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Forward Thinking Pest Control

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Forward Thinking Pest Control

EHS Pest Control

RI, MA EHS Pest Control Blog

EHS Pest Management, MA, RI
Dy Ice Proponents and collborators, left to right Norm Soep, John Stellberger, Bobby Corrigan, John Meaney and Rich Pollack

Doctor Robert Corrigan took Dry Ice to The Environmental Protection Agency and they approved it's use for open air rat control and with the help of Bell Laboratories it may very well hold the record for the shortest time from submission to approval. This White Paper is why I think it happened.

The Use of Dry Ice (CO2) For Controlling Exterior, Non-building Area Burrowing Norway Rat Infestations: A Case of Some Things Old Are Smart Again?


Rats and their associated ectoparasites occurring within the structured environment have been repeatedly shown by epidemiologists over several decades to be important public health pests (1, 2, 4, 6).

Traditionally, city public health rat infestations are addressed via integrated pest management programs employing sanitation, exclusion, and when necessary, the use of traps and poisoning campaigns (3, 7, 10). Interestingly, over the past six decades of rodent control work, not too much has changed with the exception of advances made in rodenticide technology. Some materials and approaches have always remained in vague areas as to their use to control rodents—especially homeowner materials and approaches (e.g., drowning yard rats with a water hose, pouring caustic materials down the rat holes, carbon monoxide from car exhaust and so on).

One material used during the 1940’s and 50’s (but never listed as a pesticide), was dry ice pellets inserted into rat burrows to asphyxiate the rats (3, 7, 10). But, with the advent of ready-to-use rodent baits beginning in the late 1940’s, dry ice was either overlooked thereafter, or used only for very specialized applications. Some zoological parks for example, (from their experiences of euthanizing various animals at the zoo using CO2 ) employed dry ice for exterminating zoo park rat infestations because they did not want the worry of secondary poisoning risks associated with the anticoagulant and non-anticoagulant baits on the market.

Carbon dioxide (CO2) is a colorless, odorless gas and is a by-product of everyday daily respiration by most animals. It is also a naturally occurring gas in the atmosphere (about 0.03 percent), and is necessary for photosynthesis in plants. Dry ice is the solid (frozen) form of carbon dioxide. Dry ice sublimes (i.e., changes from a solid directly into a gas with no liquid phase) at temperatures typically occurring outside (e.g., in rat burrows) regardless of the season or temperature. One pound of dry ice sublimates into 8.3 ft3 of carbon dioxide gas.

Euthanizing animals via carbon dioxide is considered an acceptable humane method by the American Veterinary Medical Association (AVMA) and this technique, via the use of CO2 chambers, is approved by nearly all states for urban wildlife control (via permits in some states). Carbon dioxide is also utilized in medical laboratories the world over to euthanize millions of lab rats and mice every year in medical research.

The Benefits of Using Dry Ice (CO2) For Burrowing Rat Control.

Pilot trials of dry ice (CO2) for exterior burrowing Norway rats over the past two years by several pest professionals, revealed that dry ice offers potentially strong advantages over the conventional uses of rodenticides for eliminating the public health threat of city rat infestations when they occur in earthen spaces away from building foundations about distances of 3m or more). Such spaces include park spaces, landscaped yards, backyards, empty lots, and so on.

Barring any possible forthcoming technical revelations/clarifications from toxicologists and/or veterinarians, there are five benefits to the use of dry ice (frozen carbon dioxide) for eliminating exterior rat infestations that occur away from buildings:

  1. Dry ice is non-toxic to humans and pets when used in the manner as prescribed for exterior rats;
  2. Dry ice is an environmentally green approach (e.g., no secondary toxic threats to hawks, owls, foxes, dogs, cats, and others) as compared to the second generation anticoagulant baits currently allowed by label to be applied directly into rat holes that occur in yards, parks, etc.);
  3. Dry ice (CO2) is an asphyxiate, not a fumigant. Thus, as per above discussion, it is a humane treatment to the rats themselves. Rats enter slumber first, and then succumb within the slumber without re-awakening;
  4. Dry ice (CO2) is highly effective on controlling burrowing rats—especially considering that some rats in urban environments will not (for various reasons) consume professionally–applied poison baits even when they are placed directly into active burrows. When such bait-aversive rats are present and pregnant females, the infestation goes on and on continuing the public health threat and causing all parties frustrations and extending the costs of achieving control.
  5. And finally, during and after the rats die in the burrows, their associated ectoparasites (e.g., fleas, lice, mites, and ticks); many of which are public health disease vectors themselves (5,8,9) also succumb to the carbon dioxide eliminating the need for follow-up “insecticidal dusting” campaigns to reduce or eliminate these potential arthropod vectors.

It is important to note that the conventional burrow baits, of course, have no insecticidal properties, and thus, will not kill rat ectoparasites. These medically important parasites can leave the burrows seeking alternate hosts such as humans, dogs, cats and/or local wildlife which, in turn, may further spread disease organisms to a community or a local ecosystem.

So, the question is : “What (ecologically speaking) is not smart about the use of dry ice and it’s specific use in this regard?”.

It should be noted that homeowners everywhere can buy dry ice at will by simply visiting their nearest local ice dealer in town. No permits are required and no labels accompany its use. Dry ice is used for parties, for cooking, for decorations, for custodial cleaning of buildings and, as mentioned earlier, by laboratory animal facilities the world over. A simple on-line search for dry ice vendors and dry ice equipment quickly reveals how pervasive the use of dry ice is to homeowners and commercial entities alike. Homeowners, if they wished, could apply dry ice to their own yards for various reasons. In fact, when homeowners are finished with their dry ice use, they typically dispose of it by spreading it out on the ground of their properties.

Additional Input Needed

There are two, and possibly three critical inputs needed to “weigh-in” on the possible future use of dry ice for rats (DIFR), both of which would prove helpful to all parties involved (EPA, State Regs, PMPs, and property owners).

First, a toxicologist(s) needs to "weigh-in" on the relative non-toxic threat of dry ice when used at the recommended: a) concentrations; b) locations and, c) application techniques, as would be done for exterior Norway rat burrows away from buildings. Although earlier research on this topic has been conducted (as cited with Meehan (1984), the work is dated and perhaps needs to be re-visited. Obviously should any toxicological issues emerge ( as per the three aspects just mentioned) that have been overlooked, then reconsiderations among all parties on the use of DIFR are obvious.

Second, for veterinarians to weigh-in as to why carbon dioxide used in this manner is such a "smart" (i.e., humane) method of killing (since presently, we still must kill these public health pests when they move into or around our yards, parks, schools, and exteriors of restaurants, housing complexes, offices, etc.).

And third, for an environmental lawyer to be consulted as to alternate “work-arounds” pending a lack of toxicological and/or humaneness concerns as is currently suggested.


  1. Battersby, S. A., R. Parsons, and J. P. Webster. 2002. Urban rat infestations and the risk to public health. Journal of Environmental Health Research 1: 57-65.
  2. Easterbrook, J.D., J.B. Kaplan, N. B. Vanasco, W. K. Reeves, R. H. Purcell, M.Y. Kosoy, G.E. Glass, J.Watson and S.L. Klein. 2007. A survey of zoonotic pathogens carried by Norway rats in Baltimore, Maryland, USA. Epidemiol. Infect. 135 (7): 1192.
  3. Federal Security Agency. 1949. Rat-borne disease. Prevention and Control. Public Health Service. Communicable Disease Center. Atlanta, GA. 292pp.
  4. Firth, C., M. Bhat, M A. Firth, et al. 2014. Detection of Zoonotic Pathogens and Characterization of Novel Viruses Carried by Commensal Rattus norvegicus in New York City. September/October 2014 Volume 5 Issue 5.
  5. Frye, M., C.A. Firth, M.J. Bhat, M.A. Firth, and W.I. Lipkin. 2015. Preliminary Survey of Ectoparasites from Norway Rats in New York City. J. of Medical Entomology. Short Communication.
  6. Himsworth, C.G., Parsons K.L, Jardine C, Patrick D.M., 2013. Rats, cities, people, and pathogens: a systematic review and narrative synthesis of literature regarding the ecology of rat-associated zoonoses in urban centers. Vector Borne Zoonotic Dis. 13:349–359.
  7. Meehan, A.P. 1984. Rats and Mice. Their Biology and Control. Rentokil Ltd., E. Grinstead, U.K. 383pp.
  8. Meerburg, B.G, G.R. Singleton, and A. Kijlstra . 2009. Rodent-borne diseases and their risks for public health. Crit. Rev. Microbiol. 35:221–270.
  9. Mullin G. and L. Durden (Eds.) 2009. Medical and Veterinary Entomology. 2nd Ed. Academic Press. San Diego, CA. 597 pp.
  10. Southern, H.N. (Ed.). 1954. Control of rats and mice. Vol. III. Oxford. Clarendon Press. 225 pp.

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