Screening Assessment of Six Substances on the Domestic Substances List: introduction


The Canadian Environmental Protection Act, 1999 (CEPA 1999) (Canada 1999) requires the Minister of the Environment and the Minister of Health to conduct screening assessments of substances that have met the categorization criteria set out in the Act to determine whether these substances present or may present a risk to the environment or human health. Based on the results of a screening assessment, the Ministers can propose to take no further action with respect to the substance, to add the substance to the Priority Substances List (PSL) for further assessment, or to recommend that the substance be added to the List of Toxic Substances in Schedule 1 of the Act and, where applicable, the implementation of virtual elimination.

Under CEPA 1999, screening assessments focus on information critical to determining whether a substance meets the criteria for defining a chemical as toxic as set out in section 64 of the Act, where

  • 64. “ […] a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that
    • have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
    • constitute or may constitute a danger to the environment on which life depends; or
    • constitute or may constitute a danger in Canada to human life or health.”

The following six substances are among 123 substances on the Domestic Substances List (DSL) that were selected for a DSL screening assessment pilot project. All six substances were determined by Environment Canada to meet ecological categorization criteria for persistence and/or bioaccumulation, and inherent toxicity to aquatic organisms (Environment Canada 2003, 2006), under subsection 73(1) of CEPA 1999. Additionally, four substances (trifluralin, atrazine, chlorothalonil and pentachlorophenol) were identified by Health Canada as inherently toxic to humans (Health Canada 2006). Pursuant to paragraph 74(a) of CEPA 1999, the Ministers of the Environment and of Health have completed a screening assessment on trifluralin, atrazine, chlorothalonil, chlorophacinone, methoxychlor and pentachlorophenol.

Table 1: Identity of the Substances Covered Under this Particular Assessment
CAS RNFootnote a Common Name DSL Name
1582-09-8 trifluralin benzenamine, 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)-
1912-24-9 atrazine 1,3,5-triazine-2,4-diamine, 6-chloro-N-ethyl-N'-(1-methylethyl)-
1897-45-6 chlorothalonil 1,3-benzenedicarbonitrile, 2,4,5,6-tetrachloro-)
3691-35-8 chlorophacinone 1H-indene-1,3(2H)-dione, 2-[(4-chlorophenyl)phenylacetyl]-
72-43-5 methoxychlor benzene, 1,1'-(2,2,2-trichloroethylidene)bis[4-methoxy-
87-86-5 pentachlorophenol phenol, pentachloro-

All six substances are registered or have been registered as active ingredients in pest control products under the Pest Control Products Act (PCPA) and have undergone an environmental and human health risk assessment by the Pest Management Regulatory Agency (PMRA) as part of their registration process (Health Canada 2007a). Two of the substances have recently undergone re-evaluation resulting in continued registration for specific applications of atrazine (PMRA 2007) and chlorophacinone (PMRA 2004a, 2006). Three of the substances are currently undergoing re-evaluation, including trifluralin (PMRA 2008a), chlorothalonil (Health Canada 2007a) and pentachlorophenol (PMRA 2008b). All pesticidal uses of methoxychlor have been discontinued as of December 31, 2005, and this substance is no longer registered under the PCPA (PMRA 2004b).

For the screening assessment under CEPA 1999 of registered pesticides on the DSL, the approach of Environment Canada and Health Canada is to conduct an entry characterization of the substances in Canada and then evaluate any non-pesticidal releases and sources. The draft of the entry characterization has undergone a 60-day public comment period. A summary of the critical information used as basis for this screening assessment is presented below.

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