Massachusetts

concentrations and for establishing the effects of subchronic and acute exposures.

The format requirements for the risk assessment report are also given.

Massachusetts

Documents:

"Massachusetts contingency plan," 310 CMR 40.000 (MCP

1993).

"Guidance for disposal site risk characterization." Massachusetts

Department Environmental Protection (BWS/ORS-95-141).

Contact:

Mr. Paul Locke, Massachusetts DEP, Office of Research and

Standards, 1 Winter Street, Boston, MA.

The Massachusetts Contingency Plan (MCP) provides a tiered approach which

uses three methods for human-health risk characterization. Each method becomes

more site specific.

1. In a Method 1 risk assessment, benchmark values or standards for

chemicals of concern in soil and groundwater are used as conservative

estimates to assess risk.

2. In a Method 2 assessment, the assessor may derive new method standards

for compounds for which the MCP does not have standards and/or may

modify existing standards based on site-specific fate and transport

information.

3. In a Method 3 risk assessment, site-specific exposure assumptions are

used to characterize potential risks.

In the cases of Methods 1 and 2 assessments, "a condition of no significant risk

of harm to health exists if no Exposure Point Concentration is greater than the

applicable standard." For a Method 3 assessment, however, the cumulative cancer

risks and cumulative noncancer risks are calculated and compared to the

cumulative carcinogenic or noncarcinogenic risk limit, respectively. The basic

steps of a risk characterization are: identify human receptors; identify

environmental receptors; identify site activities and uses; identify exposure points;

identify exposure pathways; identify exposure point concentrations; identify site

groundwater and soil categories.

Ecological risk assessments under the MCP have a two-stage approach. A

Stage I environmental screening eliminates pathways from Stage II consideration

if:

a. Significant risk is readily apparent.

b. Exposure pathway is incomplete.

c. Pathway is incomplete, but the exposure is so minimal that it clearly does

not pose a significant risk.

A21

Appendix A Summary of Federal, State, and Regional Guidance