Worldwide Residential Soil Regulatory Guidance Values for Chlorinated Ethanes

Surface soil contamination is often regulated using guidance values that specify the maximum amount of pollutant that can be present without prompting a regulatory response. In the United States, there are at least 89 value sets (and worldwide there are another 29) that provide guidance for at least one of the nine chlorinated ethanes. The most commonly regulated chlorinated ethane is 1,2-dichloroethane (108 values), and it is the third most commonly regulated synthetic organic surface soil contaminant. Pentachloroethane (17 values) is the least regulated chlorinated ethane. Overall, there are at least 690 guidance values for chlorinated ethanes. This analysis explores the origin, magnitude, and form of the variability of these values. Results indicate that the values span from 3.7 to 7.6 orders of magnitude and are distributed in patterns similar to log-normal random variables. Less than 20% of these values are similar to those of national regulatory agencies such as the U.S. EPA or the Canadian Council of Ministers of the Environment, but more than 60% of the values fall within the 95% confidence interval bounds of the uncertainty in U.S. EPA risk model calculations.