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Source: Health and Welfare Canada, 1987, Guidelines for Canadian drinking water quality. aI—Inorganic constituent; O—Organic constituent; P—Pesticide; R—Radionuclide.

bUnless otherwise specified, units are mg/L; limits apply to the sum of all forms of each substance present. MAC = maximum acceptable concentration; IMAC = interim maximum acceptable concentration; AO = aesthetic objectives.

cAn objective concentration only was set in 1978, based on health considerations. dAssessment of data indicates no need to set numerical guideline.

eNo sample should contain more than 10 total coliform organisms per 100 mL; not more than 10 percent of the samples taken in a 30-day period should show the presence of coliform organisms; not more than two consecutive samples from the same site should show the presence of coliform organisms; and none of the coliform organisms detected should be fecal coliform.

fIt is recommended, however, that the concentration of fluoride be adjusted to 1.0 mg/L, which is the optimum level for the control of dental caries. Where the annual mean daily temperature is less than 10°C, a concentration of 1.2 mg/L should be maintained. gAssessment of data indicates no need to set a numerical guideline.

hPublic acceptance of hardness varies considerably. Generally hardness levels between 80 and 100 mg/L (as CaCO2) are considered acceptable; levels greater than 200 mg/L are considered poor but can be tolerated; those in excess of 500 mg/L are normally considered unacceptable. Where water is softened by sodium-ion exchange, it is recommended that a separate unsoftened supply be retained for culinary and drinking purposes. i2-Methyl-4-chlorophenoxyacetic acid. jAs nitrate- or nitrite-nitrogen concentration. kDimensionless.

lIt is recommended that sodium be included in routine monitoring programs since levels may be of interest to authorities who wish to prescribe sodium-restricted diets for their patients.

mTrichloroacetic acid.

nFor water entering a distribution system. A maximum of 5 NTU may be permitted if it can be demonstrated that disinfection is not compromised by the use of this less stringent value.

oAt the point of consumption. Notes:

1. Under review for possible revision, deletion from, or addition to the guidelines.

2. It is proposed that a guideline be added for this parameter for the first time (A); a change be made to the previous guideline (R); or the guideline be deleted (D). If after 1 year, no evidence comes to light that questions the appropriateness of the proposal, it will be adopted as the guideline.

3. Reassessment of data indicates no need to change 1978 recommendation.

4. Adapted from Guidelines for Canadian Drinking Water Quality: 1978; reassessment considered unnecessary at this time.

5. Previously listed in Guidelines for Canadian Drinkng Water Quality: 1978 as a maximum acceptable concentration based on aesthetic considerations.

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