Jacque-Louis David
Toxicology & Public Health
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
prison.
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?
Toxicity
• 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
Dose/Response
• The dose = the
poison
Any chemical can
be toxic at some
dose
NOEL – no observed Effect
level
LD 50 – lethal dose 50%
Dose/Response
ED 50 – effective dose 50%
• In the lab chemicals are given to test animals at
higher levels than are typically in the
environment
– 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 scientifically"
Four central components:
1. taking preventive action in the face of
uncertainty;
2. shifting the burden of proof to the
proponents of an activity;
3. exploring a wide range of alternatives to
possibly harmful actions; and
4. increasing public participation in decision
making.
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
During the last 150
years, human
activities have
more than doubled
natural amounts of
mercury in the
atmosphere
• Methylmercury formed by bacteria
U.S. Environmental Protection Agency,
• CH3Hg+
1997
Source categories
– municipal and medical waste incineration (25%
each);
– 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,
http://www.epa.gov/ttn/oarpg/t3/reports/volume3.pdf
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 population.
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
http://risk.lsd.ornl.gov/tox/profiles/methyl_mercury_f_V1.shtml#te
http://www.atsdr.cdc.gov/toxprofiles/tp46-c2.pdf
Aquatic Studies of the environment
where ocean-derived salts measure less than 0.5 ‰ during the period of
average annual low flow
http://www.fcsc.usgs.gov/posters/Ecotoxicology/Mercury_in_Bass/mercur
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 sitespecific.
• 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 ppm).
• 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.
http://www.epa.gov/ost/fishadvice/advice.html
Mercury in Fish
http://www.doh.wa.gov/fish/FishAdvMercury.htm
Duwamish River
polychlorinated biphenyls (PCB), arsenic, mercury, tributyltin, and
polycyclic aromatic hydrocarbons
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.
http://www.doh.wa.gov/ehp/mercury/default2.htm
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.
http://www.doh.wa.gov/ehp/mercury/default2.htm
Types of Tuna
1. Albacore –white meat, highly migratory species
2. Yellow fin – canned, fresh, frozen, 2nd in volume and
popularity, at its fishing limits today
3. Bonito – smaller fish, moderate fat, fried or canned
4. Tongol – canned white meat, not sufficient data on the
catch available
5. Southern Bluefin- sashimi, most overexploited
6. Northern Bluefin – canned, lives to 20 years,
overexploited
7. Bigeye – light grey, fattier, similar to yellowfin
8. Skipjack – most popular for consumption, canned, fresh,
frozen,
http://www.atuna.com/index.htm
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 pounds.
http://www.atuna.com/species/species_datasheets.htm
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.
– Fish and Shellfish Consumption Advisories
in Washington State
Web Sites with Information
• EPA’s Web Site - http://www.epa.gov/mercury/about.htm
• Ecology's Web Site - http://www.mercurymess.org
• Washington’s Mercury Chemical Action Plan http://www.ecy.wa.gov/programs/eap/pbt/hginenv.html
• City/County Recycling http://www.ecy.wa.gov/programs/swfa/contact/recyclelinks.html
• The health impacts of mercury – http://www.doh.wa.gov/fish/
• Fish consumption advisories http://www.doh.wa.gov/ehp/oehas/EHA_fish_adv.htm
• Dental amalgams http://www.doh.wa.gov/ehp/oehas/amalgam_dental_fillings_122003.htm
• Nationally
– bass,
– pike and
– walleye
• have higher levels of mercury than other species.
National Mercury Studies
http://water.usgs.gov/pubs/fs/fs-016-03/
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
http://www.oceancommission.gov/documents/prelimreport/welcome.html
Farming
• 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 pollution
RED LIST
• 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
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most shark,
Chilean sea bass,
king crab,
orange roughy,
imported shrimp and
Atlantic swordfish.
YELLOW
• Seafood in the "yellow" category is a good choice,
but there are some cautionary concerns with the
way it may be caught or farmed.
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–
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This includes Swordfish from the Pacific Ocean,
king crab,
wild clams,
U.S. farmed shrimp or
U.S. trawl-caught shrimp.
GREEN
• 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
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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
gene
•U Toronto Zoology I
Why modify
• Faster growth
• Better taste
• Disease resistence