Health Risk Information about Bacillus Thuringiensis (B.t.) - EH: Minnesota Department of Health

mothHealth Risk Information about Bacillus Thuringiensis (B.t.)

The Minnesota Department of Health prepared the following information to answer frequently asked questions about health risks from exposures to Bacillus Thuringiensis (B.t.). This information refers to B.t. kurstaki which is commonly used to control gypsy moths.

B.t. Facts

  • B.t. is a naturally occurring bacteria that is commonly found in soil and food.
  • B.t. has been used safely for over 30 years to control insects in the United States, Canada, and other parts in the world.
  • B.t. operates through a well-known protein mechanism that causes toxicity in caterpillars (i.e. insect larvae). This mechanism is not known to be present in humans or other mammals, regardless of age.
  • B.t. Is a biological control method that is an alternative to chemical pesticides. B.t. does not disrupt the ecological balance or harm most non-target organisms.
  • Research shows that the level of B.t. in air decreases to very low levels within 30 to 90 minutes after an aerial application.

To Avoid Exposure

Even though B.t. is considered safe for humans, people may avoid exposures by staying indoors during applications, unless it is essential to be outdoors. You should be notified in advance by the Minnesota Department of Agriculture (MDA) with a window of time that the application will occur. If you or someone in your home has a medical problem that they believe may be made worse by the application, consult your physician or other health care professional. To avoid exposures:

  1. Stay indoors during applications (and for at least 30 minutes after applications) to allow droplets to settle.
  2. Wait until the treatment has dried before touching grass or shrubs. If there is residue on playground equipment, sandboxes, benches, or lawn chairs, spray or hose them off with water afterward.
  3. Wash exposed skin with soap and water if direct contact with the spray droplets occurs. If material should get into your eyes, flush with water for 15 minutes.


For information about B.t. applications, including general information and notification, contact the Arrest the Pest Infoline, 1-888-545-6684, or visit the Minnesota Department of Agriculture Pest Management website.

For more information about B.t. and health risks, see the resources below or see our Pesticide Contacts information.


Bacillus thuringiensis: technical fact sheet (PDF: 40KB/6 pages), National Pesticide Information Center

Reregistration Eligibility Decision: Bacillus thuringiensis (PDF: 540KB/170 pages), US Environmental Protection Agency

R.E.D. FACTS: Bacillus thuringiensis (PDF: 27KB/6 pages), US Environmental Protection Agency

What are Biopesticides, US Environmental Protection Agency

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Updated Tuesday, December 30, 2014 at 07:58AM