Projected decrease in trail access in the Arctic.

Transportation systems in northern Canada are highly sensitive to climate change. We project how access to semi-permanent trails on land, water, and sea ice might change this century in Inuit Nunangat (the Inuit homeland in northern Canada), using CMIP6 projections coupled with trail access models developed with community members. Overall trail access is projected to diminish, with large declines in access for sea ice trails which play a central role for Inuit livelihoods and culture; limits to adaptation in southern regions of Inuit Nunangat within the next 40 years; a lengthening of the period when no trails are accessible; and an unequal distribution of impacts according to the knowledge, skills, equipment, and risk tolerance of trail users. There are opportunities for adaptation through efforts to develop skillsets and confidence in travelling in more marginal environmental conditions, which can considerably extend the envelope of days when trails are accessible and months when this is possible. Such actions could reduce impacts across emissions scenarios but their potential effectiveness declines at higher levels of global warming, and in southern regions only delays when sea ice trails become unusable.

Epidemiological profile of graduates of the Wits Dental Faculty 1927-1995.

The Wits dental school was first proposed in 1921 but had no premises until a private dental clinic was taken over in 1924 by the University, the same year that the Bachelor of Dental Surgery regulations were agreed to. In 1925 the first dental students registered and a year later, in 1926, the first seven lecturers in dental surgery were appointed. Since the first two graduates in 1927, 1916 dentists have graduated from the school as have 63 oral hygienists. Of the dentists 116 are female and 127 are black, Chinese, coloured or Indian. Regarding postgraduate qualifications, 346 have been awarded by the University on behalf of the dental school. This paper describes patterns in numbers of graduates, proportions registered in South Africa and contrasts registered South African dental school graduates with registered graduates from outside the country. It is clear that the Wits dental school has made a major contribution to South African society.

Epidemiological study of the lung function of workers at a factory manufacturing polyvinylchloride.

A preliminary epidemiological study has been carried out to investigate a report that some men working in a factory manufacturing polyvinylchloride (PVC) had abnormally low values of the single breath diffusing capacity for carbon monoxide (TLCO). All monoxide (TLCO). All 265 present and past employees of the PVC factory were studied, together with 219 men from the workforce of a nearby foundry. Each man's TLCO was measured and a smoking history and detailed occupational history obtained. The distribution of standardised TLCO results from all persons examined was symmetrical and did not indicate an unexpectedly high proportion of men with having allowed for age, height, weight, and smoking habit, TLCO was associated with a history of working in the PVC factory before 1975 (when levels of vinylchloride monomers (VCM) were much higher than subsequently), and slightly associated with working in jobs where exposure to VCM was likely to have been highest. The men with low TLCO also tended to have smoked more heavily than controls. The relative importance of occupational factors and smoking in relation to low TLCO is not clear, but the results give some support to the hypothesis that work in the PVC factory before 1975 entailed exposure to a substance that caused impairment of lung function in a small number of men.

Coalworkers' simple pneumoconiosis and exposure to dust at 10 British coalmines.

Five physicians' radiological assessments of coalworkers' simple pneumoconiosis (CWP) in 2600 coalminers at 10 British collieries have been studied in relation to the individuals' estimated lifetime (mean 33 years) exposure to respirable coalmine dust. Estimates of exposure were based on 20 years of observations at each colliery. Radiographic classifications were clearly associated with the measures of dust exposure. Important unexplained differences between some of the collieries were disclosed. Among men with similar cumulative dust exposures those with longer exposure time had higher prevalence of CWP. In general there was no evidence that the quartz concentrations experienced (average 5% of mixed dust) affected the probability of developing coalworkers' simple pneumoconiosis. Some men reacted unfavourably (two or more steps of change on the 12-point radiological scale) over a 10-year period to coalmine dust with a relatively high quartz content.

Classification of chest radiographs for epidemiological purposes by people not experienced in the radiology of pneumoconiosis.

Under controlled conditions 16 people (eight non-medical) inexperienced in the radiology of occupational lung diseases repeatedly classified 300 selected chest radiographs using the 1971 ILO U/C International Classification of Radiographs of Pneumoconioses. Eight experienced medical readers had previously classified 220 of the selected radiographs for profusion of small rounded opacities. Variability among readers was greater in experimental panels than among the experienced readers. But the average consistency between pairs of novice readers in their use of the 12 categories of profusion for the same radiographs was similar (about 29%) to the average consistency among the experienced readers. Subsequent work with nine of the participants showed that eight of them were able to produce classifications of coal miners' chest radiographs that correlated well with estimates the miners' exposures to respirable coal mine dust. It is concluded that the ILO classification scheme provides a sound descriptive system for recording the appearances of chest radiographs. Under controlled conditions the scheme may be used for epidemiological studies by those with no specialist knowledge or clinical experience. This presupposes that the radiographs concerned will have been examined previously for diagnostic purposes by a suitable qualified physician.

Epidemiological study of respiratory disease in workers exposed to polyvinylchloride dust.

The respiratory health of workers exposed to polyvinylchloride (PVC) dust has been investigated in 818 men sampled from the work force of a factory manufacturing PVC. In a cross-sectional survey, the lung function and prevalences of respiratory symptoms and chest radiographic abnormalities were compared with estimates of individual PVC dust exposures based on detailed occupational histories and current measurements of respirable PVC dust. Complaints of slight exertional dyspnoea were associated with PVC dust exposure, though age and smoking effects were much stronger. The forced expired volume in one second (FEV1) and forced vital capacity (FVC) were inversely related to dust exposure after age, height, and smoking effects had been taken into account. This effect was seen principally in cigarette smokers, and there was suggestive evidence that PVC dust exposure and cigarette smoking interacted in the reduction of FEV1 and FVC. Gas transfer factor was not related to dust exposure. The chest radiographs were read according to the ILO U/C classification by three experienced readers. One reader recorded a low prevalence of small rounded opacities, and these were not related to age or dust exposure. Another reader recorded a higher prevalence of small rounded opacities category 0/1 or more, and these were related to age but not to dust exposure. The third reader recorded the highest prevalence of small rounded opacities (though none greater than category 1/1), and these were independently related both to age and to PVC dust exposure, indicating an effect of PVC dust on the appearance of the chest radiography. These appearances were so slight that only the higher sensitivity of this reader in the interpretation of profusion of small rounded opacities on the ILO U/C scale enabled detection of this effect of PVC dust. In conclusion, exposure to PVC dust is associated with some deterioration of lung function, slight abnormalities of the chest radiograph, and complaints of slight dyspnoea. The mean decline in FEV1 associated with the average dust exposure experienced in the study was small, though some of the men with higher dust exposures may have suffered clinically important loss of lung function as a result of their occupation.