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

2. 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

3. 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

4. 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

5. 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

6. 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%

7. 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

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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

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

19. 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