Particularly Hazardous Substances

A particularly hazardous substance (PHS) is defined by OSHA as either a carcinogen, reproductive toxicant, or substance with a high degree of acute toxicity.

Carcinogens are chemicals or chemical products that cause, or are suspected to cause cancer. OSHA has written standards regulating the use of carcinogens in 29 CFR 1910 Subpart Z. Known or reasonably expected human carcinogens are listed in the National Toxicology Programs Annual Report of Carcinogens. The International agency for Research on Cancer (IARC) lists Group 1 (“carcinogenic to humans”) and Group 2A or 2B (“reasonably anticipated to be carcinogens”). The State of California lists chemicals known to cause cancer or reproductive toxicity on the Proposition 65 List.

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.

Highly, acutely toxic substances include any chemical that may be fatal or cause damage to target organs as a result of a single exposure or exposure of short duration. Examples given are substances such as hydrogen cyanide, hydrogen sulfide and nitrogen dioxide. OSHA-defined categories are as follows:

• 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.


Any chemical where the hazard characteristics are unknown must be treated as particularly hazardous until proved otherwise.

Each KSU employee (researcher, PI, staff, etc.) must be aware of the hazards presented by the chemicals and chemical products that they encounter on the job. To provide additional awareness, EHS has developed written standard operating procedures for some of the most common PHSs used on KSU’s campus. These SOPs are intended to provide general guidance for working with specific substances; however, it is the responsibility of the Principal Investigator or his/her designee to develop SOPs for lab specific procedures using PHSs.

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