What volume of 0.24% (two hundred forty thousandths percent) fluoride solution is required to achieve a concentration of 1.5 milligrams per liter (mg/L)?

Fluoride Dilution Calculation for 1.5 mg/L Concentration

To achieve a concentration of 1.5 mg/L from a 0.24% fluoride solution, you would need to dilute 0.625 mL (or approximately 0.63 mL) of the 0.24% solution into 1 liter of water.

Mathematical Calculation

• A 0.24% fluoride solution contains 2,400 mg of fluoride per liter (0.24 g/100 mL = 2.4 g/L = 2,400 mg/L) 1
• To calculate the volume needed: (1.5 mg/L ÷ 2,400 mg/L) × 1,000 mL = 0.625 mL per liter 1
• This represents a dilution factor of 1:1,600 1

Clinical Context of 1.5 mg/L Fluoride Concentration

The 1.5 mg/L threshold represents the WHO maximum permissible limit for fluoride in drinking water, above which adverse health effects become more likely. 2, 3

Health Effects at This Concentration

• Consumption of fluoride at concentrations of 1.5 mg/L is primarily responsible for skeletal fluorosis in endemic areas 3
• The WHO has regulated the upper limit for fluoride in drinking water to be 1.5 mg/L, while optimal concentrations for dental health are 0.7-1.2 mg/L in the United States 1, 2
• Moderate dental fluorosis occurs in 1-2% of the population exposed to 1 mg/L, increasing to approximately 10% at 2 mg/L 4

Important Safety Considerations

• Approximately 80% of villages in fluoride-endemic rural areas have concentrations exceeding WHO permissible limits, affecting approximately 100 million people globally with skeletal fluorosis 3
• Excess fluoride can cause dental fluorosis, skeletal fluorosis, arthritis, bone damage, and in extreme conditions may adversely affect the heart, kidneys, liver, and neurological system 2
• The optimal fluoride concentration for caries prevention (0.7-1.2 mg/L) provides dental benefits while minimizing the risk of fluorosis 1

Practical Application Warning

This calculation assumes you are diluting a 0.24% fluoride solution to create drinking water at the WHO maximum threshold—this is NOT recommended for intentional water fluoridation. 1, 2

• Community water fluoridation should target 0.7-1.2 mg/L, not 1.5 mg/L 1
• The 1.5 mg/L level represents a safety threshold to avoid, not a target concentration 2, 3
• For safe community water fluoridation, you would need approximately 0.29-0.50 mL of 0.24% fluoride solution per liter to achieve the recommended 0.7-1.2 mg/L range 1