Lecture 10: Causality in Ecotoxicology (guest lecture) Flashcards
______ is the study of the
distribution , determinants , and
deterrents of morbidity or mortality in
human populations. It provides the basis
for describing, prioritizing and evaluating
public health programs. It is also useful in
identifying risk factors and causes of
disease, evaluating the efficacy of various
treatments, and investigating disease
outbreaks. Because of these applications,
epidemiology is often referred to as the
cornerstone or foundation of public
health
Epidemiology
____ evidence: What is the strength and variety of
evidence between the agent and the
response?
causal evidence
Causality strengthens the
assessment, especially for effects
observed ______
in the field
____ in ecotoxicology uses the same approaches as epidemiology?
causality
when determining causality, we often use ____ as a tool
risk assessments, helps generate a hypothesis
The organism is always
found in the diseased tissue
* The organism must be
isolated in pure culture
* The pure culture causes the
disease experimentally
* The same pathogen must
be re-isolated from
organisms infected under
experimental conditions
these are all examples of…
Koch’s postulates for diseases (1883)
what are Koch’s postulates modified for substances?
the substance must be found in greater conc. in all affected organisms, but not at all or in lesser amounts in healthy organisms
the substance must be isolated and identified chemically from an affected organism
the pure substance should cause the same effects when introduced into a healthy organism
The _________ are a set of nine viewpoints used in epidemiology to evaluate evidence for a causal relationship between an exposure and an outcome, including strength of association, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment, and analogy
Bradford Hill criteria
_____
– Stronger the association between the
independent and dependent variable, more
likely to result from causality
Strength
______
– Different studies, same results
Consistency
______
– Ideally, effect has one cause (and is easier with
unique effect)
Specificity
_______
– Cause precedes effect, i.e., the cart or the horse
– Sometimes difficult with chemicals that have a
long latency
Temporality
_________
– Concentration-response relationship in the field
Presence of a biological gradient
________
– Biologically sound (AOP)
A plausible mechanism of action
_______
– Coherent with knowledge about the effects,
toxicants and organisms impacted
Coherence
_______
– Experimental evidence confirming or denying
other hypotheses
– Laboratory-based studies
Experimental evidence
T/F: Ideally, you find something for each Bradford Hill Guideline, but
not always possible or the case
true!!
What do we use as lines of evidence for ecotoxicology?
adverse outcome pathways!
explain the decline in Gyps vultures in India
Observed extensive and rapid white-
rumped vulture population declines (from
millions to thousands) in the late 1990s
along with two others Gyps vulture
species
Death by kidney failure - visceral gout
Eliminated the obvious, such as disease,
pesticides, metals
* Zeroed in on diclofenac
* A non-steroidal anti-inflammatory drug
(NSAID), e.g., aspirin
* Used as a cheap veterinary drug in India
and elsewhere
other vulture species were unaffected! banned in 2006, species still hasn’t recovered at all
other drugs causing similar effects have also been banned recently (2023)
T/F: causality in ecotoxicology is…
Not as simple as you might think.
You must…
Avoid conclusions before evidence.
Approach these questions with an
open mind.
And be willing to let the data and
evidence guide your decisions
true!!
