Respiratory symptoms in wool textile workers. An epidemiological study of respiratory health in West Yorkshire wool textile mills

This epidemiological study was intended to investigate exposures to inspirable wool dust in selected wool textile mills, the patterns of respiratory symptoms reported by workers in the industry, and the relationships of symptoms to exposure to dust. Fifteen mills in Vest Yorkshire representing all stages of the woollen and worsted process, and production of carpet yarns, were included in the study, their size ranging from four to nearly four hundred employees.Occupational hygiene surveys of airborne dust levels were carried out at each mill by means of the IOM personal inspirable dust sampler, which was worn during 629 shifts. Inspirable dust samplers were used because we wished to examine the effects of dust inhalation throughout the respiratory tract. A further 216 samples were collected in order to compare its performance with other samplers, to study the influence of a mesh guard on the samplers to keep out flocks of dust, or to estimate the presence of endotoxin in the dust.Two thousand one hundred and fifty three current employees from these mills were interviewed, in order to obtain detailed information about respiratory and related symptoms, smoking habits and past and present occupations. A general purpose respiratory symptoms questionnaire was designed to elicit all the common respiratory symptoms, including cough, phlegm, wheeze, chest tightness, shortness of breath, rhinitis and nosebleeds. Questions on level and variability of breathlessness (intended to help identify asthma), itchy red eyes (conjunctivitis) and chills (intended to identify humidifier fever) were also included. The symptoms of cough, wheeze, rhinitis, itchy red eyes and chills were supplemented, if present, by questions intended to determine whether these symptoms were better or worse at certain times of the day, days of the week, seasons (rhinitis) and in particular situations. An occupational history questionnaire was also designed to identify all previous and current jobs, current working hours and usual shift patterns.The total working population of 2793 at these mills included over six hundred workers of Asian origins. The questionnaires were therefore translated into Urdu, and locally based Urdu-speaking clerks were trained to administer the questionnaires during the surveys at mills where Asians were employed. The dust sampling surveys indicated that dust levels ranged from zero to over 2000mg/m3. Average inspirable dust levels greater than lOmg/m3, the currently accepted nuisance dust standard, were experienced by about 92 of the workforce. Microscopic examination of wool samples and chemical and physical analysis revealed no obvious association of composition with the stage of processing. Measurement of the endotoxin levels of airborne samples revealed occasional very high concentrations.Eighty five per cent of Che currently employed workforce were interviewed and on average they reported symptoms with the following relative frequencies or prevalences: persistent cough and phlegm (chronic bronchitis), 9Z; wheeze, 31Z; breathlessness grade 3 or worse, 10Z; variable breathlessness 3Z; persistent rhinitis, 18Z; persistent conjunctivitis, 10Z; persistent chills, 2Z and more than 10 nosebleeds in the past year, 2Z. These symptoms were in general commoner in women, Europeans and smokers and they mostly showed no change or a decreased frequency with age. Cough and wheeze tended to be worse on average early in the morning, early afternoon and late evening, and better at weekends, whereas rhinitis and itchy red eyes were most often worse during working hours, week days and Spring and Summer months. A majority also reported these symptoms being worse at specific places of work.Symptoms tended to occur together in the same individual: for instance persistent conjunctivitis, persistent rhinitis, chronic bronchitis and breathlessness each tended to be associated with the others, though not invariably so.Prevalences of each of these, and other, symptoms were related to the inspirable dust concentrations in current job (76Z of the workers had done only one or two jobs in the industry). After allowing for the effects of age, sex, ethnic background, language and smoking habit, positive associations between inspirable dust concentrations and prevalences of symptoms were confirmed. This was shown clearly for persistent conjunctivitis, persistent rhinitis, chronic bronchitis, wheeze and breathlessness. Variable breathlessness was more frequent in non-process than process workers, Suggesting some selection of asthmatics out of dusty jobs. Within process workers, the relative frequency of variable breathlessness was positively associated with dust concentrations. Time off work because of chest illness was reported more frequently by processthan by non-process workers, but within the group of process workers such absences were not obviously related to dust concentration.The magnitude of the effect of dust for chronic bronchitis, for example, was estimated as a prevalence of 4.02 for 40 year old, male, European, non-smoking non-process workers, but 7.8% for non-smokers exposed to 25mg/m3 of inspirable dust. For those who smoked 20 cigarettes a day, the estimated prevalences were 14.5% and 25.5% respectively.Backwinding, blending and work with wool waste tended to be particularly dusty, and were associated with even greater frequencies of respiratory symptoms than could be accounted for by the inspirable dust concentrations in these jobs. Prevalence of symptoms was related to length of time worked in these jobs.The exposure/response relationships found in this study indicate that even at the “”nuisance dust”” level of 10mg/m3, the relative risks of dust related symptoms range from 1.3 to 1.6 times the risk for unexposed workers.This study confirms reports of respiratory illness related to dust in vool textile mills, and indicates that wool dust causes symptoms of inflammation or irritation throughout the respiratory tract. While some of these symptoms may be unpleasant but not serious, others such as chronic bronchitis and complaints of breathlessness are likely to be associated with functional impairment of the lungs. Studies of selected workers would be advisable to estimate the functional effects of exposure to dust in wool textile mills. “”