Section 7J: Particularly Hazardous Substances

SECTION 7: Safe Work Practices and Procedures

7J: Particularly Hazardous Substances

As a matter of good practice, and to satisfy regulatory requirement, particularly hazardous substances require additional planning and considerations.

A list of particularly hazardous substances is available in Appendix A of this manual. This list is not exhaustive; consult the material safety data sheet to determine whether a particular chemical may be considered a carcinogen, reproductive hazard or substance with a high acute toxicity.

Definitions (top)

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, for the purpose of the Laboratory Safety Manual, if it is included in any of the following carcinogen lists:

      • OSHA-regulated carcinogens as listed in Subpart Z of the OSHA standards. The current list of substances that OSHA regulates as carcinogens or potential carcinogens follows:
        • asbestos
        • 4-Nitrobiphenyl
        • alpha-Naphthylamine
        • Methyl chloromethyl ether
        • 3,3'-Dichlorobenzidine (and its salts)
        • bis-Chloromethyl ether
        • beta-Naphthylamine
        • Benzidine
        • 4-Aminodiphenyl
        • Ethyleneimine
        • beta-Propiolactone
        • 2-Acetylaminofluorene
        • 4-Dimethylaminoazobenzene
        • N-Nitrosodimethylamine
        • Vinyl chloride
        • Inorganic arsenic
        • Cadmium
        • Benzene
        • Coke oven emissions
        • 1,2-dibromo-3-chloropropane
        • Acrylonitrile
        • Ethylene oxide
        • Formaldehyde
        • Methylenedianiline
        • 1,3-Butadiene
        • Methylene Chloride
      • 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.

Approval Procedure (top)

Laboratory workers planning to use a particularly hazardous substance must first receive explicit written approval from their Principal Investigator and/or Chemical Hygiene Officer, per the Departmental Chemical Hygiene Plan. The following steps must be taken: 

1.  Laboratory workers must complete a Particularly Hazardous Substance Use Approval form. Information required on the form includes:

  • Identity, physical characteristics, and health hazards of the substances involved
  • Consideration of exposure controls such as fume hoods, glove boxes and personal protective equipment
  • Designation of an area (hood, glove box, portion of lab, entire lab) specifically for experimental procedures with the substances involved
  • Plans for storage and secondary containment
  • Procedures for safe removal of contaminated waste
  • Decontamination procedures

2. The laboratory worker submits the form to the Chemical Hygiene Officer and/or Principal Investigator and receives approval.

3. The area where the PHS will be used is posted as a designated area. Signs for this purpose are available through EHS or may be made by the department or laboratory worker, as long as it includes the following information:

for select carcinogens, reproductive toxins and high acute toxicity chemicals


4.  The laboratory worker proceeds with the experiment, following the practices outlined in the Particularly Hazardous Substance Use Approval form, as well as the appropriate work practices included in the remainder of the Safe Work Practices and Procedures section of this manual. All work is conducted within the Designated Area.

5.  The laboratory worker decontaminates all equipment and disposes of waste promptly, as outlined in the Particularly Hazardous Substance Use Approval form.

Working Safely with Particularly Hazardous Substances (top)

The increased hazard risk associated with Particularly Hazardous Substances (PHS) calls for more strict operating procedures in the laboratory:

Work Habits

  • There should be no eating, drinking, smoking, chewing of gum or tobacco, application of cosmetics or storage of utensils, food or food containers in laboratory areas where PHS are used or stored.
  • All personnel should wash their hands and arms immediately after the completion of any procedure in which a PHS has been used and when they leave the laboratory.
  • Each procedure should be conducted with the minimum amount of the substance, consistent with the requirements of the work.
  • The laboratory worker should keep records of the amounts of each highly hazardous material used, the dates of use and the names of the users.
  • Work surfaces, including fume hoods, should be fitted with a removable liner of absorbent plastic-backed paper to help contain spilled materials and to simplify subsequent cleanup and disposal.

Personal Protective Equipment

  • PHS may require more stringent use of personal protective equipment. Check the MSDS for information on proper gloves, lab clothing and respiratory protection.
  • Proper personal protective equipment must be worn at all times when handling PHS.
  • Lab clothing that protects street clothing, such as a fully fastened lab coat or a disposable jumpsuit, should be worn when PHS are being used. Laboratory clothing used while manipulating PHS should not be worn outside the laboratory area.
  • When methods for decontaminating clothing are unknown or not applicable, disposable protective clothing should be worn. Disposable gloves should be discarded after each use and immediately after overt contact with a PHS.


  • Most PHS work should be performed in a fume hood, glove box, or other form of ventilation. If the chemical may produce vapors, mists or fumes, or if the procedure may cause generation of aerosols, use of a fume hood is required.
  • A fume hood used for PHS must have an average face velocity of between 95 and 125 feet per minute. This measurement is noted on the hood survey sticker. If the hood has not been inspected within the past year, contact EHS at 8-5294 for re-inspection before using the hood.
  • A glove box should be used if protection from atmospheric moisture or oxygen is needed or when a fume hood may not provide adequate protection from exposure to the substance; e.g., a protection factor of 10,000 or more is needed.
  • Highly toxic gases must be used and stored in a vented gas cabinet connected to a laboratory exhaust system. Gas feed lines operating above atmospheric pressure must use coaxial tubing.

Storage and Transportation

  • Stock quantities of PHS should be stored in a designated storage area or cabinet with limited access. Additional storage precautions (i.e., a refrigerator, a hood, a flammable liquid storage cabinet) may be required for certain compounds based upon other properties.
  • Containers must be clearly labeled.
  • Double containment should also be considered. Double containment means that the container will be placed inside another container that is capable of holding the contents in the event of a leak and provides a protective outer covering in the event of contamination of the primary container.
  • Containers should be stored on trays or pans made of polyethylene or other chemically resistant material.
  • Persons transporting PHS from one location to another should use double containment to protect against spills and breakage.

Vacuum Lines and Services

  • Each vacuum service, including water aspirators, should be protected with an absorbent or liquid trap to prevent entry of any PHS into the system.
  • When using volatile PHS, a separate vacuum pump should be used. The procedure should be performed inside a fume hood.

Decontamination and Disposal

  • Contaminated materials should either be decontaminated by procedures that decompose the PHS to produce a safe product or be removed for subsequent disposal.
  • All work surfaces must be decontaminated at the end of the procedure or work day, whichever is sooner.
  • Prior to the start of any laboratory activity involving a PHS, plans for the handling and ultimate disposal of contaminated wastes and surplus amounts of the PHS should be completed. EHS can assist in selecting the best methods available for disposal.

Section 7K: Pyrophorics
Section 7I: Laboratory Equipment