Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
21 Cards in this Set
- Front
- Back
|
What differentiates a substance from being poisonous or not? What are some substances that are toxic at high doses? What about beneficial?
|
Dose, NaCl, Acetaminophen (Tylenol) |
|
|
Biological effects of exposure to "toxic" substances can include? |
Mortality Teratogenicity (birth defects) Carcinogenicity (Cancer) Mutagenicity (Heritable changes in DNA) Neurotoxicity (damage to nerves/neverous system) Epigenicity (changes to gene expression) |
|
|
Target systems / Organs: CNS is weak too? Immune system? Liver? Respiratory? Kidney? Skin? Reproductive? |
CNS: lead/mercury/pesticides Immune: PCBs Liver: Ethanol, acetaminophen Respiratory: Asbestos, ozone Kidney: cadmium, lead Skin: UV radiation, arsenic Reproduction: BPA, Phthalates |
|
|
What are windows of vulnerability? example in human and exposure? |
Human body has certain times where it is more vulnerable then others, an example is in fetal development, and exposure would e radiation as its window of vulnerability is when cells are replicating, that's why its good for cancer |
|
|
What happens when we are exposed to a toxic substance? |
AD-ME Absorption: substance crosses biological barrier Distribution: distributes throughout the body Metabolism: metabolic conversion/transformation mostly in liver Excretion: Urine, feces, exhalation, breastmilk, placenta |
|
|
What does metabolism generally do to products? |
-generally to products that are less fat soluble, moresoluble in urine -oxidation, reduction, hydrolysis and/or conjugation -metabolite may actually be more toxic than parent compound(eg. Benzene) |
|
|
What is LD_50? What is its purpose? |
Lethal dose 50, where 50% of animals die at this dose Purpose: : to compare acute toxicity of different compounds |
|
|
What information do you not get from LD_50? what are its typical units? |
Does not provide information on: -Chronic effects -Other (non-mortality) outcomes -The shape of the dose-response relationship -The presence/absence of a threshold mg/kg (body weight) |
|
|
What is NOAEL? |
No observed adverseeffect level (NOAEL) -the highest dose at which the adverse effect is notobserved |
|
|
What is LOAEL? |
Lowest observedadverse effect level (LOAEL) -the lowest dose at which the adverse effects is observed |
|
|
Whats the first thing you do when you look dose response relationship graph? |
Look for the presence/absence of a threshold |
|
|
What is Hormesis? How is it depicted in a graph? |
a situation where a chemical has a benefit at certain doses,and adverse effects at other doses (shows a dip in the graph, usually anegative number in response) |
|
|
Is lead neurotoxic? what study shows this? |
Large amount ofevidence that lead is neurotoxic (reduces IQ) -non-linear relationship -IQ decreases as blood-lead increases -Most of the IQ decrease occurs at the small doses of lead -as blood lead increases past the point there’s very littledecrease in IQ |
|
|
Hazard vs Risk |
Hazard:-intrinsic potential of a substance or agent to cause harm Risk: -Likelihood that a population will incur an increasedincidence of adverse effects -Functions of hazard, exposure, and susceptibility Something can be hazardous but if there’s no exposure,there’s no risk |
|
|
What is the 4 step risk assessment process? |
1. Hazard identification: what health problems thepollutant causes? 2. Dose-response assessment: what are the healthproblems at different exposures 3.Exposure assessment: how much of the pollutantare people exposed to during a specific time? How many people are exposed? 4.Risk Characterization: What is the extra risk ofhealth problems in the exposed population? Hazard Identification ->Dose-response assessment + Exposure assessment -> Risk Characterization |
|
|
What is the Threshold approach to determining a "margin of safety"? (ADI or RfD) |
To determine how much a humanbeing can be exposed to without incurring an unacceptable amount of risk or(acceptable daily intake ADI or Reference dose RfD)NOAEL/UFs (Uncertainty factor) Usually we apply an uncertaintyfactor of 10 for each source of uncertainty eg. Extrapolation from animals tohumans, toxicity study with inappropriate route of exposure, NOAEL notdetermined This essentially gives us a“margin of safety”, so we only let humans be exposed to a fraction of the NOAEL |
|
|
What is the Non-threshold approach? (LNT model) |
LNT = linear non-threshold -assume there is no “safe level”-risk assessment is moving away except for radiationSo what should we do if there is no threshold?-Reduce exposure to 0 (ban it)or Reduce the cancer to an “acceptable level” |
|
|
What is the IARC? |
IARC (international Agency for Research on cancer) -agency within the WHO-brings together experts on specific chemicals/pollutants toevaluate the evidence of carcinogenicity -based on evidence its put into one of five categories(Group1, carcinogenic to humans, 2A probably, 2B possibly, 3 we don’t know aboutcarcinogenicity, Group 4 probably not carcinogenic) |
|
|
Risk perceptioninfluences? |
-our individual choices and behaviours-our policy choices -Technical/quantitative risk: function of hazard, exposure,and susceptibility -Perceived risk: intuitive judgment about the nature andmagnitude of a health risk |
|
|
Why do perceived risks often differ fromtechnical/quantitative assessments of risk? |
1. There is uncertainty in risk assessment 2.Most of us are not professional risk assessorsso we must rely on available information (media, friends, observations) andmake our own risk judgments (heuristics or simplifying “rules”) 3. Perception of risk focuses on specificcomponents of the risk |
|
|
What kind of Heuristics leads to perception of more risk? |
if it’s involuntary, uncontrollable, unfamiliar, man-made,high “dread”, unevenly distributed High unfamiliar (Y) + high dread (X)= highest risk |
