochester Medical Center

• Current evidence suggests
• Small risk of MeHg exposure in the 10-20 ppm
  range from any source including fish
  
• Late effects are not known
• A significant risk from consuming pilot whale
  meat blubber
  
• Whether this is from MeHg, PCBs, or other toxins
  is not clear
  

12
Safe Levels of Consumption

• ATSDR 0.3 µg/kg bw/d
• Seychelles uncertainty factor 3
• WHO Adult 0.5 µg/kg bw/d
• Pregnancy/child 0.15 µg/kg bw/d
• 5 risk at hair level 10 ppm
• Seychelles, Faroes uncertainty factor 6.4
• EPA 0.1 µg/kg bw/d
• Seychelles, Faroes, New Zealand uncertainty
  factor 10

13
MeHg Levels in Seafood (ppm)

• Bass 0.15-5.2
• Catfish ND-0.3
• Cod ND-0.4
• Flatfish ND-0.2
• Grouper
• Halibut
• Mahi Mahi ND-0.2
• Marlin 0.1-0.9
• RBT 0.015-0.110
• N 13 avg. 0.033

• Orange Roughy 0.3-0.6
• Salmon ND-0.2
• Sea Bass ND-1.0
• Shark 0.3-4.5
• Snapper ND-1.4
• Swordfish ND-3.2
• Tuna ND-1.2
• Oysters/shrimp ND

Source FDA
14
USGS Preliminary ID Hg Data
15
Mercury In Hatchery Fish
__________________________________________________
__
From a presentation by Noguchi et al., USFWS,
presented at the National Forum on Contaminants
in Fish, Sept. 18-21, 2005, Baltimore, MD.
16
USTFA Mercury Study

• 65 fish sampled
• 553 g avg. wt. (0.82 fish/lb)
• Avg. fish age 16 months
• Muscle tissue sampled
• Reporting limit 0.05 ppm Hg
• Five feed brands represented
• ID seep water springs

17
Hg Levels By Feed Brand (ppm)
18
Mercury Levels in US Farmed Trout
Average 0.014 ppm, all samples below legal repor
ting limits for measurement by cold vapor atom
ic absorption
19
Framing The Issue

• What man desires is not knowledge but certainty
  Bertrand Russel
  
• When one looks for cases of children, for
  instance, whove had learning disorders or other
  things related to mercury, its impossible to
  find them in the literature. There are no proven
  cases of that. And the risk of the toxicity is a
  theoretical risk, still, at this point in time.
  Dr. Myers
• This is great news. Dr. Rick Maas, EQI UNCA

20
Framing The Message

• Farm raised rainbow trout is low in mercury
• True, but take away message is RBT has Hg
• Change the message
• Seafood is for everyone
• Eating more seafood is vital to American health
• Seafood is the most healthy animal protein
  choice
  
• Mothers need seafood