Occupational and environmental asthma A. H. Mehrparvar, MD Occupational Medicine department Yazd University of Medical Sciences

History Mentioned by Hippocrates to be present among metalworkers, tailors, farmers and fisherman Respiratory disease among workers appears in Egyptian papyrus and was described by Pliny in Roman times In 1713, Ramazzini described respiratory disease that appears to be asthma among handlers of old clothes and workers with flax, hemp, and silk

During the time of the Industrial Revolution, Charles Turner Thackrah mentioned asthma in hatters, and hairdressers In 1911, there was the recognition of asthma due to platinum salts use among photographic workers By the 1990s, it became appreciated that OA was the most common type of occupational lung disease

Definition variable air flow limitation caused by a specific agent in the workplace asthma caused by work new onset asthma caused by workplace exposure a disease with variable airflow limitation and/or bronchial hyperresponsiveness due to causes and conditions attributable to a particular working environment and not to stimuli encountered outside the workplace

Occupational asthma Reversible airway obstruction, with airway inflammation and bronchial hyperresponsiveness as a consequence of occupational exposures 10-15% of adult asthma the most frequently reported occupational respiratory disorder in industrialized populations

In some industries up to 50% of all long-term workers have been found to suffer from work-related asthma The annual incidence of OA ranges from 12 to 170 cases per million workers The prevalence of OA in any particular industry or work operation can range between 1% and more than 50%

Occupational asthma Work-induced Work-aggravated Animal-derived material Plant-derived material Enzymes Isocyanates Acid-anhydrides Formaldehyde Work-aggravated Dusts Smoke Fumes Cold air exercise

Risk factors for OA Exposure Characteristics Chemical Characteristics Workplace Characteristics Host Characteristics Atopy Cigarette smoking Rhinoconjunctivitis Nonspecific bronchial hyperresponsiveness

Types of asthma Sensitizer-induced Irritant-induced Work-aggravated Allergic-type OA and work-aggravated asthma occurs much more frequently than irritant-induced asthma The prevalence of irritant-induced asthma is 6% to 22% of all work-related cases

Sensitizer-induced asthma Mechanism: Type 1 immune reaction (IgE) Latent period for sensitization In a percent of workers Minimal exposure Stereotyped response PPE often insufficient to control symptoms Medical removal usually necessary Prior history of atopy does not predict risk of asthma

symptoms following repeat exposures to a specific allergen within a few months of beginning work but usually within the first few years Once sensitization develops, subsequent allergen exposure induces acute asthmatic responses The worker notices asthmatic symptoms improve when there is no workplace exposures, especially during the weekends or vacations

three distinct patterns of bronchospastic reactions occur: immediate or early (15 to 30 minutes) nonimmediate or late (begins about 1 hour after antigen challenge, generally peaks by 3 to 5 hours, and lasts 12 to 24 hours) dual or combined reactions

Common Sensitizers Low MW Isocyanates Anhydrides Metal salts Epoxy resins Fluxes Persulfate Aldehydes High MW Pharmaceuticals Animal proteins Latex Cereals Seafood Proteolytic enzymes Wood constituents

Irritant-induced asthma Atopy a risk factor Non-specific bronchial hyperresponsiveness Usually history of intolerance to second-hand tobacco smoke Some irritant exposures may also be sensitizing: TDI,TMA Any irritant Moderate to heavy exposure PPE often effective in preventing episodes Medical removal the last resort

RADS Acute onset following exposure to irritant Generally exposure of moderate severity Prognosis good but may have several years of airway hyperactivity and sequelae Independent of prior history of airways reactivity Conventional management

Criteria for diagnosis of RADS Absence of preexisting respiratory disorder Onset of asthma after a single exposure to an irritant vapor, gas, fumes, or smoke Onset of asthma within minutes to hours and always less than 24 hours after the exposure Finding of a positive methacholine challenge test following the exposure Symptoms lasting for at least 3 months

Occupations Acid workers Cotton workers Flour factory Blast Furnace operators Carpenters Cement manufacturers Chemical plant workers Chromium platers Concrete workers Cotton workers Drug manufacturers Dyers Metal smelters Welders Fertilizer workers Fish shop workers Fishermen

Food handlers Food process workers Furniture makers Hairdressers Hard metals manufacturers Insulation installers Insulation manufacturers Jewelers Laboratory technician Latex workers Librarian

Diagnostic approaches Spirometry Spirometry after bronchodilator (12% increase) Pre and post shift spirometry (10% decrease) Serial peak flowmetry (20% fluctuation) Methacholine challenge test (during work and after removal) PC20 > 3 times Specific challenge test Skin prick test