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Parameter uncertainty and variability in evaluative fate and exposure models
E G Hertwich1, T E McKone, W S Pease
1Energy & Resources Group, UC Berkeley, CA 94720-3050, USA.
Summary
Uncertainty in human toxicity potential calculations is significant, often spanning one to two orders of magnitude. Chemical-specific parameters, particularly half-lives, are the primary drivers of this variance.
Area of Science:
- Environmental Science
- Toxicology
- Risk Assessment
Background:
- Human toxicity potential (HTP) is crucial for evaluating toxic emissions in life cycle assessments and toxics release inventories.
- HTP relies on potential dose calculations and toxicity factors.
Purpose of the Study:
- To evaluate the variance in potential dose calculations for HTP.
- To identify sources of uncertainty, including chemical-specific parameters, exposure factors, and landscape parameters.
Main Methods:
- Assessed the potential dose for 236 chemicals.
- Grouped chemicals by dominant exposure route.
- Conducted Monte Carlo analysis for representative chemicals in each group.
Main Results:
- Variance in potential dose calculations is typically one to two orders of magnitude.
- Point estimates for potential dose span ten orders of magnitude across chemicals.
- Chemical-specific parameters, especially half-lives, are the main contributors to variance.
Conclusions:
- Understanding uncertainty in HTP is vital for decision-making robustness.
- Identifying uncertainty sources allows for targeted efforts to reduce it.
- Exposure factors can be important for indirect exposure routes, while landscape characteristics have minor impact.