What is Cobalt* and Why Does It Matter?

Cobalt is a naturally occurring metal found in soil, rock, and groundwater. It also enters water supplies through industrial sources — think metal processing facilities, mining operations, and the manufacturing of batteries and electronics. In some cases, aging pipes or industrial discharge carry cobalt directly into municipal water systems. It's worth noting that cobalt is an essential nutrient in tiny amounts — your body needs it to produce vitamin B12. The problem starts when levels climb beyond what your body can use.

Across the United States, cobalt has been detected in 155 water systems. The average concentration sits at 0.314 parts per billion (ppb), which sounds small — and for most systems, it is. But the maximum recorded level reaches 15.8 ppb, a number that deserves attention. At low levels, cobalt exposure is generally considered low-risk for healthy adults. At higher levels, research links cobalt to thyroid problems, heart damage, and effects on the nervous system (WHO). Children and pregnant women face greater sensitivity, since cobalt can interfere with fetal development and disrupt hormone function even at lower concentrations.

The EPA has not set a specific maximum contaminant level (MCL) for cobalt in drinking water. That's a significant gap. Without a federal limit, water utilities aren't legally required to reduce cobalt levels — even when concentrations rise. The Environmental Working Group (EWG) has flagged this absence as a concern, pointing out that many contaminants without formal limits still carry real health risks at elevated exposures. The good news here: none of the 155 systems where cobalt was detected reported levels above any existing health guideline. Still, "no limit exceeded" isn't the same as "no risk," especially for sensitive groups.

Geographically, Texas leads the country with cobalt detected in 66 water systems — far more than any other state. New Jersey follows with 21 systems, and North Carolina reports 16. New York and Delaware round out the top five with 11 and 7 systems, respectively. Texas's numbers likely reflect a combination of factors: industrial activity tied to oil and gas operations, large-scale manufacturing, and the state's diverse geology, which naturally contains cobalt-bearing minerals. New Jersey's industrial history — particularly in chemical and metal manufacturing — helps explain its presence on this list. North Carolina's mining activity and growing manufacturing sector also contribute to detections in that region.

The most effective way to remove cobalt from drinking water is reverse osmosis (RO) filtration. A quality RO system removes up to 99% of heavy metals, including cobalt, by forcing water through a semi-permeable membrane that blocks contaminants at the molecular level. Activated carbon filters alone won't do the job — they're better suited for chlorine, volatile organic compounds, and taste issues. If you live in Texas, New Jersey, North Carolina, New York, or Delaware, it's worth testing your water first to understand your actual exposure. Echo Water's whole-home and under-sink RO systems are designed specifically to address heavy metals like cobalt, giving you clean water at every tap without guesswork. Testing first, then filtering based on results, is always the smartest approach. You don't need to be alarmed — but you do deserve to know exactly what's in your water and have a clear path to removing it.

Regulatory Standards for Cobalt*

Cities With the Highest Cobalt* Levels

States Most Affected by Cobalt*

Frequently Asked Questions

Related Contaminant Guides