Statistics of injuries arising in amateur boxing in the Royal Air Force in the 14 years 1953-66 are given. There were 240 injuries including two deaths in the 14 years. During the seven years 1960-66, four men out of every thousand entering the ring received injuries to the head or neck which kept them off work for 48 hours or more. No case of the punch-drunk syndrome was seen.

This paper reports an apparent biological difference between two otherwise identical preparations of piperazine hexahydrate. It reports the cutaneous irritancy and allergenicity of this substance and records the effect of environmental temperature on those properties, particularly the former. Finally, it reports severe, delayed asthma-like response to piperazine exposure. Interrogation of companies engaged in the manufacture of the substance revealed that the unwelcome effects reported here have quite commonly affected workers in the United States, the United Kingdom, Sweden, South Africa, and elsewhere in Sydney. The only report known to me is that of Foussereau (1963), who mentions cutaneous sensitization of nursing staff. It is remarkable that the chemical companies concerned should not have published reports of these ill effects. One may conclude from this study that in seeking to prevent industrial contact dermatitis consideration of the effective environmental temperature may well prove as rewarding as other more conventional measures.

A technique has been developed for injecting metallic mercury intravenously in aqueous solution. Thirty seconds after intravenous injection of rats with 0·1 μg. metallic mercury labelled with 203Hg nearly 20% of the dose had been exhaled and the concentration in the brain was nearly as high as in the blood. After injection of mercuric ion little of the dose was exhaled, and brain uptake was much less. Oxidation of mercury in the blood was, therefore, not instantaneous, and the rapid transport of the unconverted metallic mercury to the brain and its subsequent rapid diffusion from the blood was responsible for the high level of mercury in the brain after exposure to mercury vapour. The technique might be useful for the study of the passage of highly diffusible vapours through the respiratory membranes.

The toxicity of paraquat and diquat aerosols to several species has been investigated. In order to obtain an atmosphere of `respirable' particles, an atomizer has been constructed with an upper cut-off of size by a cyclone separator, and with a calibrated reservoir to enable the concentration output to be estimated by inspection.

Paraquat has an irritant action on the lungs, and at lethal concentrations death is delayed and is associated with pulmonary haemorrhage and oedema. After single exposures the LC50 appears to be a function of the duration and of the concentration; in the rat the lethal concentration-time product (CT) is about 6 μg./l.hr. Guinea-pigs and male mice are about as sensitive as rats. Female mice and rabbits are less sensitive. The dog can tolerate a CT product of 25 μg./l. hr without ill-effects. The toxicity is a complex function of particle size. In the rat it appears that the most effective size is in the region of 3 μ, as larger particles do not reach the alveolar regions and finer particles are probably not retained there.

Repeated daily 6-hr exposures of rats to paraquat aerosols over a three-week period produce signs of lung irritation but no deaths at 0·4 μg./l., and the no-effect level is about 0·1 μg./litre.

Paraquat appears to be poorly absorbed from the lungs. After single exposures death is associated with a paraquat content of about 6 μg. in the lungs. Paraquat is subsequently cleared from the lung with a half-life of about 36 hr.

Diquat is much less irritant to the lungs than is paraquat; the no-effect levels on single and repeated exposure are at least five times larger.

It is concluded that paraquat and diquat do not present an inhalation hazard under normal conditions of application, but with paraquat under abnormal conditions it may be desirable to provide respiratory protection.

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An account is given of work in an asbestos textile factory and of the steps taken to reduce exposure to dust since the introduction of the Asbestos Industry Regulations in 1931.

Measurements of the amount of dust to which men were exposed in the scheduled areas have been made by various methods since 1951, but the data obtained by these methods are not directly comparable. Measurements made since 1960 show that the mean yearly dust level has been fairly constant from year to year and has varied from place to place between 1 and 8 particles (5 to 100 microns long and at least three times as long as they were wide) per c.c. of air.

Chrysotile was used predominantly in the factory, but small amounts of crocidolite were also processed at all relevant periods.

Death rates have been recorded for all the 256 men who were employed for at least 20 years in the scheduled areas since the first man completed 20 years' exposure in 1916, and for the 538 men and 220 women who were employed for at least 10 years in the scheduled areas but were never employed in these areas before 1933.

The results show a substantially increased mortality for men who were exposed for 10 or more years before 1933 (48 deaths from all causes against 17·1 expected).

The increased mortality among these men can be accounted for by an increased mortality from cancer of the lung (12 deaths against 1·2 expected) and from diseases of the respiratory and circulatory systems associated with asbestosis.

Men employed before 1933, but for less than 10 years, showed an increased mortality from lung cancer (5 deaths against 2·6 expected), but no significant increase from other causes. Men and women who were exposed only since January 1, 1933, have had a mortality experience close to the national average.

Analysis of the trends in mortality shows (1) a decrease in mortality from lung cancer and other deaths associated with asbestosis with reduction in length of employment before 1933, and (2) an increase in mortality from lung cancer and other deaths without asbestosis with age.

Twenty-three cases of lung cancer occurred in men who had been employed in the scheduled areas for at least 20 years. One was regarded as a pleural mesothelioma and the rest (approximately 18 in excess of expected) appear to have been ordinary bronchial carcinomas.

Four other mesotheliomas have been diagnosed since 1963, all in men and women with less than 10 years' exposure, one with only seven months' exposure, and one in a man who had been employed in the scheduled areas only since 1937.

The results provide grounds for believing that the occupational hazard of bronchial carcinoma has been largely eliminated, but the data are insufficient to estimate the extent of the risk which may remain.

Immunological investigations of 37 patients with bagassosis, 92 unaffected bagasse workers, and 150 non-exposed controls showed that precipitins against extracts of bagasse could be demonstrated just as frequently in the unaffected and the non-exposed as in the affected. However, there was a general tendency for the precipitin levels of patients with bagassosis to fall slightly with increasing time after recovery from the clinical episode. The presence of the precipitins so far demonstrated in the sera of bagasse workers therefore appears to be of no clinical significance.

Inhalation tests with an extract of bagasse, in a group of 16 patients who had had bagassosis, produced late, systemic reactions in 15 similar to those described in farmer's lung and bird fancier's lung, so supporting the hypothesis that a similar type of hypersensitivity is the cause of bagassosis. Inhalation of extracts of Thermoactinomyces vulgaris also produced typical, late reactions in 12 out of 15 subjects, whereas extracts of Micropolyspora faeni failed to produce reactions in any of 16 subjects. The specific reactions to inhalation tests with Thermoactinomyces vulgaris were typical of a precipitin-mediated type of hypersensitivity reaction and support the view that this actinomycete may be important in the aetiology of bagassosis.

An epidemiological and environmental survey of 170 bagasse workers employed by a raw sugar producing company in Trinidad was carried out in order to assess the prevalence of respiratory symptoms and to determine if exposure to bagasse was associated with alterations in ventilatory capacity.

The epidemiological survey failed to reveal a significantly increased prevalence of respiratory symptoms in the more exposed group but showed that the group of Indian workers who were regularly and continuously exposed to bagasse had a significantly lower ventilatory capacity than the control group. This diminished ventilatory capacity was demonstrated despite negligible dust concentrations in the plant. However, the possibility that persistent exposure to low concentrations of bagasse may be the cause must be considered.

During a five-year period, 17 patients with bagassosis were seen, the clinical picture being similar to that described in extrinsic allergic alveolitis from other causes.

The systematic variations demonstrated in some indices of ventilatory function in different racial groups are discussed.

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Five hundred and fifty-five acid workers were examined between March 1962 and October 1964. One hundred and seventy-six (31·7%) were affected by industrial dental erosion at the first examinations. In 33 cases (6·0%) the dentine was affected. During the period of the survey, 66 (20·4%) of 324 workers examined more than once showed evidence that erosion was progressing. The prevalence and incidence of erosion were highest among battery formation workers, lower among picklers, and least among other processes covered by the survey. The age of workers did not appear to influence their susceptibility to erosion. The habit of working with the lips slightly parted had little effect. Erosion superimposed upon attrition predisposed to more severe loss of tooth structure than either operating alone. Little inconvenience or functional disability was suffered by acid workers due to erosion. Twenty-seven (23·7%) of 114 erosions were considered to be disfiguring. Regular dental treatment was sought less by acid workers than by controls, and the oral hygiene of the latter was superior. There was no evidence to show any difference between caries experience among acid workers and controls. Calculus and periodontal disease were more prevalent among acid workers than among controls, but it was not possible to attribute this to the working environment. Black staining in iron picklers was considered to be due to the working environment. The use of closed acid containers or lip extraction on open acid vats prevented significant atmospheric contamination and diminished the prevalence of erosion. The use of wall fans and detergent foaming agents was helpful.

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