Epidemiology and Etiology
Both black and brown lung (and their medically named partial synonyms) have been the focus of many studies - and are highly controversial. Early epidemiological studies established an association between occupation and respiratory disease.
Studies of both conditions in the United States were, in general, initiated later than those in Britain for reasons that include the political roles of manufacturers and unions and the structure of public regulation as well as different perceptions of the relative importance of silica and coal dust and the amount of dust that constituted a dangerous exposure in textile manufacturing. Moreover, many epidemiological, clinical, and pathological investigations have yielded uncertain results.Aspects of coal miners’ lung distress that remain controversial include the following: (1) the mechanisms by which coal dust acts on the lungs; (2) the significance of the correlation, or lack of it, between clinical evidence of respiratory impairment and X- ray findings; and (3) the absence, in some studies, of strong, independent correlations between respiratory disorders in mining communities and work in the mines. Caplan’s syndrome is an example of the complexity and controversy surrounding coal miners’ lung conditions. This syndrome, first described among Welsh coal miners in 1953, appears to be a consequence of the interaction of characteristics of rheumatoid arthritis with a residue of silica in the lungs; yet the syndrome seems extremely rare in the United States, dispite the high incidence of both dust exposure and arthritis among miners.
For byssinosis, areas of uncertainty include the following: (1) the substance in cotton dust that causes respiratory distress; (2) lack of clear evidence linking levels of dust exposure to findings indicative of clinically defined disease; and (3) the absence of widely agreed upon findings from clinical and pathological examinations that are sufficiently specific to permit a diagnosis of disease.
Nevertheless, the contemporary literature on both conditions is widely regarded as offering considerable guidance for public action.
Most investigators agree that the relatively high incidence of respiratory distress in mining and textile workers is evidence of exposure to toxic agents in industrial dust. Many authors have hypothesized mechanisms by which these agents could operate in the lung. There is considerable agreement about clinical manifestations and pathology. And there is overwhelming consensus that reducing dust levels in the workplace contributes to reducing the incidence of both black and brown lung and the symptoms, signs, and findings defined by medical scientists as diseases among workers in dusty industries.Throughout their histories, black and brown lung have been matters of controversy involving people and institutions beyond the medical profession. The definitions of the conditions have been matters of intense political concern. Generalizations about their incidence and distribution depend on how they are defined, and defining them has long been controversial. Etiology and epidemiology remain in dispute in part because of scientific uncertainty but also because involved as well are significant amounts of money and fundamental issues about the relationship between employers and employees and the public interest in workplace health and safety. Laws and regulations are often more important sources than medical texts for understanding what clinical manifestations and pathological findings mean for treatment, compensation, and control of the environment of the workplace.
Daniel M. Fox