Turbidity is a measure of the cloudiness of water. It is used to indicate water quality and filtration effectiveness (such as whether disease-causing organisms are present). Higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches.


Sources of impurity: Soil runoff. In Canada, the maximum acceptable concentration for turbidity in drinking water entering the distribution system is 1 NTU (Nephelometric Turbidity Unit). An aesthetic objective of 5 NTU has been set for samples taken in the distribution system. Turbidity levels higher than 5 NTU can indicate severe local corrosion of the water pipes.


Additional notes from Canadian government: CANADA Turbidity – is caused by the presence of suspended matter or particles in the water.



Maine Maximum Exposure Guideline limit:

USA Primary Drinking Water Standard limit: n/a

USA Secondary Drinking Water Standard limit: n/a

Canada Health standard limit:

Canada Aesthetic standard limit:

USA daily recommended allowance:

Other standard:


Additional Resources: