Use of Biological Toxins
Biological toxins encompass a vast range of peptides, small molecules, and macromolecular proteins that cause disease by interfering with biological processes. They are produced by living organisms, are unable to replicate, and do not result in communicable diseases. Many biological toxins have been evolutionarily optimized to rapidly disrupt critical biological functions at low concentrations. Biological toxins remarkable combination of specificity and potency has resulted in widespread use for clinical and research purposes.
Laboratory workers can be exposed to biological toxins through a variety of routes, including inhalation of powders, aerosols, or volatile substances; ingestion; injection; and absorption through dermal, mucosal or ocular tissues. Due to their potency, internalization of even small doses may result in death or severe incapacitation. It is critically important for those working with biological toxins to understand and implement appropriate laboratory safety principles.
Each laboratory worker that plans to work with toxins of biological origin must be trained prior to beginning work with toxins. This training must include awareness of the risks associated with the specific toxins to be used including risks associated with transfer of solubilized toxins, manipulation of waste solutions, contamination of materials and equipment, and decontamination after routine operations and spills.
Guidelines for Biological Toxin Use
- An inventory control system should be established and audited on a regular basis to account for toxin quantity, use, and disposition
- Toxins should be stored in containers that clearly list the toxin contents, points of contact for responsible laboratory staff, and emergency contacts
- The use of locks on storage containers/locations offers additional control over toxin access and is highly recommended.
- Work with toxins should only be done in designated rooms or areas with pre-determined bench areas.
- When toxins are in use, the area should have clearly posted signage indicating that toxins are in use, minimum requirements for PPE, and emergency points of contact.
- Treatment plans for accidental exposures should be prepared and available to all laboratory staff and emergency responders
Safety Equipment and Containment
Routine operations with dilute toxin solutions are conducted under BSL-2 containment with the aid of PPE (laboratory coat, eye protection, gloves) and a well-maintained BSC, chemical fume hood or comparable engineering controls. Toxin(s) should be removed from the hood or BSC only after the exterior of the closed primary container has been decontaminated and placed in a clean secondary container. The interior of the hood or BSC should be decontaminated periodically (i.e. at the end of the day or after a spill). Selected operations with toxins may require additional precautions and potentially the use of BSL-3 containment. This will be determined by a through Risk Assessment and consultation with biosafety staff.
Many biological toxins are highly potent, and emphasis must be placed on evaluating and modifying experimental procedures to avoid inadvertent generation of toxin aerosols.
- Centrifugation of cultures or materials potentially containing toxins should only be performed using sealed, thick-walled tubes in safety centrifuge cups or sealed rotors.
- Sealed centrifuge safety cups or sealed rotor should be taken from the centrifuge to a BSC (or comparable engineering control) prior to breaking the seal and removing centrifugation tubes.
- Experiments should be planned to eliminate or minimize work with dry toxin or toxin-containing formulations. Unavoidable operations with dry toxins should only be undertaken with appropriate respiratory protection and engineering controls.
- Animal work involving aerosol exposure should be conducted in a certified Class III BSC or similar containment device.
- Vaccinations against some biological toxins are available and may be appropriate for laboratory workers.
Decontamination of a biological toxin(s) means the toxin is rendered inactive and is no longer capable of exerting its toxic effect. Toxin stability varies considerably outside of physiological conditions depending on temperature, pH, ionic strength, presence of co-factors, and other characteristics of the surrounding matrix.
Most toxins are susceptible to steam inactivation (121°C for one hour) or to chemical inactivation with dilute sodium hydroxide (NaOH) at concentrations of 0.1- 0.25 N, and/or sodium hypochlorite (NaOCl) solutions at concentrations of 0.1% - 2.5.% (w/v). However, inactivation procedures should not be assumed to be 100% effective without validation using specific toxin bioassays. Additional information related to decontamination of selected toxins can be found in Appendix I of the Biosafety in Microbiological and Biomedical Laboratories (BMBL, 6th ed.)
In the event of a liquid spill:
- Avoid splashes or generating aerosols during clean-up by covering the spill with dry paper towels of other disposable, absorbent material
- Ensure that appropriate PPE (Lab coat, gloves, eye protection) is worn during the clean-up
- Apply an appropriate decontamination solution to the spill, beginning at the perimeter and working towards the center
- Allow sufficient contact time for the decontamination solution to inactivate the toxin
- Restrict access to the contaminated area until the decontamination is complete
In the event of toxin powder:
- PPE should include respiratory protection in addition to PPE used for liquid spills
- For a spill within the BSC, gently cover the powder spill with damp absorbent paper towels to avoid raising dust than follow the steps described for a liquid spill
- For a spill outside of the BSC, the area should be immediately evacuated and the area restricted until the area has been thoroughly decontaminated (this may include turning off the HVAC system or removing and discarding HVAC filters that may have been contaminated)
HHS and the USDA have identified a group of toxins that pose a severe threat to human, animal, and/or plant health and they have been designated as Select Toxins. The Federal Select agent Program oversees possession, use, and transfer of these toxins. Registration with the CDC or USDA is required for possession, use, modification, production, storage, and/or transfer of non-exempt quantities of Select Toxins. Exempt quantities that do not require registration still need to be carefully managed to prevent loss or misuse. For further information related to Select Toxins please use the following links: