THE UNIVERSITY OF WESTERN ONTARIO Department of Epidemiology & Biostatistics. F. Lortie-Monette, MD, MSc, CSPQ, MBA OCCUPATIONAL ASTHMA

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1 THE UNIVERSITY OF WESTERN ONTARIO Department of Epidemiology & Biostatistics 2003 F. Lortie-Monette, MD, MSc, CSPQ, MBA OCCUPATIONAL ASTHMA 1

2 OCCUPATIONAL ASTHMA Occupational Asthma: the most prevalent occupational lung disease in industrial countries new onset asthma (occupational asthma) OR work-aggravation of pre-existing asthma (specially if general asthma control had been suboptimal or if asthma was relatively severe). Causes: Irritants, allergens, viral infections. 2

3 DIAGNOSIS OF OCCUPATIONAL ASTHMA: Asthma starting at work is not always workrelated asthma But work-related asthma should be considered in all working asthmatics Most commonly, occupational asthma with latency 1 (immunologic mechanism) : 1.1 sensitization to a high-molecular weight agent ( ) 1.2 sensitization to a low-molecular weight agent (these include highly reactive chemicals like isocyanates, and may act as haptens, combining with body proteins; mostly IgE independent mechanisms; 1 Sensitization accounts for over ninety percent of OA cases reported to the Ontario s Workplace and Safety Insurance Board. 3

4 Less commonly, occupational asthma without a latency period (RADS/Irritant-Induced Asthma): high level, acute exposure to an irritant (eg chlorine, ammonia) resulting in airway injury. Reactive Airways Dysfunction Syndrome (RADS): no prior lung disease; onset within 24 hours of work exposure; objective evidence of asthma; symptoms for at least 3 months (can persist for months or years) re-exposure to low levels unlikely to trigger asthma...moderate or high levels of exposure to respiratory irritants could aggravate symptoms. 4

5 Irritant-Induced Asthma (IIA): one or more high level, acute exposure to an irritant; symptoms occurring up to 7 days post exposure LOW MOLECULAR WEIGHT AGENTS CAUSING OCCUPATIONAL ASTHMA acid anhydrides chloramine-t dyes persulphate acrylates Agents Isocyanates (prevalence of isocyanate-induced asthma in exposed workers is close to 10%). wood dusts (cedar, oak) aliphatic amines (e.g., ethylenediamine) metals, fluxes, (platinum salts, cobalt, colophony) formaldehyde, glutaraldehyde drugs (e.g., antibiotics, psyllium) spray painters, insulation installers, manufacturers of plastics, rubbers, foam and coating; manufacturers of cars, planes and trains sawmills workers, carpenters users of plastics, epoxy resins shellac and lacquer handlers, solderers platinum refineries, hard metal grinding, electronic (soldering) janitorial work, cleaners textile and dye manufacturing hairdresser embalming, hospital workers adhesives handlers pharmaceutical Occupations at Risk manufacturing/packaging, health workers 5

6 Most Common Causes of Asthma Number of Allowed Claims Number of allowed claims for OA induced by diisocyanates and OA induced by other causes by year of onset. A significant change occurred in the proportion of OA induced by diisocyanates and OA induced by other causes in the years (p=0.001). 6

7 Ontario Legislation In Ontario, legislation introduced in 1983: Requiring monitoring of diisocyanate concentrations to maintain 8 hour average concentrations below 5 ppb, short term exposure concentrations below 20 ppb. Medical Surveillance Measures A pre-employment respiratory questionnaire, and spirometry; Repeated respiratory questionnaires every 6 months and spirometry at least on an annual basis. Workers with lower respiratory symptoms on questionnaire, or changes is spirometry required to have a medical assessment: ability to continue work with diisocyanates. 7

8 Changes in Rates and Severity of Compensation Claims for Asthma due to Diisocyanates In Ontario: Numbers of claims for OA induced by diisocyanates: 9-15 claims/year in claims/year in claims/year by COMMON HIGH MOLECULAR WEIGHT AGENTS CAUSING OCCUPATIONAL ASTHMA Agents Plant-derived substances: flour and grain dusts latex enzymes gums bakers, millers health workers Occupations at Risk detergent making, detergent users, pharmaceutical workers, food processing, meat tenderizer producer carpet makers, pharmaceutical workers 8

9 COMMON HIGH MOLECULAR WEIGHT AGENTS CAUSING OCCUPATIONAL ASTHMA - continued Agents Animal-derived allergens: laboratory animals crab/seafood egg protein grain mites, insects Occupations at Risk animal handlers, laboratory workers seafood processing egg production silk workers 4 CAUSES OF OCCUPATIONAL SENSITIZATION (examples) Bakeries Health care workers Laboratories Companies using or making polyurethane foam or spray paints Electronic workers wheat, other cereals, enzymes (e.g., fungal amylase) natural rubber latex in gloves, psyllium in laxatives, penicillin-derived antibiotics, glutaraldehyde animal proteins, enzymes, antibiotics, other pharmaceutical products Diisocyanates colophony, amines, acrylic glues 9

10 Diagnosing Occupational Asthma: Stepwise procedure: (i) (ii) (iii) Does the patient have asthma (variable airflow limitation/bronchial hyperresponsiveness)? Is the asthma work-related? What are the causative and/or triggering substance or work environments? What workplace modifications would make it safe for the patient to continue working or return to work and/or would protect coworkers? Diagnosing Occupational Asthma Pulmonary function tests pre- and postbronchodilator 10

11 Diagnosis! "$# " % &(' # )+*, " " " -". "!" / 0 1 " 2 "! " -" ' 3 )! "$ " " " " 6!". "-" 7" 2 "8 " 3 9 <>=?-@A,B # C. "!" ' Diagnosing Occupational Asthma: History Review the exposure history (MSDS); duration of exposure varies 40% develop symptoms within 2 years 20% after 10 years of exposure 11

12 Diagnosing Occupational Asthma:History Improvement during weekends or vacations? Patterns: if worse less than 1 hour after starting work immediate asthmatic response 4-6 hours after work start, sometimes in evening delayed/late response May have dual/biphasic response Diagnosing Occupational Asthma: Immunological Tests Skin prick tests: available for allergens such as animal or plant extracts Serum radio-immunosorbent (RAST) or enzyme-linked allergosorbent (ELISA) tests to identify specific IgE antibodies: miss common sensitizers such as isocyanates. 12

13 ADVANTAGES and DISADVANTAGES OF DIAGNOSTIC METHODS for OCCUPATIONAL ASTHMA Method Advantages Disadvantages Questionnaire Immunologic testing Bronchial responsiveness to methacholine or histamine Measurement of FEV before or after work 1 Simple, Sensitive Simple, Sensitive Simple, Sensitive Simple, Inexpensive Low specificity Only for high-molecular- weight and some low-molecular- weight agents; identifies sensitization, not work disease; many allergens not available commercially Not specific for occupational asthma; occupational asthma not ruled out by a negative test Low sensitivity and specificity Diagnosing Occupational Asthma tests positive for asthma exposure to allergen(s) at work history consistent with work-related asthma Note: specific challenge tests with suspected allergens not always possible (need specialized facilities) 13

14 Additional Tests for Occupational Asthma Serial recording of PEF values, along with diary of symptoms: qid X 2-4 weeks time consuming/subject to inaccuracies diurnal variability of at least 20% is suggestive of asthma Diagnosing Occupational Asthma Serial histamine or methacholine challenges within 24 hours of typical work exposure, and after 2-4 weeks off: normal methacholine response virtually rules out work-related asthma 14

15 Management: 1. Treat the asthma: control of nonoccupational triggers; asthma medications; patient education; 2. Work exposure for sensitizers-induced occupational asthma: avoid any further exposure by workplace modifications or moving patient: early removal from exposure best outcome. 3. Consider co-workers (are they at risk?) 4. Monitor patient s course. The majority of patients with occupational asthma with latency do not recover, even after several years away from exposure. There is bronchial hyperresponsiveness, with chronic airway inflammation. 15

16 EXAMPLES OF OCCUPATIONAL DISEASES chronic obstructive lung Infections: human-to-human animal to human soil to human granulomatous lung disease hypersensitivity pneumonitis (allergic alveolitis) cadmium tuberculosis hantavirus coccidiomycoses beryllium organic dusts pulmonary fibrosis bronchogenic carcinoma asbestos, silica asbestos Hypersensitivity Pneumonitis (allergic alveolitis) Condition localized to the alveoli Produces mainly restrictive lung disease Cause: inhalation of tiny antigens such as spores of microorganisms or avian proteins 16

17 Hypersensitivity Pneumonitis The most common: farmer s hypersensitivity pneumonitis (FHP) or farmer s lung: Symptoms most prevalent in cold wet climates that favour fungal overgrowth, and in the winter months when stored crops are used for animal feed. Hypersensitivity Pneumonitis (examples) Farmer s Lung Bird Fancier s Lung Humidifier Lung Wood Worker s Lung Mouldy hay & straw Bird droppings & feathers Water from humidifiers & air conditioners Bark stripping; wood pulp & chips 17

18 Hypersensitivity Pneumonitis: Acute Presentation Acute immunologic reaction to antigenic challenge from organic dusts: Symptoms of dry cough, dyspnea, fever, chills, and fatigue. Symptoms arise 4-6 hours after exposure, persist up to 12 hours, followed by spontaneous recovery Hypersensitivity Pneumonitis: Chronic Exposure to the sensitizing agent on a recurrent basis can result in irreversible lung damage (pulmonary fibrosis, reduced lung function and impaired gas exchange) Symptoms: Cough with sputum Dyspnea, chills and fever Fatigue & weight loss Fine basilar inspiratory crackles 18

19 Hypersensitivity Pneumonitis Treatment Stop exposure to the causative antigen Steroids The End 19

20 EXAMPLES OF OCCUPATIONAL DISEASES - continued Wood work Metal work Working with plants, fish, animals or insects wood dusts (e.g., plicatic acid in red cedar), fungal spores, phenol-formaldehyde resins, formaldehyde in particle board complex platinum salts, nickel, cobalt, chromium compounds almost any plant, fish, animal or insect protein with airborne or skin exposure 20