. (1972). Brit. J. industr. Med., 29,[169][170][171][172][173][174][175][176][177]. Chronic exposure to iron oxide, chromium oxide, and nickel oxide fumes of metal dressers in a steelworks. Occupational and medical histories, smoking habits, respiratory symptoms, chest radiographs, and ventilatory capacities were studied in 14 steelworkers employed as deseamers of steel ingots for periods of up to 16 years. The men were exposed for approximately five hours of each working shift to fume concentrations ranging from 1-3 to 294 1 mg/m3 made up mainly of iron oxide with varying proportions of chromium oxide and nickel oxide.Four of the men, with 14 to 16 years' exposure, showed radiological evidence of pneumoconiosis classified as ILO categories 2 or 3. Of these, two had pulmonary function within the normal range and two had measurable loss of function, moderate in one case and mild in the other.Many observers would diagnose these cases as siderosis but the authors consider that this term should be reserved for cases exposed to pure iron compounds. The correct diagnosis is mixed-dust pneumoconiosis and the loss of pulmonary function is caused by the effects of the mixture of metallic oxides. It is probable that inhalation of pure iron oxide does not cause fibrotic pulmonary changes, whereas the inhalation of iron oxide plus certain other substances obviously does.

In mine roadways the roof is frequently so low that it is impossible to walk in the natural erect manner and it is necessary to stoop, sometimes to a considerable extent. Indeed, in a very low place it may be necessary to travel some distance on all fours. Walking in low roadways can be very fatiguing when a pronounced stoop is necessary, for the energy cost of walking in such a posture is greater than that incurred in walking in the usual erect posture at the same speed.In a study of the energy output of coal-miners during work Moss (1935) Moss's results appeared to be of some practical significance, and soon after they were published we made a series of observations on ourselves in which we walked at various speeds and as nearly as possible in the postures described. In view of the attention now being devoted to the physiological problems of mining, it may be of some interest to report the results of those observations. Method of ExperimentThe experiments were carried out on the smooth wooden floor of a long corridor. Ordinary walking was done at rates of 2 to 5 miles an hour, half-stoop walking at 2 to 4 miles an hour, and in the full-stoop and all-fours postures the speeds ranged from 2 to 34 miles an hour.For the measurement of respiratory exchange the usual Douglas-Haldane technique was employed.Preliminary experiments showed that in the erect and half-stoop postures a steady state was readily attained, and the results for these postures presented here were obtained under steady-state conditions.Owing to the severe nature of the exercise it was found impossible to continue full-stoop walking for more than a minute or a minute and a half, or walking on all fours for more than 40 to 50 seconds, so that in estimating the energy expenditure while walking in these postures the oxygen consumption during recovery had to be ascertained and allowance made for the heavy oxygen debt. With these very short spells of exercise the estimates of total oxygen usage may be subject to some error, but they do at any rate show the order of magnitude of the oxygen consumption. 290 on 11 May 2018 by guest. Protected by copyright.

No abstract

Ten years ago, when we were making a physical study of the dust hazard in south Wales anthracite mines as part of the Medical Research Council's early investigation of chronic pulmonary disease in coal miners, we had the opportunity of examining the dust particles on two slides containing sections of a lung of a man who had died from silicosis after many years' work as a shot-firer in one of the anthracite mines included in our study.Of the two lung sections, one had been stained but was otherwise untreated, and the other had been incinerated and the soluble ash removed by treatment with hydrochloric acid. Passing reference to these observations has already been made (Bedford and Warner, 1943), but in view of the present renewed interest in particle size in relation to pneumoconiosis it seems desirable to record our data in greater detail. Method of ExaminationThe sections were examined by a technique similar to that which we employed in the evaluation of samples of air-borne dust obtained with a thermal precipitator. The microscope had a 2 mm. oil-immersion apochromatic objective, N.A. 1-37, and a X15 eyepiece, giving an overall magnification of about 1,200. The source of illumination was a 100 c.p. "pointolite" lamp with a blue-green filter. With these optical arrangements dust particles of rather less than 0-2 micron diameter could be discerned in the nodules and reticulation areas as discrete entities. For the measurement of the size of the dust particles an eyepiece graticule of the type described by Patterson and Cawood (1936) was used. When particles were massed together in an aggregate efforts were made to count and measure the individual particles comprising the aggregate.On the untreated section counts were made on three typical nodules and three typical reticulation areas. Each of these areas was indicated to us by our colleague Dr. D'Arcy Hart. Strips across each of these six areas were examined and in each area not less than 2,000 dust particles were measured. All particles greater than * Now of the scientihc staff, National Coal Board. 0 4 micron in diameter were classified into the groups "coal " and " minerals other than coal ".Coal particles and any acid-soluble ash had been removed from the other slide by the processes of incineration and acid treatment, so it was expected that the size distributions of dust particles on this slide would agree more or less closely with those of the particles of minerals other than coal on the untreated section. On this treated slide Dr. D'Arcy Hart identified two areas -one a nodule and one a reticulation area-which had been examined on the untreated section, and particle-size distributions were ascertained for these areas.We have referred to the classification of dust particles accordingly as they were of coal or of other minerals. Early in our study of air-borne dusts it had appeared to us that in the thermal precipitator records it was possible to discriminate between the coal and other particles, for what we interpreted to be anthracite particles, even down...