Observations on the mechanical fragility of the red cell in 68 workers having had exposure to lead in varying degrees, and on blood to which lead had been added in vitro in concentrations up to 5μg./ml., showed that the mechanical fragility index did not vary significantly from that of a control group.

Furthermore, the use of various anticoagulants produced no significant alterations in the mechanical fragility index. It was found, however, that in subjects suffering from anaemia of varying types, the mechanical fragility index was always greatly increased if the haemoglobin was below 80%.

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An unexpected finding in a survey of a random sample of men from the Rhondda Fach valley in South Wales suggested an association between blood group A and coal-workers' pneumoconiosis. A further and larger sample of 1,250 miners and ex-miners from the same area, covering the same age range of 35 to 64 years, was chosen at random from the population in order to verify this finding. Each man was radiographed and questioned on his history and symptoms of chronic respiratory disease, and samples of blood and of saliva were obtained. The chest radiographs were classified according to the 1953 International Classification of Pneumoconiosis, and ABO and Rhesus blood groups and the secretor status were determined.

No convincing association between ABO or Rhesus blood groups or secretor status and either pneumoconiosis or respiratory symptoms associated with bronchitis was found. If an association between the blood groups and pneumoconiosis in fact existed, it would manifest itself as an effect on the response to exposure to dust. Future investigations should therefore be concerned with variations in the dose-response relation rather than with variations in the prevalence of pneumoconiosis.

Previous evidence suggested that byssinosis in flax workers is caused by the inhalation of dust of biologically retted flax. In the present study no cases of byssinosis were found among workers in a flax plant which produces yarn by chemical degumming instead of biological retting. The absence of byssinosis in this plant could not be attributed to differences in the quantities of dust developed as compared with the conventional retting procedure.

These findings support the view that the agent in flax dust which causes symptoms of byssinosis originates during biological retting of flax and is absent from unretted flax. Chemical degumming of flax appears to be superior to biological retting procedures with respect to the health of the workers.

Following the suggestion that lead derivatives might cause cancer in man, the causes of death among workers known to have been exposed to lead were studied. A group of companies made available the records of their pension fund, and an accumulator factory provided details of men who had died whilst in their employ. Details of each man's exposure to lead were supplied.

There were 425 pensioners, of whom 184 had died; 153 deaths occurred among an unknown number of employed men who had not yet reached pensionable age. Expected deaths were calculated from the appropriate rates for all males in England and Wales.

It was concluded that there was no evidence to suggest that malignant disease was related to lead absorption. There was, however, evidence that heavy exposure to lead was associated with an increased incidence of deaths from cerebrovascular catastrophies.

In a first trial of an experimental classification of simple pneumoconiosis, each observer was asked to record, for each reading, not only the (I.L.O.) category into which he would have placed the radiograph but also whether he had seriously considered placing it in an adjacent category. Three skilled readers took part in the experiment, in which 120 films (consisting of three, taken in 1949, 1952, and 1956, for 40 subjects who had been at one colliery throughout the period) were read independently by each reader on two occasions and, subsequently, in a joint reading session. Despite the element of arbitrariness in the definition of when an alternative category should be recorded, the proportion of films for which alternates were quoted was very similar (just about half) for all three readers.

Complete agreement in the finer classification which is produced with the experimental method of reading was naturally less common than when conventional categorization was considered. However, when account was taken of the extent of the disagreements, both intra-observer error and inter-observer error were found to be considerably reduced in the experimental classification.

In studying the progression of pneumoconiosis in the subjects' films from one survey to another, it was found that there was an apparent understatement of progression when the conventional classification was adopted. This arose because, where both films for one subject were placed in the same (I.L.O.) category, there was a considerable tendency for progression to be indicated by a change in the categorization according to the experimental classification.

This paper is concerned with the problem of reading individual chest radiographs for coal-workers' pneumoconiosis in terms of the I.L.O. (1953) classifications, using a group of four readers. It represents the first of a series of investigations by the National Coal Board's Pneumoconiosis Field Research into various aspects of the general subject of the classification of chest radiographs. Later papers in this series will cover related problems, including the effect of radiographic “technique” on reading standards, the classification of a series of radiographs of the same individual, and the use of the readings in the correlation of radiographic abnormality with environmental exposure.

The effect of the circumstances under which the readings must be made in the Pneumoconiosis Field Research, including the geographical separation of the four readers into two groups of two, is described, and it is shown that any acceptable procedure must involve two distinct stages. On the “first stage” every radiograph must be read by some or all of the doctors individually, and on the “second stage” a proportion of films (those on which the individual readings are “ambiguous”) must be classified by the four doctors reading together. The general conduct of the joint reading sessions is then considered, and a description is given of a trial which was held to compare some alternative procedures. On the basis of these results an optimum reading procedure is derived. This is as follows:-

(i) Every radiograph to be read independently by one or other of the doctors from each group, in such a way that each reads half of the total number of films. The doctors from the group producing the radiograph to read alternately consecutive batches of about 50 as they are taken during the survey; the doctors from the other group to read the first and second halves of the survey, respectively, the films being arranged in serial order.

(ii) If these two independent readings are consistent, the common reading to be taken as definitive. All other films to be classified by joint consultation between the four doctors reading together, their assessment being arrived at by general discussion with each of the readers in turn giving the first opinion of the category of the film.

The underground workers in the Dutch coal-mines have been radiographed (70 mm.) seven times since 1949. The prevalence of coal-miners' pneumoconiosis shows a continuous decrease in all age groups. To evaluate the effect of the intensive system of dust suppression over this period a cohort analysis was made of the proportion of men with pneumoconiosis with the same number of years of exposure underground but who started work in different years. The results show that the number of men with pneumoconiosis decreases the longer they have worked in the period since dust suppression measures were applied intensively. The differences are significant at the 5% level.

Three main requirements influence the control of the temperatures of operating suites: (1) avoid humidities which contribute to the risks of anaesthetic explosions; (2) promote the comfort and working efficiency of the staff; and (3) conserve the patient's resources.

In the United States, an air temperature of 70 to 75°F. (21 to 24°C.) with 50 to 60% relative humidity provides a compromise between the requirements of the patients and those of the operators. In Britain, a temperature of 65 to 70°F. (18 to 21°C.) and a relative humidity of 50% is “well tolerated for many hours”. In the U.S.S.R., air-conditioning should provide in summer an air temperature of 68 to 72·5°F. (20 to 22°C.) and in winter 66 to 68°F. (19 to 20°C.) with a relative humidity of 55%.

According to the American Society of Heating, Refrigeration and Air-conditioning Engineers (1961) Guide “little is known about optimum air conditions for maintaining normal body temperatures during anaesthesia and the immediate post-operative period”. Clarke and his colleagues' observation in New York City that the patient's temperature begins to rise when the wet-bulb temperature exceeds 75°F.s (23·8°C.) fills one important gap. But this finding may not apply to other populations. Deaths from heat stress have occurred in Britain with wet-bulb temperatures of this order; and in the tropics surgeons operate successfully without air-conditioning where the ambient wet-bulb temperature rarely falls much below 75°F. (23·8°C.). When temperature control is available, it is not only at high temperatures that trouble arises. Excessive cooling of the patient leads to cardiac arrhythmias.

The patient's position is more hazardous than that of those exposed to climatic extremes in industry or in the armed forces. He is not only unconscious but his responses may be poikilothermic in character because shivering is abolished and there is peripheral vasodilatation. When he is exposed to levels of warmth at which he might not maintain thermal equilibrium, his body temperature should be recorded continuously during the period of anaesthesia in the theatre and in the ward.

This paper is based on the findings of a field study which was planned to ascertain by metabolic measurement the rates of energy expenditure of men and women on productive effort at work in modern factories.

The investigation which is described was carried out during a period of peace-time full employment, mainly in factories associated with the Slough Industrial Health Service in which a nutritional survey of the calorie intake of male operatives had been made by the Ministry of Health and the Medical Research Council in 1952.

The rates of energy expenditure of 70 men and 54 women in 27 occupational groups were measured by indirect calorimetric methods. On the basis of the criteria for the classification of work according grades to its heaviness, adopted by the Factory Department of the Ministry of Labour, muscular work grades have been ascribed to the occupations studied.

From the distribution of 390 metabolic measurements, ranges of energy expenditure have been computed for occupations classed as sedentary, light, moderate, heavy, or very heavy, Observation of recurrent phase variations in types of productive effort in the work-cycle indicated that wider work grades, such as light-to-moderate or moderate-to-heavy, are needed to cover the energy expenditure rates of men and women in many occupations.

The data obtained in this study have enabled a table termed the “Slough Scales” to be compiled giving ranges of energy expenditure and pulmonary ventilation rates for the various work grades ascribed to occupations.

The mean rates of energy expenditure of 257 workers (in industries in different parts of England and Scotland) which have been calculated from data published by other investigators have been found to fall within the ranges specified in these scales for the work grades of their occupations. It is felt, therefore, that the Slough Scales represent a reasonably true appraisal of the relation between the Ministry of Labour occupational work grades and the rates of energy expenditure of men and women at work under environmental and management conditions which usually appertain in the United Kingdom.

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Three stamped aluminium powders were injected into the lungs of rats. One powder contained stearine and another mineral oil, whilst the third had had its lubricant removed. The powders produced a rapid and marked fibrosis of equal severity. It is concluded that aluminium rather than any additive in the powders is the fibrogenic agent.

The protective action of stearine demonstrated in vitro was not confirmed in vivo, suggesting that pulmonary fibrosis may also occur in men handling stearine-containing powders. Such a case has recently been reported by McLaughlin et al. (1962), but this is exceptional to the general industrial experience.

A granular aluminium powder was also injected into the lungs of rats. In accordance with the results of in vitro experiments, this produced only minimal fibrosis, contrasting strongly with the action of the stamped powders.

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The discrepancy in previous reports of the action of aluminium on the lung may be explained by differences between stamped and granular aluminium powders. A stamped powder of the variety causing pulmonary fibrosis showed a brisk reaction with water, but a granular powder was unreactive. This difference is primarily due to the granular particles being covered by inert aluminium oxide, the formation of which is partially prevented in the stamping process by stearine and mineral oil. The reactivity of the flake-like stamped particles is also dependent on their large surface area per unit volume.

The appearance of aluminium pneumoconiosis in Britain is explained by the introduction of mineral oil into the stamping industry for, in contrast to stearine, mineral oil permits the powder to react with water. The lung damage is believed to be caused by a soluble form of aluminium.

The pottery industry in North Staffordshire was established towards the close of the seventeenth century. At first the wares which were made from local clays were rather crude but manufacturers unremittingly sought to improve the quality of their productions by the addition of other ingredients to the clays. In 1720 calcined powdered flint was introduced into the clay body. Six years later Benson described the serious effects of the dust on the lungs of millmen engaged in dry flint crushing. Later the disease became very prevalent not only among millmen but among workmen, males and females, in a wide range of pottery occupations and processes. Popularly the disease was known as potters' asthma or potters' rot, which was later identified scientifically as silicosis.

Among the workmen most seriously affected were men engaged in china biscuit bedding and placing and women in the china biscuit warehouse. The risk arose from bedding the ware in flint for the first or so-called biscuit firing. In the course of firing some flint adhered to the surface of pieces and this had to be scoured or brushed off to ensure a clean surface for glazing.

The manufacturers experimented to discover a suitable substitute for bedding flint. In due course it was proved that calcined alumina fulfilled all the practical requirements. This success immediately raised the question as to whether or not alumina was free from any risk to the health of workmen. The problem was investigated by a survey of furnacemen who had been seriously exposed for many years to the inhalation of alumina in the manufacture of aluminium. The research team concluded that alumina was safe. Thereafter manufacturers progressively substituted alumina for flint. At first this action was voluntary but it was made statutory in 1947.

Vigilant supervision of alumina workers in potteries and aluminium works was maintained between 1936 and 1962; the original findings as to the safety of alumina were confirmed.

During this period the firm of Doultons, where alumina was first introduced, experimented with firing china biscuit ware in tunnel ovens by a method in which the alumina is dispensed with. The method, profile placing, is now established and should in due course extend to all china manufactories.