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What is the definition of Particularly Hazardous Substance (PHS)?

Adapted from OSHA Laboratory Standards

For the purposes of requiring submission of a safety protocol and review by the Hazardous Chemical Safety Subcommittee, a hazardous chemical is one that falls into any one or more of the following four categories:

A chemical is considered a carcinogen and subject to safety review, if it is included in any of the following lists:

Reproductive Toxicants
Reproductive toxicants are substances that have adverse effects on various aspects of reproduction, including fertility, gestation and/or fetal development (teratogens), lactation, and general reproductive performance. See MCW’s on-line list of Particularly Hazardous Substances.

Substances with High Acute Toxicity
High acute toxicity includes any chemical that are assigned a NFPA category 2, 3 or 4 (see MSDS) or falls within any of the following OSHA-defined categories (often listed on MSDS):

  • A chemical with a median lethal dose (LD50) of 50 mg or less per kg of body weight when administered orally to certain test populations.
  • A chemical with an LD50 of 200 mg less per kg of body weight when administered by continuous contact for 24 hours to certain test populations.
  • A chemical with a median lethal concentration (LC50) in air of 200 parts per million (ppm) by volume or less of gas or vapor, or 2 mg per liter or less of mist, fume, or dust, when administered to certain test populations by continuous inhalation for one hour, provided such concentration and/or condition are likely to be encountered by humans when the chemical is used in any reasonably foreseeable manner.

Chemicals of Unknown Toxicity
For safety purposes, any chemical for which there is no known or limited toxicity data must be assumed to be Particularly Hazardous until proven otherwise.
© 2014 Medical College of Wisconsin
Page Updated 05/20/2014