Environmental toxicology

Question 1

Key factors in a risk assessment for a potential toxicant

Answer 1

hazard identification (what health problems are caused?) –> dose response assessment (what problems occur at different exposures?) –> exposure assessment (how much of the pollutant are people exposed to during a specific time period, and how many were exposed?) –> Risk characterization (what is the extra risk of health problems in the exposed population

Question 2

Genotoxicity

Answer 2

damage to genetic material caused by an external agent (chemicals, ionizing radiation)

Question 3

Lead toxicity, clinical presentation, and treatment

Answer 3

Lead mimics other divalent metals (zinc, calcium) and takes the place of them in biologically important proteins

Sx: headaches, irritability, reduced sensations, aggressive behavior, difficulty sleeping, abdominal pain, poor appetite, constipation, anemia

in children: loss of developmental skills, behavior/attention problems, hearing loss, kidney damage, reduced IQ, slowed body growth

accumulation of protoporphyrin and delta-ALA because ferrochetalase and ALA dehydratase are inhibited

Tx: EDTA (IV, along with cadmium and zinc), dimercaprol (IM), succimer (PO), penicillamine (PO, along with merc, zinc, and copper)

Question 4

Mercury toxicity, clinical presentation, and treatment

Answer 4

organic mercury is fat soluble but found as a contaminant in water; primary environmental form

binds cellular sulfhydryl groups to cause sx

Sx: pneumonitis, erethism (“mad hatter disease”), gross tremors, gingivitis, nephrotic syndrome, mercurialentis (brown discoloration of anterior capsule of lens)

Tx: dimercaprol, succimer, unithiol (PO, IM), penicillamine

Question 5

Arsenic toxicity, clinical presentation, and treatment

Answer 5

stable As-S complexes, unstable arsenoesters (with phosphate), reactive oxygen species

also, genotoxicity, altered DNA repair, signal transduction, cell proliferation, altered DNA methylation

Sx: garlic odor, delirium, night blindness, hyperkeratosis (fish scale skin), painful glove and stocking neuropathy, cardiac toxicity, Mee’s lines (horizontal lines across nails)

Tx: dimercaprol, succimer, unithiol

Question 6

Key clinical features of toxicity from manganese

Answer 6

soil, air, and water contamination

Sx: neurotoxicity manifesting as Parkinson’s disease

Question 7

Key clinical features of toxicity from bismuth

Answer 7

OTC products (pepto bismol), cosmetics

Sx: encephalopathy, blue-black gum line, lichen planus-like skin rashes, weight loss, GI sx, black stools

Question 8

Key clinical features of toxicity from cobalt

Answer 8

alloys, batteries, dyes, magnets

Sx: cardiomyopathy, deafness, tinnitus, neurological sx

Question 9

Key clinical features of toxicity from aluminum

Answer 9

cookware, personal hygiene products, dialysis

Sx: hypophosphatemia leading to anorexia, malaise tremors, muscle weakness

Question 10

Key clinical features of toxicity from silver

Answer 10

jewelry, photography, metallurgic industry

Sx: pigmentation of skin, eyes, mucous membranes

Question 11

What is a risk of heavy metal poisoning treatment?

Answer 11

Mobilization of heavy metal from hard tissues (i.e. bone) could actually increase body exposure to the neurotoxic effects of the metals

Question 12

exposure v dose

Answer 12

exposure from air, water, food, pharmaceuticals, household goods, or occupational

dose is how much enters the system

Question 13

mutagen

Answer 13

agent that causes damage to DNA

Question 14

clastogen

Answer 14

agent that causes breaks to chromosomes

Question 15

aneugenic

Answer 15

agent that affects cell division causing loss or gain of whole chromosome

Question 16

what is a heavy metal?

Answer 16

metal with atomic weight > Na(23) and a specific gravity (density) >5gm/cm3; arsenic, lead, mercury

Question 17

elemental mercury

Answer 17

stable, liquid at room temp, exposure through vapor; dental amalgam, thermometers

Question 18

inorganic mercury

Answer 18

water soluble salts (mercuric chloride)

Question 19

benefits of heavy metal chelation

Answer 19

form non-toxic complexes, remove metal from soft tissues, oral therapy available

Question 20

drawbacks of heavy metal chelation

Answer 20

redistribution of toxic metal, no removal of metal from intracellular sites, hepato- and nephrotoxicity, headaches, nausea, increased BP

Question 21

combination chelation therapy

Answer 21

incorporation of two structurally different chelating agents (lipophilic and lipophobic)

Question 22

Key clinical features of toxicity from thallium

Answer 22

manufacture of electronics, artists’ paints

Sx: GI, progressive peripheral neuropathy, scaling on palms and soles, hair loss, loss of color vision