Toxic Emissions Indices for Green Design and Inventory

Abstract

The Toxics Release Inventory (TRI) is the most comprehensive and widely reported information on hazardous discharges to the environment in the United States. Unfortunately, the fledgling nature of the TRI may lead to simplistic interpretations of the results. In particular, TRI summaries typically report total releases of toxic chemicals by weight, implicitly assuming that a discharge of substance A is equivalent to an equal weight discharge of substance B. In contrast, various indices of the toxicity to humans of the chemicals reported in the Inventory indicate that the most harmful are more than 1,000,000 times more toxic than the least harmful. Thus, the simple rankings and time trends of facilities, industries, counties, and states as sources of toxic releases can be misleading because they have neglected relevant toxicological data. We contrast the one-to-one ranking of the TRI data with a ranking based on relative toxicity, using ”threshold limit value” (TLV) indices. The weighting scheme presented here is a useful first step for correcting the TRI but is certainly not definitive. Additional study is needed of uncertainties and limitations of this proposed approach. Future applications may be found in green engineering design and manufacturing changes. The usual government response to environmental pollution has been discharge control and remediation of toxic spills. With few exceptions, federal pollution control focuses on end-of-the-pipe discharge control. More recently, the U.S. Environmental Protection Agency has given attention to pollution prevention and waste minimization (1); policies and guidelines are being developed to encourage or require polluters to reduce their generation of toxic wastes. One such tool is the Emergency Planning and . Community Right-to-Know Act (EPCRA) of 1986, also known as Title I11 of the Superfund Amendments and Reauthorization Act (SARA). In parallel with the European Community (Seveso Decree), Section 313 of SARA requires various manufacturing firms to report the total annual environmental discharges of some 370 chemicals and chemical categories by plant; these data are published by EPA as the annual Toxics Release Inventory (TRI) (2). Recent legislation (the Pollution Prevention Act of 1990) has amended the rule to require reporting how wastes are treated on site and the amount transferred to publicly owned treatment works (POW). Plants required to report TRI data are limited to manufacturing firms defined by the Department of Commerce’s Standard Industrial Classification or “SIC” codes 20-39 (3); facilities that manufacture or process more than 25,000 pounds, or otherwise use 10,000 pounds of TRI chemicals; and plants with more that 10 full-time employees. At present, plants are required to report on only 370 chemicals and chemical categories. Although these are probably the most commonly used toxic substances, the vast majority of chemicals is ignored; 60,000 chemicals are reported to be in commercial use (4). Perhaps the greatest limitation of the TRI data is their accuracy. Companies are not required to monitor discharges but rather only to estimate them by “professional judgment.” As a result, the discharge data are likely to be in error for some chemicals in some plants by several orders of magnitude. Applying mass balance methods in which input, products, and emissions are made consistent would be an improvement (5). While requiring the use of monitoring or other documented methods to improve the accuracy of reported discharges may require statutory change, EPA can pursue other improvements to the TRI on its own. For example, the reporting threshold could be lowered for highly toxic chemicals and chemical categories, with all industrial sectors reporting regardless of the size of the facility. For better data, EPA has added 286 hazardous pollutants to the TRI list (67. Another problem has been the focus on discharges rather than the environmental fate of chemicals, which results in exposure to humans and envi“.mal damage. For example, emitting a pound