Occupational asthma

Frequency of work-related respiratory symptoms in workers without asthma

BACKGROUND

Clinicians are faced with subjects complaining of work-related respiratory symptoms (WRS) without any evidence of asthma. We sought to assess the prevalence of subjects with WRS without asthma in a cohort of workers referred for possible work-related asthma (WRA) as well as compare the characteristics and the work environment of subjects with WRS to subjects with WRA.

METHODS

A prospective observational study of workers referred for possible WRA over a 1-year period. Detailed medical and occupational questionnaires were administered. Pulmonary function tests as well as specific-inhalation challenges were performed.

RESULTS

One hundred twenty workers were investigated. Fifty-one had WRA while 69 had WRS. The type and the severity of the respiratory symptoms were similar in both groups, except for wheezing which was more frequently reported in subjects with WRA (32 (62.7%)) than in subjects with WRS (16 (23.2%)) (P < 0.01). Both the workers with WRS and WRA were mainly employed in the manufacturing sector (64.7% (WRA) and 71% (WRS)). At the time of the first assessment 64.7% of subjects with WRA and 56.5% with WRS had left their workplace because of their bothersome respiratory symptoms.

CONCLUSIONS

Subjects with WRS without asthma represent a large proportion of the subjects assessed in clinics specialized in the field of WRA. Like subjects with WRA, the population with WRS is likely to represent a significant medical burden. The similarity of the symptoms between the WRA and the WRS groups emphasizes the need to perform a thorough and objective investigation to diagnose WRA.

Defining and investigating occupational asthma: a consensus approach

BACKGROUND

At present there is no internationally agreed definition of occupational asthma and there is a lack of guidance regarding the resources that should be readily available to physicians running specialist occupational asthma services.

AIMS

To agree a working definition of occupational asthma and to develop a framework of resources necessary to run a specialist occupational asthma clinic.

METHOD

A modified RAND appropriateness method was used to gain a consensus of opinion from an expert panel of clinicians running specialist occupational asthma clinics in the UK.

RESULTS

Consensus was reached over 10 terms defining occupational asthma including: occupational asthma is defined as asthma induced by exposure in the working environment to airborne dusts vapours or fumes, with or without pre-existing asthma; occupational asthma encompasses the terms "sensitiser-induced asthma" and "acute irritant-induced asthma" (reactive airways dysfunction syndrome (RADS)); acute irritant-induced asthma is a type of occupational asthma where there is no latency and no immunological sensitisation and should only be used when a single high exposure has occurred; and the term "work-related asthma" can be used to include occupational asthma, acute irritant-induced asthma (RADS) and aggravation of pre-existing asthma. Disagreement arose on whether low dose irritant-induced asthma existed, but the panel agreed that if it did exist they would include it in the definition of "work-related asthma". The panel agreed on a set of 18 resources which should be available to a specialist occupational asthma service. These included pre-bronchodilator FEV1 and FVC (% predicted); peak flow monitoring (and plotting of results, OASYS II analysis); non-specific provocation challenge in the laboratory and specific IgE to a wide variety of occupational agents.

CONCLUSION

It is hoped that the outcome of this process will improve uniformity of definition and investigation of occupational asthma across the UK.

Future advances in work-related asthma and the impact on occupational health

Work-related asthma (WRA) and WRA-like conditions refer to all situations in which asthma or asthma-like syndromes occur or worsen in the workplace. This occurs in approximately 10% of all adult-onset asthma subjects. Occupational asthma (OA) is a specific type of WRA that is 'caused' by the workplace, being mediated either by an allergic process with a latency period or by a non-allergic irritant-induced mechanism. Personal asthma can also 'worsen' at work (work-aggravated or exacerbated asthma), the reasons, mechanisms, extent and consequences of this situation being unknown. The author reviews various aspects of WRA with an emphasis on OA (about which more is known) and proposes key issues that need to be further studied, proposed and applied in at-risk workplaces in order to improve recognition, diagnosis and management of this condition. OA represents a unique situation that, unfortunately, is only very rarely provided to health-care providers: affected workers can be cured with minimal impact on quality of life. All efforts should be made to achieve this goal at an affordable socio-economic cost.

Respiratory findings in workers not exposed to air pollutants

The prevalences of acute and chronic respiratory symptoms and lung function changes were studied in a group of 806 workers working in a "clean environment." Acute symptoms during the work shift were reported by smokers but were essentially absent in nonsmokers. Chronic respiratory-symptom prevalences were similar to those reported in community-based populations, with smokers experiencing more chronic symptoms than nonsmokers. Baseline lung function measurements indicated no significant differences with values obtained from prediction equations based on community populations. There were significant across-shift increases in all ventilatory capacity tests (forced vital capacity, 1-second forced expiratory volume, and maximum expiratory flow rates at 50% and the last 25% of the vital capacity) varying from +1.9% to +9.8% of the preshift values. Workers older than 40 years of age and those employed for more than 10 years had similar across-shift changes compared with younger workers and those with longer durations of employment. Our data indicate that workers in clean work environments (with the exception of smokers) complain of few acute or chronic respiratory symptoms and have normal lung function. These workers experience increases in lung function across the work shift, probably reflecting normal diurnal variation. Smokers, although significantly more affected than nonsmokers, do not appear to have work-related findings, and smoking appears to be the most significant risk factor for the development of lung disease in unexposed workers. In this study, community-based control data was equivalent to worker control data in unexposed workers.

Occupational asthma and rhinoconjunctivitis from inhalation of dried cow's milk caused by sensitization to alpha-lactalbumin

A chocolate candy worker was diagnosed as having occupational asthma and rhinoconjunctivitis on the basis of clinical record and methacholine challenge. Positive conjunctival and bronchial challenge tests with lactalbumin showed that this protein was the pathogenetic agent. Type I hypersensitivity mechanism is demonstrated by means of skin prick test and RAST.

Usefulness of repeated measurements of bronchial hyperresponsiveness for the diagnosis of occupational asthma

To assess the usefulness of repeated measurements of nonspecific bronchial hyperresponsiveness (BHR) in the diagnosis of occupational asthma, we studied 26 consecutive patients referred to the Clinic of Occupational Medicine in Copenhagen because of suspected occupational asthma. The diagnosis of bronchial asthma was confirmed in all patients; however, 4 patients were excluded from the study as they had a baseline PC20 FEV1 histamine > 8 mg/ml. A bronchial challenge test with histamine was performed after nonspecific exposure at the workplace and after a specific bronchoprovocation test in the laboratory; substantial increase in BHR (BHRwork and BHRlab, respectively) was defined as a change in PC20 of at least one doubling concentration. A fall in FEV, of at least 20% from baseline after the specific bronchoprovocation test was defined as a positive response (SBPpos). Six patients had BHRwork and 7 patients had BHRlab; 2 patients had both BHRwork and BHRlab. Five patients had SBPpos, of whom 1 had BHRwork and 1 had BHRlab. None of the patients had three positive tests, i.e., BHRwork, BHRlab, and SBPpos. In 3 patients the specific challenge test caused a pronounced decline of lung function and deterioration in the clinical condition. With the results of the specific challenge test as the gold standard, serial measurement of histamine responsiveness may not appear to be a sensitive diagnostic test for occupational asthma. However, the high number of patients with an increase in BHR after specific and/or nonspecific occupational exposure strongly suggests that changes in bronchial responsiveness may identify patients with respiratory symptoms causally related to occupational exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

An environmental and respiratory health survey of workers in a grain mill in the Johannesburg area, South Africa

A respiratory health survey was conducted in a grain mill and the relationship of health indicators to quantitative measures of airborne dust, fungal, and bacterial contamination was examined. Respiratory symptoms were more prevalent in the high dust exposure categories; lung function levels were also higher in the high dust exposure categories, consistent with a "healthy" worker effect. Workers in the three higher dust exposure categories showed either no change or a decrease in lung function over the working week, while workers in the low exposure category demonstrated an improvement in lung function over the working week. Total dust and microbiological (fungal and bacterial) load were found to be significantly related to each other, and the relationship of microbiological load to lung function level and changes over the working week were similar to those found for total dust.

Organic dust disease of airways

Exposure to aerosols of organic dusts such as coffee, tea, spices, soy, fur, and animal food in an occupational setting can affect the respiratory health of industrial workers. Based on our experience with workers from many small industries processing organic materials, we discuss the clinical features and possible mechanisms responsible for the respiratory impairment associated with these types of dust exposure. Significantly higher prevalences for most chronic respiratory symptoms were found among exposed workers than among control workers. Smoking appears to aggravate these symptoms. A large number of exposed workers complained of acute symptoms which developed during the work shift. In exposed workers, significant across-shift reductions in lung function were recorded for all spirometric tests, but particularly for the flow rates at 50% and 25% of vital capacity on maximum expiratory flow-volume curves. Comparison of preshift measured ventilatory capacity tests with predicted normal values indicates that these workers demonstrate obstructive changes affecting primarily flow rate at low lung volumes. The data suggest that exposure to organic aerosols in industrial settings, particularly in conjunction with smoking, may be associated with the development of chronic obstructive lung disease.

Is the clinical history a satisfactory means of diagnosing occupational asthma?

In some countries a diagnosis of occupational asthma for medicolegal purposes is made when a questionnaire is suggestive and the individual is exposed to a product known to be a sensitizer. The value of an open questionnaire administered by physicians with experience in occupational asthma is unknown, however. We prospectively assessed all subjects (162) referred to our clinic because their physicians thought their asthma might be work related. The medical questionnaire included questions about the nature of the symptoms (dyspnea, wheezing, cough, and chest tightness) and the timing (worse at work or after a shift at work or improved during weekends or holidays). An initial clinical assessment was set by the physician on a scale that ranged from highly probable to probable, uncertain, unlikely, or absent. Subjects then underwent objective assessment with specific inhalation challenges (n = 72), serial monitoring of peak expiratory flow rates for periods at work and away from work (n = 29), or both (n = 61), to confirm or rule out the diagnosis of occupational asthma. A total of 75 subjects (46%) were shown to have occupational asthma. Symptoms alone (type and timing) did not provide a satisfactory differentiation between those subjects with and those without occupational asthma. For example, 66 of 75 (88%) subjects with occupational asthma said that their symptoms improved during holidays, but 66 of 87 (76%) subjects without occupational asthma experienced a similar improvement.(ABSTRACT TRUNCATED AT 250 WORDS)