FLUORIDE, IQ, AND ADVICE ON TYPE I AND II ERRORS

SUMMARY: A 38-year prospective study of 992 New Zealand children on fluoride (F)
and IQ, of whom an uncertain number (0–101) had not received, at age 5 years,
additional F with F tablets (taken: 139, not taken: 763, unknown: 90), community water
fluoridation (CWF) (lived in CWF area: 891, never lived in CWF area: 99, unknown: 2)
or F toothpaste (always used: 634, sometimes used: 240, never used: 22, unknown:
96), has led to differing advice on avoiding Type I and Type II errors. Consideration of
eight studies on F and IQ, and introducing a safety factor of 10 to allow for individual
differences in water intake and sensitivity (between- and within-subject variations),
suggests a maximum contaminant level goal (MCLG) for F in drinking water of 0.1 mg
F/L. Whilst achieving this may be difficult in many areas, at the least no active steps
should be taken to raise water F levels above 0.1 mg F/L. Some evidence suggests
that the only assuredly safe level of F in drinking water is zero.