lecture 2 - toxicology Flashcards
what is toxicology
the study of adverse SYSTEMIC effects of chemicals on living organisms
what is a toxicant
a chemical that does SYSTEMIC damage
what is a poison
reserved now for special class of toxicants that need only a small dose to cause death
founder of modern toxicology
paracelsus
paracelsus’ main contribution
dose response relationship - the observation that the effects of a poison are related to the strength of its dose
he also was the first to publish a description of the symptoms of chronic mercury poisoning, and developed a chemotherapy treatment using mercury to treat syphillis
why is arsenic called a heavy metal
has a high molecular weight
is arsenic poisonous by itself
no, arsenious oxide or arsenic trioxide are poisonous
however, there are two non-poisonous variants called arsenobetaine and arsenocholine which is found in shellfish, cod, and haddock
what was ramazzini’s contribution
he was concerned with the diseases of workers, listed the illnesses and diseases occurring in many occupations
he was an epidemiologist who studied occupational medicine
poison is dependent on
the “sufficient quantity” - all things are poisons, the dose defines the poison
rammazzini used ___ to treat malaria
the bark of a cinchona tree
ecotoxicology
concerned with the release of toxic pollutants into the environment, especially aquatic systems, by examining how they become distributed within the food chains
spectrum of toxic dose
describes the toxicity or hazards that are related to exposure to a particular chemical
dose response curve components
x axis = dose in mg per kg
y axis = response %
NOAEL = no-observed adverse effect level
LOAEL = lowest observed adverse effect level
ED50 = dose which causes an effect in 50% of population
LD50 = causes death in 50% of populatoin
toxic agent
a material/factor that can be harmful to biological (human) systems
toxicity
the degree to which something is poisonous, related to a material’s physical and chemical properties
low-toxicity means you can ingest large quantities with little effect
high-toxicity means you even small quantities can cause large effects
toxicant
toxic substances which are man-made or result from human activity
toxin
usually refers to a toxic substance made by living organisms
hazard
the inherent capability of an agent or a situation to have an adverse effect. a factor or exposure that may adversely affect health.
what information is required to identify and categorize a chemical hazard
physical and chemical properties - organic and inorganic
setting and nature - where would you encounter the hazard
CEPA 1999 - Canadian environmental protection act
threshold toxicant
assumes there is harm at a particular level of exposure
those for which the critical effect is not considered to be cancer or heritable mutations
non-threshold
substances for which the critical effect is carcinogenesis - assumes that there is some probability of harm to human health at any level of exposure
describe a population dose-response curve
- S shaped/sigmoidal curve which demonstrates the relationship of observed responses in a population to varying levels of some substance
what does the flat portion at the beginning of a dose-response curve represent
suggests that at low levels of some substances, an increase in dose produces no effect
this is referred to as the subthreshold phase
relationship between potency and LD50
a smaller LD50 indicates a more potent substance
define threshold in a dose-response curve
the threshold is the lowest dose at which a particular response may occur
maximum response/plateau/ceiling effect
point at which increases in dose no longer produce an increase in response
relationship between height of maximum response and efficacy
slopes whose plateau is higher up on the y axis (higher maximum response) are more efficient
what does slope indicate on a dose-response curve
how sharply the response changes with an increase in dose
steep slope suggests significant changes in response even with small dose variations
steeper curves are more toxic
potency and dose response curve
look at the location of the whole curve along the x axis (dose axis)
acute
single exposure for less than 24 hours
subacute
exposure for one month or less
subchronic
exposure for 1-3 months
chronic exposure
3+ months
additive chemical mixtures
combination of two chemicals produce an effect that is equal to their individual effects added together
synergism
the combined effect of exposures to two or more chemicals is greater than the sum of their individual effects
potentiation
one chemical that is not toxic causes another chemical to become more toxic
coalitive interaction
when several agents that have no known toxic effects interact to produce a toxic effect
antagonism
two chemicals administered together interfere with each other’s actions, or one interferes with the action of the other
chemical allergy
an immunologically mediated adverse reaction to a chemical resulting from previous sensitization a chemical or a structurally similar one
latency
time period between initial exposure and a measurable response
risk assessment
a process for identifying adverse consequences and their associated probability
list some factors that affect responses to a chemical
concentration
route/site of exposure
duration/frequency of exposure
dose
drug interactions
individual sensitivity
exposure route with the fastest speed of effect
blood stream
T/F - many carcinogens are believed to have a latency period of 10-40 years
true
three aspects of risk with regard to toxicology
risk assessment - science-based - hazard identification, dose-response assessment, exposure assessment, risk characterization
risk management - policy based
risk communication
risk managment
consists of actions taken to control exposures to toxic substances in the environment
T/F - exposure assessment is the weakest aspect of risk assessment
true - methods are unable to provide adequate quantitative information about human exposures
what two factors are considered when assessing level of contact for those who live near a discharge location
location of nearby populations
daily human activities that influence how often people come in contact with the chemical
what three factors are used to determine level of contact for consumer product or worker exposures
frequency of use
duration
use conditions
risk characterization integrates what three things
hazard identification
dose-response assessment
exposure assesment
what kind of summary would you present to a policymaker to decide if a risk is sufficient and needs to be addressed
risk characterization summary
