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Toolkit for
Exposure Assessment: More Advanced
Is the Chemical Sufficiently
Studied?
After a screening level evaluation is
conducted, organizations may wish to recommend decisions about
the need for further evaluation, for priority setting purposes
and communications. Such decisions typically use a weight-of-evidence
approach that takes into account the uncertainties and reliability
of both the hazard and exposure analyses, knowledge gaps,
severity of the potential hazards, etc... Typically there are three basic decision options:
- The exposure scenario/chemical
is currently recommended to be a low priority for further
work. This can be determined by:
- A qualitative evaluation where
it can be shown that there is little or no human exposure
for a particular pathway, or the chemical is widely
regarded as a low level hazard, or
- A quantitative analysis where exposure
is judged to be low relative to the thresholds of
concern for a chemical's hazards.
- The exposure scenario/chemical is recommended
for further work, based on a screening level analysis.
This recognizes that screening level evaluations are,
by nature, conservative estimates of reality that tend
to overestimate their respective endpoints. Thus, when
exposure is judged to approach thresholds that may cause
harm, a more comprehensive and accurate analysis may be
needed. Typically, this means collecting more complete
use and exposure information, and/or conducting more sophisticated
and accurate "higher tier" exposure evaluations
and/or hazard studies.
- The exposure scenario/chemical is recommended
for risk management where a screening level evaluation
indicates that exposures are toxicologically meaningful
and sufficiently well understood to recommend action,
after considering uncertainties, severity of effects,
etc...
It should be clearly recognized that decisionmaking
about risks is ultimately a complicated and often subjective
process involving a number of considerations that go beyond
the risk evaluation itself (e.g., costs, benefits, other
technologies, etc...). In general, judgments about whether or not further work
is needed can be made more objective by using a weight-of-evidence
approach that takes into account the severity and biological
relevance of potential hazards, dose responses, thresholds
of effects, the precision and accuracy of both hazard and
exposure data, reliability, statistical significance, etc.
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