SWORD '96: surveillance of work-related and occupational respiratory disease in the UK

Assessment of Respiratory Symptoms and Pulmonary Function Status among Workers of Flour Mills in Addis Ababa, Ethiopia: Comparative Cross-Sectional Study

Background

Flour dust in the respiratory tract affects lung function. Flour dust is a heterogeneous organic substance which can have a tendency to cause respiratory ailments. There is growing consensus on the deleterious effects of flour dust on respiratory symptoms and lung performance of flour mill workers.

Methods

The study design was comparative cross-sectional. A total of 54 flour mill workers who work for more than eight-hour shift per day and 54 control subjects matched for sex, age, weight, height, and area of residence were enrolled. Anthropometric measurement was done. Lung function was measured by using a digital portable spirometer (Spiro Pro) based on the ATS guidelines. FVC, FEV₁, FEV₁/FVC, PEFR, and FEF₂₅%  _-75% were measured. Productive cough, dry cough, wheeze, and breathlessness were evaluated using BMRC questionnaire guidelines, administered through face-to-face interview.

Result

This study showed statistically significant reduction in the mean values of pulmonary function tests in flour mill workers as compared to their matched controls. Reduction of pulmonary function indices in study subjects was significant for FVC (4.25±0.93 vs. 5.30±0.71, p<0.001), FEV₁ (3.46±0.86 vs. 4.50±0.72, p<0.001), PEFR (5.43±2.43 vs. 7.87±2.53, p<0.001), and FEF₂₅%  _-75%, (3.87±1.61 vs. 4.60±1.60, p<0.05), but not significant for FEV₁/FVC (81.93±12.74 vs. 83.40±12.50, p>0.05). Flour mill workers developed 27.7% of restrictive type and 11.1% of obstructive type of lung disorders. Percentage prevalence of respiratory symptoms was evaluated as dry cough (27.7% vs. 9.3%), productive cough (11.1% vs. 5.6%), wheeze (14.8% vs. 3.8%), and breathlessness (16.6% vs.7.4%) in flour mill workers and controls, respectively.

Conclusion

Based on the results of the present study, occupational exposure to flour dust could cause respiratory dysfunction, thereby reducing lung efficiency.

A compendium of causative agents of occupational asthma

Objective

The objective is to provide an evidence-based compendium of allergenic and irritant agents that are known to cause occupational asthma in order to improve diagnostics and disease management.

Methods

Two previously published reviews from our group utilized database searches to identify studies which were then rated according to the Scottish Intercollegiate Guideline Network (SIGN) grading system. The evidence level for each causative agent or worksite was graded using the Royal College of General Practitioners (RCGP) three-star system.

Results

Approximately 3,000 relevant papers were identified, which covered 372 different causes of allergic and 184 different causes of irritant occupational asthma. The highest level achieved using the SIGN grading system was 2++, indicating a high quality study with a very low risk of confounding or bias and a high probability of a causal relationship. Using the modified RCGP three-star grading system, the strongest evidence of association with an individual agent or worksite ('***') was found for exposure to laboratory animals. Associations with moderate evidence level (‘**’) were obtained for a) the allergenic agents or worksites: alpha-amylase from Aspergillus oryzae, various enzymes from Bacillus subtilis, papain, bakeries, western red cedar, latex, psyllium, storage mites, rat, carmine, egg proteins, Atlantic salmon, fishmeal, Norway lobster, prawn, snow crab, seafood, trout and turbot, reactive dyes, b) the irritant agents or worksites: benzene-1,2,4-tricarboxylic acid, 1,2- anhydride [trimellitic anhydride], chlorine, cobalt, cement, environmental tobacco smoke, grain, welding fumes, construction work, swine confinement, World Trade Center disaster 2001, and c) agents or worksites causing allergic as well as irritant occupational asthma, included farming, poultry confinement, various isocyanates and platinum salts. A low evidence level (RCGP) was obtained for 84 agents or worksites (42 from each group), providing a total of 141 conditions with a low, moderate or strong evidence level.

Conclusion

This work comprises the largest compendium and evaluation of agents and worksites causing allergic or irritant occupational asthma from the literature assessed in an evidence-based manner.

Occupational asthma due to low molecular weight agents

Occupational asthma is defined as variable airflow obstruction and airways hyperresponsiveness caused by exposure to agents present in the workplace. Low molecular weight agents such as isocyanates, aldehydes, anhydrides, colophony, dyes, persulphate, amines, acrylates and metals are steadily increasing as causative agents of occupational asthma. Isocyanates, aldehydes and anhydrides my cause sensitisation through an IgE mediated response in some workers. These agents act as haptens which combine with a carrier protein to form a complete antigen. Assays for the detection of specific IgE are standardized for very few agents and have a good specificity, but poor sensitivity. The diagnosis of occupational asthma relies not only on a suggestive hystory showing that asthma is caused or exacerbated specifically by work exposure, but in most cases needs to be confirmed by objective means. Combined monitoring of lung function parameters, such as peak expiratory flow rate at the work site and non specific bronchial hyperresponsiveness during and away from exposure, is necessary. The "gold standard" for confirming a diagnosis in an individual worker still remains the specific bronchoprovocation test, which has now reached a high degree of sensitivity, specificity and reproducibility for agents such a s isocyanates. In occupation asthma due to low molecular weight agents there are no individual risk factors which could predict the susceptibility to develop the disease. The primary prevention is based on appropriate interventions tn the workplace. The strict medical surveillance of workers may allow the early diagnosis and removal from further exposure in order to prevent morbidity and disability.

IgE-mediated natural rubber latex allergy: practical considerations for health care workers

OBJECTIVE

To focus on some specific topics of major significance for health care workers confronted with natural rubber latex (NRL) allergy: 1) sensitization and routes of exposure; 2) threshold allergen exposure levels; 3) evaluation of occupational NRL allergy; 4) prevention of sensitization and allergic reactions to NRL-containing devices; 5) selecting the right alternative; and 6) regulatory responses to NRL allergy issues.

DATA SOURCES

English and French language papers identified through a MEDLINE search and bibliographies of the identified papers and the National Institute for Occupational Safety and Health and Food and Drug Administration web sites.

RESULTS

1) The threshold levels of NRL exposure needed for sensitization and the precise way in which it comes about remain to be elucidated, but cutaneous, percutaneous, mucosal, and parenteral exposure can all give rise to symptoms. 2) Strengths and weaknesses of the questionnaire and currently available diagnostic techniques for NRL allergy are emphasized. 3) Prevention strategies should focus on dipped materials and stress upon the possibility of passive and active transmission of NRL aeroallergen. 4) Generally, vinyl gloves are an appropriate alternative for NRL gloves; however, when barrier integrity is a concern, nitrile gloves provide protection that is comparable with NRL. 5) Several government bodies, standards organizations, and regulatory agencies have issued regulations concerning the control and labeling of protein and allergen levels in NRL products.

CONCLUSION

Accurate diagnosis and management of NRL allergy is essential because of the potential for severe hypersensitivity reactions. Major developments have been made in characterizing and cloning NRL allergens, and future development in this area may lead to better diagnostic tools and possible therapeutic agents for immunotherapy. However, at present, avoidance remains the only effective approach. We hope that additional well performed prospective incidence studies will bring more accurate data concerning sensitization doses and provide the valuable information to improve prevention strategies.

Analysis of allergens in rat fur and saliva

BACKGROUND

The fur is an important source of allergens in many mammal species, but this source has not been extensively studied in rats. Rat room dust contains high-molecular-weight allergens that have been found to cross-react with fur and its presumed salivary contaminants. The role of rat fur and saliva as a source of respiratory allergens merits further investigation. The objective was to describe the allergens present in the fur and saliva of male rats.

METHODS

Allergen extracts were prepared from the saliva and fur of the pelts from adult male rats. Immunoblotting was used to describe the allergens present in rat fur and saliva with serum from 76 and 25 individuals, respectively.

RESULTS

There was considerable variation between the individuals in the binding of IgE to the separated fur and saliva allergens. Immunoblot analysis identified 23 allergens in rat fur. "Major" allergens were found at the "origin", and at 55, 51, 19, and 17 kDa, and "intermediate" allergens at 74, 67 (probably albumin), and 21.5 (diffuse) kDa. Seventeen salivary allergens were described with "major" allergens at 21.5, 19.5, 19, 18, and 17.5 kDa. Many subjects had IgE to the 67 kDa (56%) and 43 kDa (64%) allergens but the density of staining was weak.

CONCLUSION

Rat fur and saliva are the sources of many allergens. Fur contained five "major" allergens and was a complex source of allergens of relatively high molecular weight (>22 kDa). The most important salivary allergens have molecular weights of less than 22 kDa. Fur is the most probable source of the high-molecular-weight allergens found in rat room dust.

Reported incidence of occupational asthma in the United Kingdom, 1989-97

OBJECTIVES

To examine trends in estimated population based incidence of occupational asthma by age, sex, occupation, geographical region, and causal agents based on 9 years of the Surveillance of Work Related and Occupational Respiratory Disease (SWORD) data.

METHODS

In January 1989 the SWORD scheme for the surveillance of occupational respiratory disease was established in the United Kingdom to make good the lack of epidemiological information on the incidence of these diseases in the United Kingdom. Between 80% and 90% of chest and occupational physicians report voluntarily all new cases they see, on a monthly or random sampling basis. During the 9 years 1989-97, an estimated 25 674 new cases of occupational respiratory disease, including 7387 of occupational asthma, were reported. Suspected causal agents were classified into 44 categories and estimated annual incidences of asthma were calculated with denominators from the labour force survey.

RESULTS

Overall, a third of the suspected causes of asthma were organic, a third chemical, 6% metallic, and the rest miscellaneous, or in 8%, unknown. There was evidence of an increase since 1989 in cases due to latex, and possibly glutaraldehyde, and an apparent drop since 1991 in the proportion of cases attributed to isocyanates. Incidences were higher in men than women and the disparity was especially marked in the population aged 45 years or more in which rates for men were at least twice those for women. Average annual rates per million workers for 1992-7 ranged from 7 (95% confidence interval (95% CI) 5 to 9) for the lowest risk group of professional, clerical, and service workers to 1464 (95% CI 968 to 2173) for coach and other spray painters. Except for laboratory technicians, all other occupations with rates over 100 were concerned with manufacturing and processing that used chemicals, metals, and organic materials. Incidences were two to three times higher in the north and midlands than in East Anglia and the south. The introduction of a sampling scheme in 1992 doubled estimates of reported incidence of occupational asthma, but there was little evidence of other temporal changes.

CONCLUSIONS

The SWORD scheme has produced consistent estimates of the causes and incidence of occupational asthma as seen by chest and occupational physicians. It has allowed the epidemiology of occupational asthma in the population to be studied and high risk occupations to be identified. There is certainly more occupational asthma in the population than that which reaches specialists in occupational and chest medicine; therefore the incidence rates presented here are underestimates, but by how much remains unknown.

Intelligent database generated occupational questionnaire system

Obtaining an adequate occupational history requires special expertise to "ask the right questions" that are relevant to a particular patient's specific health conditions and potential exposures. This article describes a way to systematically accomplish this by means of a computer system that can overcome limited availability of necessary clinical occupational health expertise. The Intelligent Questionnaire system is a computer-based system for generating case-specific questionnaires about the influence of work on respiratory disease. Intelligent Questionnaire includes three databases: Questions, Responses, and Calls (clues to identify questions). The Questionnaire also arranges questions in a logical manner and provides a customized data entry screen for each subject. This approach provides primary practitioners with expertise on a case-by-case basis. It also facilitates occupational health surveillance because it allows acquiring detailed case-specific information in a systematic fashion. A computer-based system can facilitate obtaining occupational histories with high specificity and consistency without depending on general availability of a human occupational health clinical expertise.

The occurrence, recrudescence, and worsening of asthma in a population of young adults: impact of varying types of occupation

OBJECTIVE

To describe the rates of exacerbation of existing asthma and incidence of new disease in Israeli men during military service.

DESIGN

All 17-year-old Israeli nationals are obliged by law to appear at the Israel Defense Forces (IDF) recruiting office for medical examination. The medical history of army recruits was noted during the 30-month period after their induction into the IDF, and medical examinations were performed by pulmonary specialists in all suspected cases of asthma. The duty status of the soldiers in combat units (CUs), maintenance units (MUs), and clerical tasks was related to their asthma status.

RESULTS

Of a total of 59,058 recruits, 1.0% developed asthma during the 30 months of this study; of those in CUs, 1.2% developed asthma; of those in MUs, 0.8% developed asthma; and of those performing clerical tasks, 0.6% developed asthma. The relative risk for developing or worsening of asthma was related to both the preexisting asthma status of the recruit and the environment in which he carried out his military service. The annual incidence of occupational-related asthma in MUs was found to be 800/million: five to six times the rates reported elsewhere.

CONCLUSIONS

Service in CUs was associated with an increased frequency of exacerbation of asthma among recruits with previous disease and with the appearance of disease de novo. "Normal" conscripts with a history of childhood asthma are at a higher risk of developing overt asthma when compared to subjects with no such history. We found a 25% relative excess of incident cases of asthma in soldiers posted in MUs compared to those performing clerical tasks [(0.8 to 0.6%)/0.8%]. This difference is probably attributed to the difference in occupational hazards in these categories. Further studies are needed to determine if this represents the elicitation of underlying preexisting airway lability by new work demands or other environmental conditions, or if this represents a new development of airway lability because of specific immune or nonimmune factors.