Environmental evaluation methods

Toxic Potential Indicator (TPI)

Theoretical background for the TPI (Toxic Potential Indicator)
The Toxic Potential Indicator is an environmental screening indicator which is based on the material composition of the product as delivered. It does not extend from cradle to grave including all precursors, reaction products (e.g. from incineration) or auxiliary production materials and their effects, but rather covers toxicity aspects of the materials as employed. The toxic potential is a relative numeric score which is intended to be multiplied with material weights. However, it does not model all the life cycle stages of a material, or the dose to impact relations of actual substance releases into the environment.

The TPI is based on German legal classifications, such as risk values (R-values) from chemicals legislation, maximum workplace concentrations (MAK) or occupational exposure limits (OELs), and water pollution classes (WGK). These values are available on the material safety data sheets (MSDS), hence they are widely available and allow users to fill data gaps easily compared to other assessment approaches. In addition, carcinogenic classifications are an input to the model.

The toxic potential on the substance level is a worst case assessment aggregating the potential impacts for the period that the chemical composition stays the same. The single classifications are mapped onto an interim scale ranging from 0 (no discernible effect) to 7 (maximum effect) per effect type. These are then numerically aggregated – eliminating potential overlaps between input values – and scaled to a theoretical maximum of 100. The result is the TPI per mg of a substance.
Multiplication with the weight contributions per substance yields a TPI value for complex materials, components and products.

Input values for the TPI calculation

  • Maximum workplace concentrations (MAK)
  • Carcinogenic classification (can override the workplace concentration)
  • Risk values according to chemicals regulation (R-values)
  • Water Pollution Classes (WGK)

The TPI Calculator is free for download and free to use. Non-commercial (free of charge) dissemination is also allowed as long as the copyright reference is included. All rights reserved © Fraunhofer IZM