Lecture 9: Metal toxicity part II Flashcards
Lead
is found in ores with other metals. It can be mined but is often a byproduct of smelting other metals.
It’s dense and malleable (shape in into various forms) , and is the heaviest non-radioactive metal.
What is Pb used for?
- Humans have been using Pb for a long time
- Used as a malleable metal since at least 6500 BC in Turkey
- The Romans used a lot of Pb to make all their plumbing and much of their dishware. They even added powdered Pb to wine as a sweetener.
• Kohl is a mixture of lead sulfide and other resins that is used as a mascara developed in Egypt ~3100 BC.
– It is still used today in some cultures… but not all preparations have Pb in them.
• But Pb can still show up in make up.
What is route of exposure to lead?
from food or what we drink
What is the limit set by Health canada for lead?
Limit set by Health Canada is 10 μg/g
Explain how lead was used in gasoline
A lot of lead was used in gasoline
– Early automobiles used ethanol as an anti-knocking agent (allowed engine to run smoother and quieter) in gasoline. Could not patent this, so wasn’t profitable for corporations.
In 1921, Thomas Midgley at General Motors showed that tetraethyl lead (TEL) could replace ethanol in this function. This was patented.
– DuPont chemical owned 30% of GM and made the compound.
– They just named it ‘ethyl’ because issues with lead toxicity was already publicly known.
By 1936, 90% of all gasoline sold had TEL in it.
• In 1972, the EPA indicated that TEL was to be phased out of gasoline. Ethyl corporation promptly sued, but lost.
tetraethyl lead (TEL)
replaced ethanol in gasoline as an anti knocking agent
This was patented.
They just named it ‘ethyl’ because issues with lead toxicity was already publicly known.
What did research in 1979 show?
In 1979, research was published that showed that even low doses of lead caused developmental effects (lower IQ ratings) in exposed children. It still took until 1982 to completely ban it…
what kind of toxicant can lead be called?
teratogen
Exposure to Pb in utero and in childhood can lower IQ due to neurotoxicity.
What has happened since Pb has be phased out?
Pb in the air has decreased.
What are Other sources of Pb that we still encounter?
- Old paint
• Lead was added to oil paints up until the 1970s (10 to 50%)
• Canada Hazardous Products Act (1976) reduced to max. 5000 mg/kg (0.5%)
• In 2010, this was reduced to 0.009% - Old piping
• Lead was used as pipes and as solder joints for brass piping
• Lead pipes phased out in the 1950s, lead solder joints in 1989 - Batteries
• 88% of lead now used is in batteries - Glass and ceramics
- Ammunition
- Solder (electronics)
- Soil and food (main exposure source)
Explain how Pb can be found in ammunition and cause toxic effects
At a high enough level lead can be detected in animals
if you go shoot an animal and don’t properly get rid of all the shells/ lead in the bullets we can eat it
if animals are picking it up from the environment and its accumulating in their muscle tissue which is what we eat that is another source of lead toxicity
Describe the study of bald eagles
Researchers found evidence of chronic and acute lead poisoning in bald eagles. Acute poisoning may be associated with lead ammunition during the hunting season.
bald eagles also eat other animals
What was compared in the bald eagles to determine acute and chronic exposure?
compared lead levels in the blood which is more indicative of acute exposure
compared lead levels in bones which indicates chronic exposure bc it takes Pb longer to accumulate in the bones
Describe the Flint water crisis
Trihalomethanes
disinfectant by product; formed by reaction of chlorine (added to disinfect water) with organic matter
orthophosphates
are added to water to reduce the amount of lead leaching into it from pipes
What happened to fertility rates in Flint Michigan?
very dramatic drop in fertility rates after switching to lead pipes