Black Tea Source, Production, and Consumption: Assessment of Health Risks of Fluoride Intake in New Zealand
Before the rationing of tea was introduced, New Zealand had the third largest annual consumption of tea in the world, namely 8.2 Ib./person. Subsequently, the ration of 2 oz./wcek with extra concessions to people working in factories and offices provided an annual consumption of 6-5 lb./person. Most foods are found to be poor sources of fluorine, even when grown in fluorinerich soils, supposedly because the fluorine in the soil becomes converted to the insoluble calcium form (Smith, Smith & Vavich, 1942). Tea, which grows in relatively acidic soils, is exceptional in its faculty for taking up fluorine. As much as 176 mg. fluorinel IOO g. dry substance was found by Reid (1936) in a sample of fresh tea from a fluorspar mining area, though two roasted teas from the same area contained only 1-5 and 7-1 mg. fluorine/Ioo g. dry tea. He found that the fluorine content of Chinese teas varied from 3 to 40 mg./Ioo g., whereas Indian and Ceylon teas contained 3-8 and 0.9 mg. respectively. Cheng & Chou (1940) considered that the fluorine content of tea was in the range 0.7-9 mg./Ioo g. Reid (1936) found that 81-96 yo of the fluorine in tea was extracted from a 2% infusion in 5 min. Lockwood (1937) extracted 80% of the fluorine in an infusion made from tea containing 70 p.p.m. fluorine. Clifford (1945) reported the mean result of analyses of tea infusions in ten field stations as 1.19 p.p.m. Since tea is an important item in the Kew Zealand diet, and the water supplies are low in fluorine (Chamberlain, 1944, 1946; Denmead, 1946), its potentialities as a contributor of fluorine have been thought worthy of investigation.