Cobalt in Massachusetts Drinking Water
Ranked by max cobalt detected (µg/L) · UCMR 3 data (2013–2015) · Data from EPA SDWIS & UCMR
Cobalt in Massachusetts: what the data shows
Massachusetts has 18 cities with cobalt data from the EPA's UCMR 3 program (2013–2015). Cobalt was detected in 18 of those cities. There is no federal MCL or health advisory for cobalt in drinking water; the state average max detected level is 2.71 µg/L. Cobalt enters drinking water primarily from natural weathering of cobalt-bearing rock and from industrial sources including battery manufacturing, mining, and metal alloys. Detection rates in UCMR 3 sampling were low (~3% nationally), suggesting cobalt is generally not a widespread tap-water concern. Cobalt is an essential nutrient (a component of vitamin B12) at trace levels, but elevated waterborne exposure has been linked to thyroid effects and cardiomyopathy in occupational studies. Reverse osmosis and ion exchange systems are effective at removing cobalt.
Cities exceeding No federal MCL or HA
Cobalt data across Massachusetts
Each dot is a city with UCMR 3 cobalt testing data. Detected cities are shown — there is no federal limit. Size reflects population served.
Top 10 cities by cobalt level in Massachusetts
Highest Cobalt levels (µg/L)
All Massachusetts cities ranked by cobalt level
| # | City | Level | Level | Detected? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Foxborough | 8.10 µg/L | Detected | 11 | A- | |
| 2 | Bridgewater | 7.40 µg/L | Detected | 5 | C+ | |
| 3 | Middleborough | 4.60 µg/L | Detected | 16 | B | |
| 4 | Norton | 3.20 µg/L | Detected | 10 | B+ | |
| 5 | Swansea | 3.00 µg/L | Detected | 12 | B+ | |
| 6 | Mansfield | 2.50 µg/L | Detected | 6 | A- | |
| 7 | Milford | 2.43 µg/L | Detected | 15 | F | |
| 8 | Chelmsford | 2.10 µg/L | Detected | 1 | B- | |
| 9 | Edgartown | 2.00 µg/L | Detected | 6 | A | |
| 10 | Rowley | 2.00 µg/L | Detected | 10 | B | |
| 11 | Franklin | 1.90 µg/L | Detected | 11 | B+ | |
| 12 | Holden | 1.80 µg/L | Detected | 18 | B | |
| 13 | Acton | 1.60 µg/L | Detected | 28 | F | |
| 14 | Chatham | 1.30 µg/L | Detected | 19 | A | |
| 15 | Hanover | 1.30 µg/L | Detected | 12 | C- | |
| 16 | Medway | 1.30 µg/L | Detected | 14 | B- | |
| 17 | Scituate | 1.10 µg/L | Detected | 10 | C | |
| 18 | Somerset | 1.10 µg/L | Detected | 11 | B |
Frequently asked questions about cobalt in Massachusetts
Is cobalt in Massachusetts tap water dangerous?
There is no federal MCL or health advisory for cobalt in drinking water. 18 cities in Massachusetts had detectable cobalt in UCMR 3 testing. Cobalt is an essential trace nutrient at very low levels but has been linked to thyroid and cardiac effects at much higher chronic exposures.
How can I remove cobalt from my water?
Reverse osmosis is highly effective at removing cobalt. Ion exchange systems (water softeners) also work. Standard activated carbon filters are NOT effective against cobalt. Most household water has cobalt below detection, so testing is generally only warranted near mining or battery-industry sites.