EPA Table of Secondary Standards for Drinking Water

SMCL = Secondary Maximum Contaminant Level
Contaminant Secondary MCL* Noticeable Effects above the Secondary MCL*
Aluminum 0.05 to 0.2 mg/L* colored water
Chloride 250 mg/L salty taste
Color - Impurities 15 color units visible tint
Copper 1.0 mg/L metallic taste; blue-green staining
Corrosivity Non-corrosive metallic taste; corroded pipes/ fixtures staining
Fluoride 2.0 mg/L tooth discoloration
Foaming agents 0.5 mg/L frothy, cloudy; bitter taste; odor
Iron 0.3 mg/L rusty color; sediment; metallic taste; reddish or orange staining
Manganese 0.05 mg/L black to brown color; black staining; bitter metallic taste
Odor - Sulfur 3 TON (threshold odor number) "rotten-egg", musty or chemical smell
pH 6.5 - 8.5 low pH: bitter metallic taste; corrosion
high pH: slippery feel; soda taste; deposits
Silver 0.1 mg/L skin discoloration; graying of the white part of the eye
Sulfate 250 mg/L salty taste
Total Dissolved Solids (TDS) 500 mg/L hardness; deposits; colored water; staining; salty taste
Zinc 5 mg/L metallic taste
*mg/L is milligrams of substance per liter of water.*Secondary Maximum Contaminant Levels (SMCLs), or National Secondary Drinking Water Regulations (NSDWRs), are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards.

 

 

 
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