Individual samples of urine, fingernails, head-hair, saliva, plaque and enamel were collected from three groups of Hungarian children, aged 14 years, who were exposed to contrasting water fluoride levels (less than or equal to 0.11 ppm; 0.5-1.1 ppm; 1.6-3.1 ppm). The mean fluoride concentration of the samples increased consistently and significantly, but mostly non-proportionately, with increasing water fluoride level. With the exception of plaque, the materials examined are considered suitable indicators of exposure to or systemic utilization of fluoride for population groups. Caries experience decreased with increasing fluoride exposure. Dental fluorosis constituted no clinical or aesthetic problem.

During 1990 all present and retired china clay workers in the United Kingdom were invited to take part in a chest health survey. A total of 4401 The relation between total exposure to china clay dust and x ray film category is such that a typical non-smoker worker employed in the most dusty of current occupations may expect to reach the lower limit of category 1 after about 42 years continuous employment in that job at current exposures. Both forced vital capacity (FVC) and forced expiratory volume in one second (FEV,) were found (as in other studies) to decline with age, more rapidly for smokers than non-smokers at the rates for FVC of 0 035 Vy and 0 033 Vy, whereas for FEV, the rates are 0*039 Vy for smokers and 0*034 IIy for non-smokers. Changes in x ray film category are also related to lung function, a change of one major category being equivalent to about six years of ageing in its effect on FEV,.

The F concentrations in plaque and in underlying enamel were determined in a sample of 99 schoolchildren aged 8.4 years (S.D. = 0.37), comprising four groups, exposed life-long to contrasting concentrations of F in the water (range less than or equal to 0.12 ppm to 2.8 ppm) and to supplements of 350 mg F/kg domestic salt. The mean total F concentrations in plaque (dry wt) increased consistently with increasing exposure to F, but the absolute differences were small and the individual variation was high within each group. Significant inverse associations were demonstrated between individual plaque and surface enamel values within two groups, supported by consistent inverse trends (ns) in the remaining groups. These associations and trends are considered to reflect transfer of F from plaque to underlying surface enamel and concommitant reduction in plaque F concentration.

In 1985, employees in the china clay industry were offered chest x ray examinations and 4478 (52-6% of the total workforce) accepted. Of these, 4167 workers and pensioners of the largest single employer also completed occupational histories, respiratory symptom questionnaires, and underwent ventilatory capacity tests. The x ray readings (read to the 1980 ILO classification) of the 4167 workers and pensioners were analysed to seek relations between the indices ofpulmonary health and occupational exposure. The information available, particularly on occupational history, was more detailed than in previous studies of 1961, 1977, and 1981 In 1985 a chest x ray survey was carried out by the Nottingham based mobile unit of the National Coal Board using 40 x 40 cm films. It was offered to all people employed in the china clay industry in the south west of England. The subsequent analyses were based on a group of workers from the largest single employer, which represented 94% of the china clay industry for which full occupational details were available. For this group an overall response rate of 65% was achieved. For china clay employees in potentially dusty occupations (where measured respirable dust concentrations may exceed 0 5 mg/m3), however, the response rate was higher, at approximately 85%.

ASA standard stannous chloride solution may be stored without difficulty, the reaction 2FeCl3 + SnCl, = 2FeCl2 + SnCh may be used as the basis of a method for the determination of ferric iron. It is not only possible to carry out the reduction needed