Analysis of regulatory guidance values for six commonly regulated chlorophenols

Abstract

Regulatory guidance values (RGVs) are developed by regulators to protect human health by establishing maximum allowable contaminant concentrations. Contamination of residential surface soil is of particular concern because of its potential impact on the general population, especially children. As part of an ongoing examination of soil RGVs, this study analyses guidance values applied to chlorophenols, a class of chemicals used as pesticides, herbicides, and disinfectants. Chlorophenol RGVs have been promulgated by at least 45 US states, 38 United Nations member states, four Native American tribes, five federal agencies, and several city, county, and territorial jurisdictions. An analysis of the six most commonly regulated chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, and pentachlorophenol) demonstrates that there is great variability in the guidance values, which vary by six to eight orders of magnitude and have distributions similar to those of lognormal random variables. Clearly, there is little universal agreement on the appropriate maximum contamination levels for chlorophenols.