Nitrate in Drinking Water

Nitrate is a naturally occurring form of nitrogen that is commonly found throughout the environment. It is present at low levels in most groundwaters, but can be present significantly higher levels in areas with extensive use of fertilizers, storage and spreading of manure or widespread use of septic systems. 

What are the health concerns?

For most individuals, foods are the main source of nitrate, however when levels of nitrate in well water are elevated it can become a significant source of overall nitrate intake. The Guidelines for Canadian Drinking Water Quality recommend that nitrate levels in drinking water do not exceed 45 mg/L as nitrate, or 10 mg/L when expressed as nitrate nitrogen (NO3-N), the units of measurement used by the Provincial laboratory. The guideline is based on an association with methemoglobinemia, more commonly known as “Blue Baby Syndrome, a condition of concern to young infants. Because there may be other potential health effects may be linked to high nitrate levels, the guideline is intended to apply to all individuals.

The most immediate concern with nitrate in drinking water is the risk of “blue baby” syndrome, primarily related to feeding infants under 6 months of age, with formula made up with tap water with high nitrate levels. In this case it is recommended that an alternate source of water that is known to be safe is used for making up formula.  While other long term health effects may be associated with high nitrate levels, available studies in humans show no adverse health effect at levels below the guideline value of 10 mg/L, however in general it is recommended that nitrate levels in drinking water be kept as low as is reasonably practical.

What are the treatment options?

Elevated nitrate levels can sometimes be reduced by reconstruction of your well, or in other cases, by the use of a water treatment device. In either case 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 nitrate content of drinking water are reverse osmosis, distillation treatment systems or an ion-exchange system using a resin specifically designed for nitrate removal. 

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 ion 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 the manufacturer’s directions and its performance periodically confirmed by sampling. 


Published date: 
February 5, 2024
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