Dose-response relationship lecture

Question 1

direct toxicity

Answer 1

toxic agent acting directly on the organism

Question 2

indirect toxicity definition

Answer 2

influence of changes in the environment acting indirectly on the organism

Question 3

how does indirect toxicity flow through species

Answer 3

Species C at the top of the food chain will have a decline in population because its food source (species B is declining)
Species B will have a decline in population because of sensitivity to toxin
Species A will have a population increase and will flourish

Question 4

Who came up with dose response relationship

Answer 4

Paracelsus

Question 5

Dose/concentration-response curve of toxicant

Answer 5

increasing toxic effects with increasing dose

Question 6

NOEC

Answer 6

no observed effects concentration; safe level
- highest concentration when there is no toxic effect

Question 7

LOEC

Answer 7

lowest observed effects concentration
- lowest concentration where a toxic effect has occurred

Question 8

MATC (maximum acceptable toxic concentration) formula

Answer 8

(NOEC + LOEC)/2

Question 8

MATC (maximum acceptable toxic concentration) formula

Answer 8

(NOEC + LOEC)/2
- used to reduce toxic level of exposure to contaminants
- max amount without suffering from toxic effects

Question 9

What are the different ways toxicity can be expressed?

Answer 9

LC50 or LD50
EC50
IC50

Question 10

LC50 or LD50

Answer 10

concentration that causes 50% mortality under a defined test condition

Question 11

EC50

Answer 11

concentration that obtains 50% of expected effect/response under a defined test condition

Question 12

IC50

Answer 12

concentration that reduces the normal response of a parameter by 50%

Question 13

how do you compare the toxicity between compounds on a graph?

Answer 13

look at the LC50 values and dosage
- most toxic - lowest dosage for same LC50 value

Question 14

acute toxicity testing

Answer 14

short-term, exposure to high dose
test endpoint - mortality
- static - don’t change exposure water
- static renewal - exchanging the exposure water
- flow-through - continual supply of fresh exposure
this is the optimal test condition

Question 15

chronic toxicity testing

Answer 15

long term, exposure to low dose, single species
- test endpoint - growth & reproductive fitness

Question 16

microcosms toxicity testing

Answer 16

2 or more species, single or multiple toxicants

Question 17

criteria for selecting test organisms

Answer 17

pick the most sensitive species because you want to save majority of species and the toxicity values will be low

Question 18

additive (toxicity of pollutant mixtures)

Answer 18

sum of individual effects are identical to accumulative response

Question 19

Synergistic

Answer 19

accumulative toxic effects are greater than the sum of their individual toxic effects

Question 20

antagonistic

Answer 20

accumulative toxic effects are less than the sum of their individual toxic effects

Question 21

look at the last slide of these notes for calculation Q