Occupational Asthma Tee L. Guidotti The George Washington University

Presentation of Occ Asthma Immediate hypersensitivity reactionImmediate hypersensitivity reaction Immediate bronchospasmImmediate bronchospasm Isolated late response (usually sensitizer- induced)Isolated late response (usually sensitizer- induced) Sleep disorderSleep disorder Variable/dual responseVariable/dual response

Types of Occupational Asthma New OnsetNew Onset - Sensitizer-induced - Sensitizer-induced - Irritant induced - Irritant induced Aggravation of underlying asthmaAggravation of underlying asthma Reactive airways dysfunction syndrome (RADS)Reactive airways dysfunction syndrome (RADS) Cold air- or exercise-induced syndromeCold air- or exercise-induced syndrome Airways reactivity secondary to hypersensitivity pneumonitisAirways reactivity secondary to hypersensitivity pneumonitis

Occupational Asthma Sensitizer-induced Specific antigenSpecific antigen Minimal exposureMinimal exposure Stereotyped responseStereotyped response PPE often insufficient to control symptomsPPE often insufficient to control symptoms Medical removal usually necessaryMedical removal usually necessary Irritant-induced Any irritant Moderate to heavy exposure Often variable PPE often effective in preventing episodes Medical removal the last resort

Sensitizer-Induced Occ Asthma Sensitization to a specific antigenSensitization to a specific antigen - low molecular-weight, “hapten” - low molecular-weight, “hapten” - high molecular weight - high molecular weight Reaginic Ab, mostly IgE, mediatedReaginic Ab, mostly IgE, mediated Presentation variablePresentation variable - late phase reactivity - late phase reactivity - immediate sensitivity - immediate sensitivity - dual or variable responsiveness - dual or variable responsiveness

Sensitizer-Induced Asthma 2 Sensitization may occur at <OELSensitization may occur at <OEL Sensitizers may also be irritants (e.g. TDI,TMA)Sensitizers may also be irritants (e.g. TDI,TMA) Prior history of atopy does not predict risk of asthma!Prior history of atopy does not predict risk of asthma! Therefore no basis of exclusion of persons with allergies from workplaceTherefore no basis of exclusion of persons with allergies from workplace

Common Sensitizers (Incomplete List!) Low MW IsocyanatesIsocyanates AnhydridesAnhydrides Metal saltsMetal salts Epoxy resinsEpoxy resins FluxesFluxes PersulfatePersulfate AldehydesAldehydes High MW Pharmaceuticals Animal proteins Latex Cereals Seafood Proteolytic enzymes Wood constituents

Irritant-Induced Occupational Asthma More common, clinically, than sensitizer-inducedMore common, clinically, than sensitizer-induced Often represents clinical expression of airways hyperactivity + irritant exposureOften represents clinical expression of airways hyperactivity + irritant exposure May be induced by any irritating exposureMay be induced by any irritating exposure Usually history of intolerance to second-hand tobacco smokeUsually history of intolerance to second-hand tobacco smoke Some irritant exposures may also be sensitizing: CHO, TDI,TMASome irritant exposures may also be sensitizing: CHO, TDI,TMA Classic example is “hot wire” asthmaClassic example is “hot wire” asthma

RADS Acute onset following exposure to irritantAcute onset following exposure to irritant Generally exposure of moderate severityGenerally exposure of moderate severity Prognosis good but may have several years of airway hyperactivity and sequelaePrognosis good but may have several years of airway hyperactivity and sequelae Often associated with:Often associated with: –upper airway problems –sleep disorder Independent of prior history of airways reactivityIndependent of prior history of airways reactivity Conventional managementConventional management

Aggravational Asthma Very commonVery common Existing airways reactivity:Existing airways reactivity: –asthma –hay fever and rhinitis –other airways disease (e.g. COPD) Initial condition not occupationalInitial condition not occupational Moderate irritant exposureModerate irritant exposure Provokes airways responseProvokes airways response Usually self-limitedUsually self-limited

Patterns of Airways Response

Immediate response Same shift, rapid onsetSame shift, rapid onset Reaginic antibody if sensitizer-inducedReaginic antibody if sensitizer-induced Acute mediatorsAcute mediators Responds to conventional asthma RxResponds to conventional asthma Rx Often difficult to distinguish from conventional asthmaOften difficult to distinguish from conventional asthma Irritant-induced tends to be milderIrritant-induced tends to be milder

Late Responders Onset of bronchospasm hours after exposureOnset of bronchospasm hours after exposure Usually wheezing post-shiftUsually wheezing post-shift Often presents as a sleep disorderOften presents as a sleep disorder If isolated, usually associated with certain antigens (Western red cedar, TDI)If isolated, usually associated with certain antigens (Western red cedar, TDI) Often combinedOften combined

Dual/Variable effects Dual responders may combine immediate + late responsesDual responders may combine immediate + late responses Variations may include cyclic bronchospasm (esp. Western red cedar)Variations may include cyclic bronchospasm (esp. Western red cedar) May be prolonged, sustained response (TDI, byssinosis)May be prolonged, sustained response (TDI, byssinosis) Usually slow recovery, relatively refractory to conventional RxUsually slow recovery, relatively refractory to conventional Rx

Special Cases The following subsets of occupational asthma have special features: Laboratory animal sensitivity (high risk of anaphylaxis)Laboratory animal sensitivity (high risk of anaphylaxis) Cotton dust, byssinosisCotton dust, byssinosis Grain dustGrain dust Hypersensitivity pneumonitis may have an airways componentHypersensitivity pneumonitis may have an airways component

Cold Air / Exercise-Induced Asthma May be associated with:May be associated with: –dry cold air –exertion –hyperventilation Work in cold, dry climatesWork in cold, dry climates Immediate response, short durationImmediate response, short duration Further exercise may improve airflow!Further exercise may improve airflow! Mechanism: airway drying and coolingMechanism: airway drying and cooling –stimulates vagal receptors –histamine, mediator release from mast cells

Principles of Evaluation Demonstrate airways reactivityDemonstrate airways reactivity - History - History - Presence of wheezing - Presence of wheezing SpirometrySpirometry Methacholine challengeMethacholine challenge Bronchoprovocation or substituteBronchoprovocation or substitute - Symptom diary - Symptom diary - Pre/post shift - Pre/post shift

Methacholine Challenge + Test confirms airways reactivity only+ Test confirms airways reactivity only A functional test not specific for asthmaA functional test not specific for asthma - atopy - atopy - transient reactivity - transient reactivity Bronchoprovocation with with specific antigen preferable to diagnose sensitizer-induced asthmaBronchoprovocation with with specific antigen preferable to diagnose sensitizer-induced asthma -Tests can occur with quiescent occ asthma-Tests can occur with quiescent occ asthma

Risks of Bronchoprovocation AnaphylaxisAnaphylaxis Iatrogenic reactionIatrogenic reaction SensitizationSensitization

Ancillary Tests Clinical immunologyClinical immunology - skin prick tests - skin prick tests - RAST - RAST - ELISA - ELISA PEF or FEV 1, symptom and medication diaryPEF or FEV 1, symptom and medication diary Pre/post shift and/or holiday PFTsPre/post shift and/or holiday PFTs Work place HHEWork place HHE

Management Conventional Rx for asthmaConventional Rx for asthma Medical removal – consider optionsMedical removal – consider options Physician’s First ReportPhysician’s First Report Impairment Assessment (c.f. AMA guidelines)Impairment Assessment (c.f. AMA guidelines) Avoid irritantsAvoid irritants Evaluate PPEEvaluate PPE

Compensation Management Document causationDocument causation Document impairment (episodic?)Document impairment (episodic?) Medical removal required?Medical removal required? Claimant factorsClaimant factors - degree of impairment - degree of impairment - age - age - retraining - retraining Impairment – Disability

Pop Health Management Treat as “Sentinel event”Treat as “Sentinel event” SurveillanceSurveillance Identification of specific hazard when possibleIdentification of specific hazard when possible Hazard ControlHazard Control - engineering controls - engineering controls - PPE - PPE