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.

 

     

Effects of asbestos-related pleural disease on pulmonary function

The relationship between loss of pulmonary function and the presence of asbestos-related pleural disease was evaluated for 913 Minnesota asbestos workers. Asbestos-related pleural disease was categorized as circumscribed plaques or diffuse thickening. Compared with workers with normal pleura, workers with plaques had a decreased mean percentage for predicted forced vital capacity (FVC) and predicted forced expiratory volume in 1 s (FEV1.0). Diffuse thickening was associated with more profound decreases in FVC and FEV1.0. No relationship was seen between FEV % [(100 x FEV1.0)/FVC)] and either type of pleural disease. Dyspnea was associated with diffuse thickening more so than plaques. These results remained after control for pack-years of smoking, extent of parenchymal disease, and the presence of pulmonary disease history. Pleural plaques and diffuse pleural thickening were considered independent risk factors for the loss of lung function.     

Airway hyperresponsiveness, prevalence of chronic respiratory symptoms, and lung function in workers exposed to irritants.

The association between occupational exposure to airway irritants and the prevalence of chronic respiratory symptoms and level of lung function, and whether these associations were modified by airway hyperresponsiveness, smoking, and a history of allergy were studied in 668 workers from synthetic fibre plants. Respiratory symptoms were recorded with a self administered Dutch version of the British Medical Research Council questionnaire, with additional questions on allergy. Airway responsiveness was measured by a 30 second tidal breathing histamine challenge test. On the basis of job titles and working department, the current state of exposure of all workers was characterised as (1) no exposure, reference group; (2) white collar workers; (3) SO2 HCl, SO4(2); (4) polyester vapour; (5) oil mist and vapour; (6) polyamide and polyester vapour; (7) multiple exposure. Workers exposed to airway irritants were not simultaneously exposed to airborne dust. Airway hyperresponsiveness (AHR), defined as a 20% fall in forced expiratory volume in one second (FEV1) at < or = 32 mg/ml histamine, was present in 23% of the subjects. The association between exposure groups and prevalence of symptoms was estimated by means of multiple logistic regression; the association with level of lung function (forced vital capacity (FVC), FEV1, maximum mid-expiratory flow rate (MMEF)) was estimated by means of multiple linear regression. Both methods allow simultaneous adjustment for potential confounding factors. The exposure groups were associated with a higher prevalence of chronic respiratory symptoms. Lower prevalence of symptoms was found for workers exposed to SO2, HCl, and SO4(2-), most likely due to pre-employment selection procedures. Current smoking, AHR, and a history of allergy were significantly associated with a higher prevalence of chronic respiratory symptoms, independent of each other, and independent of irritant exposure. The association between exposure and prevalence of symptoms was greater in smokers than in ex-smokers and non-smokers. This difference was most clearly seen in the polyester vapour and polyamide and polyester vapour group. No modification of the association between exposure groups and prevalence of symptoms by airway hyperresponsiveness could be shown. The exposure groups were not significantly associated with a lower level of lung function. Adjustment for chronic respiratory symptoms did not change the results. There were no indications of a possible interaction between exposure and AHR, current smoking, or a history of allergy on lung function. Workers of the polyester vapour and the oil mist and vapour group with >10 years of exposure had a lower FEV1 (beta = -295 and -358 ml) and significantly lower MMEF (beta = -1080 and -1247 ml/s; p < 0.05) than the reference group. The number of workers of both group were, however, small (n = 10 and n = 13 respectively). More investigations between low level exposure to irritant and respiratory health.     

Abnormal pulmonary function associated with diaphragmatic pleural plaques due to exposure to asbestos

Pulmonary function was measured in 79 men with diaphragmatic pleural plaques (DPP) as the only abnormality characteristic of asbestos disease on chest radiographs. They were selected from 4572 construction and shipyard workers exposed to asbestos. Abnormalities of pulmonary function in 21 non-smokers and 43 current smokers were compared with referent values adjusted for height, age, and duration of cigarette smoking. In the non-smokers, flows (FEV1) FEF75-85 and FEV1/FVC) were reduced and TGV and RV/TGV were raised. Current smokers had similar significant reductions. Thus by contrast with some current opinion that plaques are "an index only of past asbestos exposure," workers with plaques, even limited to the diaphragm, have functional impairment typical of pulmonary asbestosis. This suggests that they have pulmonary asbestosis, which is below the threshold of radiographic recognition.     

Abnormal pulmonary function associated with diaphragmatic pleural plaques due to exposure to asbestos.

Pulmonary function was measured in 79 men with diaphragmatic pleural plaques (DPP) as the only abnormality characteristic of asbestos disease on chest radiographs. They were selected from 4572 construction and shipyard workers exposed to asbestos. Abnormalities of pulmonary function in 21 non-smokers and 43 current smokers were compared with referent values adjusted for height, age, and duration of cigarette smoking. In the non-smokers, flows (FEV1) FEF75-85 and FEV1/FVC) were reduced and TGV and RV/TGV were raised. Current smokers had similar significant reductions. Thus by contrast with some current opinion that plaques are "an index only of past asbestos exposure," workers with plaques, even limited to the diaphragm, have functional impairment typical of pulmonary asbestosis. This suggests that they have pulmonary asbestosis, which is below the threshold of radiographic recognition.     

Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study

The prevalence of respiratory symptoms and lung function impairment was studied in a sample of men from a population screening of asbestos-related disorders. When the rates were adjusted for age and smoking habits, 83 subjects with lung fibrosis had an increased prevalence of respiratory symptoms, in particular, phlegm when coughing and breathlessness grades 1-3. Among 200 subjects under 70 years of age who had pleural plaques only, a statistically significant increase was observed in the prevalence of breathlessness grade 1 compared to an external reference population. Among 98 asbestos-exposed subjects who had normal chest X-rays, there was an increase in the prevalence of breathlessness grade 2, cough during the day, and phlegm when coughing. There was a higher proportion of subjects with lung fibrosis who were below 80% of the predicted values for forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) than in the other groups. There was also a higher proportion of subjects with pleural plaques only who were below 90% of the predicted value for FVC than in a group of 90 subjects without asbestos exposure. In accordance with previous studies, these results indicate that pleural plaques in asbestos workers may be of greater importance as a clinical feature than has been recognized in the past.     

An 11-year longitudinal study of the occupational dust exposure and lung function of polyvinyl chloride, cement and asbestos cement factory workers

Standardized questionnaires and lung function tests were administered in 1973, 1980, and 1984 to 126 workers occupationally exposed to polyvinyl chloride (PVC) dust, to cement dust, or to asbestos cement dust until 1974-1978 and to PVC thereafter. The workers in the last group were assigned to two asbestos exposure categories (heavy and slight). The decline in forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1.0) was analyzed with regard to the length of time since the data of first employment. After adjustment for age, height, and smoking status at the date of first employment, the decline in FVC and FEV1.0 among the nonsmokers-light smokers was slightly accelerated with length of employment in the PVC and slight asbestos exposure groups and markedly accelerated with time since first employment in the heavy asbestos exposure group. The heavy smokers in all the exposure groups had FVC and FEV1.0 predicted values that were lower than those of the nonsmokers-light smokers; these differences remained constant with length of employment. Cessation of asbestos exposure for about 10 years did not seem to change lung function decline.     

Relation of spirometric function to radiographic interstitial fibrosis in two large workforces exposed to asbestos: an evaluation of the ILO profusion score.

OBJECTIVES: To analyse quantitatively the relations of spirometric lung function (forced vital capacity (FVC)) to radiographic interstitial pulmonary fibrosis (assessed by the International Labour Organisation (ILO) profusion score of small irregular opacities) in two large workforces exposed to different intensities of asbestos. These analyses consider the question whether a similar profusion score n differently exposed workers is associated with a similar effect on lung function. METHODS: Surveys of two workforces, insulators (n = 2611) and sheet metal workers (n = 1245), by the same investigators allowed comparison of the effects of the two levels of exposure to asbestos. The two groups were of similar age and had similar percentages of non-smokers and smokers. All radiographs were read by the same expert reader. RESULTS: Consistent with their less continuous and less intense exposure to asbestos, metal workers had: (a) far less frequent radiographic asbestosis (profusion score > or = 1/0, 17.5% v 59.6% for insulators): (b) less severe radiographic asbestosis (only 1.1% had scores > or = 2/1 v 13.3% of insulators); (c) a similar slope to that seen in insulators for the relation between FVC and profusion score when pleural thickening was absent; (d) less frequent pleural fibrosis (36% v 75%); and (e) less frequent restrictive impairment (23% v 33%). In both insulators and metal workers, lung function was below normal even when lung fields were normal, FVG fell with increasing profusion, it was lower in smokers and in those with pleural thickening at comparable profusion scores, and these was no difference in FVC between scores 0/1 and 1/0. CONCLUSION: The decrease in FVC with increasing profusion score in both workforces as well as the similar slopes for the relation between FVG and profusion score and the similar FVG at similar scores in the absence of pleural thickening confirm the ILO profusion score as an acceptable assessment of pulmonary fibrosis.     

Lung function among asbestos cement factory workers: cross-sectional and longitudinal study

Ventilatory capacity tests and standardized respiratory questionnaires were used in 1973 and in 1980 to measure the effect of mixed dust exposure in the asbestos cement industry on respiratory symptoms and lung function in 65 exposed workers and 30 controls (exposed to polyvinyl chloride but not to asbestos). Workers exposed to asbestos had 1) a higher prevalence of breathlessness and chest pain, and a higher incidence of breathlessness; 2) lower 1980 values of forced vital capacity (FVC) (0.27-0.83 liters) and forced expiratory volume in 1 sec (FEV1) (0.23-0.62 liters); and 3) a faster decline (nearly 40 ml/year) in FVC and FEV1 between 1973 and 1980. The FVC annual decrease was 52.5 ml in the subjects with more than 15 years since first asbestos exposure, whereas it was 24.3 ml in those with less than 15 years, suggesting a faster decline after 15 years of exposure. The effect of asbestos exposure and smoking habits was less than additive as regards pulmonary function.     

Respiratory findings among ironworkers: results from a clinical survey in the New York metropolitan area and identification of health hazards from asbestos in place at work.

Diseases associated with asbestos are prevalent in the construction trades primarily as the result of the previously widespread use of insulation materials containing asbestos in the building industry. Workers in metal related trades, who are employed at construction sites, but who do not routinely use such materials in their work, may also be at risk for asbestos hazards. To assess such risk, a clinical survey was conducted on 869 ironworkers from the New York metropolitan area. A high prevalence of abnormalities on chest radiographs was found. Three hundred and twenty nine (38%) of the examined workers had pleural abnormalities on their chest radiographs consistent with asbestos induced effects. The prevalence of radiographic abnormalities indicating interstitial lung disease was low (7%) as was the prevalence of restrictive pulmonary function impairment (7%). Association was found between forced vital capacity (FVC) and pleural abnormalities on chest radiographs. Although ex-smokers appeared to have the highest prevalence of abnormalities, regression analyses showed that duration of employment in the ironworkers' trade was the most important factor associated with them.     

Respiratory findings among ironworkers: results from a clinical survey in the New York metropolitan area and identification of health hazards from asbestos in place at work

Diseases associated with asbestos are prevalent in the construction trades primarily as the result of the previously widespread use of insulation materials containing asbestos in the building industry. Workers in metal related trades, who are employed at construction sites, but who do not routinely use such materials in their work, may also be at risk for asbestos hazards. To assess such risk, a clinical survey was conducted on 869 ironworkers from the New York metropolitan area. A high prevalence of abnormalities on chest radiographs was found. Three hundred and twenty nine (38%) of the examined workers had pleural abnormalities on their chest radiographs consistent with asbestos induced effects. The prevalence of radiographic abnormalities indicating interstitial lung disease was low (7%) as was the prevalence of restrictive pulmonary function impairment (7%). Association was found between forced vital capacity (FVC) and pleural abnormalities on chest radiographs. Although ex-smokers appeared to have the highest prevalence of abnormalities, regression analyses showed that duration of employment in the ironworkers' trade was the most important factor associated with them.     

High prevalence of reversible airway obstruction in asbestos-exposed workers

In this retrospective study of 97 male workers exposed to asbestos for 2-50 yr, data were collected on chest x-ray findings and lung function, including lung volumes, forced expiratory flow rates (i.e., forced expiratory volume in 1 sec [FEV1.0], forced expiratory flow measured between 25% and 75% of forced vital capacity [FEF(25-75%)]), airway resistance (R(aw)), carbon monoxide (CO)-diffusing capacity, and the existence of airway obstruction reversible by a beta-adrenergic agonist (RAO). The authors performed multiple-regression analyses to correlate the variations in lung function data with age, smoking habits, duration of asbestos exposure, and time since last exposure. Occupational activities of subjects that might induce specific lung abnormalities were also considered. No significant decrease was seen in lung volumes or CO-diffusing capacity; however, a decrease in FEV1.0 and an increase in R(aw) were measured in 65% of the subjects, and an isolated decrease in FEF(25-75%) occurred in only 18%. There was no difference in lung-function data between subjects who had chest x-ray signs of abnormalities (n = 59) and those who did not (n = 38). A significant relationship was found between the decrease in FEV1.0 and age; however, no correlation was noted between altered lung function and cigarette smoking, duration of asbestos exposure, or time since last exposure. RAO prevalence was higher (34%) than previously reported (9%) in subjects with chronic obstructive pulmonary disease (COPD) who were not exposed to asbestos or outdoor pollution. The RAO prevalence in asbestos-exposed workers was nearly the same as that measured in COPD subjects who lived downtown and who were exposed to outdoor pollution (36%). The high RAO prevalence in asbestos-exposed workers was found in 43% of subjects who were exposed only to asbestos, and in 33% of subjects who were also exposed to air pollution due to their occupational activities. It is hoped that the observations in this study will encourage practitioners to check for RAO in asbestos workers who use inhaled bronchodilators.     

A follow-up study of lung function among ex-asbestos workers with and without pleural plaques

BACKGROUND: Pulmonary function testing is widely accepted as an integral part of medical surveillance of occupational lung diseases. There are several cross-sectional studies evaluating lung function among asbestos-exposed workers, but only few longitudinal surveys have been performed. OBJECTIVES: To evaluate, over a mean follow-up period of 3.7 (SD 1.8) years, the loss of lung function in a group of 103 workers with previous exposure to asbestos (mainly ship building/repairing), according to the presence or absence of pleural plaques at radiological examination. METHODS: Chest radiographic examination was used to ascertain the presence/absence of pleural plaques. If chest X-ray films were positive for pleural plaques, HRCT (High Resolution Computed Tomography) was used to exclude any parenchymal disease. The assessment of lung function over time included repeated measurement of vital capacity (VC), forced expiratory volume in one second (FEV1) and total lung capacity (TLC). Smoking was assessed in terms of pack-years. A Generalized Estimating Equations (GEE) approach to repeated spirometric measurement was used to investigate the relationship between the loss of pulmonary function and (i) presence/absence of pleural plaques, (ii) smoking status, and (iii) work seniority in workplaces with exposure to asbestos. RESULTS: In the ex-asbestos workers, mean age at the first examination was 49 (SD 6) years and work seniority averaged 25 (SD 7) years; 36% were non-smokers, 27% smoked < 15 pack-years, and 37% smoked > or = 15 pack-years. Thirty-six workers showed pleural plaques at radiological examination. Overall, 236 measurements of VC and FEV1, and 234 determinations of TLC were available. Multivariate GEE approach to age- and height-adjusted spirometric data showed that pleural plaques were not associated with a significant loss of pulmonary function during the follow-up. When compared with non-smokers, heavy smokers (> or = 15 pack-years) showed on average a significant loss of VC (-5.3%, IC 95%: -9.4 - -1.2%), FEV1 (-8.4%, IC 95%: -13.2 - -3.5%), and TLC (-4.0%, IC 95%: -7.4 - -0.5%). An occupational history of previous exposure to asbestos was significantly associated with an 10-year decrease in VC (-3.1%, IC 95%: -5.9 - -0.3%) and FEV1 (-4.9%, IC 95%: -8.3 - -1.5%). CONCLUSIONS: The results of this follow-up study showed that smoking and previous asbestos exposure were associated with a mild, but statistically significant, loss of lung function. Radiological findings of pleural plaques were not related to deterioration of lung function over the follow-up period.     

胸膜增厚对石棉工人肺功能的影响

[目的]探讨胸膜增厚对石棉工人肺功能的影响。[方法]接触组为某温石棉厂134名男性工人，对照组为同一地区不接触粉尘、劳动强度与接触组大体相似的某仪表厂135名男性工人。对两组对象的肺功能测定和后前位X射线胸片检查结果进行对比分析。[结果]与对照组相比，在控制了肺内小阴影改变和累积吸烟量等混杂因素的影响后，石棉接触工人中胸膜正常细和双侧胸膜增厚组用力肺活量（FVC）和一秒钟用力呼气容积（FEV1）均显著下降（P〈0．05），单侧胸膜增厚组仅FVC显著下降（P〈0．05）；而与胸膜正常组相比，在控制了肺内小阴影改变、累积吸烟量和接尘年限等混杂因素的影响后，双侧胸膜增厚组FVC和FEV1显著下降（均为P〈0．05）；在控制了肺内小阴影改变、累积吸烟量和接尘年限等混杂因素的影响后，胸膜增厚范围与FVC呈负相关，与弥散系数（Kco）呈正相关（均为P〈0．05）。[结论]胸膜增厚范围越大，肺功能损害也越严重，呈限制性肺功能障碍的特征。     

Dynamics of the lung function in asbestos pleural disease

As a rule, asbestosis is a disease of workers who are occupationally exposed to inhalation of asbestos dust, leaving permanent alterations on the lung parenchyma or pleura. In our ten-year study, we investigated 318 workers with pleural asbestosis from whom we took medical history which included occupational exposure to asbestos, radiological examinations and lung function, which is mandatory for the diagnosis and the follow up of the disease. We analysed functional parameters such as forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1) and intermediate forced expiratory flow at 25% to 75% (FEF25%-75%). In addition, we investigated the predicted values of functional parameters according to smoking and non-smoking habits. We found a significant reduction in vital capacity, particularly in smokers after 25 years of exposure to asbestos. During the first 15 years, values of vital capacity on the group basis remained inside the 80% of the normal values and were not significant for assessing the dynamics of the lung function. To better assess the effects of occupational asbestos exposure, it is necessary to interpret lung function data not only on the group basis, but also for each subject individually.     

Predictors of spirometric test failure: a comparison of the 1983 and 1993 acceptability criteria from the European Community for Coal and Steel.

OBJECTIVES--To identify, in this general population study, predictors of spirometric test failure on the 1983 and 1993 acceptability criteria from the European Community for Coal and Steel (ECCS). METHODS--All men aged 30-46 years living in western Norway (n = 45,380) were invited to join a cross sectional community survey. Respiratory symptoms, smoking habits, and marital status were found from self administered questionnaires, and measurements of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were performed with dry wedge bellow spirometers. RESULTS--Altogether 29,611 subjects (65%) participated in this survey. Spirometric recordings were obtained in 26,803 of these (91%) of whom 1.6% failed the 1983 criterion (< or = 300 ml between the two highest FVC values) and 9.5% failed the 1993 criteria (< or = 5% or 100 ml between the two highest FEV1 and the two highest FVC values). Spirometric failures on both criteria were more prevalent in never smokers, single men, and subjects with respiratory symptoms than in ever smokers, married, and asymptomatic subjects. Failure of the 1993 criteria increased with age and declining height. Morning cough and phlegm, breathlessness uphill, attacks of breathlessness, and wheezing were related to failure of the 1993 criteria after adjustment for demographic variables and smoking, whereas only breathlessness uphill was related to failure of the 1983 criterion. CONCLUSIONS--In men aged 30-46 years, spirometric test failures on both the 1983 and 1993 ECCS acceptability criteria occurred more often in never smokers than in smokers and ex-smokers after adjustment for other covariables. Spirometric test failure with the 1993 criteria also varied with height and most respiratory symptoms. The higher failure rates found in non-smokers, in shorter, and in single men could be due to late compression of the airways, smaller lung volumes, and poor general health, respectively.     

Decreased lung function in long-term asbestos cement workers: a cross-sectional study

The effect on lung function of exposure in an asbestos cement plant was investigated in male workers, employed more than 10 years. The exposed group was selected to exclude subjects with pneumoconioses and ex-smokers and consisted of 77 smokers and 48 never-smokers. Referents were chosen from plants where asbestos had not been in use and restricted to those without X-ray signs of chest disease. The primary type of asbestos used was chrysotile and the general dust level in the two decades 1950-1970 seems to have been around 10 mg/m3 while the asbestos fiber concentration averaged 2 fibers/ml. The mean differences between exposed and referents were statistically significant for forced vital capacity and forced expiratory volume, -0.25 and -0.30 liters, respectively, after adjustment for age, height, tracheal area, and smoking category. No significant differences were detected between those with and without pleural plaques. Smokers and never-smokers were similarly affected. In conclusion, the group exposed to dust with comparatively low asbestos fiber concentration had a minor impairment of lung function, mainly due to obstructive changes.     

Study of smoking behavior in asbestos workers.

BACKGROUND: Asbestos exposure and concomitant cigarette smoking markedly increase the risk of lung cancer and contribute to the prevalence and severity of pulmonary interstitial fibrosis. METHODS: A cross-sectional survey of 214 asbestos workers was initiated to determine the prevalence of smoking and their readiness to quit smoking using the stage of change theory. RESULTS: The study was comprised of 61 never smokers (28.5%), 118 ex-smokers (55.1%), and 35 current smokers (16.4%). Reasons for smoking cessation in ex-smokers included perception of ill-health (51%) and knowledge of smoking-asbestos hazards (3.4%). Stage of change of current smokers revealed: precontemplation (26.5%), contemplation (35%), preparation (29%), and action (8.8%). Current smokers had the highest prevalence of small airway obstruction on spirometry. CONCLUSIONS: A detailed smoking history during medical surveillance activities will enable the occupational physician to identify asbestos workers who have difficulty quitting and to develop a system in which such individuals can be referred to comprehensive smoking cessation programs.     

Pulmonary function in long-term asbestos workers in China

The relationship of pulmonary function to exposure to asbestos and radiographic abnormalities has been controversial, especially when smoking is present as a confounder. The aim of the study was to provide further understanding on the radiographic-physiologic associations in nonsmoking and smoking asbestos workers. Radiographic asbestosis, pleural lesion, and pulmonary function were studied in 269 Chinese asbestos workers, with average exposure years of 23 for male workers and 18 for female workers. Their functional data were compared with those of 274 controls without exposure to dust. Although most of the male workers were smokers, none of the female workers smoked. In comparison with controls, asbestos workers had significantly lower lung volume and diffusing capacity, irrespective of gender. Female workers and smoking male workers had lower measurements of forced expiratory volume in 1 second and instantaneous forced expiratory flow at 50% and 25% of forced vital capacity. After adjustment for relevant covariates, asbestos exposure, asbestosis, and pleural abnormalities were associated with decreased parameters of pulmonary function, including lung volume, diffusing capacity, and airway flow. These data indicate that asbestos-related functional defects manifested by lung restriction and mild airway obstruction correlate with exposure to asbestos and with parenchymal and pleural abnormalities, independent of smoking.     

Decline in annual lung function in workers exposed to asbestos with and without pre-existing fibrotic changes on chest radiography.

OBJECTIVES--To examine whether or not workers with pre-existing mild pulmonary fibrosis have accelerated decline in forced expiratory volume in one second (FEV1) or forced vital capacity (FVC), under low level exposure to chrysotile asbestos. METHODS--All male workers in two asbestos manufacturing factories were followed up annually for six years to compare their declines in FEV1 and FVC. The values of FEV1 and FVC were divided by the square of the person's height to adjust for body size differences (FEV1/Ht2 and FVC/Ht2, respectively). Annual change was calculated for each subject as a slope of the simple linear regression with FEV1/Ht2 or FVC/Ht2 regressed according to age. Analysis was conducted on 242 middle aged workers who had normal routine spirometry values, normal chest radiographs or mild pneumoconiosis up to 1/2 grade, without changes either in smoking habit or severity of pneumoconiosis during the study period, and with acceptable spirograms in three or more surveys. The occupational environment, in terms of chrysotile asbestos, had been well controlled below the threshold limit value of Japan at that time--namely, 2 fibres/micromilligrams. RESULTS-There was no significant effect from the interaction between pre-existing mild pulmonary fibrosis and low level of exposure to chrysotile asbestos on the accelerated annual decline of FEV1/Ht2, or FVC/Ht2. Fibrosis significantly contributed to annual changes in FEV1/Ht2, even after adjustment for mean FEV1 and smoking. The point estimate of the contribution was - 4.9 ml/m2/y. No significant independent contribution of exposure was found in decline of either FEV1/Ht2 or FVC/Ht2. CONCLUSIONS--Pre-existing pulmonary fibrosis is an independent risk factor for accelerated annual decline of FEV1, even when mild and stable. Additional decline due to exposure to chrysotile asbestos is less probable if it is well controlled under the current threshold limit value.