How Toxic is Toxic?

The US Environmental Protection Agency's Toxics Release Inventory (TRI) provides data on releases of approximately 600 toxic chemicals into air, land, and water by industrial facilities across the United States. These releases are reported annually in terms of pounds of chemicals.

The chemicals on the TRI list vary in toxicity by up to seven orders of magnitude: that is, pound-for-pound, some of the listed chemicals are ten million times more toxic than others.

Based on an extensive peer review of scientific evidence, the EPA has developed “toxicity weights” that rank chemicals in terms of their relative toxicity. This review was conducted as part of the EPA's Risk-Screening Environmental Indicators (RSEI) project.

The EPA's inhalation relative toxicity weights are summarized in the table that can be accessed by clicking below. The data in the table are organized as follows:

Column 1: Name and CAS number of chemical
Column 2: Carcinogenic (cancer-causing) classification
Column 3: Relative inhalation toxicity.

To view this table, download this Excel file.