Bioaccumulation and Toxicokinetics Flashcards
What is net bioaccumulation?
uptake - elimination
Why does bioaccumulation occur?
The elimination process is slower than the uptake
What are the two phases of bioaccumulation?
accumulation and depurination
What is the depurination phase?
excretion of chemical is greater than accumulation
Why is the rate of excretion so dependent on the chemical itself?
lipophilicity and ability to be biotransformed
What is the phenomenon known as growth dilution?
[toxicant] can decrease in growing organism due to the fact that the tissue growth is greater than the rate of uptake
What type of chemicals exhibit growth dilution and where in the world does it commonly occur?
seen with some elements and warmer climates because cold inhibits tissue growth
What is bioconcentration?
uptake of a dissolved phase of a toxicant to achieve total body conc. that exceed those in water
What is biomagnification?
levels of toxicant increases as trophic levels increase
What are some examples of toxicants that undergo biomagnification?
highly lipophilic toxicants
What are three factors that contribute to the bioavailability of a toxicant?
physical, chemical and biological
What two factors are toxicity defining?
chemical and physical factors of environment and toxicant
What two factors influence absorption the most?
lipophilicity and concentration gradient
What are the channels used for facilitated diffusion and what toxicants do they transport?
Ion gated-Ca2+ analogs like lead and Na+ analogs like Ag+ and Cu+
Ion non gated-Ca2+ analogs
OATS-for oxyanions like AsO3-
What is the pump used for active transport and what does it transport?
Na/K pump can pump Cu and Ag against gradient
What type of toxicants transported by endocytosis?
often large particles, ex ultrafine particles in lungs
What is paracellular transport?
When very small toxicants can enter cell through gap junctions
What are the factors affecting distribution?
lipophilicity and carrier proteins
What are examples of carrier proteins?
albumin-binds all sorts of toxicants
ferritin-used in body for iron but can bind cadmium
What is biotransformation?
Chemically changing the toxicant so it can be excreted in the body
Why is the process of biotransformation so highly conserved if toxicants were never seen in the early days of life?
These processes were/are used to excrete steroid hormones
Why do some toxicants not need a second biotransformation phase?
hydrophilic molecules are easier to excrete and do not need extra hydrophilic groups
What are the main ways of excretion?
urine, feces, bile and respiration
What are some examples of major organic pollutants?
Polycyclic aromatic hydrocarbons-napthalene
Polychlorinated biphenyls
Chlorinated phenols, dioxins and dibenzofurans (POPs)
Pesticides
Aromatic herbicides
What are examples of inorganic pollutants?
metals and metalloids
nonmetal inorganics-Cl and ammonia
Inorganic gases-CO2
What are the other three classes of pollutants?
Radionuclides-uranium
Nutrients-PO4, NO3
Organometallics- methyl mercury, tributyl tin
What is bioavailability?
the extent at which a contaminant is available for uptake
What are some of the ways organic pollutants are made less bioavailable in the environment?
degradation from microbes or sunlight, and sequesteration
What is the range for LogKow and what occurs at high lipophilicity?
-3 -7, will precipitate and leads to greater bioaccumulation
What is LogKoa?
a measure of volatility and lipophilicity
What is the relationship between volatility and lipophilicity?
As lipophilicity increases, volatility decreases
What are the two abiotic factors affecting toxicity?
Natural organic matter and temperature
How does temperature affect toxicity?
as temperature increases, membrane fluidity increases and therefore toxicity increases
How does natural organic matter affect toxicity?
Highly lipophilic poles that can absorb contaminants and therefore cannot be taken up by organisms
What are the biotic factors affecting toxicity?
age, sex, genetics and disease
