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EESA10H3 Lecture Notes - Asthma, Blood Sugar, Chisso

Environmental Science
Course Code
Jovan Stefanovic

of 4
Lecture 5
Heavy Metals and Human Health
Heavy Metals
- Naturally occurring extracted from the earth’s crust
o Toxic even at LOW concentrations mostly are in the industrial section.
o Wide environmental dispersion
Impacts the water, air, soil enters the food chain ultimately affects humans.
Biomagnification increase accumulation as you go up in the food chain
Bioaccumulation accumulation of one compound/chemical in a tissue
o E.g. Arsenic goes directly into nails and accumulates
- Metals are classified according to toxicity and importance to the biological system:
o Class B > Borderline > Class A
o Class A
Essential for biological processes
Macronutrients animals need these in their bodies
Very low toxicity
Form ionic bonds (attraction between positive and negative ions)
E.g. K, Na, Mg, Ca
o Class B
Not important for biological processes
Very toxic in ANY form
E.g. Mercury is toxic in its organic and inorganic form
Form covalent bonds (two ions share electrons very strong bond)
They are also organometallics complexes between metals and organic
In addition to this, they are also soluble when they enter the body that’s
why they are very toxic
Eg. Hg, Ti, Pb, Ag, Au
o Borderline
Important for biological processes in very LOW concentrations (as opposed to
Eg. Arsenic (As)
Belongs to the borderline group
o It’s not essential and not even a metal but belongs here because of
its toxicity.
Eg. Cr, Fe, Co, Ni, Cu, Zn, Mn
- Mechanism of Toxicity
o Metals can:
Block functional groups such as proteins and enzymes so proteins cannot
carry anything
Displace other metals
Non-essential ones can replace the essential metals in our bodymostly
Class B’s and borderlines
Change/modify the conformation of biomolecules Class B
Make them inactive
- Coping Mechanisms
o Resistance
Some species have mechanisms not to take toxic metals in their system.
E.g. Plants have a mechanism not to take in toxic chemicals
o Tolerance the capacity of organism to withstand high levels of metals
Internal detoxifying mechanisms
Bind to nonsensitive compound structures
o Metals will bind to other less crucial chemicals instead to essential
proteins in the body so won’t affect the metabolism.
Metabolic transformations to less toxic form
o Methylation of Arsenic (As) in marine biota
Arsenic is converted from a toxic inorganic form to a less
toxic organic form
E.g. As III to As V
Can develop multiple tolerance
o E.g. Cu, Pb, Zn, Cd
- Bioavailability of Metals
o Species of a metal
Free ions some are more available than others
E.g. Charged Zn (Zn2+) ions are more available than neutral Zn
pH affects bioavailability
Metals are more bioavailable and toxic in acidic solutions
o E.g. in acidic soil, plants accumulate more Lead (Pb)
Redox potential (ability of the medium to oxidize or reduce a metal)
More oxygen = Increased oxidization = Less toxic metals
Less oxygen = decreased oxidization = more toxic metals
- Routes of Exposure
o Plants accumulate metals
Generally, roots accumulate more metals than leaves
Seeds have the less concentration of metals
Better to grow something from seeds corn, wheat, seeds
Roots are not good for us carrots, beans
Potato is more of a storage than a root
o Inhalation (dust, particulate matter (PM), fumes, gas)
Can enter through the skin, inhalation, ingestion (through roots and leaves of
Accumulate in bones, liver, tissues, kidney etc…
Damage bodily systems/organs carcinogens
Very hard to diagnose common s/s such as headaches, flu, weakness,
Mercury (Hg)
- Toxic in any form (organic or inorganic)
o E.g. batteries, dental amalgams (can release mercury at a high level), thermometers (not
toxic until it evaporates)
o Exception = liquid form not a significant hazard until it evaporates
When spilled, it scatters into silver puddles that releases invisible vapor that is
heavier than air hazard especially to children and pregnant women.
Infant and fetus systems are sensitive to low concentrations of Hg mental
retardation, language, memory, and cognitive problems are expressed during
Fumes are very toxic
Delirium, tremors, excitability, memory loss, insomnia Hatter madness
- Bioaccumulate mostly in fish
o Reaches the top of the food chain when eaten
o Tuna fish, seafood
Case Studies
Minamata disease 1st time the effects of Mercury were realized raised global awareness
- Chisso Factory dumped methyl mercury in the surrounding waters 1932 -1968
o First discovered in 1956 as a significant number of the population became very ill
- Mercury biaccumulated in the wildlife shellfish, fish
o Top of the food chain were affected dogs, cats, birds, eventually humans
- Caused deaths and sickness which continued for over 30 more years (lack of government
o s/s: Ataxia (lack of muscle coordination), numbness, muscle weakness, decrease in field
vision, difficulty in hearing and speech
In extreme cases: paralysis, insanity, coma, death
Congenital birth defects affected fetuses in wombs of pregnant mothers
Environmental impact of CCA wood preservative
- Wood preservatives pesticides that prolong the life of woods used in
homes/buildings/playgrounds protects wood from insects, rotting, etc…
- CCA-C most used chromated-copper-arsenate
o Water borne preservative soluble in water = acidic help in wood preservation
o Vacuum pressure impregnation treatment of wood
Lumber goes inside a chamber water and air is pulled out from the wood
CCA solution is incorporated under high pressure
Retort-fixation process - components of the wood, such as ash, minerals, etc…
react with the CCA solution this prevents these components from leaking out
of the wood thus prolonging the life of the wood.
This process occurs outside (open air) and takes about 2-3 weeks to
- Production of CCA wood before 2003
o 100% of residential lumber ; 70% of all wood products important industry in North
- Positive aspects of CCA preservation
o Really good preservative (can last up to 50 years or more)
contributes in sustaining the forest since there is less demand for wood cutting