Establishment of an Exposure Level to Tetrachloroethylene in Ambient Air in Vermont

Where environmental contaminants pose potential health hazards, health departments are involved in complex and often controversial situations. Often the rapid formation of a threshold exposure level is required to protect public health. A decision making process was implemented in Vermont when it became necessary to have an interim ambient air exposure level to test for tetrachloroethylene contamination in the water, air, and soil of a community. Contamination of public and private drinking water and ambient air in schools and homes was discovered as a result of uncontrolled waste disposal from an industrial uniform laundry and drycleaning plant. A telephone survey was conducted to determine action taken by the other 49 States regarding emission standards for tetrachloroethylene into ambient air. There were no guidelines in 25 States, and there were guidelines in the remaining 25. Vermont's Commissioner of Health convened a multidisciplinary group of public health professionals to review various approaches to the establishment of an ambient air standard. A decision making action using modified Delphi and nominal group consensus methods set the interim standard at 67 micrograms per cubic meter in ambient air. The drycleaning plant had been closed voluntarily before the standard was established, and the interim standard was used to prevent reopening of the plant through a health order issued by the Vermont Health Department. The standard was also useful for guidance during environmental remediation.