Problem Formulation - trdoer40023

Problem Formulation

The problem formulation of a risk assessment is a systematic planning stage that

identifies the major factors considered in the assessment, and establishes its goals,

breadth, and focus (USEPA/ERT 1997). It is essentially a scoping activity and is

fundamental to the success of all subsequent components in the risk assessment.

There are four general activities within problem formulation.

a. Statement of objectives: The risk manager initiates the problem formulation

with a statement of objectives. Subsequent selection of assessment

techniques and procedures largely depends on this objective statement.

Consequently, time spent by the dredged material manager in addressing

why the risk assessment is being performed will substantially improve the

decision-making process.

b. Development of a conceptual model: The conceptual model specifies the

pathways by which a contaminant of concern might move from the

management area to a human or organism of concern.

c. Selection and characterization of receptors: This task selects and describes

organisms and humans which best represent the types of organisms and

human activities that may contact contaminants from the dredged material

management site.

d. Identifying endpoints: The human health risk assessment has numerical

endpoints specified by convention to protect humans against carcinogenic

and noncarcinogenic health risks. However, for ecological receptors, the

risk assessment will use endpoints which depend upon the ecological

characteristics of the management area and management activity under

consideration. Assessment endpoints are the valued characteristics of a

management site or adjacent ecosystem that should be protected. In

selecting appropriate assessment endpoints, some factors to be considered

include the ecological relevance of the endpoint, policy goals and societal

values, and susceptibility to the contaminant. Measurement endpoints are

discrete observations that can be related to the assessment endpoint.

Generally, we must extrapolate from the measurement endpoints back to

the assessment endpoints in judging whether the value expressed by the

assessment endpoint is at risk.

Chapter 2 Problem Formulation