Chloride in Drinking Water
Health Canada has established a Health Based Value (HBV) of 470 mg/L and an aesthetic objective level (AO) of 250 mg/L for chloride concentrations in drinking water.
Chloride is a naturally occurring element that is common in most natural waters and is most often found as a component of salt (sodium chloride) or in some cases in combination with potassium or calcium. Chloride is considered an essential nutrient for human health and is mainly sourced from foods. The presence of excess chloride in PEI groundwater is most often the result of sea-water intrusion, road salt application or proximity to road salt storage. Other contributors such as salt bearing geological formations exist, but occur less frequently and are generally understood to be less impactful. In PEI, chloride levels in raw groundwater are typically low and normally would not exceed these guidelines.
The Health Based Value is used to help assess potential health concerns, and is not regarded as a strict regulatory limit, or maximum acceptable concentration.
What are the health concerns?
Studies in humans have found that increased intake of chloride, as sodium chloride, may elevate blood pressure. A health-based value of 470 mg/L is established for chloride based on an increased risk of elevated blood pressure.
Chloride is considered to be an essential nutrient for human health and the main source of chloride is from foods, with drinking water making up only a small portion of normal dietary intake. Chloride itself in drinking water is not harmful at typical levels; however, at very high concentrations it may contribute to increased blood pressure, particularly due to the association with elevated sodium levels. If testing shows ongoing elevated levels of chloride, well reconstruction, treating the water, or switching to an alternate source can reduce elevated chloride levels. Bathing or showering with water that contains chloride is not a health concern.
What are the aesthetic concerns?
The Guidelines for Canadian Drinking Water Quality recommend an aesthetic objective for chloride levels of 250 mg/L, based on the potential for undesirable tastes at concentrations above this level, and the increased risk of corrosion of pipes.
What are the treatment options?
Elevated chloride levels typically are addressed by reconstruction or relocation of your well away from the suspected source of salt. In other cases the use of a water treatment device may be an option. It is recommended that advice from a qualified groundwater professional be sought prior to deciding what solution best meets your particular situation. The most common water treatment devices for reducing the chloride content of drinking water are reverse osmosis, anion exchange or distillation treatment systems.
The Department does not recommend specific brands of treatment devices; however, it is recommended that consumers purchase devices bearing a label stating they are certified to NSF /ANSI Standard 58 (for reverse osmosis drinking water treatment systems), NSF/ANSI Standard 62 (for drinking water distillation systems) or for anion exchange systems, a device constructed with materials certified to NSF/ANSI Standard 61 (for drinking water system components – health effects).
As with the use of any drinking water treatment device, the effectiveness of treatment should be verified by sampling after installation. In addition, it is important to ensure the device is used and maintained according to the manufacturer’s directions and its performance periodically confirmed by sampling.