Unit 8 - Toxicology Flashcards
What is toxicity?
An adverse health effect caused by a chemical.
What is toxicology?
The study of how chemicals interfere with the normal function of the biological system to cause an adverse health effect. This has a particular focus on human health.
What is LD50?
The median dose of a material that causes the death of 50% of tested organisms when delivered all at once.
What is LC50?
The median concentration of a material that causes the death of 50% of tested aquatic organisms.
If the material has a high LD50 or LC50, is it more or less toxic?
Less toxic.
What do LD50 and LC50 provide?
A quantitative measure of the acute (given all at once) toxicity of a material.
What is toxicity a function of?
The dose, the exposure and the time exposed to it.
What are the determining factors of toxicity?
Route of exposure - through skin, ingesting, inhaling.
Dose - the amount of the chemical.
Frequency of exposure.
Duration of exposure.
ADME - absorption, distribution, metabolism, excretion/elimination.
Biological properties - age, gender, ethnicity.
Chemical properties.
What is an example of occupational exposure triggering awareness to the threat of certain chemicals?
Neurological problems in rubber workers who used CS2 as a solvent.
Poisoning in children by lead in white paint (on toys).
Mercury poisoning in making felt for hats.
What are the aims of testing toxicity?
To identify a substances adverse effects on humans, plants, the environment.
This can be tested by acute exposure or multiple-exposure.
What are methods of testing toxicity?
In vivo - in a living organism.
In vitro - within a test tube or petri dish.
In situ - in its original place.
In silico - using computer programs.
How does in silico testing complement in vitro and in vivo tests?
It can reduce the cost and the need for animal testing as well as improving toxicity prediction and safety assessment.
It also poses a unique advantage of testing the toxicity of compounds that haven’t been synthesised.
What are QSARs?
Quantitative Structure-Activity Relationships.
They are a computational technique used to predict the reactivity and properties of an unknown set of molecules. It is based on analysis connecting the structures of molecules to their respective measured activity and property.
Why was lead put into petrol?
Early engines struggled going up hill or with quick acceleration due to poor combustion so Pb(Et)4 was added to remedy this.
What are the features of tetraethyl lead?
It is a liquid that is miscible with petrol and was well known to be poisonous. When it is burned, PbO and PbCl2 is released but no one considered what happened after it came out of the exhaust pipes.
