Dose Responses

Question 1

Hazard

Answer 1

intrinsic toxic properties of a toxicant mixture

Question 2

Risk

Answer 2

Probability of an adverse outcome based on the exposure and potency of the hazardous toxicants

Question 3

risk assessment

Answer 3

characterization of the probability of potentially adverse health effects from human exposures to hazardous agents

Question 4

risk management

Answer 4

process by which policy actions are chosen to control hazards

Question 5

epidemiology

Answer 5

studies the patterns, causes, and effects of health and disease conditions in defined populations

Question 6

epidemiology data

Answer 6

correlative

Question 7

correlation

Answer 7

• whether two variables are changing together

- correlation does not indicate causation

Question 8

bioassays

Answer 8

• prove causation
• quantitative estimation of the intensity or concentration of a biologically active chemical
• measured via some biological response under standardized conditions

Question 9

goals of toxicity testing

Answer 9

• determine the range of doses over which the toxic responses are produced
• identify the nature of the responses to a toxicant
• extrapolate these results for risk assessment analyses for human exposure

Question 10

uses of bioassays in environment toxicology

Answer 10

• determine of the most sensitive species or life stage in an assemblage of organisms
• compare effects of different pollutants on a single organism
• compare effects of other environmental factors acting with the pollutant that modify its effects
• determine the maximum level of a pollutant that may occur in the environment without causing biological change

Question 11

dose-response

Answer 11

-quantify the relationships between the exposure concentration and a defined endpoint

Question 12

endpoints

Answer 12

whatever we are most interested in measuring

Question 13

dose-response relationships

Answer 13

• standardize the doses to body weight
• duration and frequency important
• often the endpoint is mortality
• compare relative toxicity of toxicants
• ranked into toxicity classes

Question 14

acute exposure

Answer 14

hours to days

Question 15

chronic exposure

Answer 15

months to years

Question 16

lethal concentration

Answer 16

how long an individual was exposed to a toxicant to reach the endpoint

Question 17

lethal dose

Answer 17

taken orally

Question 18

graded dose response

Answer 18

• use a continuous variable and occur in a single individual

- characterized by a dose-related increase in the severity of the response

Question 19

quantal dose response

Answer 19

• occur in a population

- individual is classified as a “responder” or “non-responder”

Question 20

route of exposure

Answer 20

• change dose-response curves
• injection, inhalation, ingestion, dermal
• speed of the response is related to how quickly a toxicant enters the bloodstream

Question 21

linear relationships

Answer 21

• y-axis converted to “probits”
• Normal equivalent deviation
• 5=50% of the population

Question 22

effective dose (ED50)

Answer 22

where the drug is doing what we want it to do in 50% of the population

Question 23

toxic dose (TD50)

Answer 23

where bad things start happening in 50% of the population

Question 24

lethal dose (LD50)

Answer 24

lethal in 50% of the population

Question 25

therapeutic index (TI)

Answer 25

- ratio of TD50 and ED50 - high values drug is relatively safe - low values rejection of the drug from further clinical testing

Question 26

potency

Answer 26

the amount required to produce an effect of given intensity

Question 27

efficacy

Answer 27

refers to the maximum response achievable

Question 28

No observable effect concentration (NOEC)

Answer 28

highest concentration with no mortality

Question 29

Lowest observable effect concentration (LOEC)

Answer 29

point of first effect or mortality

Question 30

vehicle or carrier

Answer 30

- distribute the contaminant to the animals | - contaminants are usually hydrophobic

Question 31

u-shaped curves

Answer 31

essential nutrients can have adverse effects at low and high doses

Question 32

hormesis

Answer 32

compounds that are beneficial/stimulatory at low doses but toxic at high doses

Question 33

nonmonotonic dose-response curves

Answer 33

- toxicants have effects at low levels - low levels they interact with a hormonal receptor - high levels receptor can burn out, response decreases

Question 34

sub-lethal responses

Answer 34

toxic events occur before the animals die

Question 35

subchronic bioassay

Answer 35

- high dose that causes toxicity but not more than 10% fatalities - an intermediate dose - low dose that should cause no toxic effects - exposure for longer periods of time

Question 36

why do a sub chronic test

Answer 36

- information on all types of sub chronic toxicity that might occur - establish dose regimens for chronic studies - provide data which will allow an estimate to be made of the MTD (maximum tolerable dose), no significant impairment of growth - biomarkers of exposure

Question 37

observed during the study

Answer 37

- altered growth rate | - behavioural changes

Question 38

after the exposure period see what deviates from normal

Answer 38

- mass - blood chemistry - biochemical - cell membrane permeability - enzyme activity - organ and tissue damage

Question 39

Biomarker

Answer 39

a cellular or biochemical response to a toxicant that is measurable in a biological system or sample

Question 40

biomarkers include

Answer 40

- enzyme activity - changes in cellular receptor amount and activity - changes in hormone levels - increased/decreased expression of genes that respond to toxicants - changes in the histology of cells to detect cellular damage

Question 41

carcinogens

Answer 41

- classified based upon what is known from humans and animals - experiments are expensive

Question 42

reasons for low testing of chemicals

Answer 42

- not required - lack of funds - expensive - difficult to test interactions

Question 43

test results and who does them

Answer 43

- considered innocent until proven guilty - government does not test - industry conducts tests and gives the results to the government