Factors Influencing Toxicity

Question 1

what determines toxicity? broadly (3)

Answer 1

1. chemical factors: toxicant factors of physical/chemical properties, presence of other chemicals and potential interactions
2. biological factors: host factors, environmental factors
3. exposure factors: route and duration

Question 2

what are the 4 responses to 2 or more chemicals in a system at the same time?

Answer 2

1. additivity: a combination of two or more chemicals is the sum of the expected responses
2. antagonism: exposure to one chemical results in a reduction in the effect of the other chemical
3. potentiation: exposure to one chemical results in the other chemical producing an effect greater than if given alone
4. synergism: exposure to one chemical causes a DRAMATIC increase in the effect of another chemical

Question 3

what are 5 host factors that can influence toxicity? describe

Answer 3

1. species: different species metabolize chemicals different ways, can have up to 5 possible metabolites for one chemical depending on the species and their pathway of metabolization, as well as excretion pathways, anatomy/physiology of the GI/resp tract, and target receptor density/subtypes
2. age: due to differences in enzyme expression, organ function, and presence of protective barriers, young animals are usually more sensitive to toxicants
3. nutrition: many toxicants are oxidants, so if one’s diet consists of many antioxidants, it can have a protective effect and decrease toxicity of many toxicants
4. health status: how organs are functioning (esp kidney and liver), if fever leads to increased blood flow and metabolism, if the animal is dehydrated, or if they are experiencing inflammation and have looser junctions between cells can all affect toxicity
5. sex: dif between male and female i guess

Question 4

what are 5 environmental factors that can influence toxicity?

Answer 4

1. housing
2. ventilation
3. temperature
4. soil pH (nitrate concentration due to runoff)
5. precipitation

Question 5

what 4 factors affect the degree of absorption of a toxicant?

Answer 5

1. route/duration of exposure
2. ability to cross the cell membrane: related to polarity, size, and structure, as most toxicants cross GI lumen via transcellular simple diffusion
3. concentration gradient
4. degree of ionization: most toxicants are weak acids or weak bases; see pharmacology lecture about how this works, as only non-ionized forms of a chemical can passively diffuse