Lung function tests in steel works with special reference to mixing efficiency.

In 1952-53 a survey was carried out in a Steelworks, in order to compare the state of the lungs of furnace repairers, working with silica bricks, with that of a group of rolling mill workers. This showed that, apart from age and the presence or absence of a history of specific Pulmonary diseases, the principal factor Which influenced the symptoms and the results of quantitative tests was Tobacco consumption. When allowance was made for these, a slight difference could be discerned to the disadvantage of the group of bricklayers working with silica bricks.
After a lapse of twelve years, this study was repeated in order to ascertain the deterioration of the different groups in respect of lung function.
During this follow-up study the co-operation of the potential subjects was much less complete than in the original investigation, only 43 bricklayers and dismantlers participated out of a possible 150 remaining from the original study; while from the rolling mills 67 out of 128 volunteered. The changes observed in the two groups showed no consistent differences.
The ratio of residual volume to total lung capacity increased in almost all subjects. The amount of the increase did not differ significantly between the mill workers and the furnace repairers.
In respect of mixing efficiency, some individuals improved while others deteriorated. In the case of the mill workers the mean change was -4% which is less than the standard error of the difference , while for the furnace repairers the change was +7.1% (S.E 3.30) which is significant at the 5% level. These may be compared with an expected change of about -4.5%.
The values of the Maximum Breathing capacity showed a marked decline. However, an uncertain proportion of this must be attributed to personal differences between the observers.