INDUSTRIAL HYGIENE

Industrial Hygiene



Abstract

This paper reports on an intensive study into releases of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from 19 chemical production facilities in the United States producing, or using, large volumes of chlorine. Releases on-site to air, water and to landfill were assessed as were transfers off-site in materials for disposal or additional treatment. The primary purpose was to develop estimates of releases on a site-specific basis that could be used in the US EPA inventory of dioxin-like compounds, it also serves to increase the database on releases from this industry which are comparatively poorly studied. Releases varied considerably and a prime conclusion of the study is that the presence of multiple processes using different technologies and common wastewater treatment facilities often found on integrated chemical sites means that sector-level approaches in inventory estimates will not give appropriate estimates at the site level. A more detailed study is required using site-specific data where possible. Transfers of data should only be carried out when fully justified on the basis of process characteristics.

The largest estimated flows were in residues being transferred off-site for treatment (incineration) or disposal, generally in secure landfills. Releases to water varied widely from essentially non-detectable amounts to more than 5 g of PCDD/F (as I-TEQ) annually.

Where sites took measures to upgrade processes, air pollution controls and wastewater treatment systems, substantially reductions in releases were observed.

Industrial Hygiene

Introduction

There is continuing concern over the exposure of humans and ecosystems to trace levels of highly toxic organic compounds, in particular chlorinated dibenzo-p-dioxins and dibenzofurans (PCDD and PCDF). The US Environmental Protection Agency (EPA) is developing inventories of releases of PCDD/F. As a contribution to this effort the Chlorine Chemistry Council (CCC, a business council of the American Chemistry Council) worked with EPA to develop estimates of releases of PCDD/F to the environment and off-site transfers from selected chemical production facilities in the US that produce or use large quantities of chlorine.

In addition to the US EPA inventory, inventories are increasingly being compiled in various countries, either as on-going government efforts to quantify releases or in preparation for, and demonstrating compliance with, international agreements such as the Stockholm convention.

There is no single consistent approach to compiling inventories of PCDD/F and inventory efforts differ in scope, coverage and, sometimes, in the way that data are treated and presented. Over recent years most inventory efforts have focused on data expressed as toxic equivalent (TEQ) values and most inventories consider the 17 congeners of PCDD/F that have been assigned toxic equivalency factors (TEFs) by NATO/CCMS (1988) and then WHO (Van den Berg et al., 1998). In some cases the congeners of PCB that show similar toxicity are also included (e.g. in Japan) but this is not yet common. Most inventories use the TEFs established by NATO/CCMS and known as International or I-TEFs although some more recent use the WHO TEF values for PCDD/F. In order to compare inventories it is important to carefully note the conventions used to compile ...