Canadian Municipal Water eBulletin

New Consultations on Guidelines for Drinking Water

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Health Canada is currently consulting on three proposed guidelines on drinking water quality – cadmium in drinking water, total coliforms and natural organic matter.

Cadmium in Drinking Water:

A maximum acceptable concentration (MAC) of 0.005 mg/L (5 µg/L) is proposed for total cadmium in drinking water. According to the proposed guidance document the primary source of cadmium are naturally (leaching from soil), as a result of human activities (as a by-product of refining or from its use in technological applications) or through leaching from some pipes and well components.

Total Coliforms in Drinking Water:

This consultation is different than most undertaken by Health Canada. Instead of proposing a revised guideline, this consultation is being used to determine if updates to the existing guideline are necessary. The 2012 Guideline on Total Coliforms on Drinking Water established a maximum acceptable concentration (MAC) of total coliforms in water leaving a treatment plant and in non-disinfected groundwater leaving the well of none detectable per 100 mL. The Guideline also states that total coliforms should be monitored in the distribution system because they are used to indicate changes in water quality. Detection of total coliforms from consecutive samples from the same site or from more than 10% of the samples collected in a given sampling period should be investigated (Health Canada, 2012).

Health Canada reviewed the scientific literature related to total coliforms in 2017. Based on this review, a full update of this guideline technical document is not required at this time, as science continues to support the MAC established in 2012.

Organic Matter in Drinking Water:

Natural organic matter (NOM) is an extremely complex mixture of organic compounds and is found in all groundwater and surface waters. Although NOM has no direct impact on health, it affects the efficacy of drinking water treatment processes and consequently the safety of drinking water. NOM may also affect consumer satisfaction because it can contribute to undesirable colour, tastes and odours in drinking water.

Health Canada completed its review of NOM in drinking water and the impact that it can have on drinking water treatment processes. This guidance document reviews and assesses risks associated with the impact of NOM on drinking water treatment processes and the safety of drinking water. It is important to note that it does not establish a numerical limit on NOM.

Comments on all three consultation documents are due on May 21. CWWA’s drinking water quality committee will be reviewing all three and submitting comments if needed.