Epidemiological study of hard metal asthma.

OBJECTIVES: To elucidate factors contributing to hard metal asthma, the entire workforce of a corporation producing hard metal tools (n = 703) was examined. METHODS: The variables evaluated were the atopy reflected by immunoglobulin E (IgE) antibody against mite allergen, history of exposure to hard metal, smoking, concentration of airborne cobalt, specific IgE antibody reaction against cobalt, and the respiratory symptom of attacks of reversible dyspnoea with wheeze (asthmatic symptoms). RESULTS: Univariate analysis showed that the prevalence of the asthmatic symptoms was significantly higher in formerly and currently exposed male workers than in non-exposed male workers. Positive IgE reaction against cobalt was found in seven men (2.0%), all of whom had asthmatic symptoms. Furthermore, it was found that atopy, positive IgE antibody against cobalt, and age of 40 or older were significantly correlated with asthmatic symptoms. Multilogistic analysis on the same factors and smoking in all of the workers showed that the age, experience of hard metal exposure, and atopy were significant risk factors associated with the asthmatic symptoms. Multilogistic analysis of data for currently exposed and non-exposed workers also showed that age and atopy were risk factors, and that the exposure to cobalt at the low concentration (at or below 50 micrograms/m3) but not at the higher concentration was a significant risk factor. Exposure to mist of coolants containing ionic cobalt, used during grinding, was not found to be any more hazardous in terms of onset of asthmatic symptoms than exposure to hard metal dust containing metallic cobalt. CONCLUSIONS: Accordingly, it is concluded that both environmental factors and individual susceptibility should be taken into consideration in efforts to reduce the prevalence of hard metal asthma.     

Respiratory symptoms and impairment in shipyard welders and caulker/burners

All 607 men, aged 17 to 69, comprising a stratified sample of workers from one shipyard completed a respiratory questionnaire, clinical examination, and detailed spirometry. Chest radiographs were available on 332 men. Among the men aged 50-69 the prevalence of persistent cough and phlegm (chronic bronchitis) was 40%, of wheeze on most days 25%, and undue breathlessness on exertion 25%. After allowing for age the relative risk of welders and caulker/burners having these symptoms were respectively 2.8, 2.2, and 3.1 compared with other shipyard tradesmen. The effects were of comparable magnitude to and interacted with those of current smoking. Among the welders and caulker/burners who smoked, the relative risk of developing chronic bronchitis or undue breathlessness was related to the average fume exposure; the relative risk of wheeze was related to the average fume exposure in all smoking categories, with the strongest association in the ex-smokers. The occurrence of wheeze was also associated with a history of previous metal fume fever. A history of pleurisy but not of pneumonia was related to the fume exposure in the welders. After allowing for age and stature, forced expiratory volume (FEV1) was on average higher in young welders (age less than 30) than other tradesmen. In welders and caulker/burners who were current or ex-smokers, FEV1 and PEF were reduced in relation to the average fume exposure (mean reductions respectively 0.25 l and 0.99 l s-1). The FEV1% (of forced vital capacity), the flow rates at small lung volumes (MEF50%FVC and MEF25%FVC), the mean transit time, and its standard deviation were also reduced by fume exposure or the declines with age were increased, or both. No impairment was demonstrable in the non-smokers and many men had given up smoking with apparently beneficial results. The occupational component of the respiratory impairment related mainly to exposures in the past; information was needed on the effects of present conditions in the industry.     

Respiratory symptoms and impairment in shipyard welders and caulker/burners.

All 607 men, aged 17 to 69, comprising a stratified sample of workers from one shipyard completed a respiratory questionnaire, clinical examination, and detailed spirometry. Chest radiographs were available on 332 men. Among the men aged 50-69 the prevalence of persistent cough and phlegm (chronic bronchitis) was 40%, of wheeze on most days 25%, and undue breathlessness on exertion 25%. After allowing for age the relative risk of welders and caulker/burners having these symptoms were respectively 2.8, 2.2, and 3.1 compared with other shipyard tradesmen. The effects were of comparable magnitude to and interacted with those of current smoking. Among the welders and caulker/burners who smoked, the relative risk of developing chronic bronchitis or undue breathlessness was related to the average fume exposure; the relative risk of wheeze was related to the average fume exposure in all smoking categories, with the strongest association in the ex-smokers. The occurrence of wheeze was also associated with a history of previous metal fume fever. A history of pleurisy but not of pneumonia was related to the fume exposure in the welders. After allowing for age and stature, forced expiratory volume (FEV1) was on average higher in young welders (age less than 30) than other tradesmen. In welders and caulker/burners who were current or ex-smokers, FEV1 and PEF were reduced in relation to the average fume exposure (mean reductions respectively 0.25 l and 0.99 l s-1). The FEV1% (of forced vital capacity), the flow rates at small lung volumes (MEF50%FVC and MEF25%FVC), the mean transit time, and its standard deviation were also reduced by fume exposure or the declines with age were increased, or both. No impairment was demonstrable in the non-smokers and many men had given up smoking with apparently beneficial results. The occupational component of the respiratory impairment related mainly to exposures in the past; information was needed on the effects of present conditions in the industry.     

Respiratory health of cobalt production workers

BACKGROUND: Cobalt production workers are exposed to metallic cobalt and nickel and their compounds and to different irritant gases. The aim of our study was to determine whether long-term exposure is associated with an increased occurrence of respiratory symptoms and findings or diseases, other than asthma, which is a known hazard, among cobalt processing workers. METHODS: The study population was comprised of 110 current and former cobalt workers who had worked more than 10 years in a cobalt plant. The reference group consisted of 140 unexposed workers. All the participants were men. The analysis was based on exposure history, pulmonary function, chest X-ray findings, and symptom questionnaires. RESULTS: Symptoms of asthma based on questionnaire responses were statistically more prevalent among the exposed workers. The respiratory flow rates MEF25 and MEF50, which refer to smaller airways, were significantly lower among the smoking exposed workers than among the smoking unexposed workers. The causative factors of these symptoms and pulmonary function changes could not be determined by the study. One new case of cobalt asthma and one case of allergic asthma were diagnosed in the exposed population. No cases of hard metal disease or fibrosing alveolitis were found. CONCLUSIONS: No chronic respiratory diseases, except asthma, were found among cobalt production workers in this study.     

Respiratory findings in spice factory workers

The respiratory consequences of working in the spice industry were studied in 92 female spice factory workers (mean age, 36 yr; mean exposure, 12 yr). A control group of 104 female workers employed in a nondusty industry was also studied. The prevalence of chronic respiratory symptoms was significantly higher in the exposed than in the control group. In particular, the prevalence of dyspnea (57.6%), chronic cough (22.8%), chronic phlegm and chronic bronchitis (19.6%), nasal catarrh (37.0%), and sinusitis (22.2%) was high when compared to controls (p less than .01). Among spice factory workers, a high prevalence of acute symptoms during the workshift was recorded. Acute reductions in lung function were statistically significant over the workshift for forced vital capacity (FVC), -2.0%; forced expiratory volume in one second (FEV1.0), -3.0%; and for maximum expiratory flow rates at 50% (FEF50), -8.3% and at 25% (FEF25), -15.2% measured on maximum expiratory flow-volume (MEFV) curves. No difference was found in across-shift ventilatory function in workers with or without chronic respiratory symptoms, except for FEF25 (with symptoms, 16.7%; without symptoms, 9.6%). Preshift administration of 40 mg of disodium cromoglycate (DSC) inhaled 15 min before the workshift significantly diminished acute reductions in FEF50 and FEF25 in exposed workers. Monday preshift FEF50 and FEF25 in exposed workers were significantly lower than in control workers (p less than .01), which suggests an early irreversible component to this illness.     

Chronic and acute respiratory effects among grain mill workers

Exposure to flour dust may induce chronic respiratory manifestations as well as acute ventilatory effects. We compared the prevalence of respiratory symptoms, ventilatory impairment, and variations in pulmonary function over the workshift in a group of mill workers exposed to wheat flour and in referent workers. One hundred and forty-two men exposed to flour in a mill and 37 referent workers were included in this study. Each subject completed a standardized questionnaire. Pulmonary function tests were performed before and after the workshift. The assessment of environmental exposure to flour showed high concentrations during some jobs with a high percentage of inhalable particles and a low concentration of respirable particles. The exposed workers had a significantly higher prevalence of usual cough and usual phlegm than the referents. The prevalence of asthma, based on the questionnaire, was similar. Before the workshift, the exposed workers had significantly lower mean lung function values for peak flow rate and forced expiratory flow rate at 75% of the vital capacity than the referents. After the workshift, all the lung function values showed a slight decrease, significant for forced vital capacity and forced expiratory volume during 1 s in both groups. Among the exposed workers, the asthmatic subjects had a significantly higher decrease across the shift than the nonasthmatic workers. This result is probably linked to bronchial hyperreactivity. Among nonasthmatic subjects, the decrease was larger in nonexposed workers than in exposed workers. A higher prevalence of respiratory symptoms and lower pulmonary function values were observed among mill workers by comparison with referents. Moreover, the data suggest that asthmatic status and the time of spirometric measurements need to be taken into account in epidemiological studies on exposure to airborne allergens. In addition, the study does not exclude a healthy worker effect with selection of dust-resistant subjects or better identification of asthmatic subjects among the workers exposed to an allergenic substance than among the nonexposed workers.     

Effect of hard metal dust on ventilatory function

The effect of hard metal dust generated in shaping on ventilatory function has been studied, in particular, the relation between levels of exposure to cobalt and changes in ventilatory function. In 15 healthy young men a significant decrease in FVC occurred after a six hour exposure to hard metal dust containing cobalt at a mean concentration of 38 micrograms/m3 (range 14-76 micrograms/m3). No dose-effect relation could be discerned between the decrease in FVC and the hard metal concentration or the cobalt concentration. All the subjects complained of irritation of the airways. On the other hand, in 42 shaping workers exposed to cobalt at an average concentration of 85 micrograms/m3 no significant decreases in ventilatory function were detected after seven hour exposures to hard metal, although in 42 shapers, who had been exposed to cobalt at a mean concentration of 126 micrograms/m3, the FEV1% was significantly decreased compared with matched controls. This finding suggests that hard metal dust containing cobalt at a mean concentration of 126 micrograms/m3 causes chronic bronchial obstruction.     

Effect of hard metal dust on ventilatory function.

The effect of hard metal dust generated in shaping on ventilatory function has been studied, in particular, the relation between levels of exposure to cobalt and changes in ventilatory function. In 15 healthy young men a significant decrease in FVC occurred after a six hour exposure to hard metal dust containing cobalt at a mean concentration of 38 micrograms/m3 (range 14-76 micrograms/m3). No dose-effect relation could be discerned between the decrease in FVC and the hard metal concentration or the cobalt concentration. All the subjects complained of irritation of the airways. On the other hand, in 42 shaping workers exposed to cobalt at an average concentration of 85 micrograms/m3 no significant decreases in ventilatory function were detected after seven hour exposures to hard metal, although in 42 shapers, who had been exposed to cobalt at a mean concentration of 126 micrograms/m3, the FEV1% was significantly decreased compared with matched controls. This finding suggests that hard metal dust containing cobalt at a mean concentration of 126 micrograms/m3 causes chronic bronchial obstruction.     

Respiratory symptoms and lung function in wool textile workers

Our study investigated a group of 216 wool textile workers (158 women and 58 men). Respiratory symptoms were assessed by questionnaire in wool textile workers and in 130 not exposed (control) workers. Ventilatory capacity was measured in wool workers by recording maximum expiratory flow-volume (MEFV) curves on Monday before and after the work shift. Forced vital capacity (FVC), 1-second forced expiratory volume (FEV₁), and flow rates at 50% and the last 25% of the vital capacity (FEF₅₀, FEF₂₅) were measured on the MEFV curves. Analysis of the data demonstrated a significantly higher prevalence of all chronic respiratory symptoms in wool workers than in controls. being the highest in wool workers for nasal catarrh (M: 63.8%; F: 44.9%) and for sinusitis (M: 62.1%; F: 43.0%). A high prevalence of acute symptoms, associated with the work shift, was also noted in wool workers. Exposure to wool dust caused significant across-shift reductions of ventilatory capacity varying from 1.4% for FEV, to 9.1% for FEF₅₀. Textile workers exposed to wool for > 10 years in the workplace had similar across-shift reductions of ventilatory capacity tests as those with shorter exposures. In a large number of these wool workers, FEF₅₀ and FEF₂₅ were below 70% of predicted normal values. Smokers had acute and chronic lung function changes similar to those of nonsmokers, indicating that smoking did not account for all the respiratory effects seen in wool processing workers. Our data suggest that dust exposures in wool textile mills may be associated with the development of chronic respiratory symptoms and impaired lung function.     

Lung function in workers exposed to polyvinyl chloride dust.

Several reported studies on the effects of polyvinyl chloride (PVC) dust in animals and man have been conflicting. The present study of the ventilatory function of 509 male workers exposed to PVC dust was made in 1977. Altogether 104 men exposed to PVC dust only, 112 men exposed to non-chlorinated solvents only, and 293 men exposed to a mixture of both completed the MRC questionnaire on respiratory function and performed simple spirometric tests (forced expiratory volume in one second and forced vital capacity). No differences were found between the three groups after allowance was made for age, height, and smoking. When exposure and smoking effects were considered separately, the latter was shown to be the dominant cause of reduced lung function. In this study work with PVC dust has not produced deleterious effects on ventilatory function.     

A follow-up study of respiratory function in workers exposed to acid aerosols in a food-processing industry

A follow-up investigation was performed on 49 female workers studied 2 years earlier in a vegetable-pickling plant. Acute and chronic respiratory symptoms and ventilatory capacity measurements were recorded during the original and the follow-up studies. Maximal expiratory flow-volume (MEFV) curves were recorded during the Monday morning work shift. The forced vital capacity (FVC), 1-s forced expiratory volume (FEV1), and flow rates at 50% and the last 25% of the FVC (FEF50, FEF25) were measured. There were small increases in the prevalence of chronic symptoms between the two studies for both smokers and nonsmokers, but these did not reach statistical significance. Five workers at the time of the initial study had a diagnosis of occupational asthma; only one of these was still working at the time of follow-up. Workers lost to the follow-up had lower lung function than those seen at follow-up. In workers who were followed, larger than expected mean annual declines were noted for all ventilatory capacity parameters in both smokers (FVC 0.070 l, FEV1 0.070 l; FEF50 0.355 l/s, FEF25 0.270 l/s) and nonsmokers (FVC 0.045 l, FEV1 0.045 l, FEF50 0.285 l/s; FEF25 0.130 l/s). The decrease was particularly pronounced for FEF50 and FEF25. The accelerated decline in ventilatory capacity tests noted in the female nonsmokers suggests an independent effect on lung function of work exposure in this environment. Our data confirm that work in the pickling industry, particularly in small, poorly regulated plants, has deleterious effects on respiratory function. Received: 24 September 1996 / Accepted: 19 June 1997     

Lack of combined effects of exposure and smoking on respiratory health in aluminium potroom workers

OBJECTIVE: To investigate the combined influence on respiratory health of smoking and exposure in an aluminium potroom. METHODS: In a cross sectional study of 75 potroom workers (23 never smokers, 38 current smokers, 14 ex-smokers) and 56 controls in the same plant (watchmen, craftsmen, office workers, laboratory employees; 18 non-smokers, 21 current smokers, 17 ex-smokers), prevalences of respiratory symptoms and spirometric indices were compared. RESULTS: Smokers in the potroom group had a lower prevalence of respiratory symptoms than never smokers or ex-smokers, which was significant for wheezing (2.6% v 17.4% and 28.6% respectively, both p < 0.01), whereas respiratory symptoms in controls tended to be highest in smokers (NS). No effects of potroom work on the prevalence of respiratory symptoms could be detected. In potroom workers, impairment of lung function due to occupational exposure was found only in non-smokers, with lower results for forced vital capacity (FVC) (98.8% predicted), forced expiratory volume in one second (FEV1) (96.1% predicted) and peak expiratory flow (PEF) (80.2% predicted) compared with controls (114.2, 109.9, and 105.9% predicted; each p < 0.001). Conversely, effects of smoking on lung function were only detectable in non-exposed controls (current smokers v non-smokers: FVC 98.8% v 114.2% predicted; p < 0.01; FEV1 95.5 v 109.9% predicted; p < 0.05). CONCLUSIONS: In a cross sectional survey such as this, the effects of both smoking and occupational exposure on respiratory health may be masked in subjects with both risk factors. This is probably due to strong selection processes which result in least susceptible subjects continuing to smoke and working in an atmosphere with respiratory irritants.

 

     

Epidemiological Survey of Workers Exposed to Cadmium

Pulmonary ventilatory function and various biological indices have been investigated in three groups of workers exposed to cadmium dust (women with less than 20 years’ exposure [E1], men with less than 20 years’ exposure [E2], and men with more than 20 years’ exposure [E3]) and in three matched control groups. The current airborne Cd dust concentration in the workrooms was below the actual American threshold limit value (200μg/cu m). A slight but significant reduction in forced vital capacity, in forced expiratory volume in one second, and in peak expiratory flow rate was found in E3 workers. Kidney damage was more prevalent than pulmonary ventilatory changes, since excessive proteinuria was observed in 15% of E2 workers and in 68% of E3 workers. The electrophoretic pattern of the urinary proteins suggests that the lesion is first glomerular and later becomes predominantly tubular (mixed proteinuria).     

Respiratory symptoms and ventilatory function in workers exposed to portland cement dust

The healthy worker effect and incomplete exposure information have been problems in former studies regarding the association between exposure to Portland cement dust and respiratory effects. We included former workers and made an individual estimation of particle exposure to reduce the selection bias in this controlled cross-sectional study on the effects of cement dust exposure on respiratory symptoms and ventilatory function in long-term exposed Norwegian cement plant workers. A total of 119 workers from the largest cement plant in Norway and 50 workers from a nearby control plant, born 1918 to 1938, performed spirometry and gave information on respiratory symptoms in 1998 and 1999. The prevalence of symptoms and mean pulmonary function indices were similar for exposed workers and controls. There was no dose-response-related increase in symptoms or decrease in lung function indices. The estimated power to detect a true difference between forced expiratory volume in one second (FEV1) in the two groups of 0.3l was 0.90, assuming 95% significance level. The prevalence of chronic obstructive pulmonary disease was 14.3% in the exposed group and 14.0% among the controls. These findings do not support the hypothesis that cement dust exposure has a negative impact on lung function or gives an increase in respiratory symptoms.     

Lung function in retired coke oven plant workers.

Lung function was studied in 354 coke oven plant workers in the Lorraine collieries (Houillères du Bassin de Lorraine, France) who retired between 1963 and 1982 and were still alive on 1 January 1988. A spirometric examination was performed on 68.4% of them in the occupational health service. Occupational exposure to respiratory hazards throughout their career was retraced for each subject. No adverse effect of occupational exposure on ventilatory function was found. Ventilatory function was, however negatively linked with smoking and with the presence of a respiratory symptom or discrete abnormalities visible on pulmonary x ray films. The functional values were mostly slightly lower than predicted values and the most reduced index was the mean expiratory flow, FEF25-75%. The decrease in forced expiratory volume in one second (FEV1) was often parallel to that in forced vital capacity (FVC), but it was more pronounced for subjects who had worked underground, for smokers of more than 30 pack-years, and for subjects having a respiratory symptom. Pulmonary function indices were probably overestimated because of the exclusion of deceased subjects and the bias of the participants.     

Exposure to hydrogen sulphide and respiratory function.

A study was carried out to assess possible effects of low concentrations of hydrogen sulphide on respiratory function. The cohort comprised 26 male pulp mill workers (mean age 40.3, range 22-60 years) with a daily exposure to hydrogen sulphide in the workplace, and 10 volunteers, who had asthma (three men, mean age 40.7, range 33 to 50 years, and seven women, mean age 44.1, range 31 to 61 years). The respiratory function of the pulp mill workers was monitored by measuring forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and bronchial responsiveness after at least one day off work and at the end of a workday. Bronchial responsiveness was tested by challenge with histamine. The 10 asthmatic subjects were exposed in laboratory conditions to 2 ppm of hydrogen sulphide for 30 minutes in an exposure chamber. Airway resistance (Raw) and specific airway conductance (SGaw) were assessed by a body plethysmograph, and the ventilatory capacities were measured with a flow volume spirometer. No significant changes in respiratory function or bronchial responsiveness related to exposure to hydrogen sulphide in the pulp mill workers were found. In the asthmatic subjects, Raw was increased by 26.3% and SGaw was decreased by 8.4% on average after exposure to hydrogen sulphide. These changes were not statistically significant. In two subjects, however, changes were greater than 30% in both Raw and SGaw, indicating bronchial obstruction. It is concluded that exposure for a relatively short time to hydrogen sulphide concentrations appreciably higher than those existing in ambient air do not cause noticeable effects on respiratory function.     

Exposure to hydrogen sulphide and respiratory function

A study was carried out to assess possible effects of low concentrations of hydrogen sulphide on respiratory function. The cohort comprised 26 male pulp mill workers (mean age 40.3, range 22-60 years) with a daily exposure to hydrogen sulphide in the workplace, and 10 volunteers, who had asthma (three men, mean age 40.7, range 33 to 50 years, and seven women, mean age 44.1, range 31 to 61 years). The respiratory function of the pulp mill workers was monitored by measuring forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and bronchial responsiveness after at least one day off work and at the end of a workday. Bronchial responsiveness was tested by challenge with histamine. The 10 asthmatic subjects were exposed in laboratory conditions to 2 ppm of hydrogen sulphide for 30 minutes in an exposure chamber. Airway resistance (Raw) and specific airway conductance (SGaw) were assessed by a body plethysmograph, and the ventilatory capacities were measured with a flow volume spirometer. No significant changes in respiratory function or bronchial responsiveness related to exposure to hydrogen sulphide in the pulp mill workers were found. In the asthmatic subjects, Raw was increased by 26.3% and SGaw was decreased by 8.4% on average after exposure to hydrogen sulphide. These changes were not statistically significant. In two subjects, however, changes were greater than 30% in both Raw and SGaw, indicating bronchial obstruction. It is concluded that exposure for a relatively short time to hydrogen sulphide concentrations appreciably higher than those existing in ambient air do not cause noticeable effects on respiratory function.     

Respiratory symptoms in fish processing workers on the Adriatic coast of Croatia

This article describes respiratory symptoms and lung function in 98 fish processing female workers employed in a fish processing plant located on the Croatian Adriatic coast and 95 matching controls. The study included chronic and acute respiratory symptoms which developed during the shifts. Lung function measurements included forced vital capacity (FVC), one-second forced expiratory volume (FEV(1)) and maximal expiratory rates at 50 % and the last 25 % (FEF(50), FEF(25)). Chronic respiratory symptoms were significantly dominant in fish processing workers compared to controls. The most common chronic symptoms were hoarseness (57.1 %), nasal catarrh (51.0 %), chronic cough (42.9 %), chronic phlegm (34.7 %), and frequent chest cold (35.7 %). Exposed smokers and nonsmokers had a similar prevalence of chronic respiratory symptoms. Acute symptoms over the work shift were high, with headache in lead (smokers: 62.5 %; nonsmokers: 56.1 %). Most of the ventilatory capacity parameters were significantly lower than predicted, FEF(25) in particular, indicating obstructive changes predominantly in the smaller airways. These findings suggest that fish processing workers are prone to developing acute and chronic respiratory symptoms as well as to lung function changes. This calls for medical and technical preventive measures to be introduced in the work environment of the fish processing plant.     

Respiratory symptoms and ventilatory capacity in soy bean workers

Respiratory function was studied in a group of 29 soy workers exposed to soy bean dust produced after extraction of soy oil. The prevalence of all chronic respiratory symptoms was consistently higher in exposed than in control workers, although the differences were not statistically significant. During the Monday work shift there was a significant mean acute across-shift decrease in maximum expiratory flow rates at 50% and 25% vital capacity (FEF50: -6.4%; FEF25: -12.4%). Changes in vital capacity (FVC: -3.6%) and 1-sec forced expiratory volume (FEV1: -2.7%) were smaller, but still statistically significant. There were also statistically significant acute reductions in all ventilatory capacity parameters over the work shift on the following Friday, although the changes were in general smaller than on Monday (except for FEV1). An analysis of Monday preshift values of ventilatory capacity in soy bean workers suggests that exposure to soy bean dust may lead to chronic respiratory impairment in some workers.     

Follow-up study of respiratory function in Hemp workers

A 3-year follow-up study was performed on 38 women and 28 men from the originally studied textile workers employed in a soft hemp processing mill. Acute and chronic respiratory symptoms and ventilatory capacity were recorded during the cross-sectional and the follow-up studies. Maximum expiratory flow-volume (MEFV) curves were obtained on these workers, and forced vital capacity (FVC), 1-second forced expiratory volume (FEV₁) and flow rates at 50% and at 25% of the VC (FEF₅₀, FEF₂₅) were measured. High prevalences of acute and chronic respiratory symptoms persisted at the follow-up study. In particular, high prevalences of byssinosis were documented at both studies (women: 47.4% and 47.4%; men: 64.3% and 67.9%, respectively). Statistically significant mean across-shift reductions were recorded for all ventilatory capacity tests at the initial study. A large mean annual decline was calculated for FEV₁ in women and for all ventilatory capacity parameters in men; these declines were greater for workers with symptoms of byssinosis than for those without. The accelerated decline in FEV₁ noted in the women workers, who were predominantly nonsmokers, suggests an independent hemp effect. Exposures in the work environment were measured with Hexhlet filters and revealed very high dust concentrations (mean total: 21.4 mg/m³, 22.4 mg/m³; respirable: 8.4 mg/m³, 9.9 mg/m³) at both initial and follow-up studies. These levels are much higher than those found in mills processing organic materials in North America. Our data demonstrate that work in the hemp industry, particularly in small poorly regulated mills, continues to have deleterious effects on respiratory function.