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Flashcards in Principles of toxicology 1 Deck (13):
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what is a toxicant ?

man made/ synthetic chemical that has the potential to cause harm

1

what is a xenobiotic ?

a chemical that is foreign to life
- any chemical that is not part of the metabolic processes that maintain life
- includes both toxicants and toxins

2

what is the most common relationship between exposure and response to chemicals ?

most produce a hyperbola
the range of exposure is generally very large

3

what does response mean in the response exposure relationship ?

it is a measure of organisms in a sample that show a toxic effect
- show signs of toxicity and it is expressed as a percentage
- it is a quantal response in which it is an all or nothing response - either toxic effects are shown or not

4

what do toxicologists do to the response exposure graph ?

they produce a log to the base 10 of exposure to prevent data clumping together
- transforms graph into distinct regions= threshold region, linear region and plateau region to the maximum response

5

what is the threshold region ?

it is the first points at which a response is detected
- it is these organisms which are the most vulnerable

6

what is the TD 50 ?

its used to determine the median toxic dose
- it is the level of exposure that produces the toxic effects in 50% of the population

7

what is the LD50 ?

it is the median lethal dose
-the dose at which is lethal to 50% of the population

8

how is potency calculated using the log10 exposure response graphs ?

the toxin furthest to the left is the most potent- it has the smallest TD50 so it is the most potent
if the TD50s of different chemicals are divided by each other, their relative potencies can be determined

9

what does NOAEL stand for ?

No Observed Adverse Effect Level
- it is the highest level of exposure that does not produce any adverse effects

10

what does LOAEL stand for ?

Lowest Observed Adverse Effect Level
- lowest level of exposure thats produces a significant level of toxicity
- greater than this there is increasing toxicity

11

what does POD stand for ?

Point Of Departure
- initial curve linear threshold region stops and turns into a linear region

12

why is it important to look at the slope of the exposure response curve ?

important to look at when carrying out a risk assessment
- the slope of the graph can be very steep (organophosphate nerve agents) this almost represents an all or nothing response, therefore for a very narrow range of exposures there is a large increase in toxicity which is more dangerous
- a very steep slope can often indicate that the chemical has only 1 molecular target