This week, the City of Baltimore's public water system cut fluoride levels in its drinking water nearly in half. It's a response to strains in the supply chain caused by the conflict in the Middle East.

"We were alerted that our supplier was going to be reducing the supply from three deliveries per month to two," says Matthew Garbark, director of the Baltimore City Department of Public Works.

In response, the water system, which serves 1.8 million customers, is lowering the fluoride levels from 0.7 milligrams per liter, as recommended by the U.S. Public Health Service, to 0.4 mg/L.

Baltimore City isn't alone. U.S. water systems are facing a shortage of hydrofluorosilicic acid, a chemical used to fluoridate drinking water to prevent cavities and tooth decay.

The specialized chemical is mainly sourced from a small pool of international producers. And the conflict in the Middle East is disrupting the supply chain. Managers of U.S. water systems say the shortage in fluoridation chemicals is unprecedented.

Companies make the acid in large factories, primarily overseas. U.S. suppliers import and deliver the product. The acid arrives at water treatment plants across the U.S. in liquid form, transported in 5,000 gallon tanker trucks. "We don't manufacture it, we don't produce it. All of our chemicals are purchased, and they rely on the supply chain in order to get to our plants," Garbark says.

Factory staff deployed

Israel is one of the world's leading producers of the chemical. "As we understand it, one of the main suppliers in Israel lost a number of employees temporarily, because they've been called up into service in the Israeli military," says Dan Hartnett, chief policy officer at the Association of Metropolitan Water Agencies. "That essentially shut down production at their facility in Israel. They haven't been producing acid. They haven't been able to ship it out."

Hartnett says he isn't hearing widespread concerns from city water managers yet. If the shortage continues, however, more may be forced to cut back on fluoride or to stop adding it to the water. "There's concern that if this conflict in Iran goes on for longer and the supply chain continues to be disrupted, a growing number of systems may start to face those similar types of challenges," he says.

Around 60% of the U.S. population receives fluoridated drinking water. Many communities have chosen to add fluoride to the tap water for decades, as a public health measure that is estimated to reduce cavities by around 25%.

Lowering fluoridation levels in drinking water due to supply chain constraints is a new development, separate from efforts by activists who have campaigned to stop the practice for health concerns, though the medical community supports low levels of fluoride in drinking water as safe.

Shortage leads to rationing

While global disruptions like the COVID pandemic have caused delays for certain water treatment chemicals in the past, "we never had a point where we started reducing our chemical usage," says Ben Thompson, director of production at WSSC Water, which serves 1.9 million residents in the Maryland suburbs outside Washington, D.C.

Like Baltimore City, WSSC Water decided to reduce fluoride levels, from 0.7 mg/L to 0.4 mg/L. WSSC's supplier told the utility by letter that it would be receiving 20% less of the chemical going forward, due to the national shortage.

"We're trying to stretch out our supplies, because it's unknown to what extent or how long this will continue," Thompson says. Water consumption increases in summer months, so he's taking steps to "sustain the level floor" and keep some consistent fluoride in the water supply.

Pencco, the Texas-based supplier for both Baltimore City DPW and WSSC Water, did not respond to an interview request.

In Pennsylvania, water systems for Lititz Borough in Lancaster County and Hanover Borough in York County reported similar shortages in March involving other suppliers. The supply crunch led them to consider temporarily halting community water fluoridation, though in both cases the supply issues were resolved within weeks.

The water utilities reducing fluoride say the drinking water remains safe. Fluoride is not required by the Environmental Protection Agency, which regulates drinking water. "The reduction does not in any way impact water quality, it is simply a reduction in the fluoride treatment," Thompson says.

Other sources of fluoride include fluoridated toothpastes, and certain teas and foods.

Thompson says these reductions are temporary. WSSC aims to bring fluoride levels back fully in line with public health recommendations when the supply returns. But he couldn't predict when that would be.