Does the Atlantic RBCA software calculate cumulative risks?
The use of cumulative risks in developing remediation objectives for contaminated sites is appropriate for chemicals that have the same biological end-points. The current Atlantic RBCA model uses cumulative risks for dealing with TPH and BTEX. However, for chemicals that have differing biological end-points, the summation of exposures or risks is not toxicologically sound and has little practical meaning. The User Guidance manual outlines how cumulative risks are considered in the RBCA process. It also clearly indicates that the use of the Atlantic RBCA model for compounds other than BTEX and TPH can only be done in consultation with local regulators. Such consultation would also likely require input from a toxicologist or similar professional who can properly address the issues relating to interactive effects between chemicals. The Site Professional must also consider the potential for cumulative risks from exposure to the same chemical through multiple pathways (e.g., indoor air and
