This chapter supplements previous chapters by giving specific extra precautions, postings, training, and protective equipment necessary when working with substances that are highly toxic and/or select carcinogens. The appendices at the end of the chapter are a thorough (but not exhaustive) list of substances that might be present in your lab that are highly toxic and/or carcinogenic.

Work with highly toxic chemicals or select carcinogens require special containment practices in addition to those described in Chapter 6 for toxic chemicals. Highly toxic compounds have the ability to cause harmful effects, which can be local or systemic, after a single exposure. Among the most useful parameters for assessing the risk of acute toxicity of a chemical are its LD50 and LC50 values, the mean lethal dose or lethal concentration causing death in experimental animals. Per the Health Hazards Definitions of the OSHA Hazard Communication Standard, a substance is highly toxic if:

  • the oral LD50 for albino rats is less than 50 mg/kg or
  • the topical LD50 for albino rabbits is less than 200 mg/kg or
  • the LC50 in albino rats is less than 200 ppm for one hour.

Examples of highly toxic substances include hydrogen cyanide, osmium tetroxide, phosgene, sodium azide, and tetrodotoxin. For a thorough (but not exhaustive) list of highly toxic substances, refer to Appendix 7-A.

A select carcinogen is a chemical agent that causes a malignant disease or statistically increases the risk of cancer, whether by initiation or promotion. Appendix 7-B lists select carcinogens that are:

  1. listed as a known or reasonably anticipated human carcinogen in the biennial Report on Carcinogens published by the National Toxicology Program
  2. listed as carcinogenic to humans (Group 1), probably carcinogenic to humans (Group 2A), or possibly carcinogenic to humans (Group 2B) by the International Agency for Research on Cancer (IARC)
  3. regulated by OSHA as a carcinogen

Some of these compounds are common materials used in many laboratories, such as acrylamide, chloroform, carbon tetrachloride, benzene, hydrazine, and thiourea. More than two-thousand substances exhibit some evidence for carcinogenicity. Many of these also warrant careful planning and control procedures.

Laboratories working with highly toxic chemicals and/or select carcinogens must include standard operating procedures in the Laboratory Safety Plan (LSP) describing the hazards of the compounds, safety precautions and emergency procedures in the event of a spill. Refer to Chapter 2 for instructions on completing an LSP. In addition to the safety practices described for use of toxic materials, several other special safety precautions are necessary for highly toxic chemicals and select carcinogens.
Establish a “designated area,” with access restricted to personnel who are aware of the hazards of the substances in use and the necessary precautions. A foot or elbow operated handwashing facility and an eyewash facility must be available within the work area. A shower facility, other than emergency drench showers, must be located in the building.

Exhaust ventilation systems are designed to maintain an inflow of air from the corridor into the work area. The exhaust air from the work area must discharge directly to the outdoors, and clear of occupied buildings and air intakes. Exhaust air from the work area must not recirculate. The exhaust air from glove boxes must filter through high-efficiency particulate air (HEPA) and charcoal filters. EHS shall determine the need for and type of treatment for other primary containment equipment. Exhaust air treatment systems that remove toxic chemicals from the exhaust air by collection mechanism such as filtration or absorption must operate in a manner that permits maintenance, to avoid direct contact with the collection medium. All exhaust air from primary containment equipment must discharge directly to the outdoors and disperse clear of occupied buildings and intakes. Exhaust systems for highly toxic substances must contain engineered fail-safe mechanisms to prevent loss of containment due to utility outages.

The EHS Director (or designee) must approve the purchase and installation of any non ducted hoods. EHS will not approve non-ducted hoods for use with volatile chemicals. Approval will be granted only in exceptional cases, and only when particulate handling (e.g., weighing solids) is its sole use.

Refer to Chapter 5: Protective Clothing and Equipment

Wear a full-fastened laboratory coat or a disposable jump suit in any area where highly toxic chemicals or select carcinogens are in use. The Principal Investigator is to provide clean clothing weekly and you cannot wear it outside of the work area. Following an obvious exposure, decontaminate or dispose immediately all clothing contaminated by highly toxic chemicals. Do not send contaminated clothing to the laundry until decontaminated. Wear appropriate gloves (Appendix 5-B) when handling. Double gloving is recommended. Discard disposable gloves after each use and immediately after known contact with a highly toxic chemical or select carcinogen.

Procedures involving volatile chemicals, and those involving solid or liquid chemicals that may result in the generation of aerosols, must occur in a laboratory hood, glove box, or other suitable containment equipment. Examples of aerosol-producing procedures include: opening of closed vessels; transfer operations; weighing; preparing feed mixtures; and the application, injection or intubation of a chemical into experimental animals. Class II, type B biological safety cabinets are suitable for the conduct of tissue culture and other biological procedures involving highly toxic chemicals, reproductive toxins, and select carcinogens. The Principal Investigator is to obtain guidance from EHS on the selection and use of Class II biological safety cabinets. For more information on biological safety cabinets, refer to Chapter 16: Biological Safety Cabinets. Primary containment equipment used for chemical carcinogens must display a label bearing the legend: CAUTION – HIGHLY TOXIC CHEMICAL (OR SELECT CARCINOGEN), Authorized Personnel Only. The examples below in Figure 7.1, Figure 7.2, and Figure 7.3 are available on the EHS Safety Labels webpage for printing.

A clean bench (Chapter 16, Section III) is a laminar flow cabinet that provides a flow of filtered air over the work service and offers product protection, not personnel protection. Do not use highly toxic chemicals or select carcinogens in them. These are posted by the lab or EHS with the information in Figure 7.2.

Figure 7.1
Figure 7.1. Examples of postings for storage areas or primary containment equipment where highly toxic chemicals or select carcinogens are present.
Figure 7.2
Figure 7.2. Example posting for clean benches.
Analytical instruments, when used with highly toxic chemicals and select carcinogens, must be located entirely within a laboratory hood. When this is impossible, capture the vapors or aerosols produced by these instruments through local exhaust ventilation at the site of their production. When you remove a sample from the analytical instrument, place it in a tightly stoppered sample tube, or otherwise safeguarded from contaminating the laboratory. Do not use contaminated analytical equipment until it has been completely decontaminated. The following are some decontamination guidelines. Contact EHS if you have additional questions about equipment decontamination.

Safely remove, drain, or discharge chemicals from the equipment, collecting the chemicals for re-use or hazardous waste disposal. If applicable, use an inert gas or liquid to purge the chemical residues. In some cases, the rinsate might require disposal as hazardous waste. For equipment with non-permeable surfaces, decontaminate by scrubbing with warm, soapy water. For equipment that also might contain biological contamination, follow the soapy water wash with a 1:10 bleach solution soak. Rinse the equipment after at least 10 minutes contact time with the bleach.

Stock quantities of chemical carcinogens are to be stored in designated storage areas. Post these storage areas with signs bearing the legend: CAUTION – HIGHLY TOXIC CHEMICAL (OR SELECT CARCINOGEN), Authorized Personnel Only (Figure 7.1).

Label all storage vessels containing stock quantities with the following information: CAUTION – HIGHLY TOXIC CHEMICAL (OR SELECT CARCINOGEN). You may use these smaller labels available at the EHS Safety Labels webpage.

Keep quantities of highly toxic chemicals, and select carcinogens in the work area to a minimum. Quantities should not exceed the amounts normally required for use in one week. Use the label depicted in Figure 7.3 (or similar) for storage vessels containing working quantities of highly toxic chemicals or select carcinogens.

Figure 7.3
Figure 7.3. Labels for storage vessels that contain highly toxic chemicals or select carcinogens.
Place storage vessels containing highly toxic chemicals or select carcinogens in an unbreakable outer container before transporting them from storage areas to laboratory work areas. Place contaminated materials to transfer from work areas to disposal areas in a closed plastic bag or other suitable impermeable and sealed primary container, and place the primary container in a durable outer container before transporting. Label the outer container with both the name of the substance and the warning from Figure 7.3.
Each vacuum service, including water aspirators, must have protection via an absorbent or liquid trap and a HEPA filter to prevent entry of any highly toxic chemical or select carcinogen into the system. When using a volatile chemical, use a separate vacuum pump or other device placed in an appropriate laboratory hood.
Package highly toxic chemicals and select carcinogens to withstand shocks, pressure changes and any other condition that could cause the leakage of contents incident to ordinary handling during transportation. Shipments must be in accordance with DOT and IATA regulations. These regulations state that you must receive specific training in order to ship a hazardous chemical legally. Contact EHS to receive this training and for guidance on shipping and labeling.
Highly toxic chemicals and select carcinogens that have spilled out of a primary container to create a hazard must be inactivated in situ or absorbed by appropriate means for subsequent disposal. Contaminated materials require decontamination by procedures that decompose the chemical, or removal for subsequent disposal. Write these decontamination protocols into your Laboratory Safety Plan, and update the protocols as necessary. Means for assuring the adequacy of clean up are required; for instance, wipe tests or fluorescence tests.
EHS must approve all plans for handling and ultimate disposal of contaminated wastes. You must have written procedures in the Laboratory Safety Plan, Schedule B, and you must fully describe the highly toxic and/or carcinogenic substances in your waste stream when submitting an online hazardous materials transfer form. Refer to Chapter 12: Management of Laboratory Wastes for additional guidance.
In all circumstances, research and animal care personnel must wear a disposable jumpsuit or lab coat, shoe coverings, hair covering, gloves, and a respiratory comfort mask when entering DLAM animal housing facilities or procedure rooms (refer to Chapter 14: Safe Handling of Laboratory Animals). As discussed in Chapter 5, comfort masks and surgical masks are not respirators. The comfort masks and surgical masks provided in several DLAM facilities do not protect you from airborne exposures; instead, they protect the lab animals from your exhalations. Personnel engaged in procedures with exposure to airborne particulates contaminated with highly toxic chemicals or select carcinogens must wear an appropriate respirator of N95 or higher protection, rather than a comfort mask or surgical mask. Refer to the Respiratory Protection section of Chapter 5: Protective Clothing and Equipment, for a description of respirator types. The use of primary containment may eliminate the need to wear a respirator.

EHS must approve the selection and use of respirators, and wearers are to participate in the UNC Respiratory Protection Program.

Do not wear masks or respirators outside of the animal room or procedure room. For tight-fitting cartridge respirators, dispose of used filters and decontaminate the respirator housing daily.

Back to Chapter Six
Proceed to Chapter Eight