Activated carbon filters remove some fluoride, especially from the pure-water solution. Filtering a pure water solution with a fluoride concentration of 0.8 mg F/L reduced the fluoride concentration until 210 L of the solution had been filtered. However, filtering a tap-water solution of 0.8 mg F/L reduced the fluoride concentration only until 8 L had been filtered. The concentration of absorbed fluoride in the filter at 10 L of filtration was 4.7 mg/kg activated carbon. To summarize, activated carbon can remove fluoride to some degree (40-60%), especially synthetic fluoride. We cannot claim to remove fluoride since the reduction rate is < 97%.