Longitudinal Analysis of Fluoride Levels in Irish Water Supplies: A 52-Year Review

The Health (Fluoridation of Water Supplies) Act of 1960 in Ireland mandates monthly fluoride sampling in Public Water Supplies (PWS). In 2007, authorities adjusted the mandated fluoride concentration from 0.8-1.0 to 0.6-0.8 mg/L. Approximately 71% of the Irish population has access to fluoridated drinking water. This study aimed to analyse fluoride measurements in Irish water supplies for five decades (1964-2016) to assess compliance and effectiveness of the fluoridation programme.

Data were sourced from government records and Environmental Protection Agency (EPA) reports. Analysis focused on fluoride concentration measurements, compliance rates, and data completeness across public, private, and group water supplies. Descriptive statistics were used to evaluate trends and patterns in fluoride levels over time.

By 2000, over 90% (n = 307) of PWS, each serving more than 1000 persons, were fluoridated. In the early monitoring period (1964-69), missing data were substantial at 66%, with satisfactory fluoride results (0.8-1.00 mg/L) at only 17% and marginal results (0.70-0.80 and > 1.00-1.10 mg/L) at 15%. Compliance improved steadily, reaching peak performance in 1994-99 with 57% satisfactory results. Following the 2007 adjustment in target concentrations, missing data decreased significantly to 18%, with satisfactory results (0.60-0.80 mg/L) increasing from 40% to 49% and marginal results (0.50-0.60 mg/L and > 0.80-0.90 mg/L) stabilising at 7%-13%. Analysis of private and group supplies revealed evolving trends: from 2000 to 2006, 21% of fluoride testing results were satisfactory and 75% marginal, while the 2007-2016 period showed 39% satisfactory and 48% unsatisfactory results, though only 1% exceeded 0.9 mg/L.

The fluoride control in PWS has been largely effective, with consistent improvements in monitoring practices and compliance with target levels over the study period.