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About Other Aesthetic Contaminants - Secondary Standards
Since the passage of the Safe Drinking Water Act (SDWA) in 1974, the United States Environmental Protection Agency (USEPA) has been responsible for developing standards limiting exposure to contaminated drinking water. Under the SDWA, a list of standards sets monitoring requirements and limits on the maximum acceptable levels of specific contaminants allowed in drinking water supplied by public systems (i.e., not including private wells serving fewer than 25 persons).
There are two types of standards that regulate contaminants in drinking water:
Continue reading for the full list of secondary standards from the USEPA and resources for each contaminant.
Since the passage of the Safe Drinking Water Act (SDWA) in 1974, the United States Environmental Protection Agency (USEPA) has been responsible for developing standards limiting exposure to contaminated drinking water. Under the SDWA, a list of standards sets monitoring requirements and limits on the maximum acceptable levels of specific contaminants allowed in drinking water supplied by public systems (i.e., not including private wells serving fewer than 25 persons).
There are two types of standards that regulate contaminants in drinking water:
- The National Primary Drinking Water Regulations (NPDWR) regulates substances harmful to human health, including: Arsenic, Cryptosporidium, Lead & Legionella
- Secondary standards addresses substances that may cause foul tastes and odors in the public water supply. Acceptable secondary maximum contaminant levels (MCLs) are recommended, but not enforced.
Continue reading for the full list of secondary standards from the USEPA and resources for each contaminant.
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WQRF Contaminant Occurrence Map
Check out the Contaminant Occurrence Map for visual representations of drinking water quality data for public water systems across the US. Map data is available for several secondary contaminants, including: iron, manganese, and pH. To View the Data:
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Contaminant
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Secondary MCL*
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Noticeable Effects
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Resources
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Chloride
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250 mg/L
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salty taste
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USGS: Chloride, Salinity, & Dissolved Solids [Link]
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Color
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15 color units
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visible tint
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USGS: Water Color [Link]
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Corrosivity
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Non-corrosive
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metallic taste; corroded pipes/ fixtures staining
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USGS: Corrosivity [Link]
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Foaming Agents
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0.5 mg/L
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frothy, cloudy; bitter taste; odor
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Iron
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0.3 mg/L
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rusty color; sediment; metallic taste; reddish or orange staining
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USGS: What can be causing our drinking water to have a reddish color? [Link]
Contaminant Map Aesthetics > Iron |
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Manganese
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0.5 mg/L
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black to brown color; black staining; bitter metallic taste
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Odor
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3 TON (threshold odor number)
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"rotten-egg", musty or chemical smell
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WQA Technical Factsheet: Taste & Odor [Link]
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pH
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6.5 - 8.5
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low pH: bitter metallic taste, corrosion; high pH: slippery feel, soda taste, deposits
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Sulfate
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250 mg/L
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salty taste
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USEPA: Sulfate in Drinking Water [Link]
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Total Dissolved Solids (TDS)
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500 mg/L
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hardness; deposits; colored water; staining; salty taste
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USEPA: Total Solids [Link]
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Zinc
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5 mg/L
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metallic taste
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CDC: Zinc [Link]
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*MCL = Maximum Contaminant Level - The highest level of a contaminant that is allowed in drinking water
**Higher levels of these contaminants are enforced and require notification under the NPDWR
**Higher levels of these contaminants are enforced and require notification under the NPDWR
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