Draft technical document guidelines for Canadian drinking water quality - Antimony: Management strategies, international consideration

On this page

Management strategies

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, 2011, 2012). 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. Operational monitoring is then established, and operational/management protocols are instituted (for example, standard operating procedures, corrective actions and incident responses). Compliance monitoring is determined and other protocols to validate the water safety plan are implemented (for example, record keeping, consumer satisfaction). Operator training is also required to ensure the effectiveness of the water safety plan at all times (Smeets et al., 2009).

Control strategies

In water sources with higher than acceptable antimony concentrations a treatment option discussed in the section on treatment considerations may be implemented, or non-treatment strategies such as blending or alternative water supplies can be considered. When the option of a treatment technology is chosen, the species of antimony should be identified and pilot-scale testing is recommended to ensure the source water can be successfully treated and process design is established. Attention must be given to the water quality of a new source prior to making any changes (for instance, switching, blending and interconnecting) to an existing water supply. For example, if the new water source is more aggressive, it may cause leaching of lead or copper in the distribution system.

As it is difficult to control the accumulation and release of antimony and other contaminants of health concern in the distribution system, the control strategy should minimize the antimony concentration that enters the distribution system from the treatment plant. Generally, the distribution system should be managed such that drinking water is transported from the treatment plant to the consumer with minimum loss of quality. As source waters, treatment plants and distribution systems can differ significantly, a system-specific control strategy would be necessary.

Monitoring

Source water characterization

Water sources should be characterized to determine if antimony is present. Monitoring of source water should be conducted yearly. Authorities may consider reduced monitoring when it has been demonstrated that antimony is not present and/or appropriate treatment is in place.

Treatment

Where treatment is required to remove antimony, operational monitoring should be implemented to confirm whether the treatment process is functioning as required (that is, paired samples of source and treated water to confirm the efficacy of treatment). The frequency of operational monitoring will depend on the treatment process. For example, if adsorption is used, at least quarterly monitoring should be conducted or a method to estimate BVs to breakthrough should be used to predict media replacement.

Compliance monitoring

When treatment is in place for antimony removal, it is recommended that compliance monitoring for total antimony be conducted annually, at a minimum, to confirm the proposed MAC is not exceeded. Samples should be collected after treatment prior to distribution (typically at the entry point prior to the distribution system) and analyzed by an accredited laboratory.

Distribution system

Like other inorganics, antimony can accumulate in distribution systems and later be released. Consequently, monitoring should also be conducted throughout the distribution system when antimony is or was historically present in the source and/or distributed water. Monitoring programs should be designed on a system-specific basis to verify that control strategies are operating as intended and consider risk factors that contribute to the likelihood that antimony may be elevated within the drinking water system. Factors that influence antimony accumulation and mobilization, such as changes to water chemistry and physical/hydraulic disturbances in the distribution system, could be used as indicators of when and where to monitor for antimony release.

Monitoring for total antimony and other contaminants (for example, iron, manganese, arsenic, lead) should be conducted when water quality changes or physical disruptions occur in the system. The release of antimony and other contaminants may be indicated by the presence of discoloured water or increased turbidity resulting from the release of deposits or scales present on the pipe wall. The number and location of sites for monitoring of antimony in the distribution system, including sampling at the tap, should take into consideration the site-specific accumulation and release risk factors. However, the absence of discoloured water should not be interpreted as the absence of a metals release.

Water utilities that have baseline data indicating that antimony is not present within the distribution system may conduct less frequent monitoring.

Residential

Households with private wells are encouraged to have their water tested for total antimony to ensure that the concentration in their water supply is below the proposed MAC. In addition, homeowners with private wells using residential treatment devices should conduct routine testing on both the water entering the treatment device and the treated water to verify that the treatment device is effective.

International considerations

Other national and international organizations have drinking water guidelines, standards and/or guidance values for antimony in drinking water. Variations in these values can be attributed to the age of the assessments or to differing policies and approaches, including the choice of key study and the use of different consumption rates, body weights and source allocation factors.

Table 15. Comparison of international drinking water values for antimony

Agency

(year)

Value (mg/L) Key endpoint (reference) NOAEL/ LOAEL (mg/kg bw per day) UF TDI (mg/kg bw per day) BW (kg)

DW

intake

(L/d)

AF (%)

Health Canada - proposed MAC

(2022)

0.006 Liver effects: anisokaryosis; biochemical changes related to liver histological changes (Poon et al., 1998) 0.06 (NOAEL) 300 0.0002 74 1.53 30

U.S. EPA-MCL

(1992; 2018)

0.006 Decreased lifespan, increased blood glucose and cholesterol (Schroeder, 1970) 0.43 (LOAEL) 1 000

0.0004

(RfD)

70 2 40

WHO

(2003)

0.02 Reduced body weight gain and reduced food and water intake in rats (Poon et al., 1998) 6 (NOAEL) 1 000 0.006 60 2 10
Australia (NHMRC and NRMMC, 2011) 0.003 Decreased lifespan, altered blood glucose and cholesterol (Schroeder, 1970) 0.43 (LOEL) 500 N/A 70 2 10

EU

(2020)

0.01 N/A N/A N/A N/A N/A N/A N/A

AF – allocation factor; BW – body weight; DW: drinking water; LOAEL – lowest-observed-adverse-effect-level; LOEL – lowest-observed-effect-level; MAC – maximum acceptable concentration; MCL – maximum contaminant level; N/A – not available; NOAEL – no-observed-adverse-effect level; RfD – reference dose; TDI – tolerable daily intake; UF – uncertainty factor

Page details

Date modified: