Two Welsh surveys of blood lead and blood pressure.

The relationship between blood pressure and blood lead was examined in two population samples. One of these consisted of 1137 men aged 49 to 65 years, the other of 865 men and 856 women aged 18 to 64 years. Neither population had any known important exposure to lead, and the 95% ranges of blood lead levels were 6 to 26 micrograms/100 mL and 6 to 23 micrograms/mL in the men and 5 to 18 micrograms/100 mL in the women. No significant relationship between blood pressure and blood lead was detected in either of the population samples, and the regression coefficients suggest that if there were a real effect, then the mean difference in blood pressure per 10 micrograms difference in blood lead is likely to be 0.7 mm Hg in both systolic and diastolic pressures. In the survey of 1137 men, the rise in blood pressure was measured during the cold pressor test. This test is likely to be affected if lead were to affect neurogenic mediators of blood pressure. The mean change in systolic pressure was 24 mm Hg and the 95% range was -6 to 60 mm Hg, but there was no evidence of any association with blood lead level.

Blood pressure and blood lead in surveys in Wales.

The association between blood pressure and blood lead level was examined in two population surveys in Wales. In a survey of 1,721 male and female subjects throughout the principality, there was evidence of a marked relation of blood pressure with age, but when this was removed no residual association with blood lead remained. In a survey of 1,164 older men in Caerphilly, there was no evidence of an association between blood lead and either resting blood pressure or the rise in blood pressure during a cold pressor test.

Mortality of slate workers in north Wales.

In a study in 1975 of the mortality experienced over six years by two groups of men one group had been exposed to slate dust and the other had had no previous exposure to dust. In non-smokers there was no material excess mortality associated with past exposure to dust but in smokers there was a pronounced (26%) excess. In the slate workers the risk for smokers was on average 76% greater than for non-smokers, and increased with severity of pneumoconiosis; in those who had not been exposed to dust the risk was 50% greater for smokers than non-smokers. In ex-smokers among those who had been exposed to slate dust the risk of death was higher in those with the lower lung function initially. No such association was detected in the other groups.

Estimation of the FEV.

The procedure recommended by the Medical Research Council for estimating a subject's forced expiratory volume in one second (FEV1) is to require five separate attempts, discard the first two results, and average the last three. The most popular alternatives are to use the largest of the last three or the largest of a smaller number of results. Nine different indices derived from some or all of five attempts were compared in two studies. In one 40 normal subjects were studied. In the other 335 men exposed to industrial dust, whose forced expiratory volume declined with their degree of radiological pneumoconiosis as well as with age, were studied. There were small but consistent differences between indices. The index which emerged as the best overall in both studies was the mean of the largest three results from five attempts. It was better than the recommended index for all the comparisons made, but at the same time it gave a very similar mean value for the FEV1. Excluding the lowest two results rather than the first two from five blows is a rational procedure, and it should be formally recognised as providing the best index available.

Pneumoconiosis in Cornish china clay workers.

A radiological survey of men employed in the china clay industry in Cornwall was carried out in 1977. Each man completed a short questionnaire on respiratory symptoms and smoking habits, his occupational history was determined, and his forced expiratory volume and vital capacity were measured. The radiographs were read independently by three observers, using the 1980 ILO classification. Of the 1728 men in the study, 23 had had dust exposure elsewhere, mostly in tin mining, and were excluded. Readings of the radiographs were available for 1676 men: 77.4% were within category 0, 17.9% in category 1, and 4.7% in categories 2 and 3. In 19 men (1.1%) one or more readers recorded the presence of a large shadow and read it as complicated pneumoconiosis, but in only four men were the readers unanimous. Every job recognised as dusty contributed significantly to the amount of simple pneumoconiosis, and in two jobs the conditions were such that the average worker would reach category 2 in a working lifetime. Smoking appeared unrelated to the radiographic appearance. Vital capacity showed a significant reduction with increasing amount of pneumoconiosis, but not, when this was allowed for, on the duration of exposure in any of the job categories. In addition it depended, as would be expected, on smoking. The effect of one category increase in pneumoconiosis was equivalent to 4.1 years of age in smokers, 3.9 years of age in ex-smokers, and 5.4 years of age in non-smoker. Forced expiratory volume did not decline significantly with amount of pneumoconiosis, so that FEV% VC showed an increase, though not to a significant extent. No extent. No relationship between symptoms and past exposure was detected.

Effects of exposure to slate dust in North Wales.

In a study of slate workers in four areas in North Wales 725 workers and ex-workers who had been exposed to slate and to no other dust were seen, together with 530 men from the same area who had never been exposed to any dust. Evidence of pneumoconiosis was found in one-third of the slate workers, and 10% had degrees of pneumoconiosis that would attract compensation (category 2 or higher). The prevalence of respiratory symptoms was high, and there was evidence of an effect of both simple and complicated pneumoconiosis on lung function additional to that of age. There was a high prevalence (40-50%) of radiological lesions suggestive of healed tuberculosis in men aged over 55. Either pneumoconiosis or old tubercular lesions (or both together) could account for the current symptomatology and disability of the men.

Assessment of cell-mediated immunity to malignant mesothelioma by microcytotoxicity tests.

Cell cultures were established from pleural effusions of patients with pleural mesothelioma, and peripheral mononuclear effector cells were tested for cytotoxicity against these cells by means of microcytotoxicity assay. Effector cells were obtained from normal healthy donors and from persons exposed occupationally to asbestos, including apparently healthy persons, patients with benign pleural conditions and patients with malignant mesothelioma. The overall incidence of cytotoxicity was low, and there was no evidence of increased cytotoxicity in mesothelioma patients or other asbestos-exposed donors. It is concluded that little or no tumour-directed cell-mediated immunity is detectable against malignant mesothelioma by microcytotoxicity methods.