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Document ID ca-gcdwq-2023-01-20-4 Title Guidelines for Canadian drinking water quality – Malathion: Management strategies, international considerations URL https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-supporting-documents-malathion/management-strategies-international-considerations.html Jurisdiction /ca Subdomain(s) Drinking water, Water quality standards, Monitoring and analysis Language en Status completed Analyzed at 2026-03-18 14:56:52.039614+00:00 Relevance Provides management strategies, monitoring protocols, and MAC for Malathion.

14 Qualitative 10 Quantitative 5 Definitions

Q Qualitative Requirements (14)

Req ID	Category	Intent	Legal Status	Name	Subdomain(s)	Context	Conditions	Confidence
#Q001	operational	health	recommended	Risk Management Approach Implementation	drinking water	All water utilities should implement a risk management approach, such as the source-to-tap or water safety plan approach, to ensure water safety (CCME, 2004; WHO, 2017b, 2012).		high
#Q002	operational	operational	mandatory	System Assessment Requirements	drinking water	These approaches require a system assessment to characterize the source water, describe the treatment barriers that prevent or reduce contamination, identify the conditions that can result in contamination and implement control measures.		high
#Q003	monitoring	operational	mandatory	Operational Monitoring and Protocols	drinking water	Operational monitoring is then established and operational/management protocols are instituted (for example, standard operating procedures, corrective actions and incident responses).		high
#Q004	monitoring	operational	mandatory	Compliance Monitoring and Plan Validation	drinking water	Compliance monitoring is determined and other protocols to validate the water safety plan are implemented (for example, record keeping, consumer satisfaction).		high
#Q005	operational	operational	mandatory	Operator Training	drinking water	Operator training is also required to ensure the effectiveness of the water safety plan at all times (Smeets et al., 2009).		high
#Q006	operational	operational	recommended	Assessment of Source Water Potential	drinking water	Water utilities should consider the potential for malathion to enter source water (for example, raw water supply to the drinking water system) based on site-specific considerations.		high
#Q007	monitoring	operational	recommended	Source Characterization Monitoring	drinking water	When it is determined that malathion may be present and monitoring is necessary, then surface and groundwater sources should be characterized to determine the concentration of malathion.	When it is determined that malathion may be present and monitoring is necessary	high
#Q008	monitoring	operational	recommended	Peak Use and Rainfall Event Monitoring	drinking water	This should include monitoring of surface water sources during periods of peak use and rainfall events and/or monitoring of groundwater annually.		high
#Q009	monitoring	operational	guidance	Reduced Monitoring Allowance	drinking water	Where baseline data indicate that malathion is not present in source water, monitoring may be reduced.	Where baseline data indicate that malathion is not present in source water	high
#Q010	monitoring	treatment	recommended	Treatment Operational Monitoring	drinking water	Where treatment is required to remove malathion, operational monitoring should be implemented to confirm whether the treatment process is functioning as required.	Where treatment is required to remove malathion	high
#Q011	operational	treatment	recommended	Awareness of Natural Organic Matter Impacts	drinking water	Responsible authorities should be aware of the impact of natural organic matter on activated carbon systems, as it may impact water quality objectives for malathion removal.		high
#Q012	monitoring	treatment	recommended	Compliance Monitoring for Treatment	drinking water	Where treatment is in place for malathion removal, compliance monitoring (i.e., paired samples of source and treated water to confirm the efficacy of treatment) should be conducted at a minimum on an annual basis.	Where treatment is in place for malathion removal	high
#Q013	monitoring	operational	recommended	Quarterly Monitoring for Contaminant Breakthrough	drinking water	When routine operational monitoring indicates the potential for contaminant breakthrough, such as with GAC, monitoring should be conducted at least quarterly to plan for change-out of media.	When routine operational monitoring indicates the potential for contaminant breakthrough, such as with GAC	high
#Q014	monitoring	operational	recommended	By-product Formation Monitoring	drinking water	When a degradation process, like oxidation, is utilized, monitoring of by-product formation should also be considered.	When a degradation process, like oxidation, is utilized	high

P Quantitative Requirements (10)

Req ID	Category	Intent	Legal Status	Name	Subdomain(s)	Limit Type	Limit Value	Context	Conditions	Confidence
#P001	chemical	health	mandatory	Malathion	drinking water	MAC	0.29 mg/L	Health Canada - MAC (2020) for malathion in drinking water.	Increase in severity of chronic kidney disease in a 2-year toxicity and carcinogenicity study in rats	high
#P002	chemical	health	guidance	Malathion	drinking water	unknown	0.5 mg/L	U.S. EPA (2009; 2018) non-regulatory lifetime health advisory	Erythrocyte ChE inhibition in offspring from the comparative ChE multiple dose oral study in rats	high
#P003	chemical	health	guidance	Malathion	drinking water	unknown	2 mg/L	U.S. EPA Drinking Water Equivalent Level (DWEL)		high
#P004	chemical	health	guidance	Malathion	drinking water	unknown	0.9 mg/L	WHO (2004; 2017b) non-regulatory HBV	Decreased survival, reduced body weight and decreased ChE activity in a 2-year toxicity and carcinogenicity study in rats	high
#P005	chemical	health	guideline	Malathion	drinking water	unknown	0.07 mg/L	Australia (NHMRC and NRMMC, 2011) guideline value	Erythrocyte ChE inhibition in 2-year rat study	high
#P006	chemical	unknown	unknown	any individual (single) pesticide	drinking water	unknown	0.1 µg/L	EU value for any individual (single) pesticide found in drinking water	Values are based on a policy decision to keep pesticides out of drinking water, rather than health effects	high
#P007	chemical	unknown	unknown	total pesticides	drinking water	unknown	0.5 µg/L	EU value for total pesticides found in drinking water	Values are based on a policy decision to keep pesticides out of drinking water, rather than health effects	high
#P008	operational	operational	recommended	Compliance monitoring frequency	drinking water	requirement	>= 1 per year	Where treatment is in place for malathion removal, compliance monitoring (i.e., paired samples of source and treated water to confirm the efficacy of treatment) should be conducted at a minimum on an annual basis.	Where treatment is in place for malathion removal	high
#P009	operational	operational	recommended	Breakthrough monitoring frequency	drinking water	requirement	>= 4 per year	When routine operational monitoring indicates the potential for contaminant breakthrough, such as with GAC, monitoring should be conducted at least quarterly to plan for change-out of media.	When routine operational monitoring indicates the potential for contaminant breakthrough, such as with GAC	high
#P010	operational	reporting	recommended	Groundwater monitoring frequency	drinking water	requirement	1 per year	When it is determined that malathion may be present and monitoring is necessary... groundwater sources should be characterized... [including] monitoring of groundwater annually.	When it is determined that malathion may be present and monitoring is necessary	high

D Definitions (5)

Req ID	Name	Context	Confidence
#D001	NHMRC	Australian National Health and Medical Research Council	high
#D002	MCL	maximum contaminant level	high
#D003	WHO	World Health Organization	high
#D004	EU	European Union	high
#D005	DWEL	Drinking Water Equivalent Level	high