Byssinosis, despite years of investigation and research, remains an enigma. The cause remains unknown, the ability of cotton dust to produce irreversible airway changes is disputed and it is not known whether current dust levels are still able to cause this disease in new textile workers.

The progressive reduction in dust levels in cotton mills over the past twenty years has been associated with a falling prevalence of byssinosis. The most recent cross sectional study in the Lanchashire cotton mills reveals a prevalence of 4.2% (l). This study also examined the respiratory systems, apart from chest tightness, experienced by byssinotic subjects. The prevalence of cough, sputum, wheeze and breathlessness increased with the grade of byssinosis (table 1). The prevalence of these symptoms was not influenced by smoking habits, except amongst exsmokers who had a significant excess of cough, sputum and breathlessness. The symptoms themselves are all consistent with an asthmatic process.

The cigarette smoking habit itself increases the risk of developing byssinosis (2). There is also evidence that other host factors may influence the development of respiratory disease amongst cotton workers. One type of textile dust has been shown to produce a greater deterioration in lung function across the working shift in atopic compared to nonatopic individuals (3). A study of byssinotic subjects (4) revealed a significantly lower prevalence of atopy than in a control group of subjects matched for sex and age, suggesting that atopic individuals select out of the industry at an early stage. It is likely that individuals with hyperactive airways (an abnormality frequently found in atopic subjects) will rapidly develop symptoms on exposure to cotton dust simply due to its irritant nature.

The airway responses in byssinotics (measured on a peak expiratory flow meter) usually show a work related deterioration in lung function which varies from small consistent deteriorations of 10% or less to large falls of 20% or greater consistent with a diagnosis of occupational asthma. Byssinosis appears to be exclusively a disease of the airways. The presence of emphysema is rare and is determined by the smoking habits of the individual (5,6).

The way forward in byssinosis research which will answer some of the many unanswered questions is a prospective study over a 5-10 year period in the cotton textile mills. The study should examine all new textile workers and those leaving, combined with all existing workers. Each of this latter group of workers could be given an estimated dust burden according to their work years and position in the mill. New and retiring workers would be assessed by medical history, smoking status, atopic status, airway reactivity and lung function. All workers would be assessed annually. Regular estimations of cotton dust levels would be made in each work area using area and personal sampling techniques.

Although byssinosis is a declining respiratory disease in Western countries, it is likely to remain a major occupational problem in the Meddle and Far East for many years.