Evaluation of Pesticide Incident Report 2011-4412

Background

Pest control products are only registered by Health Canada's Pest Management Regulatory Agency (PMRA) for use if there is reasonable certainty that no harm to human health or the environment will result from exposure to, or use of the product as directed on the label. Health Canada collects incident reporting data under the authority of the Pest Control Products Act. If a pesticide manufacturer receives information about an incident involving one of their products, they are required by law to submit that information to Health Canada. Members of the public may also submit information about an incident directly to Health Canada. It is important to note that the information presented in incident reports reflects the observations and opinion of the person reporting it, and does not include any assessment by Health Canada, nor does it confirm an association between the pesticide and the effects reported.

Health Canada considers the reported information to determine if there are potential health or environmental risks associated with a pesticide and, if necessary, takes corrective action. Such action could range from minor label changes to discontinuation of the product.

Incident Report 2011-4412

According to the incident report, bee mortality was observed by a bee keeper in a group of 25 bee colonies located in an agricultural municipality in the Montérégie region of Québec. The bee hives were surrounded by agricultural fields in which corn and soybean are grown and the incident occurred during the sowing of corn and soybean seeds.  The first signs of the colony being affected were noted on June 1, 2011. Dead bees from the site were collected and analyzed by the Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec (MAPAQ). Residues of the pesticides clothianidin, thiamethoxam, fenitrothion, and atrazine were detected at concentrations of 0.0004 µg/bee, 0.00005 µg/bee, 0.009 µg/bee, and 0.00006 µg/bee, respectively.

In accordance with the Pest Control Products Incident Reporting Regulations classification system, this incident was classified as Environment Major. This incident report is available through the PMRA electronic Public Registry on the Health Canada website.

Health Canada Evaluation

If used according to label directions, atrazine (registered herbicide for use in corn) is not known to be harmful to bees. Clothianidin, thiamethoxam and fenitrothion, on the other hand, are highly toxic to bees.

Clothianidin and thiamethoxam are conditionally registered in Canada for use as a seed treatment, foliar spray and in-furrow applications to control insects. These are systemic pesticides, thus they are taken up by the plant's leaves or roots and transported throughout the plant. Possible exposure to bees could occur from contact or oral exposure to drift from foliar application, dust-off from treated seeds at planting, and oral uptake of residues that may be found in nectar, pollen and guttation droplets.

Fenitrothion is no longer registered for use in Canada. It is not clear how bees were exposed to this pesticide in this incident. Historically, fenitrothion was used as a foliar spray in apples, forests, woodlots, tree nurseries and Christmas tree plantations. Given the relatively short half-life of fenitrothion, it is thought that residues observed in the dead bees were related to a recent exposure to this compound. 

Health Canada Conclusion

The PMRA concluded that it is highly probable that exposure to clothianidin and/or thiamethoxam and/or fenitrothion caused the bee mortality in this incident. Even though it is not clear how the bees were exposed to these compounds in this incident, this conclusion is supported by the fact that residues of clothianidin, thiamethoxam and fenitrothion were found in dead bees and that these compounds are known to be highly toxic to bees. In addition, clothianidin and/or thiamethoxam were detected in other incidents where high bee mortality was observed.

It is unlikely that atrazine contributed to the bee mortality observed in this incident, as this pesticide is not known to be hazardous to bees.

This is the fourth incident reported to the PMRA involving clothianidin and/or thiamethoxam and bee mortality. A trend analysis will therefore be initiated by the PMRA to further its understanding of the issue. In addition, as clothianidin and thiamethoxam are conditionally registered, all incidents involving these compounds will be considered during the evaluation for full registration along with other requested data. It should finally be noted that pollinator issues are identified as a PMRA priority. Within this context, the PMRA is working with federal, provincial and international partners as well as other stakeholders including industry to improve risk mitigation measures for pollinators. With regards to fenitrothion, an inspection will be carried out to verify the possible use of this non-registered product.

The causality of this incident was assessed based on evaluated information present at the time of the review. It should be noted that any additional information regarding this incident that is provided to the PMRA will be taken into consideration and may change this conclusion.

More information about the Pesticide Incident Reporting Program is available on the Health Canada Web site. Should you require further information please contact the Pesticide Incident Reporting Program.