The fluoride content in the urine, hair, and nails of 106 workers employed in a phosphate fertiliser plant was significantly raised above the control level. Positive correlations were found between the group means for concentrations of fluorides in urine and hair (r = 0 77), urine and nails (r = 0-99), and hair and nails (r = 0 70). Individual values in the whole population gave significant correlations between concentrations in urine and nails (r = 0-73). The obtained results indicate that the fluoride content in hair and nails may be used as an indicator of occupational exposure to fluorides.Fluoroapatites and phosphorites are used in manufacturing phosphate fertilisers. About 3% or 4% of these raw materials is fluoride. During the preparation of soluble phosphates, treatment with sulphuric acid releases about half the fluoride in gaseous form, mostly as hydrogen fluoride (HF). The reaction of hydrofluoric acid with silica present in the rock also produces silicon tetrafluoride. During the whole procedure workers are exposed to fluoride gases and dusts. Also, the finished phosphates contain some fluoride and are potentially dangerous. The exposure. to fluorine compounds may be evaluated. by air analyses.It is generally accepted, however, that a better index of exposure is urinary fluoride excretion. Continuous fluoride inhalation at low concentrations creates a steady state in fluoride balance.At steady state fluorine concentration in air correlates with the average urine concentration of fluoride in samples collected during the shifts and in the 24 hour urine samples. The best correlation occurred when postshift urine samples were evaluated."2 More recently hair analyses were used also to evaluate exposure. It is not a routine procedure but it is gaining importance especially in the evaluation of environmental exposure. Raised hair concentrations of different elements (arsenic, cadmium, and mercury) reflect industrial and envirornmental exposure from air pollution and the contamination of drinking water and food.34 Balazova ascertained increased fluoride concentrations in the urine, hair, and nails of children exposed to gaseous fluoride compounds emitted from an aluminium smelter.56 One of us (JK) found a positive correlation between the duration of exposure of welders and the fluoride level in hair.7 Also the fluoride content in the hair of rats was increased by sodium fluoride in drinking water.8The aim of the present study was to evaluate the exposure of fertiliser plant workers employed on different posts and exposed to fluorine compounds. The exposure may be crudely graded into three levels.High exposure was at workplaces where superphosphate, fluorosilicate, and phosphoric acid were produced (mean HF concentrations 0 5-3 0 mg/m').Median exposure was in groups 2 and 7 (table 1), where mean HF concentrations were below 0 5 mg/ mi.Low exposure was in units located in the vicinity ofthe plant (laboratory, office, production of sulphuric acid). The employees are exposed mostly on gaseous fluorine co...

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The disappearance of 14C-carbendazim in rat (i.v. 12 mg/kg) followed the kinetics of a two-compartment open-system model. Half-lives of the alpha-phase were 0.1 h (blood), 0.16 h (liver), 0.25 h (kidney), and of the beta-phase: 2.15 h, 6.15 h, respectively. Two metabolites: methyl 5-hydroxy-2-benzimidazolecarbamate (5-HBC) and 2-aminobenzimidazole (2-AB) were formed very rapidly. Their peak concentrations in liver and kidney were 15 min after i.v. injection. Unchanged carbendazim was found in highest concentrations in blood. 5-HBC prevails in organs. 2-AB was present only in minor amounts. The extent of bioavailability in orally administered 14C-carbendazim (12 mg/kg) was about 85%. The disposition of radioactivity in subcellular fractions was not uniform, its highest concentration was in cytosol, the lowest in microsomes. The elimination of 14C-carbendazim in urine is biphasic. Half-lives of the alpha-phase were 1.4 h (i.v.) and 2.5 h (oral), and of the beta-phase 11.2 h and 12.1 h, respectively. Irrespective of the route of administration, 95% of the radioactivity in urine was composed of 5-HBC. The concentration of unchanged carbendazim in blood and of 5-HBC in urine may be of diagnostic value in acute poisoning with carbendazim.

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