Chemical Hazards – can also be found in soil, food, vegetation, air, basically everywhere
Contaminants – any substance that MAY harm human health (but not necessarily)
Pollutants – any substance that is MORE LIKELY to harm human health – toxic
People think that if something is synthetic, then it is dangerous not
necessarily true some natural contaminants/pollutants are very
dangerous to human health.
- Endocrine disruptors
o Chemicals that interfere with normal hormonal functions in our body – create
adverse side effects eg. Cancers, birth defects, etc.
- Chemical body burdens
o Chemical pollutants are often called body burdens mimic body hormones
(same as endocrine disruptors) they can accumulate in the body = body
burdens can also be from industrial wastes
o We don’t know enough about these chemicals and how they affect human health
o Most studies and conclusions are based on animal studies that have similar
physiologies as humans (eg. rats, pigs)
- These chemicals disrupt the normal function of the endocrine system pituitary, pineal,
hypothalamus, etc… all produce hormones (these are chemicals that regulate many
important processes in our body)
o These disruptors bind to hormone receptors in the body (the body thinks this is
acceptable because they mimic the appearance of these hormones).
Note: Hormones are produced in low amounts
o Direct alteration of genes (appearance and function) disrupt protein
production (remember genes regulate proteins)
o Indirect alters hormone production, transportation, metabolism
o These are very dangerous especially to fetuses since the thyroid hormone is
primarily responsible for the brain development of fetuses in the womb.
o In adults, health consequences is not permanent recovery is possible.
- DES (diethylstilbestrol)
o During 1948-1971, this synthetic estrogen hormone was prescribed to prevent
spontaneous abortion among expecting mothers more than 1 million took this
in a period of 10 years, 1960-1970 administered during the first 35 weeks of
However, the resulting children had a wide range of health problems when
they reached 20-30 years of age.
During the 1980’s, problems started to show up in the offspring of the
mothers who took the hormone:
Reproductive organ dysfunction
Fertility problems in both sexes Immune system disorders
Endocrine Disruptors – Health Implications
- Affect behaviours - feminization of males (also in roosters), abnormal sexual behaviours
- Birth defects
- Altered puberty process (very early or very late)
- Cancers mammary glands or testes
- Thyroid dysfunction – PCB’s affect function of the thyroid gland
o TSH produces T3 and T4 which regulates the normal function of a fetus’ brain
and CNS development.
o In adults, hypothyroidism can occur.
- Neurobehavioural effects – mostly as a result from pre/post natal exposure to disruptors
affects mental development, decreases IQ, learning disabilities
o Post natal – from breast milk and other types of exposure e.g. baby formula
PCB (polychlorinated biphenyl contaminants)
Impaired learning in nonhuman primates - poor IQ tests
Delayed psychomotor development (eg. 4 year old moving like a 2
year old) - distractibility
Organophosphates – affects brain development
Chemical body burdens
- Every year thousands of chemicals are released – research can take a long time so the
adverse effects of these cannot be readily identified
- Body burdens endocrine disruptors are under this category it is basically the
number of chemicals accumulated inside the body or the total amount of all the chemicals
in the body (humans accumulate these chemicals throughout their lives since
conception…through breast milk…etc.)
o How much depends on location and mode of transmission.
o These are hard to metabolize in the body so they accumulate in body tissues
They are not distributed homogenously in the body – some accumulate
in hair, skin and some in livers or muscle some chemicals concentrate
in certain parts of the body.
E.g. Arsenic – accumulate mostly in hair
- Monitoring body burdens
o Computer modelling helps with predicting levels in the body can change since
they are excreted through sweat, urine, tears, etc. they can also be degraded
and changed to other forms most are persistent (can accumulate)
o Biomonitoring –
We try to monitor levels in the body; problem is that we don’t know the
We don’t have a technique to detect these chemicals in low amounts, PPB
(parts per billion).
Most techniques have detection levels – limitations Researchers usually test two groups of people – those who are exposed to
high concentrations and those who are exposed to “normal”
They compare these groups and try to figure out the consequences
of such exposure (health)
There are new chemicals as years go by and we have limited knowledge
on them and therefore not have the ability to detect them.
- Most are organic substance – they have Hydrogen and Carbon e.g. fats – plus they have
- DDT: insecticides, Dioxins: by-product of many processes
o Both are:
POP (persistent organic pollutants) – they don’t break down in the
environment and stay there for a very long time also stay in body for a
very long time and don’t break down.
Bio accumulating – buildup in tissues of humans and/or other organism
Bio magnification – buildup within the food chain – lowest get less, and
highest gets more (humans)
- These are group of chemicals with no usefulness and with similar chemical formula
(characteristics) but differ in their toxicity.