Which of the following is a common issue when feeding fluoride to water supplies?

The correct choice highlights a notable concern regarding the addition of fluoride to water supplies. Overfeeding fluoride can lead to a condition known as dental fluorosis, which manifests as mottling or discoloration of tooth enamel during early childhood when excessive fluoride is ingested while teeth are still developing. This condition is characterized by white spots or streaks on the teeth and, in more severe cases, brown stains and surface irregularities.

The careful management of fluoride levels is essential to ensure that they remain within recommended guidelines. When levels exceed these recommendations, the risk of mottling increases, making it crucial for water treatment facilities to monitor and adjust fluoride concentrations appropriately. This issue emphasizes the need for adherence to dosage guidelines during the fluoridation process to prevent any adverse effects on dental health.

In contrast, the other options do not typically relate to the fluoridation process: ozone depletion is pertinent to environmental concerns involving atmospheric chemistry, chlorine reactions typically involve interactions between chlorine and other chemicals during disinfection, and water discoloration can stem from various sources but isn't specifically tied to fluoride overfeeding. This underscores why the concern regarding mottling due to overfeeding is particularly relevant in the context of water treatment practices involving fluoride.