Water supplied to the Cities of Mississauga and Brampton and Town of Bolton is drawn from Lake Ontario. Quality of lake water is relatively low in sodium with seasonal fluctuations mainly contributed by snow meltdown and run-off conditions.
Source of treated water supplied to Town of Caledon communities is groundwater, with elevated sodium concentrations found in some areas. Sodium found in groundwater is naturally occurring and several communal wells in Caledon yield water with a sodium concentration above 20 mg/l. Although not considered toxic to humans, sodium in drinking water in excess of 20 mg/l may be of significance to individuals with hypertension or cardiovascular diseases. The Medical Officer of Health is notified when the sodium concentration in a municipal water supply exceeds 20 mg/l so that the information may be disseminated to local physicians.
Other source of elevated sodium in drinking water may be water softening as domestic water softeners turn naturally occurring calcium and magnesium (“hardness”) to soft salts such as sodium.
For more information on sodium in drinking water, visit Health Canada.
Sodium levels in Peel’s drinking water supplies are unlikely to be a significant contribution to adverse health effects.
The sodium levels are regularly monitored in water supplied to Peel’s consumers. Samples collected are analysed at accredited and licensed laboratories and test results compiled and made available to the public. The summary of sodium test result for January to May 2010 is presented in the table below:
| Drinking Water System | Sodium Concentration (mg/L) | |
| Min | Max | |
| Alton | 46.7 | 71.3 |
| Caledon Village | 10.6 | 34.9 |
| Caledon East | 6.7 | 68.7 |
| Palgrave | 6.05 | 6.05 |
| Cheltenham | 25.4 | 27.6 |
| Inglewood | 16.5 | 26.1 |
| South Peel (Mississauga, Brampton, Bolton) | 14.0 | 21.6 |