Page 3: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Trihalomethanes
1.0 Guidelines
The maximum acceptable concentration (MAC) for trihalomethanesFootnote 1 (THMs) in drinking water is 0.100 mg/L (100 µg/L) based on a locational running annual average of a minimum of quarterly samples taken at the point in the distribution system with the highest potential THM levels.
The maximum acceptable concentration (MAC) for bromodichloromethane (BDCM) in drinking water is 0.016 mg/L (16 µg/L) monitored at the point in the distribution system with the highest potential THM levels.
Utilities should make every effort to maintain concentrations as low as reasonably achievable without compromising the effectiveness of disinfection.