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Cornell-style notes, lecture 5

Environmental Science
Course Code
Jovan Stefanovic

of 3
Human Health and the Environment Study Notes
Lecture 5
Key pointsNotes
Heavy MetalsNaturally occurring and extracted in the form of ore
Toxic even in low levels
Accumulates in selected organs—bioaccumulates
Wide environmental dispersion
Classification of
Class A:
Essential to biological processes
Forms ionic bonds
Low toxicity
Class B:
Nonessential elements
Covalent bond (very strong)
Organometallics: complexes between metals and
organic compounds—very soluble when they enter
your body. Very toxic
Micronutrients: needed for some biological processes,
but in low concentrations
Toxicity: class B>Borderline>Class A
Mechanisms of
toxicity: (a.k.a how it
works in order to be
1.Blocking essential functional groups such as proteins,
and enzymes
2.Displaces other metals
3.Modifying the active conformation of biomolecules
Coping mechanisms1.Resistence
2.Tolerance: metals may exist in our bodies but a
tolerance allows us to be unaffected: internal
detoxifying system, metabolic transformation:
transforming toxic metals into less toxic organic forms
Bioavailability of
metalsBioavailability: the proportion of a metal that enters
the circulation when introduced into the body and so
is able to have an active effect.
Not all metals ingested become bioavailability
pH affects this
Acidic solutions =more bioavailable and toxic
Redox potential The ability of the medium to oxidize or reduce metals
More oxygen = better oxidization or reduced metals
Less oxygen = reduced conditions = more toxic
Routes of exposure1.Inhalation
2.Ingestionplants absorb in roots and fruit also
becomes infected
3.Through the skin
Health effectsAccumulates in the liver, kidney and bones
Damages brain, kidney and some carcinogens
Difficult to diagnose (weakness, headache,
MercuryToxic in any other form other than pure form which is
a liquid
Very toxic when it evaporates
Organic and inorganic forms = toxic
Bioaccumulation: biggest source of mercury found in
fish specifically tuna fish
Tremors, excitability, memory loss, insomnia and
sometimes delirium
Great effect on children and fetuses. Especially in
their nervous system
Can result due to exposure to low levels: mental
retardation, language, memory and neural problems
CCA wood
preservativeChemical used to prevent wood rotprolongs age of
wood products
CCA-C: chromated-copper-arsenate
Pros: efficiently contributes to sustainability of
Cons (environmental concerns): leaching into water
and soil, which can lead to ingestions, inhalation,
plants, soil organisms and ground water
Different CEC
CEC: caution exchange capacitydifferent capacity to
hold and uptake the cautions. The ability of soil to
hold metals gives soil an opportunity to make a
barrier against toxicity
When max is reached leaches into ground water.
Ar+Cr =carcinogens, Cu= not
ToxicityAs—accumulates in nails, hair and skin
Dangerous carcinogen= skin, bladder, lung, liver and
kidney cancer
Immune suppression
Cardiovascular disease
Low level =change in hormone function
Cr—carcinogenic: lung cancer
Cu—vomitting, diarrhea, stomach cramps, nausea
Liver damage (young child, and high dose)
Toxic in aquatic environment
Present situation Prerequisition principle—better safe than sorry
Experimenting with ACQuses Cu instead of As
Less toxic to people, but more toxic to aquatic life.