On August 30 1980, an outbreak of minor illnesses consisting of nausea and vomiting affected 22 individuals attending a farmers market at a school. Illness was associated with the consumption of beverages made from school water (Xc2 = 65.6, p less than .0001); analysis of the water showed high levels of fluoride (1,041 mg/l). The most likely source of the contamination was the school fluoridator, which had accidentally been left on continuous operation.
Of the 44 vendors who attended the farmers market, 40 (91 per cent) were contacted. Inclusion of their family members brought the total subjects to 82; of these, 22 (27 per cent) reported a characteristic illness on the day of the market. All had onset of symptoms between 8:30 and 10:30 am. Of those ill, nausea was reported by 16 and vomiting by 13. Other symptoms included headache (5), cramps (4), dizziness (3), and diarrhea (2). Duration of the illness ranged from 1-24 hours. The age range of the ill persons was 9-70 years with a median of 36 years. None of the ill individuals saw a physician. Illness was strongly associated with drinking beverages made from school water (XC2 = 65.6, p < .0001).
… The ingestion of a concentrated solution of fluoride causes gastric irritation and may cause salivation, abdominal pain, nausea, vomiting, and diarrhea. The concentrations of fluoride that produced nausea and vomiting in this outbreak were slightly higher than those reported by Theines(8). He estimated that as little as 7 mg of fluoride could produce nausea, and 29 mg could produce vomiting. Higher levels of fluoride ingestion would be expected to cause other symptoms such as muscle twitching, cardiac arrhythmias, convulsions, and shock; none of these symptoms were apparent in this outbreak. The lethal dose of fluoride in acute accidental ingestion is 2.5-5.0 grams in a 70 kg man (9). …
8. Theines CH, Haley TJ: Clinical Toxicology. Pennsylvania: Lea and Febiger, 1972, pp 176-179.
9. Peach MJ: Anions: Phosphate, iode, fluoride, and other ions. In: Goodman LS, Gilman A (eds): The Pharmacological Basic of Therapeutics. New York: Macmillan Publishing Company, 1975, pp 804-805.