A supply disruption is leading some water systems to reduce the amount of fluoride in drinking water. Joe Raedle/Getty Images hide caption toggle caption Joe Raedle/Getty Images 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.…