Rachel Carson Council's
Follow-up Report on Zinc Phosphide
February 2, 2012
Rachel Carson Council sent a letter dated 11-25-11 to EPA requesting immediate action to give a higher level of protection for pets and the people who care for them from the hazardous effects of zinc phosphide, a rodenticide bait that generates toxic phosphine gas when exposed to water or stomach contents. Recent incident reports had shown toxicity of the baits especially those sold over the counter directly to homeowners. A copy of information that RCC sent to EPA is available as a PDF at "RCC's 2011 letter to EPA: Zinc Phosphide Summary."
EPA responded to RCC in a letter dated December 22, 2011 explaining the Agency's risk assessment procedures and indicating that EPA would review incident reports for zinc phosphide at a future time. Our call for immediate action to help reduce the adverse impact of zinc phosphide on pets and people was not addressed directly.
The letter from EPA indicated that Agency regulations require assessment of the risks from rodenticides used around the home only to human health and the environment. The letter did not mention doing risk assessments specifically for pets exposed to rodenticides. This failure to address the risks to pets may explain why dogs and cats have been suffering adverse effects from zinc phosphide as detailed in RCC's information sent to EPA and in "The "ides" of Autumn." These incidents describe how pets poisoned by zinc phosphide can become sources of the toxic phosphine gas resulting in illness in non-target species including innocent human bystanders, a population that should be covered by the Agency's risk assessment requirements.
RCC is not dropping the issue and we intend to contact the Agency again about problems with zinc phosphide bait in another letter.
The following summarizes the previous 4 letters (both RCC's and EPA's) and includes relevant comments from RCC. The update has 3 parts: Part I: RCC's 2011 Action Requests; Part II: EPA's Response/RCC's Comments; Part III: RCC's 2012 Follow-Up Recommendations for Agency Action; Part IV: Appendix.
In conjunction with our RCC Alert, "The 'Ides' of Autumn," Rachel Carson Council (RCC) sent a letter to Dr. Steven Bradbury, Director Office of Pesticide Programs (OPP) at the US Environmental Protection Agency (EPA) asking for better protection of pets and the people who care for them from the hazards of rodenticides containing zinc phosphide that are offered for sale directly over the counter (OTC) to home owners.
Part I. RCC's 2011 Action Requests
In RCC's 11-25-11 letter to Dr. Bradbury, we requested that the EPA take the following actions:
- Add information to product labels reflecting the Michigan State Guidance (Appendix: #1) that warns about zinc phosphide toxicity.
- Send out information to veterinarians, to pet publications, and to garden publications reflecting the Michigan State Guidance.
- Provide EPA reviewers of zinc phosphide products with copies of relevant toxicity data from current veterinary medical science sources (e.g. Small Animal Toxicology, eds. Osweier, G. et al, Wiley-Blackwell, 2011) as well as all relevant incident reports.
- Review the appropriateness of existing labeling for zinc phosphide bait products sold directly to homeowners OTC for use in killing moles in residential settings considering the beneficial aspects of moles to gardens and the potential hazards of zinc phosphide to pets, people and non-target wildlife.
Part II. EPA's Respsonse & RCC's Comments
Dr. Bradbury sent a letter in response, dated December, 22, 2011, to RCC. Our comments on Dr Bradbury's letter as well as excerpts from his letter follow:
RCC has no objection to the existing EPA labeling statements pertaining to pets as described to us; these are: A statement recommending treatment for pets poisoned with zinc phosphide bait (Appendix: #2) and a warning about dogs feeding on animals that have eaten zinc phosphide bait (Appendix: #3).
We have concerns regarding certain statements in Dr. Bradbury's letter. Below are direct quotations from that letter followed by RCC's comments:
1) USEPA Statement: EPA does not allow any pesticide to be labeled as "safe." However, "EPA ensures that pesticide products on the market can be used safely."
RCC Comment: That pesticides can be used safely does not necessarily mean that such products will be used safely. Further it also implies that they can be used unsafely, which unfortunately the incident reports for zinc phosphide confirm. The growing number of incident reports and the need for creation of the Michigan State Guidance indicate that serious safety issues attend zinc phosphide bait applications especially when OTC products are used around residences.
2) USEPA Statement: "EPA... [reviews data] to be certain that when used according to label directions and precautions, these products will not pose unreasonable risks to human health or the environment."
RCC Comment: Apparently, our concerns about hazards to pets are not addressed in the current EPA regulations; the only groups mentioned by the Agency under the risk standards are "humans" and "the environment." If, as it appears, that the EPA does not include pets in assessing the risks of rodenticides such as zinc phosphide, then it is no wonder that dogs are getting sick from them. Pet poisonings frequently result in anguish for human families, yet it's as if pets do not exist so far as the USEPA risk standard is concerned. Since it is acknowledged by the Michigan State Guidance and other sources that humans become ill from exposure to intestinal contents from poisoned pets-is this considered "a not unreasonable risk" (or in other words "a reasonable risk") to human health? Shouldn't such a risk be included on the label? The EPA's response did not mention the Michigan State Guidance that was developed in response to a need for better protection of pets and people from zinc phosphide toxicity and was incorporated into our letter. The EPA's response failed to indicate as well whether the Agency would send out any alerts pertaining to zinc phosphide toxicity, incorporating the Michigan State Guidance, to pet or garden publications as well as to veterinarians, which we also requested. We find this unacceptable and to remedy this omission, recommend that every package of zinc phosphide rodenticide sold OTC include a copy of the Michigan State Guidance.
The standard of "no unreasonable risks" is not the EPA's highest standard of protection for human health. Under the 1996 Food Quality Protection Act (FQPA) the standard is "reasonable certainty of no harm." Apparently this new standard has not been adopted for rodenticides.
3) USEPA Statement: The label restricts sites for zinc phosphide application to "...outdoor underground sites or areas that are inaccessible to children or pets."
RCC Comment: The implication from this statement is that "outdoor underground sites" are inaccessible to pets or children. We know that dogs can access outdoor underground sites by digging with their paws. Children can dig with shovels. By using the terms "either...or" the label could leave pets and children open to contact with toxic material applied to underground sites if they dig. In our opinion, to protect pets and children there should be an additional statement after "outdoor underground sites" advising users to keep pets and children away for the time during which the bait remains active-this needs further research to be determined. To protect children and pets from exposure to underground zinc phosphide bait as a result of digging activity, we recommend adding a statement to the labeling, that pets and children should be prevented from digging in the area where underground zinc phosphide bait has been placed.
4) USEPA Statement: "EPA will monitor the number of pet poisonings through [the NPIC portal] and if the number of zinc phosphide reports does not diminish once the approved revised labels are on the market, EPA will consider taking action to limit this use prior to further scheduled review."
RCC Comment: This is the only action that USEPA indicated it would be taking in response to our raising the issue of zinc phosphide toxicity to pets and people based on the recent increase and serious nature of incidents. Although it is encouraging, it does not put any time frame on the period during which the Agency promises to monitor the incident reports before taking action. Could it be up to 5 years? The letter also states, that registration review for zinc phosphide will take place in 2017, 5 years from now (2012).
Part III. Follow-up RCC Recommendations for EPA Action
Dr. Bradbury's response to our 11-25-11 letter addressed some RCC concerns but not others. We are contacting EPA with the following four recommendations for action with respect to OTC zinc phosphide products (intended for home owners).
- Include companion animals (pet dogs and cats) in future risk assessments for zinc phosphide containing products and other pesticides used in residential settings.
- Include a copy of the Michigan State Guidance in every package of zinc phosphide sold-this is critical for OTC products.
- If moles remain on the zinc phosphide bait labels, include a statement about the benefits that moles provide to gardeners due to their feeding on insects.
- To help protect children and pets from exposure to underground zinc phosphide bait as a result of digging activity, add a statement to the labeling that pets and children should be prevented from digging in the area where underground zinc phosphide bait has been placed.
Part IV. Appendix
1] MICHIGAN STATE GUIDANCE re: ZINC PHOSPHIDE
"The Michigan State Department of Community Health tracked a series of incidents involving zinc phosphide, in pets and people. To help reduce future hazards, Michigan health workers developed guidance for those confronting such poisoning as follows:
- Check to see if the dog has eaten a product that contains zinc phosphide.
- If the product does contain zinc phosphide, have the dog vomit outdoors, where there is plenty of air and the area can be hosed down with water.
- Stand upwind of the dog. Do not lower your head down to the dog. Phosphine is heavier than air and will sink to the ground.
- After the dog has finished vomiting, move it away from the vomit.
- Hose down the area with lots of water while standing upwind of the vomit. It can be washed down a storm sewer or off a hard surface onto grass. There will be enough air movement out-doors to prevent the phosphine from reaching levels that can harm humans or pets.
- Make sure the vomit is diluted enough so it does not attract other dogs or animals. The poison in any remaining pellets in the vomit will be released by the water, making them non-toxic. If the dog vomits indoors:
- If the dog vomits indoors, the phosphine gas may reach levels that could be harmful to people.
- Remove people and pets from the area and open doors and windows to ventilate the area.
- Run a fan at floor level. The gas is heavier than air and will sink to the floor. Running the fan will help move the gas out of the area.
- Call 911 to reach your local fire department. Most fire departments can determine whether or not the air is safe."
2] "TREATMENT FOR PET POISONING: If animal eats bait, call veterinarian at once."
"NOTE TO PHYSICIAN OR VETERINARIAN: Contains phosphine-producing active Zinc Phosphide. Probable mucosal damage may contraindicate the use of gastric lavage. For animals ingesting bait and/or showing poisoning signs, induce vomiting by using hydrogen peroxide. Sodium bicarbonate can be given orally to neutralize the stomach acidity. The stomach and intestinal tract can be evacuated, oxygen administered and cardiac and circulatory stimulants given."
3] "Dogs and other predatory and scavenging mammals might be poisoned if they feed upon animals that have eaten this bait."