Mar. 7, 2017
The Canadian Pest Management Regulatory Agency (PMRA) invites the public to submit written comments on Regulatory Proposal PRO2017-01, Cumulative Risk Assessment Framework. This proposal is being distributed for information and comments.
For the purpose of this policy, cumulative assessment is aimed at identifying the risks associated with co-exposures to two or more chemicals that cause a common toxic effect(s) by the same, or essentially the same, sequence of major biochemical events (that is, a common mechanism of toxicity). Concurrent exposure routes ( oral, dermal, inhalation) and pathways (for example, diet, drinking water, residential use) to chemicals that share a common mechanism of toxicity are assessed to determine the potential for cumulative effects, based on the likelihood that people may be exposed to more than one of these chemicals at the same time. Cumulative assessment is undertaken to explore the possibility that low-level exposures to specific multiple chemicals could lead to the same or increased health risk relative to a higher level of exposure to any of these chemicals individually.
The consideration of the cumulative effects of pesticides was mandated in the modernization of Canadian pesticide legislation and reflects the application of modern science. Specifically, sections 7, 11 and 19 of the Pest Control Products Act
(PCPA, 2006) requires the consideration of “available information on…cumulative effects of the pest control product and other pest control products that have a common mechanism of toxicity” in evaluating the health risks of a pesticide. In some scientific circles, exposure to multiple chemicals by multiple routes and pathways is referred to as combined exposure to multiple chemicals rather than cumulative exposure; however, the terminology used through this document reflects that used in the PCPA for the assessment of pesticides. The scope of this policy does not extend to the consideration of mixtures of chemicals that may result in cumulative effects through disparate mechanisms of toxicity; however, it is worth acknowledging that this is an area of interest in the international regulatory community to be closely monitored.
Assessing the cumulative effects of pesticides to human health differs from aggregate assessment, which considers the risk from exposure (non-occupational) to a single chemical via all relevant routes and exposure pathways. Aggregate risk assessments have been fully implemented in the review of both new and re-evaluated pesticides and are supported by policy (Health Canada, 2003).
Currently, the PMRA is completing individual assessments for pesticides within the same common mechanism group through its re-evaluation program. It is essential that toxicological and exposure assessments of individual chemicals are up-to-date prior to undertaking the complex task of cumulative assessment. Cumulative assessments of pesticides that are known metabolites of one another (for instance, acephate and methamidophos) have been undertaken by the PMRA as the Agency continues to build its methods in this emerging area of science. The PMRA continuously monitors method development as well as specific cumulative assessments at the international level to determine their relevancy to the Canadian context.
This consultation is open for comment from 1 March 2017, to 15 April 2017 (45 calendar days).