HLTC23H3 Lecture Notes - Lecture 5: Dibenzofuran, Akwesasne, Peroxidase

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28 Jan 2013
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HLTB02 LECTURE FIVE = ENVIRONMENTAL FACTORS
Determinants of Human Growth:
Genetic
Endocrine system
Cultural factors
Environmental factors
Environment
Bergman‘s Rule: populations in colder climates are fenerally larger, with wider torsos/stockier stature,
since reduced surface area relative to body weight limits heat loss
Allen‘s Rule: populations in colder climates will have shorter arms and legs relative to height (to limit
heat loss), while those in warmer climates will have longer arms/legs
Note: improved nutrition, particularly in tropical regions, is now reflected in weaker climate-body size
relationships than in past
Environment:
Temp
o Cold requires higher rate of basal metabolic rate and robs body of energy used for
growth
Energy used to keep body alive instead of growth
Altitude
o Reduced oxygen hypoxia, high solar radiation, cold, low humidity, high wings, rough
terrain
Limits life and agricultural productivity
o Hypoxia: most severe climatic stress
Less oxygen reach body tissues, can‘t be compensated by cultural or behavioural
adaptions
Normal RBC saturated with oxygen 97%, at 3000 m, 90% only
Enough to disrupt cellular growth and metabolism
Ex. lower birth weight, Bolivia = 3.1 kg vs. 3.4 kg
o Hypoxia + poor nutrition (synergy must be together to have worse effect than either
individually) = shorter lighter kids, reduced rate of growth
Other studies suggest the ooposite: better growth rates in high altitude vs. low
altitude kids in same region
Poorer health and nutrition ‗cause malaria and parasites in lower altitudes
(moist, warm, humid)
Seasonality
o Temperate latitudes climate can affect growth (spring births vs. fall births could be
sunlight)
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Could act on human endocrine system directly, synchronize body‘s natural
fluctuations in growth regulating hormone activity
o Height: vitamin D, increases intestinal absortion of Ca and controls the rate of skeletal
remodeling and mineralization of new bone
Hypothalamus releases hormones that stimulate/inhibit release of pituitary
hormones
Pituitary gland releases hormones into circulation moving to specific target
tissues
Thyroid hormones = thyroxin, triiodothyronine
Gonadal hormones = luteinizing hormone, follicle-stimulating hormone]
Adrenal hormones from kidneys = glucorticoids, ex. cortisol and androgens
Growth hormone from liver
o Weight: can be product of food availability (seasonal food shortages)
Pollutants:
o Natural and anthropogenic
Anthropogenic:
Air
o Smoke cooking, fire, coal-burning respiratory diseases, lung
cancer, cigarettes
Second-hand smoke, during pregnancy lower birth
weight, altered fetal growth but continued exposure =>
respiratory conditions, Sudden Infant Death Syndrome
(SIDS), ADHD, depression, cognitive impairment, later
adult health problems, cancer
o Smog burning of fossil fuels, mixed with fog: photochemical
smog action of sunlight on chemicals found in air pollution
(car exhaust)
o Industrialization chemicals CO, nitrogen oxides, asbestos, etc.
Water pollution contamination from landfills and waste water from
industrial plants; natural disasters and hurricanes
o Chemical fertilizers, seepage down to water table, leaching from
plant, to soil to earth to layers to water reservoirs and shit
o Health effects: leukemia, cancer, neurological disorders
Solid Waste Pollution
o leads to air and water burned shit, crap seeps into water
poisoning, respiratory problems, etc.
Ex. Minamata Bay methylmercury contamination of bay in Japan (aka
Minamata disease)
CNS impairment due to severe mercury poisoning
o Symptoms: numbness in limbs, muscle weakness, lack of
coordination, vision and hearing damage, impaired speech,
paralysis, coma and death
o Congenital: affected fetuses, showing impairments similar to
cerebral infantile paralysis (worse effect that on adults)
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