An environmental risk assessment is a tool that supplies information about risks to human or ecological receptors due to exposure to identified hazards that relies on environmental media data, site use, fate and transport, and toxicological information. The goal of a risk assessment is to establish whether a condition of “No Significant Risk” (NSR) exists or has been achieved. The three Methods for Risk Characterization described in 310 CMR 40.0941(3) have been developed to provide a range of approaches which vary in detail and circumstances of use, each of which provides equivalent levels of protection to health, public welfare, and the environment. The specific Risk Characterization approach used shall depend upon the nature of the risk being assessed, the response action being performed and the nature of the disposal site.
- A Method 1 Risk Characterization, pursuant to 310 CMR 40.0970, uses a set of soil and groundwater standards that are compared directly to Site exposure point concentrations (EPCs). The Method 1 Standards were developed by MassDEP according to a defined set of exposure scenarios that represent a conservative estimate of potential exposures that could occur at most sites.
- A Method 2 Risk Characterization, pursuant to 310 CMR 40.0980, entails the derivation of additional standards for those compounds for which MassDEP has not developed a Method 1 Standard. In addition, site-specific fate and transport factors and considerations may be used in Method 2 to modify certain Method 1 Standards.
- The Method 3 Risk Characterization, pursuant to 310 CMR 40.0990, recognizes site-specific exposure routes, contaminant concentrations and distribution, and other site-specific information in evaluating the risk posed by a site. Regardless of approach, the goal of the Risk Characterization is to demonstrate that a level of no significant risk (NSR) of harm to health, public welfare and the environment exists or has been achieved.