Heavy Metals

Question 1

potential routes of exposure to heavy metals?

Answer 1

skin
ingestion
inhalation
ocular

Question 2

what does LD50 stand for?

Answer 2

median lethal dose
causes death in 50% of the group given toxic substance
the lower the LD50= THE MORE TOXIC IT IS

Question 3

five mechanisms of toxicity for heavy metals?

Answer 3

1. enzyme/cofactor inhibition or potentiation
2. disruption of membrane and other transport processes
3. disruption of mitochondrial function–> fatigue
4. decreased neuronal function and nerve conduction
5. bind sulfhydryl groups on proteins and a.a.s

Question 4

how are people exposed to lead?

Answer 4

home: dust, paint, soil, imported remedies, some cosmetics, miniblinds, metal wicked candles
work: swallowing lead dust, contaminated air, contact, bring home from work
hobbies: car repair, artistic painting, stained glass, pottery glazing, soldering, target shooting, making bullets, slugs or fishing sinkers
drinking water: boiling does not get rid of!
products: computers, solder, pewter, ceramic glazers, jewelry, automotive batteries, imported or older pre-regulation products
environment: soil near roadways, businesses with lead

Question 5

what population is at most risk for adverse effects dt lead exposure?

Answer 5

children living in older houses

PG women and the developing fetus

Question 6

health effects of lead?

Answer 6

most excreted but that which is not can move between blood, soft tissues and mineralizing tissues
affects all organ systems
developmental: crosses placenta, neurological effects on kids
neuro: targets hippocampus, decreases ASA activity
endocrine: effects vit D levels, may alter thyroid fxn w/chronic exposure
cardio: increases risk of HTN

Question 7

lead poisoning mechanism?

Answer 7

interferes w/heme synthesis by diminishing delta-ALA dehydratase activity= microcytic, hypochromic anemia w/basophilic stippling

Question 8

ssxs of lead poisoning?

Answer 8

irritability
anorexia
malaise
H/A
constipation
abd pain
renal toxicity
acute lead encephaloptahy

Question 9

how to best test for lead levels in the body?

Answer 9

BLOOD

adults: should be less than 20 mcg/dL
children: should be less than 5 mcg/dL

Question 10

how do you manage lead toxicity?

Answer 10

remove exposure to toxic substances
chelation: if very high blood levels
eat diet high in calcium and iron as these displace lead

Question 11

major source of mercury poisoning for the population at large?

Answer 11

inhalation of elemental mercury volatilized from dental amalgams

Question 12

3 forms of mercury

Answer 12

elemental mercury

organic: methylmercury, ethylmercury
inorganic: mercuric chloride, mercuric sulfide

Question 13

where do you find methylmercury? what can it cause?

Answer 13

find when person has eaten large amounts of fish over weeks to months - 95% comes from food
damages nervous system, infants can be born with cerebral palsy –> all because can cross the BBB

Question 14

where do we get exposure to ethylmercury from?

Answer 14

break down of thimerosal

excreted from body more quickly than methyl

Question 15

where are inorganic mercury forms mostly found?

Answer 15

skin lightening creams

should be less than 5 microg/L

Question 16

predominant commercial use of cadmium?

Answer 16

battery manufacturing

Question 17

airborne cadmium exposure occurs via what substances? can also be found where

Answer 17

burning fossil fuels
incineration of multiple waste materials
zinc, lead, copper or smelters
cigarette smoke inhalation
can also be found in the soil- has a high rate of transfer to plants such as cereal grains, wheat, rice, potatoes and seeds

Question 18

health effects of cadmium exposure?

Answer 18

can lead to iron deficiency
decreased olfactory fxn
accumulates in liver and KDs (irreversible proteinuria and progressive reduction in GFR) where it binds to metallothionein
can result in painful osteomalacia or osteoporosis
severe pneumonitis
emphysema
associated with lung CA
reproductive and teratogenic effects, increase in endometrial CA, may have a role in prostate CA

Question 19

historical uses of arsenic?

Answer 19

medicines, cosmetic lighteners, paint pigments, wood preservation

Question 20

two forms of arsenic? which is more toxic?

Answer 20

organic: excreted quickly via urine

inorganic is MUCH MORE toxic- well absorbed from GI tract, come from water, cigarette smoke and poultry

Question 21

health effects of inorganic arsenic on the body?

Answer 21

inhibition of numerous enzymes, substitution in phosphate metabolism, interference in signal transduction pathways, alters gene expression

Question 22

3 provocative chealtors?

Answer 22

DMSA
DMPS
EDTA