week 9- environment Flashcards
• Common wastewater contaminants:
o antibiotics, perfumes, detergents, drugs, steroids, disinfectants, etc.
o surface water and ground water
o runoff from large areas → concentrated
o potential risks to human health if → drinking water
• toxicants: sources, transport/transform, removal, effects:
o S: industry, transportation, sewage plants, agriculture, fire
o T: sun, winds, clouds
o R: rain or dry deposition
o E: drinking water, human health, ground water, agriculture, smog, soils
• Airborne toxicants:
o Volatile chemicals travel far in winds
o Polychlorinated Biphenyl: similar to dioxin. Industry. carcinogenic, neurotoxin, endocrine disruptor
o PCBs: carried 1000s miles to arctic, found in polar bears and seals
o At low latitude, pollutant evaporation > deposition
o high: deposition > evaporation
• persistence:
o Some chemicals more stable, persist longer in environment
o DDT and PCBs are persistent
o Bt toxin in GM crops is not persistent
o Temp, moisture, sun, etc, affect rate of degradation
o Most toxicants degrade into simpler breakdown products
o Some of these are also toxic
o (DDT breaks down to DDE, also toxic)
• Bioaccumulation:
o Poisons accumulate in tissues
o body may excrete, degrade, or store toxicants
o Fat-soluble ones are stored.
o DDT is persistent and fat soluble → builds up in tissues
o → can move up the food chain
• Biomagnification:
o Poisons move up the food chain
o At each trophic level, chemical concentration ↑= biomagnification.
o DDT conc ↑ from plankton to fish to fish-eating birds
• Dose-response analysis:
o to determine toxicity by measuring response to different doses
o Lab animals used →Mice and rats breed quickly
o relevant to humans dt shared mammal physiology
o plotted on dose-response curve
• dose-response curve:
o threshold= dose at which response begins
o LD50= dose lethal to 50% of test animals
o Allow to predict effects of higher doses
o Extrapolation: predict how will affect humans at various conc
o usu response ↑ w dose
o OR: curve may not be linear
o endocrine disruption: may ↓
• endocrine disruption:
o Some chemicals in vivo “mimic” hormones
o Can bind → inappropriate response
o Normal: hormone system works w tiny conc
o → so it can respond to tiny conc of toxicants
• Signal words:
o relative acute toxicity of pesticide seen on label
o The (toxicologically) appropriate signal word MUST appear on every pesticide label
o The three possible signal words are:
o 3 words: danger, warning, caution, (notice?), (poison)
• CAUTION:
o lowest toxicity o All pesticides w LD50 > 500 mg/kg must display o 2 groups: o “Relatively nontoxic” (>5000) o “slightly toxic” (500 – 5000)
• WARNING:
o intermediate toxicity
o All pesticides w LD50 50-500 mg/kg must display
o = “moderately toxic”
• DANGER, POISON:
o highest toxicity
o All pesticides w LD50 ↓ 50 mg/kg must display
o = “highly toxic”
o POISON= same thing, Legally defined term
o Label must have both “DANGER” and “POISON”
o also skull and crossbones icon
• factors affecting toxicity:
o Sensitivity to toxicant can vary w sex, age, weight, etc
o Babies, older, poor health → more sensitive
o acute = high exposure in short period of time
o chronic = lower amounts over long period of time
• synergistic effects:
o Substances can interact when combined
o → mb effects greater than sum of their individual effects
o Challenge: no way to test all possible combinations!
o → environment has complex mixtures of many toxicants
• Exposure:
o route (site) helps determine dose: diff routes → diff rates of absorption o Ex: Dermal (skin), Inhalation (lung), Oral ingestion (GI), Injection o route important if there are tissue-specific toxic responses → local or systemic o Time: how long exposed o Duration and freq contribute to dose, both may alter toxic effects o Acute = usu single exposure o Chronic = mult exposures over time (frequency)
• Transport and storage of toxins on body:
o T: Lymphatics, blood; usu via blood protein that binds toxicant, eg a lipoprotein
o S: Liver, Lungs, Kidneys, Bone, Adipose (fat)
o mb stored in one reservoir, later transported elsewhere
o Storage site may or may not be site of toxic effect
o Pb stored in bone, but toxic to liver
o DDT stored in fat but toxic via prolonged gradual release
• Detoxification in vivo:
o Some chem transformed/metabolized to aid excretion o Detox → less toxic metabolic product o Kidney → urine o Liver → feces, bile o Lung → expired air
• Types of toxicants:
o Carcinogens → CA
o Mutagens → mutations in DNA
o Teratogens → birth defects
o Allergens → unnecessary immune response
o Neurotoxins: damage nervous system
o Endocrine disruptors: interfere w hormones
• Environmental toxicity assessment:
o Toxin exposure hx most important factor to determine appropriate testing
o Detailed chronological hx, determine jobs, hobbies, geographical areas
o Acute & Chronic:
o In utero
o Childhood: vaccines, meds, food, water, air, environment, hobbies
o Dental: Hg, Ni
o Workplace: sick-buildings, agriculture, industry, military
o Age of house: Pb paint phased out 1978 (now only 0.06% Pb allowed)
• Heavy metal toxicity:
o Pb, Hg, Cd, As, Mn, Ni → Inorganic and Organic salts
o Heavy metals = protoplasmic poisons
o Impair cell fxn
o Astringent, corrosive, caustic to skin
o Lethal to microorganisms
o Accumulate in body on chronic exposure
o Damage liver, kidney, bone marrow, GI mucosa, neurons, skin
o not immediately recognized dt wide range of non-specific sxs
• mecanisms of heavy metal toxicity:
o usu mult o inhibit/potentiate Enzyme/cofactor o Disrupt membrane, transport processes o Disrupt mitochondrial fxn → fatigue o ↓ neuronal fxn & nerve conduction o Ability to bind to -SH groups on proteins & amino acids
• Lab tests for heavy metals:
o Hair o Serum o RBC analysis o Urine challenge: DMPS, DMSA o Blood chem, CBC, CC, CMP o Genetic: detox, cord blood, placenta
• Blood tests for heavy metals:
o Best for short-term acute exposure
o Metals cleared rapidly from blood, accum in storage depots
o T1/2 blood (days): long term deposition
o Pb 30-60 d: bone 25 yr
o Cd up to 120 d: liver & kidney 10-20 yr
o Hg 60-70 d: organic forms lipid soluble adipose, PNS, CNS for yrs
o As 2-12 hrs: liver, kidney, muscle, skin, brain
o Mn 10-42 d: bone and brain
o Ni 24 hrs: lungs, thyroid, adrenals
