Dry ice and rodenticide use in Chicago: Is it safe, effective, and legal?

animal-1239219_1920The following was a press release for October 28, 2016. The EPA has since contacted the City of Chicago about the unregistered use of dry ice as reported by USA Today. To see a translation of this press release in Portuguese, please click here

The Midwest Pesticide Action Center (MPAC), the only organization based in the Midwest focused on reducing the health risks and environmental impacts of pesticides by advancing safer alternatives, is concerned about some of the practices taken by the City of Chicago to abate rodents outlined by DNAInfo’s “Chicago Puts Rats on Notice – New Push to Focus On Killing Rodents.” The practices that concern us the most include (1) the City’s use of rodenticides for their potential human health and pet effects and (2) the use of the dry ice treatment “off-label”, raising  questions regarding the practice’s legality. MPAC recommends the City increase its emphasis on prevention, before resorting to these two questionable strategies.

Just like us, rats and mice are warm-blooded mammals and, therefore, the use of chemicals to kill rodents will impact our biology in similar ways. The City of Chicago uses a rodent baiting system, where rats will eat the rodenticide and die later. When taking the appropriate precautions, baited chemicals are unlikely to come in contact with humans and the doses used will likely have minimal effects on the average adult.  In fact, thanks to the pressure by MPAC and other like-minded organizations, manufacturers of these products have increased their safety by decreasing the likelihood of unintended contacts.

However, dangers still persist especially for wildlife and our pets. Anticoagulants are the most popular bait rodenticides and work by thinning the blood and preventing blood clots of nearly all warm-blooded animals when consumed. Dogs could be at the greatest risk of anticoagulant poisoning with their smaller size and behavior of smelling, licking, and/or even consuming rodents or rodent carcasses.

The City of Chicago does not indicate what type of rodenticide they use on their website, but nearly all chemicals used to control rats have similar health concerns associated with their use.

As for the City’s use of dry ice, while the practice appears more environmentally friendly at first glance, the relative newness of the tactic brings a lot of uncertainty and questions about its legality.  Dry ice has been used for some years to “humanely” kill lab rats by displacing oxygen with carbon dioxide and suffocating the rats. The practice in municipalities, however, has not been implemented till as recently as April, 2016 by the City of Boston.

We don’t know the environmental or health effects that result from placing an extremely cold, solid substance (-109 ◦F) that instantly converts to potentially hazardous carbon dioxide gas. Our sources at the Environmental Protection Agency (EPA) tell us that dry ice is not a legally approved and labeled method for pest control under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), meaning that the product cannot be used to kill pests and, also, no codes or guidelines exist for municipalities to follow when storing, handling, and applying dry ice.*

Already, we have seen the potential hazards that could result from the City implementing this practice with no codes. In a YouTube video released by USA Today titled “Chicago battles rats with dry ice” a city worker can be seen shoveling dry ice at :05 without protective eyeware and what appears to be standard work gloves.  When outlining general precautions for working with dry ice in a laboratory, the Occupational Safety and Health Administration (OSHA) states “to use cryogenic gloves, which are designed specifically for working freezers below -80 ◦C and for handling containers or vials stored in these freezers” and to “always use appropriate eye protection” when handling dry ice. If mishandled or an accident takes place, dry ice can cause severe skin and eye damage to unprotected city workers.

The risks for both rodenticides and dry ice are too large at this point to warrant their use for mitigating rodents in Chicago and other urban areas. Proven methods, however, do exist to manage rat populations, starting with preventative measures that the City has identified as part of their rodent control program.

Eliminating access to food will best reduce habitat for rats. The City could do well by educating residents how to do their part in controlling rat populations. MPAC has successfully worked with the City before to educate the community about safe and effective pest control. Most recently, we partnered with the Chicago Park District to message about dandelions and provide education on bed bug control that dramatically reduced complaints and improved quality of life for residents. Some preventative measures residents can take today to eradicate rats include:

  1. Frequent collection of garbage and use of tight-fitting covers to prevent access.
  2. Clean up dog droppings which are a food source for rats.
  3. Keep firewood and other outside household items off the ground to eliminate shelter opportunities.
  4. Exclude access by using chicken wire or hardware cloth in locations where rats burrow such as raised flower beds and under porches.

For more tips on rodents and other pests, please visit our website resources page at

Thank you,

Ruth Kerzee
Executive Director
Midwest Pesticide Action Center

* FIFRA is a United States federal law that set up the basic U.S. system of pesticide regulation to protect applicators, consumers, and the environment.

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