Toxic Emissions Indices: A Tool for Green Design and Performance Measurement

Arpad Horvath, Chris Hendrickson, Lester Lave, Francis McMichael and Tse-Sung Wu
Green Design Initiative
Engineering Design Research Center
Carnegie Mellon University

Introduction

In an era of global competition, rapid technological change and increasing concern for the environment, reliable environmental data is of paramount importance. The Environmental Protection Agency's Toxics Release Inventory (TRI), mandated by Title III of the Superfund Amendments and Reauthorization Act (SARA) of 1986, is the most comprehensive and widely reported information on hazardous discharges to the environment in the United States. Manufacturing companies in many industrial sectors have to report every year their releases to the air, water, land and underground, as well as transfers off-site of some 370 (recently expanded to 660) toxic chemical substances. The EPA makes the report available to the public, for better information. Various environmental stakeholders and the media have used the TRI data to name environmental "leaders" and "laggards".

Problem statement

No comprehensive and practical environmental performance measurement system is available today. For the TRI data, their interpretation has often been simplistic, 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 SARA chemicals 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.

Proposed Approach

The work of the Green Design Initiative researchers contrasts the one-to-one ranking of the TRI data with a ranking based on relative toxicity, using the American Conference of Governmental Industrial Hygienists' (ACGIH) Threshold Limit Value indices, a widely available toxicity measure.

EPA-TRI: total discharges per year, as reported in the TRI [10^4 lb]
EPA-TRI(TLV): total releases for which TLVs are known [10^4]

CMU-Equivalent Toxicity = (Xi . wi) for all i=1 to n
                           wi = TLV(Reference) / TLVi
                           TLV(Reference) = 1 mg/m^3

Toxicity Ratio = CMU-ET / EPA-TRI(TLV)

Example: Total Releases and Transfers (10^4 pounds)

	1987	1988	1989	1990	1991	1992
EPA-TRI	1,647	1,191	912	840	1,302	1183
EPA-TRI TLV	1,509	1,147	850	773	1,169	1,036
CMU-ET	256	363	245	156	528	692
Toxicity Ratio	0.17	0.32	0.29	0.20	0.45	0.67

Time trends of the TRI total releases and transfers of the U.S. computer and office equipment industry (SIC 357) from 1987 to 1992. The CMU-ET falls less than the number of pounds in the period 1987-90, and it increases from 1990 to 1992. The Toxicity Ratio is also larger in 1991 and 1992 than in previous years.

Application

The weighting scheme devised can be used for practical environmental performance measurement in green design and inventory by industry, government, process and product designers, the general public, media, etc. It allows for comparison of facilities, companies and industries, as well as different geographical regions (e.g., counties and states) and products. The toxic emissions indices help decision-making, track environmental performance over time and space, facilitate pollution prevention, provide better public information.

Reference

"Toxic Emissions Indices for Green Design and Inventory," A. Horvath, C. Hendrickson, L. Lave, F. McMichael and T-S. Wu, Environmental Science & Technology, pp. 86A-90A, Vol. 29, No. 2, 1995.

For more information contact

Chris Hendrickson
(412) 268-2948
Email: cth@cmu.edu

Financial support

Green Design Initiative of CMU's Engineering Design Research Center
IBM Environmental Research Program
National Science Foundation