Notice of Objection Chlorpyrifos (Environment)

The Pest Management Regulatory Agency (“PMRA”) of Health Canada recently re-registered chlorpyrifos for spraying on mosquitos, in buildings, around structures, on trees (mountain pines and elm) and on outdoor and greenhouse ornamental plants. This chemical is highly neurotoxic, banned in Europe, and has been proposed for addition to the Stockholm Convention on Persistent Organic Pollutants.

How did PMRA do this? By not conducting a valid evaluation of the chemical. It separated out the assessment of risks to the environment from the risks to human health, which is not a justified approach. Then in its environmental risk assessment, it did not assess the extent of exposure in terms of concentrations in the environment as it was required to do. It used inaccurate information and faulty assumptions, it did not examine certain environmental harms, it made completely wrong extrapolations of the science from one species to another, and it presented unsupportable value propositions.

Ten organizations presented their objections to PMRA on the re-registration. A link to the February 8, 2021 Notice of Objection is above, and below the objections are described point by point. The Notice of Objection was filed by:

  • Association pour la santé environnementale du Québec – Environmental Health Association of Québec (ASEQ-EHAQ) 
  • Edmonton Chapter, Council of Canadians
  • Parkinson Québec
  • Pesticide Free Edmonton
  • Peterborough and Kawarthas Chapter Council of Canadians
  • Powell River Council of Canadians
  • Prevent Cancer Now
  • Safe Food Matters Inc.
  • Victimes des pesticides du Québec
  • Victoria Council of Canadians


  • Chlorpyrifos enters surface water (it sorbs to soil and then runs off into surface water)
  • It is volatile or semi-volatile, and moves long distances by the “grasshopper effect”
  • It is persistent or moderately persistent
Fundamental concern:

The conclusion of the Pest Management Regulatory Agency (PMRA) following its risk assessment was that the risk to the environment from the permitted uses of chlorpyrifos were “acceptable” with required mitigation measures. The legal standard for whether a risk is “acceptable” is whether there is a “reasonable certainty that no harm to human health, future generations or the environment will result from exposure to or use of the product” taking into account the conditions of registration (labels). 

The objection indicates PMRA said the risks were reduced, not eliminated.  Because risks are not eliminated, PMRA’s conclusion that that “no harm” to the environment will arise is wrong. Risks still exist.

Use on Standing water – temporary pools to kill mosquito larvae.

i) PMRA said there is “limited potential for environmental exposure”, but it did not assess the extent of exposure. In accordance with its own stated decision-making approach, it was supposed to assess the extent of exposure in terms of concentrations in soil, surface and ground water. It did not do so.

ii) PMRA stated that temporary pools do not require a separate risk assessment because: “their ecological function as a habitat is limited by their short duration during the growing season”, and that “it is not relevant to conduct a temporary pool risk assessment for drift or runoff resulting from adult mosquito control as chlorpyrifos is registered for direct application to such pools for mosquito larvae control”. 

PMRA used information that is not accurate or made assumptions that are not plausible. Temporary pools are home to many species and have their own ecological function and species that adapt to the temporary nature of the pools.

iii) PMRA misunderstood the nature of temporary pools – standing water. It said they are “temporary”; however this is wrong because some standing water, like sloughs, are permanent. Also some “temporary” pools can become permanent because of additional and unexpected rain or unexpected drainage from other sources.  

iv) PMRA said it is not relevant to conduct a temporary pool risk assessment for runoff because chlorpyrifos is to be applied directly to water. However PMRA itself has indicated that once chlorpyrifos enters water it sinks to the bottom and sorbs to the soil. This soil would be subject to runoff, so a risk assessment for runoff is relevant.

v) Environmental harm can be predicted even with direct application. Beyond the already documented harm to aquatic biota, chlorpyrifos causes blue-green algae to grow, according to the EPA.

vi) With respect to value, PMRA said chlorpyrifos is “valued in mosquito larval control programs for rotation with other insecticides to delay the development of insecticide resistance, since mosquitos have been documented to develop resistance.” No explanation of this resistance was provided, and the proposition for value is not supportable. Mosquitos develop resistance very quickly and easily, and studies show the application of pesticides exacerbates the problem of resistance. Also the cities of Winnipeg and Edmonton, who initially sprayed chlorpyrifos to kill mosquito larvae, have discontinued this use.

Use outdoors to kill adult mosquitos.

The technique of “fogging” with spray is used outdoors to kill adult mosquitos.

i) PMRA again said there is “limited potential for environmental exposure”, but it did not assess the extent of exposure to the environment (concentrations in soil and water) from this use. The exposure in the environment across Canada is likely to be extensive, because the use extends to outdoor areas throughout Canada.

Residues on vegetation, surface water and soil last for a long time and provide continued exposure to non-target organisms.  Condensation can deposit residues as well.

ii) The information used and assumptions made by PMRA were not accurate or valid. PMRA indicated there is limited potential for exposure to pollinators and beneficial insects because they are not present in the evening when spraying occurs. This explanation is not accurate, because some pollinators and insects are active at night, and “solitary bees” and insects come into contact with plants and soil on which the chemical lands.

Some birds, bats and other species are present in the evening and at night, and will be affected by fogging as well.

PMRA indicated inhalation by birds is not a concern, because of a “lack of observed toxicity” in a 1984 study on rats.  One problem is the study is confidential so could not be reviewed. The second is that the use of this rat study as representative of birds is not justifiable, because birds breathe differently than mammals.  Air flows in only one direction through bird lungs, and this makes birds more sensitive to harm from inhaled toxins.  

The exposure to birds occurs via multiple routes, more than just inhalation. The EPA has found that chlorpyrifos is very highly toxic via the oral route to birds, indicating that dietary and drinking water routes are potentially of concern.  

PMRA did not assess the risks to animals that feed on mosquitos at dusk, such as bats, dragonflies and damselflies.  The EPA assessment showed high risk to dragonflies and damselflies.

Science shows that the long-range effects of pesticide spraying can actually increase the number of mosquitoes by destroying their natural predators.

iii) PMRA spoke of mitigation measures of spraying with “ULV” applications of “ASABE” droplets, but there are concerns with the mitigation measures. First, label amendments do not mandate such applications.  

Also PMRA indicated that when fogging occurs, chlorpyrifos will be “intercepted” by “cryptic habitat” when sprayed, and presumably would not land on water or the ground.  The “cryptic habitat” was described as the undersides of leaves, vegetation and structures at the “sites” sprayed.   One problem is no explanation was provided of how the “site characteristics” would “intercept” chlorpyrifos and stop it from hitting the ground or groundwater.  Another is that the cryptic habitat can actually filter out the spray and shelter the mosquitoes from direct impact with the spray. Also, terrestrial species will still come into contact with the “cryptic habitat” and be exposed.

iv) With respect to value, there are concerns with PMRA’s assessment. Less toxic alternatives exist for killing mosquitos. Significantly, the efficacy of fogging to kill mosquitos is very low. For effective mosquito control, at least 90% of the adults must be killed; however calculations and studies show the spray comes into contact with only a small percentage of mosquitos. As indicated, “cryptic habitats” can filter out the spray and prevent it from reaching the mosquitos. Neither Winnipeg or Edmonton use chlorpyrifos as a mosquito adulticide.

Use inside and outside non-residential structures.

This use includes “broadcast spraying” of chlorpyrifos inside and outside of “non-residential structures”.  Such structures “include, but are not limited to, industrial/commercial indoor sites (for example, laboratories, warehouses, food granaries); modes of transport in areas where passengers are not present (for example, cargo areas, railcars); animal housing (for example, livestock housing, pet kennels); and areas within specific residential structures where the general public, including children, will have no access such as furnace rooms, storage areas in multi-unit dwellings, etc.”

i) PMRA again said there is “limited potential for environmental exposure”, and stated that “environmentally-relevant concentrations are not expected from these uses”, but it did not assess the extent of exposure (concentrations in soil and water) to the environment from this use in and on structures.

ii) The information used and assumptions made by PMRA were not accurate or valid. With broadcast treatment, the chemical will land on and sorb to soil and “can enter surface water through runoff as surface soil particles are dislodged due to rainfall”. The chemical will get into soil, onto foliage, and into air, and various species in the environment will be exposed, including beneficial arthropods, mammals, birds and others through direct contact, diet, inhalation or dermal contact.

Indoors, chlorpyrifos will be redistributed in the indoor space for at least 2 weeks after application and settle on indoor objects.  It can be inhaled.

People will be exposed. The fact that the general public has “limited access” to “non-residential” structures does not mean that there will not be access by individual people to the structures.  Some structures, such as “industrial plants” and “areas within specific residential structures”, can be expected to contain individual people for long periods of time. Many people work in food processing plants and meat packing plants and the food is subject to exposure. Based on conservative Statistics Canada employment numbers, the number of people potentially exposed is over 11 million people.

There is also a risk to animals, including animals raised for consumption, because “structures” include “animal housing and factories.  

PRMA separated the human health risk assessment from the assessment of the risks to the environment.  The pest control regime does not contemplate such a separation, likely because the risks to human health and the environment overlap. The human health assessment must consider the effects on human health from the use of chlorpyrifos in and on structures.

iii) With respect to value, there are alternatives for the use of chlorpyrifos both inside and outside of structures. In reevaluations, alternatives (including non-chemical) are to be considered. If a manufacturer has not registered an alternative, PMRA can takes the steps to register it under the URMULE program.

Use to kill elm bark beetle and mountain pine beetle.

PMRA stated that the “the environmental exposure of chlorpyrifos use for elm bark beetle and mountain pine beetle control is expected to be low, because chlorpyrifos is directly applied to the lower portion of the tree trunk and is not broadcast into the surrounding environment”.

i) PMRA indicated the environmental exposure is expected to be low, but again did not assess the extent of exposure to the environment (concentrations in soil and water) from this use.

ii) PMRA relied on the rat study described above to indicate inhalation is not of concern. The same concerns with this study as indicated above are relevant here. Plus, more current science based on rats indicates chlorpyrifos is “moderately toxic” to rats, which contradicts the dated confidential study relied upon by PMRA.

iii) PMRA incorrectly misapplied the science on elm bark beetle to the mountain pine beetle. Chlorpyrifos is effective at killing the elm bark beetle when applied to the lower portion of the tree trunk because that is the location where the elm bark beetles locate to overwinter. However the mountain pine beetle does not bore into the base of trees to overwinter, but rather spends its entire life under the bark except when it emerges, anywhere along the trunk, to attack healthy trees. Spraying for mountain pine beetle requires spraying of most of the trunk of the tree, to a “height of at least 3 m or until a bole diameter of 12.5 cm is reached”.

iv) With respect to value, chlorpyrifos does not contribute to management of the mountain pine beetle. The mountain pine beetle infestation has reached epidemic proportions, largely because of unusually hot, dry summers and mild winters. For the elm bark beetle, there are alternatives available, including the chemical bifenthrin (which is less toxic) and alternative pest control strategies including targeted rapid removal.

 Toxic Substances Management Policy Considerations.

The PMRA concluded that chlorpyrifos does not meet all Track 1 criteria, and is not considered a Track 1 substance. The European Chemicals Agency, in contrast, is of the view that the chemical meets the criteria for persistence, bioaccumulation and bioconcentration and applied in its December 2020 Stockholm Proposal for chlorpyrifos to be included as a persistent organic pollutant in the Stockholm Convention on Persistent Organic Pollutants. By virtue of the discrepancy in findings, concerns are raised about the approach of PMRA to the Toxic Substances Management Policy and about the evidence it relied upon for its findings.

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