Evaluation of the use of effects screening levels to ensure public health: A case study in Texas

Much attention has been turned recently toward the application of quantitative risk assessment to protect and ensure public health. This is especially true in the legislative process of our government where more emphasis is being placed on cost/benefit analyses. That is, as it pertains to our discussion, the public health cost versus economic benefits to society. In this paper we elaborate on some of the many shortcomings of risk assessment as they currently exist; using the State of Texas' effects screening levels approach as an example. Effects Screening Levels (ESLs) are level of concern indicators for ambient air and are not regulatory standards. Most ESLs are derived from Threshold Limit Values (TLVs), developed as occupational exposure guidelines. As in all quantitative risk assessment practices, a safety factor (usually 1/100 or 1/1000) is applied to convert the TLV to the respective ESL, and this is assumed to adequately protect even the most sensitive in the population. However, as pointed out, ESLs are seriously flawed due to their blanket trust in TLVs, from which most are ultimately derived. This paper looks at the historical development of TLVs to elucidate the faulty basis of the ESL system. Furthermore, the self- prescribed uncertainty factors applied in the transformation of the TLV to the ESL are evaluated in terms of their ability to truly protect all members of society. In order to demonstrate how the State of Texas trust in ESLs may be dangerously misleading, an example of an industry in Texas is examined and raises some sobering questions about public safety. Finally, a rational alternative approach is put forward that will put exposed communities at the forefront o frisk assessment policy and decision making.