Maximum likelihood estimate risk assessment

The rationale supporting use of EDi0 as the benchmark dose is that a 10 percent response is at or just below the limit of sensitivity in most animal studies. Use of the lower confidence limit of the benchmark dose, rather than the best (maximum likelihood) estimate (EDio), as the point of departure accounts for experimental uncertainty the difference between the lower confidence limit and the best estimate does not provide information on the variability of responses in humans. In risk assessments for substances that induce deterministic effects, a dose at which significant effects are not observed is not necessarily a dose that results in no effects in any animals, due to the limited sample size. NOAEL obtained using most study protocols is about the same as an LED10. 

A few court decisions, however, have been more skeptical of the linear model. Eor example, the U.S. EPA s use of the linear, no-threshold model in its risk assessment for drinking water chlorinated byproducts was rejected by the court because it was contrary to evidence suggesting a nonlinear model that had been accepted by both the U.S. EPA and its Science Advisory Board (CCC 2000). On the other hand, the U.S. OSHA s departure from the linear, no-threshold model in its formaldehyde risk assessment was likewise rejected by the court (lU 1989). The court held that the U.S. OSHAhad improperly used the maximum likelihood estimate (MLE) rather than the upper confidence limit (UCL) to calculate risk, and the UCL but not the MLE model was consistent with a linear dose-response assumption. The court held that the U.S. OSHA had failed to justify its departure from its traditional linear, no-threshold dose-response assumption. 

Risk analysis is an assessment of the likelihood (probability) of an accidental release of a luizardous material and tlie actual consequences tliat might occur, based on tlie estimated vulnerable zones. It provides an estimation of tlie likelihood (probability) of an accidental release, tlie severity of consequences of human injuiy that may occur, the severity of consequences on critical facilities, tlic severity of consequences of damage to property, and the severity of consequences of damage to tlie enviromnent. Risk characterization estimates tlie healtli risk associated with tlie process under investigation. The result of tins cliaracterization is a number tliat represents tlie probability of adverse healtli effects from tliat process or from a substance released in tliat process. Tire major types of risk include Individual Risk, Maximum Individual Risk (MIR), Population Risk (PR), Societal Risk, and Risk Indices. 

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