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Work-Related Asthma Dr. Nayak CS,  Consultant Occupational Medicine  MB BS MD DOH FIIRSM MAOEM
<ul><li>About 20 million Americans currently have asthma Occupational factors account for 9-15% of cases of asthma in adul...
<ul><li>Up to 20% of all adult asthma cases maybe work-related asthma </li></ul><ul><li>Of those diagnosed with work-relat...
<ul><li>Olaus Magnus 1555: &quot;When sifting the chaff from the wheat, one must carefuly consider the time when a suitabl...
<ul><li>“ Occupational asthma is a disease characterized by variable airflow  limitation and / or airway hyper- responsive...
Types of Work-related Asthma
Types of Work-related Asthma
<ul><li>Work-aggravated asthma: </li></ul><ul><ul><li>Exacerbation of preexisting asthma due to non-specific  irritants en...
<ul><ul><li>Sensitizer-induce OA  ( immunologic  )   reversible air-flow obstruction / airway hyper-responsiveness due to ...
<ul><li>Asthma like disorders  ( OTDs) </li></ul><ul><ul><li>expose to vegetable dust ,animal confinement  building </li><...
<ul><li>Sensitizer-induced   </li></ul><ul><li>Specific antigen  </li></ul><ul><li>Minimal exposure </li></ul><ul><li>Ster...
<ul><li>Sensitizer Occupational Asthma   is caused by  sensitization  to a specific chemical agent in the workplace over a...
<ul><li>LMW Agents (< 5Kd) </li></ul><ul><ul><li>Too small to be complete allergens </li></ul></ul><ul><ul><li>Immunologic...
<ul><li>High MW </li></ul><ul><li>Pharmaceuticals  </li></ul><ul><li>Animal proteins </li></ul><ul><li>Latex </li></ul><ul...
<ul><li>Irritant Induced Occupational Asthma  usually develops after a  single, very high exposure  to an irritant chemica...
Reactive airways dysfunction syndrome (RADS) 1.  Single or several exposures to gas, smoke, fume or vapor which was presen...
<ul><li>Very common </li></ul><ul><li>Existing airways reactivity:  </li></ul><ul><ul><li>asthma </li></ul></ul><ul><ul><l...
Occupational Asthma
Asthma Pathophysiology
Triggers and Irritants Things that may initiate an asthma attack
Exposure to nickel dust
Acute, high RADS Chronic, low  high Chronic bronchitis Asthma  Asthma-like syndrome Sensitizer Atopic asthma Irritant Mod...
Airway  Remodeling Symptoms Smooth Muscle  Dysfunction Airway  Inflammation Asthma Pathophysiology
INFLAMMATION Pathogenesis: Airflow Limitation SYMPTOMS Cough  Wheeze Dyspnoea TRIGGERS Allergens, Exercise,  Cold Air, SO2...
The bronchial epithelium is highlighted as  a key site for
Leukotrienes C4, D4 & E4 Asthma Pathology - Modern view
Diagnostic Approach
Diagnostic Criteria
<ul><li>Objective testing </li></ul><ul><ul><li>Spirometry </li></ul></ul><ul><ul><li>Tests of NSBH </li></ul></ul><ul><li...
Exposure  challenge testing   Spirometry <ul><li>at and away from work </li></ul><ul><li>cross-shift </li></ul>
<ul><li>Impractical for screening worker populations </li></ul><ul><li>No evidence that pre-screening can predict developm...
<ul><li>Bronchoprovocation Study:  methacholine or histamine induced fall in FEV1  >  20%  </li></ul><ul><li>PC20 ( provoc...
<ul><li>“ Gold-standard”  </li></ul><ul><li>Decrease in FEV1 of  >  20% in response to specific agent </li></ul><ul><li>Pe...
Exposure chamber
<ul><li>PEF vs Time over several weeks,  including work and free days </li></ul><ul><li>Diurnal variation of  >  20% on wo...
<ul><li>At least 2 weeks at work and off work </li></ul><ul><ul><li>(often longer...) </li></ul></ul><ul><li>At least 4 ti...
<ul><li>False positive </li></ul><ul><li>Subject not exposed during monitoring </li></ul><ul><li>Poor compliance  </li></u...
Serial monitoring of PEF in the diagnosis of OA Improvement of PEF when away from work and deterioration of  PEF on return...
<ul><li>Computer generated diagnostic aid </li></ul><ul><li>Provides a probability score based on the  plotted data </li><...
<ul><li>Exhaled nitric oxide (eNO) correlates with measures of airway inflammation </li></ul><ul><ul><li>Mirrored environm...
<ul><ul><li>Skin Test: ( IgE ) </li></ul></ul><ul><ul><ul><li>Valid for HMW allergens (eg. baker’s asthma) & rarely for LM...
<ul><li>  Byssinosis in a 56-year-old woman who had had frequent episodes of “Monday fever” and dyspnea while working in a...
<ul><li>High-resolution CT scan shows numerous ill-defined small nodules with ground-glass attenuation in both lungs.  (c)...
<ul><li>Isocyanate-induced acute hypersensitivity pneumonitis in a 36-year-old man who presented with severe cough and dys...
<ul><li>High-resolution CT scan obtained on the 2nd day of hospitalization shows patchy areas of consolidation and ground-...
Compatible clinical history and exposure Skin testing and/or specific IgE (if possible) Assessment of NSBH Normal Increase...
Management
<ul><li>Complete avoidance </li></ul><ul><li>Medication not better than avoidance </li></ul><ul><li>Protective devices? </...
Management
1.Pre-placement Assessment 2. Exposure control 3. PPE & Awareness MSDS Medical Surveillance 1.Employee Accommodations 2. J...
<ul><li>Occupational asthma, based on sensitization to agents  encountered at work, is the best defined and  documented ty...
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Work Related Asthma

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Work-Related Asthma is leading cause absenteeism among workforce

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  1. 1. Work-Related Asthma Dr. Nayak CS, Consultant Occupational Medicine MB BS MD DOH FIIRSM MAOEM
  2. 2. <ul><li>About 20 million Americans currently have asthma Occupational factors account for 9-15% of cases of asthma in adults of working age with almost 90% of those cases being attributed to an allergic response. The substances responsible for this are known as sensitizing agents, and many are well known. </li></ul>Overview
  3. 3. <ul><li>Up to 20% of all adult asthma cases maybe work-related asthma </li></ul><ul><li>Of those diagnosed with work-related asthma: </li></ul><ul><ul><ul><li>20-27% are individuals with pre-existing asthma who react to substances in the workplace </li></ul></ul></ul><ul><ul><ul><li>Up to 80% develop asthma due to work-place exposures </li></ul></ul></ul>Overview-2
  4. 4. <ul><li>Olaus Magnus 1555: &quot;When sifting the chaff from the wheat, one must carefuly consider the time when a suitable wind is available that sweeps away the harmful dust. …congests in the throat and threatens the life organs..&quot; </li></ul><ul><li>Ramazzini 1713: flour dust caused asthmatic symptoms in millers and bakers. </li></ul><ul><li>1911-1936 platinum salts, chromium and phthalic anhydride - the first chemicals causing asthma </li></ul><ul><li>Diagnostics: bronchial provocation tests by Prof. Pepys and coworkers began 30 years ago at Brompton Hospital, London UK </li></ul>Historical view
  5. 5. <ul><li>“ Occupational asthma is a disease characterized by variable airflow limitation and / or airway hyper- responsiveness and / or inflammation due to causes and conditions attributable to a particular occupational environment and not to stimuli encountered outside the workplace.“ </li></ul>Definitions of Work- Related Asthma (Centers for Disease Control and Prevention, 2004)
  6. 6. Types of Work-related Asthma
  7. 7. Types of Work-related Asthma
  8. 8. <ul><li>Work-aggravated asthma: </li></ul><ul><ul><li>Exacerbation of preexisting asthma due to non-specific irritants encountered at work </li></ul></ul><ul><li>Occupational asthma: </li></ul><ul><ul><li>New-onset asthma’ from workplace exposure to sensitizers and/or irritants </li></ul></ul>Types of Work-related Asthma-2
  9. 9. <ul><ul><li>Sensitizer-induce OA ( immunologic ) reversible air-flow obstruction / airway hyper-responsiveness due to a sensitizing agent encountered in the workplace” </li></ul></ul><ul><ul><ul><li>HMW sensitizers </li></ul></ul></ul><ul><ul><ul><li>LMW sensitizers </li></ul></ul></ul><ul><ul><li>Irritant-induce OA ( non-immunologic) </li></ul></ul><ul><ul><ul><li>Reactive airways dysfunction syndrome (RADS) </li></ul></ul></ul><ul><ul><ul><li>Persistent asthma symptoms induced by a one-time, high-level irritant. </li></ul></ul></ul><ul><ul><ul><li>Others </li></ul></ul></ul>Types of Occupational Asthma
  10. 10. <ul><li>Asthma like disorders ( OTDs) </li></ul><ul><ul><li>expose to vegetable dust ,animal confinement building </li></ul></ul><ul><ul><li>associated with systemic symptoms </li></ul></ul><ul><ul><li>no latency periods </li></ul></ul><ul><ul><li>neutrophillic airway inflammation </li></ul></ul><ul><li>Eosinophillic bronchitis </li></ul><ul><ul><li>develop chronic airway obstruction </li></ul></ul>ORGANIC TOXIC DUST SYNDROME Asthma like disorders
  11. 11. <ul><li>Sensitizer-induced </li></ul><ul><li>Specific antigen </li></ul><ul><li>Minimal exposure </li></ul><ul><li>Stereotyped response </li></ul><ul><li>PPE often insufficient to control symptoms </li></ul><ul><li>Medical removal usually necessary </li></ul><ul><li>Irritant-induced </li></ul><ul><li>Any irritant </li></ul><ul><li>Moderate to heavy exposure </li></ul><ul><li>Often variable </li></ul><ul><li>PPE often effective in preventing episodes </li></ul><ul><li>Medical removal the last resort </li></ul>Occupational Asthma
  12. 12. <ul><li>Sensitizer Occupational Asthma is caused by sensitization to a specific chemical agent in the workplace over a period of time . This is the mechanism for the vast majority (>90%) of cases of occupational asthma. The sensitization process does not occur after one exposure but develops over time (i.e., latency period ). </li></ul><ul><li>Sensitization to a specific antigen </li></ul><ul><ul><li>low molecular-weight. </li></ul></ul><ul><ul><li>high molecular weight. </li></ul></ul>Sensitizer-Induced Occupational Asthma
  13. 13. <ul><li>LMW Agents (< 5Kd) </li></ul><ul><ul><li>Too small to be complete allergens </li></ul></ul><ul><ul><li>Immunologic mechanisms less well characterized </li></ul></ul><ul><ul><li>Specific Ig-E to isocyanates & plicatic acid found in only 15-30% </li></ul></ul><ul><li>Low MW </li></ul><ul><li>Isocyanates </li></ul><ul><li>Anhydrides </li></ul><ul><li>Metal salts </li></ul><ul><li>Epoxy resins </li></ul><ul><li>Fluxes </li></ul><ul><li>Persulfate </li></ul><ul><li>Aldehydes </li></ul>Common Sensitizers
  14. 14. <ul><li>High MW </li></ul><ul><li>Pharmaceuticals </li></ul><ul><li>Animal proteins </li></ul><ul><li>Latex </li></ul><ul><li>Cereals </li></ul><ul><li>Seafood </li></ul><ul><li>Proteolytic enzymes </li></ul><ul><li>Wood constituents </li></ul><ul><li>HMW Agents (> 5Kd) </li></ul><ul><ul><li>Organic proteins/ polysaccharides </li></ul></ul><ul><ul><li>Type-I Hypersensitivity </li></ul></ul><ul><ul><li>Often skin or serologic evidence of sensitization </li></ul></ul><ul><ul><li>Atopy typically a predisposing condition </li></ul></ul>Common Sensitizers-2
  15. 15. <ul><li>Irritant Induced Occupational Asthma usually develops after a single, very high exposure to an irritant chemical. It is a direct “burn” effect on the airways and is not related to the immune system. </li></ul><ul><li>Often represents clinical expression of airways hyperactivity + irritant exposure </li></ul><ul><li>May be induced by any irritating exposure </li></ul><ul><li>Usually history of intolerance to second-hand tobacco smoke </li></ul><ul><li>Some irritant exposures may also be sensitizing: Isocyanides . </li></ul>Irritant-Induced Occupational Asthma
  16. 16. Reactive airways dysfunction syndrome (RADS) 1. Single or several exposures to gas, smoke, fume or vapor which was present in very high concentrations and was irritant in nature. 2. Dyspnea, cough, asthmatic symptoms occurring usually within 24 hours after the exposure. 3. No latency time before symptoms. 4. Obstruction in spirometric values or in PEF follow-up or unspecific bronchial hyperreactivity in histamine or metacholine challenge test. 5. Possible earlier obstructive lung diseases clearly distinguished from the accidental incident. 6. Symptoms and functional findings last several months or remain permanent Piirilä et al. Ärsytyksen aiheuttama astma. Duodecim 2002;118
  17. 17. <ul><li>Very common </li></ul><ul><li>Existing airways reactivity: </li></ul><ul><ul><li>asthma </li></ul></ul><ul><ul><li>hay fever and rhinitis </li></ul></ul><ul><ul><li>other airways disease (e.g. COPD) </li></ul></ul><ul><li>Initial condition not occupational </li></ul><ul><li>Moderate irritant exposure </li></ul><ul><li>Provokes airways response </li></ul><ul><li>Saarinen et al. Eur Respir J 2003;22 2613 asthmatics, 969 currently employed 21% reported work-aggravated symptoms </li></ul><ul><ul><li>exposure to dusts </li></ul></ul><ul><ul><li>abnormal temperatures </li></ul></ul><ul><ul><li>poor indoor air quality </li></ul></ul><ul><ul><li>physicaally strenuous work </li></ul></ul><ul><ul><li>chemicals </li></ul></ul>Work-aggravated Asthma:
  18. 18. Occupational Asthma
  19. 19. Asthma Pathophysiology
  20. 20. Triggers and Irritants Things that may initiate an asthma attack
  21. 21. Exposure to nickel dust
  22. 22. Acute, high RADS Chronic, low  high Chronic bronchitis Asthma Asthma-like syndrome Sensitizer Atopic asthma Irritant Modified from do Pico 2004 Workplace exposure
  23. 23. Airway Remodeling Symptoms Smooth Muscle Dysfunction Airway Inflammation Asthma Pathophysiology
  24. 24. INFLAMMATION Pathogenesis: Airflow Limitation SYMPTOMS Cough Wheeze Dyspnoea TRIGGERS Allergens, Exercise, Cold Air, SO2 Particulates Airway Hyperresponsiveness INDUCERS Allergens, Chemical sensitizers, Air pollutants,
  25. 25. The bronchial epithelium is highlighted as a key site for
  26. 26. Leukotrienes C4, D4 & E4 Asthma Pathology - Modern view
  27. 27. Diagnostic Approach
  28. 28. Diagnostic Criteria
  29. 29. <ul><li>Objective testing </li></ul><ul><ul><li>Spirometry </li></ul></ul><ul><ul><li>Tests of NSBH </li></ul></ul><ul><li>- Specific inhalation challenge </li></ul><ul><li>- PEFR monitoring </li></ul><ul><li>- Immunologic testing </li></ul>Principles of Evaluation New Devices to measure FEV1
  30. 30. Exposure challenge testing Spirometry <ul><li>at and away from work </li></ul><ul><li>cross-shift </li></ul>
  31. 31. <ul><li>Impractical for screening worker populations </li></ul><ul><li>No evidence that pre-screening can predict development of OA </li></ul><ul><li>For workers with high risk, use to evaluate for OA while still actively exposed at work </li></ul>* Non-specific Bronchial Hyper-reactivity NSBH Tests of NSBH
  32. 32. <ul><li>Bronchoprovocation Study: methacholine or histamine induced fall in FEV1 > 20% </li></ul><ul><li>PC20 ( provocative concentration ) < 8 mg/ml (normal >16 mg/ml) </li></ul><ul><li>Correlates with asthma severity </li></ul>Bronchial Responsiveness
  33. 33. <ul><li>“ Gold-standard” </li></ul><ul><li>Decrease in FEV1 of > 20% in response to specific agent </li></ul><ul><li>Performed at specialized centers; limited by precise knowledge of the agent </li></ul><ul><li>Indications </li></ul><ul><ul><li>Diagnosis in doubt </li></ul></ul><ul><ul><li>Potential “new” agent </li></ul></ul><ul><ul><li>Finding exact agent in complex workplace </li></ul></ul><ul><ul><li>Medical-legal purposes </li></ul></ul>Specific Inhalation Challenge (SIC)
  34. 34. Exposure chamber
  35. 35. <ul><li>PEF vs Time over several weeks, including work and free days </li></ul><ul><li>Diurnal variation of > 20% on work days </li></ul><ul><li>Sensitivity 75% / Specificity 100% </li></ul><ul><li>Limitations: </li></ul><ul><ul><li>Compliance </li></ul></ul><ul><ul><li>Falsification </li></ul></ul><ul><ul><li>Confounding factors </li></ul></ul><ul><ul><li>Variable interpretation </li></ul></ul>Peak Flow Monitoring
  36. 36. <ul><li>At least 2 weeks at work and off work </li></ul><ul><ul><li>(often longer...) </li></ul></ul><ul><li>At least 4 times daily, preferably every 2 hours </li></ul><ul><li>Medication allowed: </li></ul><ul><ul><li>keep constant & at minimum dose... </li></ul></ul><ul><ul><li>beta-2 agonist on demand only </li></ul></ul><ul><ul><li>continue inhaled steroids/theophylline </li></ul></ul><ul><ul><li>avoid, if possible, long-acting beta-2-agonist </li></ul></ul>Peak Flow Monitoring
  37. 37. <ul><li>False positive </li></ul><ul><li>Subject not exposed during monitoring </li></ul><ul><li>Poor compliance </li></ul><ul><li>False negative </li></ul><ul><li>Change in medication (inhaled steroids) </li></ul><ul><li>Bronchitis </li></ul><ul><li>Malingering (falsification of results) </li></ul>Peak Flow Monitoring
  38. 38. Serial monitoring of PEF in the diagnosis of OA Improvement of PEF when away from work and deterioration of PEF on returning to work
  39. 39. <ul><li>Computer generated diagnostic aid </li></ul><ul><li>Provides a probability score based on the plotted data </li></ul><ul><li>More sensitive than experienced visual analysis </li></ul>OASYS
  40. 40. <ul><li>Exhaled nitric oxide (eNO) correlates with measures of airway inflammation </li></ul><ul><ul><li>Mirrored environmental pollutant levels </li></ul></ul><ul><ul><li>Increased in symptomatic aluminum workers </li></ul></ul><ul><li>Sputum analysis </li></ul><ul><ul><li>Cell counts change before spirometry or BHR </li></ul></ul>Novel Diagnostic Tools
  41. 41. <ul><ul><li>Skin Test: ( IgE ) </li></ul></ul><ul><ul><ul><li>Valid for HMW allergens (eg. baker’s asthma) & rarely for LMW agents (eg. diisocyanates) </li></ul></ul></ul><ul><ul><ul><li>Requires good allergen extracts </li></ul></ul></ul><ul><ul><ul><li>Frequently not available commercially </li></ul></ul></ul><ul><ul><ul><li>When positive, means presence of sensitization </li></ul></ul></ul><ul><ul><li>RAST </li></ul></ul><ul><ul><li>ELISA </li></ul></ul>Immunologic testing
  42. 42. <ul><li>  Byssinosis in a 56-year-old woman who had had frequent episodes of “Monday fever” and dyspnea while working in a cotton quilt factory over a 7-year period. (a) Chest radiograph shows diffuse, ill-defined haziness, predominantly in the lower lung zones. </li></ul>Byssinosis (Asthma like RADS)
  43. 43. <ul><li>High-resolution CT scan shows numerous ill-defined small nodules with ground-glass attenuation in both lungs. (c) High-resolution CT scan obtained 23 days later shows resolution of the ground-glass attenuation with fewer residual small nodules than were previously noted. No abnormality was seen at high-resolution CT performed 1 year after the patient quit her job. In spite of prolonged exposure, the patient’s respiratory symptoms and pulmonary functional impairment resolved completely. </li></ul>Byssinosis
  44. 44. <ul><li>Isocyanate-induced acute hypersensitivity pneumonitis in a 36-year-old man who presented with severe cough and dyspnea after spray painting in a ship repair plant. (a) Chest radiograph shows patchy airspace consolidation throughout both lungs. A predominantly peripheral area of consolidation is seen in the right lung. </li></ul>    Isocyanate-induced acute hypersensitivity pneumonitis in a 36-year-old man who presented with severe cough and dyspnea after spray painting in a ship repair plant Kim K et al. Radiographics 2001;21:1371-1391 ©2001 by Radiological Society of North America
  45. 45. <ul><li>High-resolution CT scan obtained on the 2nd day of hospitalization shows patchy areas of consolidation and ground-glass attenuation in both lungs and less profuse small nodular hyperattenuating areas. Note the pneumomediastinum, which is probably associated with the severe cough. Follow-up high-resolution CT performed 9 days later showed complete resolution of the parenchymal hyperattenuating areas. </li></ul>Isocyanate-induced acute hypersensitivity pneumonitis in a 36-year-old man who presented with severe cough and dyspnea after spray painting in a ship repair plant
  46. 46. Compatible clinical history and exposure Skin testing and/or specific IgE (if possible) Assessment of NSBH Normal Increased Subject still at work Subject no longer at work Subject still at work Laboratory challenge tests Positive Negative Consider return to work Workplace challenge tests PEF monitoring, or both Positive Negative No asthma Occupational asthma Non occcupational asthma Use of other means (induced sputum, exhaled NO ) Chan Yeung M, Malo JL. NEJM 1995; 333:107 Algorithm for investigation of occupational asthma
  47. 47. Management
  48. 48. <ul><li>Complete avoidance </li></ul><ul><li>Medication not better than avoidance </li></ul><ul><li>Protective devices? </li></ul><ul><li>Lower exposure? </li></ul><ul><li>Allergen immunotherapy? </li></ul>Management
  49. 49. Management
  50. 50. 1.Pre-placement Assessment 2. Exposure control 3. PPE & Awareness MSDS Medical Surveillance 1.Employee Accommodations 2. Job Retraining 3. upgrading standards of care 3. upgrading accessibility of care primary prevention Tertiary prevention Secondary prevention Prevention & Control 1. map the magnitude of OA 2. analyse OA determinants 3. monitor future trends
  51. 51. <ul><li>Occupational asthma, based on sensitization to agents encountered at work, is the best defined and documented type of work-related asthma but under diagnosed. </li></ul><ul><li>RADS is a special subgroup of occupational asthma induced without a latency period by a high level of exposure to irritants. </li></ul><ul><li>Prevention (decreasing exposure) is important, because the prognosis is not very good. </li></ul><ul><li>Work-related asthma includes also worsening of pre-existing asthma due to harmful exposure at work, and presumably also asthma developed in long-term but not very high exposure to irritants, not defined as occupational diseases to-day. Prevention of exposure is most important. </li></ul>Conclusion
  52. 52. THANK YOU
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