3 Pb

Question 1

what is Pb?

Answer 1

lead
-atomic number 82
-non-essential metal
-denser than most metals, soft malleable metal, low melting point
-exists primarily in two oxidation states Pb(II) and Pb(IV)
-organic forms

Question 2

what are the sources of lead?

Answer 2

-paint
-leaded gasoline
-mining and smelting
-urban runoff
-recreational shooting
-soldering
-making jewelry, pottery, stained glass
-water supply pipes (plumbing)
-batteries
-radiation shielding
-house renovations

Question 3

what is the exposure to lead?

Answer 3

water
-lead contamination of soil and water from extraction, production, use and disposal of lead

air
-atmospheric emissions peaked during the industrial revolution but still remains a substantial concern from bioaccumulation and coal burning

soil
-lead in soil can inhibit photosynthesis
-impacts on growth and survival of plants

diet
-bioaccumulation can allow lead to ascent the food chain
-many animals can exhibit toxicity in similar ways as humans

Question 4

what is the fate of lead?

Answer 4

environment
-water soluble
-streams, lakes, rivers

vertebrates
-short-term exposure lead detected in the blood, liver and kidneys
-long-term exposures->bone

Question 5

what are the effects of lead?

Answer 5

Question 6

how does it interact with essential metals, proteins and nucleic acids?

Answer 6

effects protein synthesis

interferes with enzyme function:
1. binds to sulfhydryl groups (-SH)
-change enzyme configuration
-decrease ATP production in mitochondria
2. mimicking/displacing essential metal co-factors in enzymatic reactions
-calcium, iron, zinc

Question 7

how is there organ and system dysfunction?

Answer 7

main systems affected
-nervous (central nervous system)
-hematopoietic
-renal
-bone

other effects
-reproduction and endocine
-cardiovascular
-immune
-carcinogenicity

Question 8

what are the effects on the CNS?

Answer 8

brain
-cross the BBB by mimicking calcium
-organic forms enter brain
-encephalopathy

neurons
-degrade myelin sheaths of neurons
-decrease the number of neurons
-interferes with neurotransmission
-decreases neuronal growth

behavior
-hyperactivity
-decreased learning
-increased aggression

Question 9

what are the effects on hematopoietic?

Answer 9

-heme synthesis
-anemia
-basophilic stippling
-fragile RBCs

Question 10

what are the effects on the kidneys?

Answer 10

acute nephrotoxicity
-tubular necrosis
-fanconi’s syndrome-> glucose and amino acids in urine

chronic nephrotoxicity
-fibrosis
-progressive nephron loss
-azotemia-> high levels of urea and creatinine in the blood
-kidney failure

Question 11

what are the effects on bone?

Answer 11

-lead substitutes for calcium in bones
-impacts on osteoblasts-> delayed fracture repair

Question 12

what are the effects on reproduction and endocrine systems?

Answer 12

-chromosome breakage
-gametotoxic (sperm dysfunction)
-embryotoxic (miscarriages)
-weak teratogen

-thyroid and ACTH function impaired

Question 13

what are the effects on the cardiovascular system?

Answer 13

-hypertension
-ECG changes

Question 14

what are the effects on the immune system and others?

Answer 14

immune system
-decreased macrophage activity
-decreased antibody production
-increased susceptibility to endotoxins

carcinogenicity
-weak carcinogen or cocarcinogen
-implications from immune suppression

Question 15

what is the excretion of lead?

Answer 15

-urine
-feces

Question 16

what is the treatment of lead?

Answer 16

chelation therapy

medical procedure that involves the administration of chelating agents to remove heavy metals from the body
-administered under very careful medical supervision due to various inherent risks

chelators
-dimercaprol
-dimercaptosuccinic acid
-penicillamine
-ethylenediamine tetraacetic acid (EDTA)

does not reverse damage, but can prevent further damage

Question 17

what are the side effects of chelation therapy?

Answer 17

-vomiting and fever
-low blood calcium (hypocalcaemia)
-cytotoxicity and genotoxicity
-kidney damage
-can have reproductive and developmental effects (rodent experiments)
-death

Question 18

what is the risk of lead? who is at risk?

Answer 18

-children
-pregnant women
-medical condition
-genetic susceptibility

Question 19

what are the case studies of lead?

Answer 19

1. lead in ancient rome
2. lead in the news-Flint, Michigan
3. wildlife lead poisoning
4. franklin expedition

Question 20

what was lead in ancient rome?

Answer 20

-used in pipes that channeled water into homes
-neurotoxicity
a) interferes with enzymes
b) mimics calcium
c) displaces other metal cofactors
-fatigue, problems with sleep, headaches, stupor, slurred speech, anemia

Question 21

what happened in Flint, Michigan?

Answer 21

source
a) changed the water source from Detroit supplied Lake Huron to Flint River
b) corrosion of lead pipes partially due to ferric chloride treated water

fate
a) high levels of lead leached into the drinking water

effects
a) fetus and children particularly vulnerable to neurological impacts
b) long term effects being monitored

Question 23

what was wildlife lead poisoning?

Answer 23

-lead shot (hunting) and lead sinkers (fishing)
-~1 million bird deaths every year

ingestion by fish and wildlife
-slow digestion in gizzard or gut, release to bloodstream
acute or chronic
-emaciation, death
-sublethal effects on nervous system

Question 24

what was franklin’s expedition?

Answer 24

-1845 expedition to the arctic by ship
-never returned
-lead in bones
-tin cans? ship water?