Appropriate Use of 'Occupational' Exposure Levels vs. 'Risk-Based' Levels in Assessing Vapor Intrusion Exposures in Occupational Settings

摘要

In the United States, many governmental bodies enforcing environmental regulations utilize "risk-based" assessments focused on the most sensitive subpopulations when analyzing environmental exposures, including those associated with vapor intrusion. In occupational settings, exposures are regulated based on the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs) and further analyzed based on other consensus standards such as the American Conference of Governmental Industrial Hygienist Threshold Limit Values (TLVs). These occupational exposure levels are generally based on the assumed exposure of adult workers. When vapor intrusion from subsurface contamination may represent a potential exposure at an occupational location, the decision to utilize "risk-based" or "occupational-based" levels can be complicated and confusing. These complications can be further compounded at sites where the chemicals related to vapor intrusion may be used in the manufacturing process and differentiating the portion of exposure associated with the industrial process from the portion associated with vapor intrusion can be important depending on the question being asked (e.g., is this safe work environment) or the decision which may need to be made (e.g., is remediation or exposure control warranted). This presentation will evaluate the underlying assumptions in the development of these exposure levels and provide attendees with the knowledge to determine appropriate exposure levels to use to support decision making for specific sites. We will demonstrate that the use of exposure levels which have been developed specific to the population at risk will result in more efficient and defensible decision making, which is particularly important in a resource limited world.