The Origin and Health Risks of PCDD and PCDF

PCDD/PCDF are ubiquitous in the emissions of trash-burning incinerators. They are synthesized in the cooler parts of the incinerator, and emissions are not reduced by controlling combustion conditions. Estimates of maximum lifetime risks of PCDD/ PCDF emissions range over two orders of magnitude from a minimum of one per million. This risk is greater than that which has triggered regulatory procedures against airborne carcinogens by U.S. EPA. Computations based on PCDD/PCDF in adipose tissue of a representative sample of the U.S. population indicate a national lifetime cancer risk of 330-1400 per million depending on the choice of equivalence methodology. In comparison, U.S. EPA has regulated environmental exposure to benzene based on a national lifetime cancer risk of 71.4. Because waste-burning incinerators contribute significantly to this risk, it is the authors' opinion that their PCDD/PCDF emissions should be reduced if U.S. EPA is to be consistent in its regulatory practice.