Occupational exposures associated with severe exacerbation of asthma

BACKGROUND

The exacerbation of asthma by workplace conditions is common, but little is known about which agents pose a risk.

OBJECTIVE

We used data from an existing survey of adults with asthma to identify occupational exposures associated with severe exacerbation of asthma.

DESIGN

Questionnaires were completed by 557 working adults with asthma. Severe exacerbation of asthma in the past 12 months was defined as asthma-related hospitalization, or reports of both unplanned asthma care and treatment with a short course of oral corticosteroids. Occupational exposures for the same time period were assessed using an asthma-specific job exposure matrix. We modeled severe exacerbation to yield prevalence ratios (PRs) for exposures while controlling for potential confounders.

RESULTS

A total of 164 participants (29%) were positive for severe exacerbation, and 227 (40.8%) were assessed as being exposed to asthma agents at work. Elevated PRs were observed for several specific agents, notably the irritant subcategories of environmental tobacco smoke (PR 1.84, 95%CI 1.34-2.51) among all participants, inorganic dusts (PR 2.53, 95%CI 1.37-4.67) among men, and the low molecular weight subcategory of other highly reactive agents (PR 1.97, 95%CI 1.08-3.60) among women.

CONCLUSION

Among working adults with asthma, severe exacerbation was associated with several occupational agents.

The occupational contribution to severe exacerbation of asthma

The goal of this study was to identify occupational risk factors for severe exacerbation of asthma and estimate the extent to which occupation contributes to these events. The 966 participants were working adults with current asthma who participated in the follow-up phase of the European Community Respiratory Health Survey. Severe exacerbation of asthma was defined as self-reported unplanned care for asthma in the past 12 months. Occupations held in the same period were combined with a general population job-exposure matrix to assess occupational exposures. 74 participants reported having had at least one severe exacerbation event, for a 1-yr cumulative incidence of 7.7%. From regression models that controlled for confounders, the relative risk (RR) was statistically significant for low (RR 1.7, 95% CI 1.1-2.6) and high (RR 3.6, 95% CI 2.2-5.8) biological dust exposure, high mineral dust exposure (RR 1.8, 95% CI 1.02-3.2), and high gas and fumes exposure (RR 2.5, 95% CI 1.2-5.5). The summary category of high dust, gas, or fumes exposure had RR 3.1 (95% CI 1.9-5.1). Based on this RR, the population attributable risk was 14.7% among workers with current asthma. These results suggest occupation contributes to approximately one in seven cases of severe exacerbation of asthma in a working population, and various agents play a role.

Exposure to metalworking fluid aerosols and determinants of exposure

Metalworking fluid (MWF) aerosols are associated with respiratory disorders including asthma and hypersensitivity pneumonitis. The aims of this study were to describe exposure to inhalable MWF aerosols and volatile compounds in machine shops, to estimate the influence of important determinants of exposure and to compare different sampling techniques for MWF aerosols. Personal full-shift air samples of inhalable aerosol (PAS-6 sampler) and total aerosol (open-faced sampler) were collected on operators in five medium to big-sized machine shops in three companies. The filters were analysed gravimetrically and extracted by supercritical fluid extraction for MWF aerosol and triethanolamine content. In addition, personal measurements were taken for formaldehyde and volatile compounds on adsorbent samplers. Continuous dust measurements were performed with a real-time instrument (DataRAM) during 2 h periods, using 1-min average values. In total, 95 measurements of inhalable aerosol and extracted MWF aerosols on 51 operators were conducted. Within the companies, the average exposure to inhalable aerosol ranged from 0.19 to 0.25 mg m(-3) with geometric standard deviations from 1.56 to 1.79. On average, the extracted fraction of MWF aerosol was 67% of the inhalable aerosol concentration. The exposure levels of triethanolamine, formaldehyde and volatile compounds were generally low. About 45% of the between-worker variance could be explained by use of compressed air, lack of complete enclosure of machines or grinding as cutting task. In 21 workers with continuous aerosol measurements, short-term peak exposures during 6% of the work time contributed to approximately 25% of the average concentration of inhalable MWF aerosol. Inhalable MWF aerosol concentration measured with the PAS-6 sampler was a factor 2 higher than the concentrations derived from the open-faced sampler. These findings suggest that control measures, such as full enclosure of machines and the elimination of the use of compressed air as cleaning technique, are required to reduce the exposure to MWF aerosols to levels below the expected threshold for adverse respiratory health effects.

A population-based study on welding exposures at work and respiratory symptoms

In the first European Community Respiratory Health Survey (ECRHS I), an excess asthma risk was associated with high exposure to gases and fumes, mineral and biological dusts. In a 9-year follow-up study (ECRHS II), the aim was to study if welding at work increases the risk of asthma symptoms, wheeze and chronic bronchitis symptoms. The study also aimed to identify specific welding risk factors. In a random population sample of individuals from 22 European centres in 10 countries, 316 males reported welding at work during the follow-up period. These individuals responded to a supplemental questionnaire about frequency of welding, use of different methods and materials, welding environment and respiratory protection. Cumulative exposure to welding fumes for the follow-up period was estimated by using a database on welding fume exposures. Log-binomial regression models were used to estimate prevalence ratios (PR) with 95% confidence intervals (CIs) for prevalence of asthma symptoms or asthma medication, wheeze and chronic bronchitis symptoms in relation to welding methods and welded materials as well as estimated cumulative welding fume exposure compared to an external reference group. In the study population of 316 males, 62% performed welding <1 h day(-1), 23% 1-3 h day(-1) and 15% >4 h day(-1). Welding was a common task in many occupations and only 7% of the individuals actually called themselves welders and flame cutters, while the largest groups doing welding worked in construction or were motor, agricultural and industrial mechanics and fitters. Welding at work was not associated with an increased prevalence of asthma symptoms or wheeze but there was an association with chronic bronchitis symptoms (PR = 1.33, 1.00-1.76). Using assigned cumulative exposure in tertiles showed that the lowest exposed tertile had the highest PR of bronchitis symptoms. Chronic bronchitis symptoms was significantly higher in those frequently welding in galvanized steel or iron (PR = 2.14, 1.24-3.68) and in those frequently manual welding stainless steel (PR = 1.92, 1.00-3.66). There was also an increase in the prevalence of wheeze in individuals welding painted metal (PR = 1.66, 0.99-2.78; PR = 1.83, 0.90-3.71). Welding with manual metal arc technique <1 day week(-1) showed a prevalence risk of 1.69 for wheeze (CI = 1.16-2.46). In conclusion, the present study shows an association between welding in galvanized material and stainless steel and chronic bronchitis symptoms. There was also an increased prevalence of wheeze and welding in painted metal. The results support that welding in coated material is a respiratory hazard underscoring the importance of preventive actions.

Obesity and nocturnal gastro-oesophageal reflux are related to onset of asthma and respiratory symptoms

Several studies have identified obesity as a risk factor for asthma in both children and adults. An increased prevalence of asthma in subjects with gastro-oesophageal reflux (GOR) and obstructive sleep apnoea syndrome has also been reported. The aim of this investigation was to study obesity, nocturnal GOR and snoring as independent risk factors for onset of asthma and respiratory symptoms in a Nordic population. In a 5-10 yr follow-up study of the European Community Respiratory Health Survey in Iceland, Norway, Denmark, Sweden and Estonia, a postal questionnaire was sent to previous respondents. A total of 16,191 participants responded to the questionnaire. Reported onset of asthma, wheeze and night-time symptoms as well as nocturnal GOR and habitual snoring increased in prevalence along with the increase in body mass index (BMI). After adjusting for nocturnal GOR, habitual snoring and other confounders, obesity (BMI >30) remained significantly related to the onset of asthma, wheeze and night-time symptoms. Nocturnal GOR was independently related to the onset of asthma and in addition, both nocturnal GOR and habitual snoring were independently related to onset of wheeze and night-time symptoms. This study adds evidence to an independent relationship between obesity, nocturnal gastro-oesophageal reflux and habitual snoring and the onset of asthma and respiratory symptoms in adults.

Incidence of asthma in female Swedish hairdressers

OBJECTIVE

To investigate the risk of asthma in hairdressers.

METHODS

The incidence of asthma was retrospectively estimated in a Swedish nationwide study including all female hairdressers certified from vocational schools from 1970 to 1995, and a stratified sample of women from the general population were referents. A postal questionnaire included questions on respiratory tract symptoms, atopy, smoking, working periods as a hairdresser, and number of specific hair treatments performed/week. Reported exposures were validated by occupational hygienists. Rate ratios of incidence (IRRs) of asthma were estimated by Poisson regression, adjusted for calendar year of observation, hay fever, smoking, and region of domicile.

RESULTS

The crude incidences of asthma/1000 person-years were: 3.9 during active years as a hairdresser, 2.8 among the hairdressers when not working in the profession, and 3.1 among the referents. The corresponding IRR for being an active hairdresser compared with the referents was 1.3 (95% confidence interval (95% CI) 1.0 to 1.6). Moderate effects on risk of asthma were found both from hairdressing work (IRR=1.6 (1.1 to 2.2) among never-smokers) and from smoking (IRR=1.6 (1.2 to 2.2) among referents). However, the combined effect from hairdressing work and smoking (IRR=1.5 (1.0 to 2.1)) was less than expected (p=0.02). No effect modification by respiratory atopy was found. The hairdressers most often performing hair bleaching treatments (IRR=1.5 (0.7 to 3.0)) or using hair spray (IRR=1.4 (0.8 to 2.4)) had, compared with the most infrequent users, a slightly, but not significantly higher incidence of asthma. Exposure to persulphates in hair bleach was estimated to be 0.04-0.15 mg/m(3) during mixing of the powder. Reported average number of bleaching treatments agreed well with those performed according to a diary.

CONCLUSIONS

Active hairdressing work was associated with a moderately increased incidence of asthma among lifelong non-smokers. The results are moderately supportive, but not conclusive, of associations between asthma and exposure to hair bleach or hair spray.

Comparison of four methods to assess fungal alpha-amylase in flour dust

The aim of the study was to compare four different immunological methods to analyse fungal alpha-amylase in flour dust samples. Three European research groups have independently developed four immuno assay based methods to measure alpha-amylase in air samples. Three of the methods use polyclonal antibodies and one method uses monoclonal antibodies. Eighty personal samples have been collected during two to three work-shifts in four bakeries. Sampling was performed with PAS-6 inhalable dust samplers and aliquots from each sample were analysed by the three laboratories. The agreement between the four methods was high compared with agreement between immunological methods to measure other allergens in the air, e.g. for rat allergens. For the three methods with polyclonal antibodies the mean differences for individual samples was less than a factor of two. The arithmetic means (AM) of the estimated alpha-amylase exposure were 12.5, 11.3, 8.6 and 25.9ng/m(3) for the respective methods with values ranging from below the detection limit to 192, 215, 207 and 615 ng/m(3). The AM for all samples analysed by the methods with polyclonal antibodies varied by about a factor of 1.5. About one-third of the values were below or at the detection limit for all methods. In a regression analysis the squared correlation coefficients (R(2)) between the methods varied between 0.91 and 0.95 for the log transformed values. For workplace monitoring, results from the methods using polyclonal antibodies will be relatively comparable. High levels of alpha-amylase might differ in absolute numbers with a factor of two or more between the different methods but will anyway be considered as high and should result in preventive actions. On the other hand, this study also shows that despite the relative agreement between methods, there is a clear need for standardization.

Exposure-response relations for self reported asthma and rhinitis in bakers

OBJECTIVES

To explore relations between two estimates of exposure to inhalable flour dust, and the incidence rates (IRs) of asthma and rhinitis in bakers.

METHODS

This was a retrospective cohort study among 2923 bakers. A posted questionnaire registered the disease and work history. For every year, each baker was assigned an estimate of the exposure concentration to inhalable flour dust derived from reported job-tasks and dust measurements. Exposure at onset of disease was expressed as current dust exposure concentration, and as cumulative dose of exposure to dust. A multiple Poisson regression analysis assessed the impacts of the exposure estimates on the IRs of asthma and rhinitis.

RESULTS

IRs of asthma and rhinitis increased by dust concentration at onset of disease. The IR of asthma for the bakers with highest exposure (dough makers) was 7. 3/1000 person-years in men and 6.5 in women and for rhinitis 43.4 and 38.5, respectively. There was a significant association between the dust concentration at onset of disease and the risk for asthma or rhinitis, but not of the cumulative exposure.

CONCLUSION

The risk of asthma seemed to be increased at inhalable dust concentrations >/=3 mg/m(3) (dough making or bread forming), whereas the risk of rhinitis was increased at all concentrations >/=1 mg/m(3), indicating an increased risk in all bakery job-tasks. The risks seemed to be less dependent on the cumulative exposure dust than the inhalable dust concentrations.

Adult-onset asthma and occupational exposures

OBJECTIVES

This study examined certain occupational exposures and the risk for adult-onset asthma.

METHODS

A nested case-referent study of adult-onset asthma was performed on a random population sample (N=15813), aged 21 to 51 years. Cases for the study included 2 groups: subjects reporting "physician-diagnosed" asthma (N=251) and a broader "asthma" group (N=362). The "asthma" group consisted of subjects with "physician-diagnosed" asthma (N=251) and subjects reporting asthma-like symptoms without having "physician-diagnosed" asthma (N=111). The referents (N=2044) were randomly selected from the whole population sample. The case-referent sample was investigated with a comprehensive questionnaire about occupational exposures, asthma, respiratory symptoms, smoking, and atopy. Odds ratios were calculated with stratification for gender, year of diagnosis, and birth year.

RESULTS

The highest odds ratio for "physician-diagnosed" asthma was associated with exposure to flour dust [odds ratio (OR) 2.8, 95% confidence interval (95% CI) 1.5-5.2] and the occupational handling of resin-based paints (isocyanates) (OR 3.0, 95% CI 1.6-5.9). Exposure to welding fumes, textile dust, and work with glues containing acrylates was also associated with an increased odds ratio for "physician-diagnosed" asthma. Including persons with asthma-like symptoms (ie, the asthma group) showed similar results.

CONCLUSION

This population-based case-referent study from Sweden indicates that occupational exposure to acrylate-based compounds and welding fumes is associated with increased risk for adult-onset asthma.

Nasal symptoms and indices of nasal inflammation in flour-dust-exposed bakers

OBJECTIVE

To analyze whether indices of nasal airway inflammation in bakers were related to nasal symptoms and exposure to airborne flour dust.

METHODS

A cross-sectional study was performed in 12 currently flour-exposed bakers. They were examined by nasal lavage (NAL), visual inspection, a test of mucociliary clearance, and nasal peak expiratory flow (nasal PEF). NAL fluid was analyzed according to the inflammatory markers eosinophil cationic protein (ECP), indicating eosinophilic activity; myeloperoxidase (MPO), indicating active neutrophils; hyaluronic acid (HA) from active fibroblasts; tryptase, indicating activation of mast cells; and albumin, indicating plasma exudation. The bakers were also questioned about respiratory symptoms and working history. Their current and cumulative exposure to inhalable flour dust was estimated after exposure measurements and information about earlier work tasks. Office workers (n=16) without occupational exposure to dust or any other known nasal irritant or sensitizer served as controls.

RESULTS

Personal inhalable dust measurements among the bakers working as dough makers or bread formers ranged from 1.0 to 3.8 mg/m3. Of the 12 bakers, 10 reported at least 1 nasal symptom (crusts, blockage, or a runny nose), a proportion significantly greater than that of the controls (P=0.009). Bakers with nasal symptoms had higher concentrations of markers of inflammation in their NALs as compared with nonsymptomatic bakers. The difference was significant for MPO (P=0.02) and HA (P=0.04) in relation to a runny nose. Tryptase was detected in only one NAL of the bakers. There was a positive correlation between the cumulative dose of inhalable flour dust and concentrations of MPO and HA in NAL. Two bakers were sensitized to wheat; they had the highest NAL concentrations of inflammatory markers.

CONCLUSIONS

Our results indicate that flour dust exposure in bakers at levels below the current occupational exposure limit causes nasal mucosal inflammation, which, in turn, is related to nasal symptoms. We propose that the inflammation may be nonallergic, characterized by activation of neutrophils and fibroblasts.

Variability in the skin exposure of machine operators exposed to cutting fluids

OBJECTIVE

This study describes a new technique for measuring skin exposure to cutting fluids and evaluates the variability of skin exposure among machine operators performing cyclic (repetitive) work.

METHODS

The technique is based on video recording and subsequent analysis of the video tape by means of computer-synchronized video equipment. The time intervals at which the machine operator's hand was exposed to fluid were registered, and the total wet time of the skin was calculated by assuming different evaporation times for the fluid. The exposure of 12 operators with different work methods was analyzed in 6 different workshops, which included a range of machine types, from highly automated metal cutting machines (ie, actual cutting and chip removal machines) requiring operator supervision to conventional metal cutting machines, where the operator was required to maneuver the machine and manually exchange products.

RESULTS

The relative wet time varied between 0% and 100%. A significant association between short cycle time and high relative wet time was noted. However, there was no relationship between the degree of automatization of the metal cutting machines and wet time.

CONCLUSIONS

The study shows that skin exposure to cutting fluids can vary considerably between machine operators involved in manufacturing processes using different types of metal cutting machines. The machine type was not associated with dermal wetness. The technique appears to give objective information about dermal wetness.

Characterization of exposure to inhalable flour dust in Swedish bakeries

Bakery workers are at risk of developing respiratory symptoms, such as asthma and rhinitis. Exposure to inhalable flour dust in 12 Swedish bakeries was therefore determined: concentrations of airborne inhalable flour dust were measured with the IOM personal inspirable dust sampler and the particle size distribution assessed using the IOM personal inspirable aerosol spectrometer, and the fractions of alpha-amylase, water-soluble protein and total protein in flour dust were determined. A total of 129 measurements were performed of which 77 were repeated measurements. There was a clear hierarchy in geometric mean exposure among bakery workers, with in descending order doughmakers (5.46 mg m-3), bread-formers (2.69 mg m-3), oven workers (1.17 mg m-3), and packers and confectionery workers (0.53 mg m-3). The repeated measurements revealed that within each task group there were considerable differences in mean exposure among the workers: this was demonstrated by geometric standard deviations of between-worker variance of 1.63-1.77. Partitioning of the total variability of inhalable flour dust exposure showed that the task group was the principal source of variance, accounting for 61-69% of the total variability. The optimum grouping strategy was independent of whether the oven workers and the packers were assigned to the same or to different task groups. The doughmakers and the bread-formers are two clearly distinguishable exposure groups with largely overlapping exposure distributions. On average, the flour dust contained 9% total protein, 2.3% water-soluble protein and 0.03% alpha-amylase. The inhalable flour dust was characterized by a substantial proportion of particles with a d(ac) above 10 microns. It was estimated that the thoracic subfraction contributed 39% to the total mass of inhalable dust, and the respirable subfraction 19%.

Health effects of tank cleaners

A total of 29 tank cleaners and 31 referent controls participated in the study. In most cases, the tank cleaners were employed in small companies, usually specialized subcontractors such as firms only working in refineries cleaning oil tanks and handling oil spills. The air concentrations of hydrocarbons (HCs) in tanks containing residuals from heavy fuel oil were generally low, unless the oil was still warm. Addition of light fuel oil to facilitate the cleaning of tanks containing viscous, heavy fuel oils resulted in total airborne HC levels of 1000-1500 mg/m3. High levels of HC were measured in tanks with low-boiling petroleum fractions (naphtha and light fuel oils) of 1000-2600 mg/m3 (maximum). Today, most cleaners use air-supplied respirators or air-purifying respirator cartridges inside tanks with petroleum products or other chemicals. The exception is small firms handling fuel oils for heating purposes where only 50% of the workers use protective equipment regularly; the other workers only occasionally use protective equipment even if the air concentrations of HC are high. Protective equipment is rarely used in small, domestic tanks. Measurements of heart rate showed that tank cleaning is, at times, a highly strenuous job. No differences between tank cleaners and controls were found with respect to spirometry, liver enzymes, or frequency of micronuclei. Acute intoxications were not frequently reported in this group. However, this investigation may underestimate the true risk, as it is a cross-sectional study that found that exposures were highly variable, both quantitatively and qualitatively. In many cases, the tank cleaners knew very little about the potential hazards or the proper use of protective equipment.(ABSTRACT TRUNCATED AT 250 WORDS)

Cancer morbidity among men exposed to oil mist in the metal industry

The cancer morbidity pattern among 788 men with at least five years' exposure to oil mist was investigated. Based on measurements, interviews of workers and a survey of changes over the years, the average exposure level was estimated to have been 5 mg/m3 or more prior to 1965. Exclusive of cancer of the scrotum, there were 39 observed cases of cancer compared to 52.9 expected. There were four cases of cancer of the scrotum among the turners but none among the grinders. Three cases of lung cancer were found, compared to 5.4 expected. Among the grinders there was a doubled, but not statistically significant, increase in cancer of the stomach. The mortality from all causes showed a so-called "healthy worker effect," that is, 126 deaths compared to 154.3 expected.

Method of the cohort study--a practical example

The method is demonstrated in connection with a study of lung cancer among metal-workers exposed to oil mist. As exposure to oil mist is uncommon and lung cancer is common, the cohort study is the method of choice. Estimation of exposure, problems of selection, calculation of person-years etc is discussed. There was no increased morbidity from lung cancer.

Effect of a sequential oestrogen-progestin therapy on the plasma level of oestrogens and lipids in post-menopausal women

With the aim of minimizing side effects of substitution therapy a natural synthetic oestrogen, oestrone sulphate, and norethisterone acetate were administered to 6 oophorectomized women and 4 women with physiological menopause cyclically in order to follow the pattern of physiological variations during the menstrual cycle as closely as possible, without causing bleedings. In addition to assessing the clinical effects and analyses of plasma oestrone and oestradiol-17β, the metabolic effects on plasma triglycerides, cholesterol and individual phospholipid levels, as well as on the fatty acid composition of lecithin were followed.

The oral administration of oestrone sulphate in doses varying with the "cycle" from 0.5 to 1.5 mg/day gave in these women plasma concentrations of oestrone in the lower pre-menopausal physiological range causing cyclic variations in plasma lipids similar to those during a physiological menstrual cycle but did not normalize the plasma oestradiol concentrations and did not give acceptable therapeutic effect. Total phospholipids, total and free cholesterol, triglycerides and the percentage of lecithin were higher, and the percentage of lysolecithin lower in the oestrogen phase, than in the progestin phase. The changes in linoleic acid in lecithin varied inversely with changes in arachidonic acid in lecithin and cyclic variations also occurred in the content of palmitic and stearic acid in lecithin.

When previous treatment with ethinyloestradiol was exchanged with oestrone sulphate the total cholesterol values in plasma varied in the opposite direction. The results obtained in this and previous studies suggest different effects of ethinyloestradiol and oestrone (oestrone sulphate?) in the metabolism of certain sterols, and that the effect of oestrone (or oestrone sulphate?) on plasma cholesterol dominates during physiological condition in the follicular phase of the menstrual cycle.

Determination of plasma cholesterol: comparison of gas-liquid chromatographic, colorimetric and enzymatic analyses

The efficacy of methods for plasma cholesterol analyses based on gas-liquid chromatographic (GLC) or enzymatic cholesterol determinations was tested on commercially available standard serum, plasma obtained in a study of an age stratum of the population and on plasma from a number of patients from an out-patient department. These results were compared with colorimetric cholesterol determinations on chloroform/methanol extracts from plasma using the ferric chloride/sulphuric acid reagent. The GLC-based procedure gave values 12% lower than the colorimetric determinations. This discrepancy seemed to be explained, to a marked extent, by the fact that cholesterol metabolites interfere with the colorimetric determinations. The GLC-based method was apparently accurate since it has the advantage of specificity and is easy to standardize with the internal standard technique. Enzymatic total cholesterol analyses gave slightly (2%) lower values than the GLC-based analyses, apparently because of an incomplete hydrolysis of cholesterol esters. Enzymatic analyses of free cholesterol gave similar results to those of the GLC-based method.