A toxin’s LD50 is used to classify its acute (i.e., short-term) toxicity. Specifically, the LD50 indicates the amount of material that causes death in 50% of a group of test animals and is usually expressed as a mass of toxin administered per mass of animal body weight. Note that a toxin may have multiple LD50s depending on the exposure route of the toxin. For example, the LD50 of saxitoxin is 5.7 micrograms per kilogram body weight via ingestion and 0.6 micrograms per kilogram body weight via injection.

Toxins with LD50 ≤ 100 μg / kg are considered acutely toxic and require special biosecurity precautions including secure storage and an inventory control log. They may also need to be registered with federal agencies. Contact the Biosafety Program to discuss use of biotoxins in this category.

The Federal Select Agent Program (FSAP) oversees possession, use, and transfer of a specific list of Select Agents & Toxins that have potential to pose a severe threat to public, animal, or plant health. Possession of Select Toxins in this list is strictly limited to specific permissible amounts and must comply with additional biosecurity measures and all FSAP due diligence requirements. If you need to use a Select Toxin in your research, contact the Biosafety Program before obtaining materials or beginning work.

When working with any toxins that pose a risk to human health, be sure to consider the following during your risk assessment to develop appropriate work procedures:

• Agent-specific hazards: Consider potential routes of exposure, exposure dosage, and signs & symptoms of exposure. Exposure routes will depend on the procedures used and may include inhalation, skin contact, mucous membrane contact, ingestion, and injection. If you are working with quantities at or near your toxin’s LD50, you may need to consider additional PPE and primary containment. If an exposure event may lead to severe or debilitating symptoms, you should consider requiring that certain procedures never be conducted alone; a buddy system ensures that someone will always be available to respond to an acute exposure event.
• Lyophilized versus reconstituted toxins: Consider how you will handle toxins from purchase through all the stages of your experiments. Most toxins are purchased in a lyophilized powder form, which is highly concentrated and susceptible to aerosolizing. Serum bottles containing lyophilized toxins should only be opened after the toxin has been reconstituted in a diluent.
• Aerosol-generating procedures: Lyophilized toxins in powder form should always be considered susceptible to aerosolizing. Other procedures with reconstituted toxins may also generate aerosols. Any aerosol-generating procedures must be conducted in a biological safety cabinet or fume hood, depending on the agent, and respirators may also be required. Aerosol-generating procedures typically include the following:
  • Centrifuging
  • Grinding
  • Blending
  • Vigorous shaking or mixing
  • Sonication
  • Opening pressurized containers (e.g., opening serum bottles)
  • Intranasal inoculation of animals
  • Harvesting toxin-containing tissues or eggs

Researchers working with toxins should be especially conscious of hand contamination, as this can lead to accidental ingestion and mucous membrane exposures in the lab. Always use gloves when handling toxins.

Because of the high risk of aerosols associated with some toxins, respirators may be required in addition to working in primary containment. Note that if a spill of dry toxin material occurs outside of primary containment, individuals should evacuate the lab and should not attempt to re-enter or clean up the spill without respiratory protection.

Medical consultations may be recommended for some toxin work. Additionally, vaccinations should be recommended if available. Consult with the Biosafety Program to discuss options.

All work with biological toxins requires review and approval of a biosafety protocol by the IBC. Protocols are approved for 3-year periods.

• Submit to the IBC online via iManager. Click here to access the submission system and submission instructions. Fill out the form as completely as possible, and provide any additional pertinent information that may assist the committee in assessing risks associated with your work.
• The IBC will determine the final biosafety level appropriate for the work proposed. Research should not begin until IBC approval is granted.

Biosafety training is required for all individuals conducting research with biological toxins. Find complete biosafety training requirements on the Biosafety Training webpage.