Chapter 7: Highly Toxic Chemicals and Select Carcinogens
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.
- 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:
- listed as a known or reasonably anticipated human carcinogen in the biennial Report on Carcinogens published by the National Toxicology Program
- 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)
- 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.
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.
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.
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.
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.
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.
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.