The literature reveals several episodes of acute mass poisoning due to sodium fluoride which had been mistaken for flour, sugar, and baking powder and added to food [1]. The number of persons affected ranged from 5 to 280. The most severe accident -with 47 deaths occurred in Salem, Oregon, where a helper in the kitchen mistakenly had added 17 Ib of a roach powder containing 90% sodium fluoride to a 10-gal mixture of scrambled eggs. In other cases the doses of fluoride involved were estimated to be in the range of 0.5 to 2.6 g.

During recent years, three instances of multiple poisoning due to mechanical difficulties with fluoridation equipment have come to my attention.  In 1965 in the Hungarian town of Szolnok [2], about 80 individuals in a restaurant and a school became ill with nausea and vomiting within minutes after drinking soda water or an orangeade made with the soda water. Apparently everyone recovered spontaneously. The contaminated beverage contained 300 to 900 ppm fluoride, which had been collecting in a temporary unused supply pipe to the bottling plant.

In 1974, fluoridation equipn1ent at a rural school in Stanly County, North Carolina, pumped excess fluoride into the water [3]. All 201 children aged 6 to 12 and seven of the 12 adults vomited shortly after drinking orange juice from an uncontaminated concentrate diluted with tap water. Analysis of the reconstituted beverage revealed 270 ppm fluoride.

A third episode occurred on November 22, 1977, at Harbor Springs, Michigan, when the fluoride feeder pump at one of the city’s three wells malfunctioned [4]. Construction workers had cut down a tree that accidentally fell across city power lines which caused the mechanical control of the fluoride feeder pumps to malfunction. For about 20 min an estimated 86 kg of 25% hydrofluosilicic acid injected into the discharge line of a reserve well brought the fluoride ion concentration in water delivered to some of the residences up to 2390 ppm. Four persons were known to have suffered nausea and vomiting.

Another equipment failure occurred in Marin County, California, due to a breakdown of a valve [5]. The fluoride level of drinking water rose as high as 5.4 ppm on October 27, 1977 (normal 0.7 ppm). This high level lasted about 2 weeks.

On November 11, 1979, an employee of the municipal waterworks facility at Annapolis, Maryland, failed to close a control valve of the equipment which meters hydrofluosilicic acid into the water supply at a concentration of 1 ppm fluoride. During an 18-h period, approximately 30 times the desired concentration of fluoride escaped into the drinking water. Since the water authority failed to notify the health department immediately, the public and medical profession were unaware of the fluoride spill. It was detected when eight patients on hemodialysis suffered adverse symptoms, mainly nausea, vomiting, and headaches. In one of the subjects afflicted with advanced heart disease, health authorities believed that the excess fluoride contributed
to fatal cardiac arrest [6]…

References:

[1.]  G.L. Waldbott, Acute Fluoride Intoxication, Acta Med. Scand., Suppl. 400, 174 (1963).

[2.]  L. Horvath, J. Palicska, and I. Hanny. Szikvizzel terjedo tomeges fluormergezes (Mass intoxication with fluoride in soda water), Orv. Hetil., 108, 306-307 (1967).

[3.]  R. Clark, J. Welch, G. Leiby, W.Y. Cobb, and J.N. MacCormack. Acute fluoride poisoning, Morbid. Mortal. Weekly Report, (Communicable Disease Control Center, USPHS, Atlanta, Gerogia), 23, 199 (1974).

[ 4.]  Public Health Service, Center for Disease Control. Fluoride Poisoning in Michigan, December 14, 1978.

[5.]  P. Peterzell. 5 towns in Marin affected. Independent J. (San Rafael, California), (November 25, 1977).

[6.]  Personal Communication with Dr. Greg Mitchell, Bio-Medical Applications of Annapolis, December 3, 1979.