Manganese in New Hampshire Drinking Water
Ranked by max manganese detected (µg/L) · UCMR 4 data (2018–2020) · Data from EPA SDWIS & UCMR
Manganese in New Hampshire: what the data shows
New Hampshire has 21 cities with manganese data from the EPA's UCMR 4 program (2018–2020). Manganese exceeded the 50 µg/L EPA secondary MCL in 7 of those cities. The state average max detected level is 89.9 µg/L. Manganese occurs naturally in groundwater and surface water. Elevated levels are common in areas with iron-rich geology and in systems that draw from reservoirs with low dissolved oxygen. The secondary MCL of 50 µg/L is based on aesthetic concerns (taste, staining), but health-based guidelines suggest neurological effects at higher concentrations. Emerging research links chronic manganese exposure in drinking water to neurodevelopmental effects in children, including reduced IQ and behavioral issues. Oxidation filtration and water softeners are effective at removing manganese from household water.
Cities exceeding 50 µg/L EPA Secondary MCL
Manganese data across New Hampshire
Each dot is a city with UCMR 4 manganese testing data. Cities where manganese exceeds the 50 µg/L EPA secondary MCL are highlighted. Size reflects population served.
Top 10 cities by manganese level in New Hampshire
Highest Manganese levels (µg/L)
All New Hampshire cities ranked by manganese level
| # | City | Level | Level | Over SMCL? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Merrimack | 390.0 µg/L | Over SMCL | 13 | B+ | |
| 2 | Hudson | 342.0 µg/L | Over SMCL | 27 | B | |
| 3 | Dover | 254.0 µg/L | Over SMCL | 10 | B+ | |
| 4 | Portsmouth | 211.0 µg/L | Over SMCL | 12 | B+ | |
| 5 | Seabrook | 190.0 µg/L | Over SMCL | 29 | C+ | |
| 6 | Durham | 157.0 µg/L | Over SMCL | 26 | B | |
| 7 | Rochester | 104.0 µg/L | Over SMCL | 49 | F | |
| 8 | Thornton | 46.6 µg/L | No | 69 | F | |
| 9 | Keene | 32.9 µg/L | No | 13 | A- | |
| 10 | Ashland | 29.4 µg/L | No | 10 | C+ | |
| 11 | Bristol | 24.0 µg/L | No | 4 | A- | |
| 12 | Lebanon | 18.0 µg/L | No | 33 | B- | |
| 13 | Manchester | 17.6 µg/L | No | 5 | D+ | |
| 14 | Derry | 14.5 µg/L | No | 63 | F | |
| 15 | Salem | 13.3 µg/L | No | 37 | D | |
| 16 | Conway | 10.6 µg/L | No | 95 | F | |
| 17 | Exeter | 10.0 µg/L | No | 60 | F | |
| 18 | Concord | 7.9 µg/L | No | 1 | D+ | |
| 19 | Somersworth | 6.0 µg/L | No | 35 | A- | |
| 20 | Laconia | 5.2 µg/L | No | 13 | C+ | |
| 21 | Nashua | 4.6 µg/L | No | 3 | A- |
Frequently asked questions about manganese in New Hampshire
Is manganese in New Hampshire tap water harmful?
The EPA secondary MCL for manganese is 50 µg/L, set primarily for aesthetic reasons (taste, color, staining). 7 cities in New Hampshire exceed the secondary MCL. However, emerging research links chronic manganese exposure above 50–100 µg/L to neurodevelopmental effects in children, including reduced IQ.
How can I remove manganese from my drinking water?
Oxidation filtration (such as greensand or birm filters) is the most common and effective method for removing manganese from well water. Water softeners using ion exchange also work well. Standard carbon filters provide limited manganese removal. If your water has a metallic taste or brown/black discoloration, manganese may be the cause.
What causes high manganese in New Hampshire water?
Manganese occurs naturally in groundwater and surface water, particularly in areas with iron-rich geology. Low dissolved oxygen conditions (common in deep wells and reservoir bottom waters) increase manganese solubility. Industrial sources include mining, steel production, and battery manufacturing. Seasonal changes in reservoir water chemistry can cause manganese spikes.