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Do not eat any shark, swordfish, tilefish, king mackerel or fresh caught or frozen tuna steaks. ... one ounce for a twenty pound child, to three ounces for a ... – PowerPoint PPT presentation

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Title: Toxicology

Toxicology Public Health
Jacque-Louis David
  • In 399 B.C. Socrates was accused of "impiety", of
    "neglect of the Gods whom the city worships and
    the practise of religious novelties" and of the
    "corruption of the young". Friends were willing
    to arrange for his escape Socrates, in deference
    to the rule of law, he took the poison Hemlock in

Cicuta maculata Cicutoxin
  • On October 5, 1992, a 23-year-old man and his
    39-year-old brother were foraging for wild
    ginseng in the midcoastal Maine woods. The
    younger man collected several plants growing in a
    swampy area and
  • Younger one took three bites from the root of one
    plant. His brother took one bite of the same
    root. Within 30 minutes, the younger man vomited
    and began to have convulsions they walked out of
    the woods, and approximately 30 minutes after the
    younger man became ill, they were able to
    telephone for emergency rescue services. He died
    approximately 3 hours after ingesting the root.
  • Although the older brother was asymptomatic when
    he arrived at the emergency department, he was
    treated. He began to have seizures and exhibit
    delirium 2 hours after eating the root he was
    stabilized and transferred to a tertiary-care
    center for observation. No additional adverse
    effects were reported.
  • The root ingested by the two brothers was
    identified as water hemlock (Cicuta maculata).
    Cicutoxin, a poisonous substance in water hemlock
    is the suspected killer

  • What are toxic substances?
  • How do we know they are toxic?
  • What do we do to manage toxic substances?

  • Negative effect of a chemical on the health of
    people and animals
  • Cancer effects (Carcinogen)
  • Leukemias, tumors
  • Noncancer effects
  • immune function,
  • allergies,
  • mutagenic,
  • hormone system

  • The dose the poison
  • Any chemical can be toxic at some dose

NOEL no observed Effect level LD 50 lethal
dose 50 ED 50 effective dose 50
  • In the lab chemicals are given to test animals at
    higher levels than are typically in the
  • From different doses a curve is drawn the
    amount that would kill 50 of the study animals
    is the LD50
  • ED50 is the level at which 50 of the population
    is affected

Precautionary Principle
  • A 1998 consensus statement
  • "when an activity raises threats of harm to human
    health or the environment, precautionary measures
    should be taken even if some cause and effect
    relationships are not fully established
  • Four central components
  • taking preventive action in the face of
  • shifting the burden of proof to the proponents of
    an activity
  • exploring a wide range of alternatives to
    possibly harmful actions and
  • increasing public participation in decision

Innocent until guilty
  • Testing for toxicity is a long, long process
  • One approach is to put substances out without
    exhaustive testing
  • Benefits advancement of new technologies
  • Downside is some things may be more harmful than
    originally thought.

Studying Toxins - Mercury
  • Mercury in the environment from dental work,
    manufacturing, also used in pesticide
    formulations in the past
  • Methylmercury formed by bacteria
  • CH3Hg

During the last 150 years, human activities have
more than doubled natural amounts of mercury in
the atmosphere
U.S. Environmental Protection Agency, 1997
Source categories
  • municipal and medical waste incineration (25
  • utility boilers (21)
  • commercial/industrial boilers (12) and (2).
  • Natural sources volcanic emissions, degassing
    from soils, and volatilization from the ocean.

USEPA Mercury Study Report to Congress,
Studying Toxins - CH3Hg
  • Methyl Mercury is the form that is highly toxic
    and easily assimilated in the body
  • Transported in red blood cells
  • Readily penetrates membranes resulting in
    widespread distribution in the body

Studying Toxins - CH3Hg
  • Central Nervous System is the target organ.
  • In the CNS, methyl mercury remains in the organic
    form but in other tissues is converted and stored
    as inorganic mercury

Studying Toxins - CH3Hg
  • LD50 values for various rodent species range from
    21 to 57.6 mg/kg
  • Blood mercury level of 200 µg/mL, is a level
    associated with minimal health effects in humans
  • (mg 0.001 L)

Studying Toxins - CH3Hg
  • Contaminated grain- Iraqi flour epidemic
  • Most severely affected infants had mercury blood
    levels ranging from 319 to 422 µg mercury/dL. (dL
    0.1 liter ug 1E-06)
  • 45 infant mortality rate was reported for
    pregnant women with signs of mercury poisoning
    versus a 7 mortality rate for the general

Studying Toxins - CH3Hg
  • Rats-changes in liver structure
  • Mice-behavioral changes, some tumor development
  • Monkeys- visual effects at low doses, decreases
    in pregnancy increase in lost pregnancies
  • Accumulates in fish tissue

Aquatic Studies of the environment
where ocean-derived salts measure less than 0.5
during the period of average annual low flow
Results of these types of studies
  • CH3Hg Bioaccumulates
  • (higher concentrations in tissues of aquatic
    plants and animals than in water)
  • factors can influence the bioaccumulation of
    mercury in aquatic biota. These include, but are
    not limited to, the acidity (pH) of the water,
    length of the aquatic food chain, temperature,
    and dissolved organic material. Physical and
    chemical characteristics of a watershed, such as
    soil type and erosion or proportion of area that
    is wetlands, can affect the amount of mercury
    that is transported from soils to water bodies.
    Interrelationships among these factors are poorly
    understood and are likely to be site-specific.
  • CH3Hg Biomagnifies
  • (higher concentrations at increasingly higher
    levels in the food chain)
  • Predatory fish have even more

Managing Toxins in the Environment
  • EPA limit of 2 parts of mercury per billion parts
    of drinking water (2 ppb).
  • FDA has set a maximum permissible level of 1 part
    of methylmercury in a million parts of seafood (1
  • OSHA has set limits of 0.1 milligram of organic
    mercury per cubic meter of workplace air (0.1
    mg/m³) and 0.05 mg/m³ of metallic mercury vapor
    for 8-hour shifts and 40-hour work weeks.

Mercury in Fish
  • http//
  • Duwamish River
  • polychlorinated biphenyls (PCB), arsenic,
    mercury, tributyltin, and polycyclic aromatic
  • Shiner perch, flounder, English sole, rockfish
    from Elliot Bay, shellfish, and crab
  • Consume no more than one meal of any of the above
    mentioned fish per month.  Do not eat the
    hepatopancreas of crabs or the livers from above
    mentioned fish.  Do not eat shellfish (clams,
    mussels) from the Duwamish River. 

Mercury in Fish 5/06
  • advice for women who plan to get pregnant, are
    pregnant, nursing or children under six
  • For sport caught fish
  • Eat no more than two meals per month of
    largemouth and smallmouth bass from fresh
    waterbodies in Washington State. 
  • For commercially bought fish
  • Do not eat any shark, swordfish, tilefish, king
    mackerel or fresh caught or frozen tuna steaks.
  • Limit the amount of canned tuna you eat, based
    on your bodyweight.

Types of Tuna
  • Albacore white meat, highly migratory species
  • Yellow fin canned, fresh, frozen, 2nd in volume
    and popularity, at its fishing limits today
  • Bonito smaller fish, moderate fat, fried or
  • Tongol canned white meat, not sufficient data
    on the catch available
  • Southern Bluefin- sashimi, most overexploited
  • Northern Bluefin canned, lives to 20 years,
  • Bigeye light grey, fattier, similar to
  • Skipjack most popular for consumption, canned,
    fresh, frozen,

Chunk Light Tuna 5/06
  • Women of childbearing age should limit the amount
    of canned chunk light tuna they eat to two cans
    of chunk light tuna per week (one can six
    ounces, two cans twelve ounces) based on your
    body weight. If you weigh 135 pounds you can eat
    one can (six ounces) per week, plus another fish
    meal low in mercury (see the list below). This
    second fish meal can include another serving of
    chunk light tuna that week.
  • Children under six can eat one half can (three
    ounces) serving of chunk light tuna per week,
    plus another fish meal low in mercury that week.
    Specific weekly limits for children under six
    range from one ounce for a twenty pound child, to
    three ounces for a child weighing about sixty

Canned Albacore (White) Tuna 5/06
  • Women of childbearing age should limit the amount
    of canned albacore (white) tuna to one can per
    week. If you weigh 135 pounds you can eat up to
    one can (six ounces) per week, but no other fish
    should be eaten that week.
  • Children under six should eat less than one half
    a can (three ounces) of canned albacore (white)
    tuna per week. If your child has eaten canned
    albacore (white) tuna, your child should not eat
    any other fish that week. Specific weekly limits
    for children under six range from one ounce for a
    twenty pound child, to three ounces for a child
    weighing about sixty pounds.

To Further Reduce Your Exposure to Mercury
  • Choose canned chunk light tuna over canned
    albacore (white) to further reduce your exposure
    to mercury. Chunk light tuna has three times less
    mercury than canned albacore tuna.
  • Eat fish that are low in mercury light tuna,
    salmon, cod, flounder, pollock (imitation crab,
    surimi), catfish, and shrimp are smart choices.

  • The major pathway for human exposure to
    methylmercury is consumption of contaminated
  • Fish and Shellfish Consumption Advisories in
    Washington State 

Web Sites with Information
  • EPAs Web Site -  http//
  • Ecology's Web Site - http//
  • Washingtons Mercury Chemical Action Plan
  • City/County Recycling - http//
  • The health impacts of mercury
  • Fish consumption advisories - http//www.doh.wa.go
  • Dental amalgams - http//

(No Transcript)
  • Nationally
  • bass,
  • pike and
  • walleye
  • have higher levels of mercury than other species.

National Mercury Studies
  • http//

Different kinds of hazards
  • Chemical
  • Physical
  • Catastrophic events, explosions
  • Political
  • Decisions favoring development over environmental
    health concerns
  • Social/Cultural
  • Environmental justice issues

Issues with Fishing
  • Some say nearly 70 of the fish are at risk
    (Monteray Bay Aquarium)

US Commission Study-2004
  • 20 of seafood farmed
  • Farm-raised shellfish such as oysters, clams and
    mussels. EAT THEM
  • These shellfish are filter feeders, eating
    plankton from the water, and so do not require
    wild fish for feed. These species can improve
    water quality.
  • Farming shellfish in nets, trays, or racks
    suspended in the water is an ocean-friendly
    alternative to dredging

Not so good farming
  • Farmed salmon is on the "avoid" list.
  • Dense living conditions in net pens along coastal
    waters lead to disease, requiring use of
    antibiotics in fish feed.
  • Steroids, chemical dips, vaccinations and added
    coloring also are widely used in farmed salmon.
  • Hundreds of thousands of farmed Atlantic salmon
    have escaped, competing with wild salmon and
    diluting native genetic stocks.

  • The waste from closed systems is easier to
    process and closed systems can better control
    pollution and escapes.
  • "Open systems" with ponds or nets containing the
    fish in wetlands or at river mouths are more
    problematic than closed systems in general.
  • Then again, some Atlantic salmon farmers in Maine
    use "open systems" and rotate their fish-raising
    pens to give these areas time to recover. This is
    proving effective in reducing disease and

  • Seafood on the "red" list should be avoided
    because it's over-fished or caught or farmed in
    ways that harm marine life and the environment.
  • Fish in the red category includes
  • most shark,
  • Chilean sea bass,
  • king crab,
  • orange roughy,
  • imported shrimp and
  • Atlantic swordfish.

  • Seafood in the "yellow" category is a good
    choice, but there are some cautionary concerns
    with the way it may be caught or farmed.
  • This includes Swordfish from the Pacific Ocean,
  • king crab,
  • wild clams,
  • U.S. farmed shrimp or
  • U.S. trawl-caught shrimp.

  • The best seafood choices always are in a "green"
    category, which means the fish are abundant, well
    managed and caught or farmed in environmentally
    friendly ways. These fish typically include
  • Alaskan wild Salmon,
  • wild Halibut,
  • farmed abalone,
  • farmed catfish,
  • farmed oysters,
  • trap-caught wild shrimp, and
  • farmed sturgeon.

Genetically Modified
  • Ti plasmids in plants that infects the DNA
  • Fertilized eggs can be injected with gene of
    interest, electrify test for presence of that
  • U Toronto Zoology Image

Why modify
  • Faster growth
  • Better taste
  • Disease resistence