Particularly Hazardous Substances

Particularly hazardous substances (PHS) require additional planning and considerations. A description of particularly hazardous substances is available from the Occuptional Safety and Health (OSHA) website here. Consult the safety data sheet to determine whether a particular chemical may be considered a carcinogen, reproductive hazard or substance with a high acute toxicity and therefore identified as a PHS.


The OSHA Laboratory Standard defines particularly hazardous substances as:

Carcinogens – A carcinogen is a substance capable of causing cancer. Carcinogens are chronically toxic substances; that is, they cause damage after repeated or long-duration exposure, and their effects may become evident only after a long latency period.  A chemical is considered a carcinogen if it is included in any of the following carcinogen lists:

  • OSHA-regulated carcinogens as listed in Subpart Z of the OSHA standards.
  • Under the category "known to be carcinogens" in the Annual Report of Carcinogens published by the National Toxicology Program (NTP) latest edition
  • Group 1 ("carcinogenic to humans") of the International Agency for Research on Cancer (IARC), latest edition. Chemicals listed in Group 2A or 2B ("reasonably anticipated to be carcinogens") that cause significant tumor incidence in experimental animals under specified conditions are also considered carcinogens under the OSHA Laboratory Standard.

Reproductive Toxins – Reproductive toxins are substances that have adverse effects on various aspects of reproduction, including fertility, gestation, lactation, and general reproductive performance. When a pregnant woman is exposed to a chemical, the fetus may be exposed as well because the placenta is an extremely poor barrier to chemicals. Reproductive toxins can affect both men and women. Male reproductive toxins can in some cases lead to sterility.

Substances with a High Acute Toxicity – High acute toxicity includes any chemical that falls within any of the following OSHA-defined categories:

  • 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.



Stanley Howell
Sr. Program Manager
Chemical Safety

Steve Elwood
Associate Director for Laboratory Safety