Transcript Asthmacolor - University of Western Ontario

THE UNIVERSITY OF WESTERN ONTARIO
Department of Epidemiology & Biostatistics
2003
F. Lortie-Monette, MD, MSc, CSPQ, MBA
OCCUPATIONAL ASTHMA
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.
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.
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.
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
Agents
Isocyanates
Occupations at Risk
(prevalence of isocyanate-induced
asthma in exposed workers is close to
10%).
spray painters, insulation installers,
manufacturers of plastics, rubbers, foam
and coating;
manufacturers of cars, planes and trains
wood dusts (cedar, oak)
sawmills workers, carpenters
acid anhydrides
users of plastics, epoxy resins
aliphatic amines (e.g., ethylenediamine)
shellac and lacquer handlers, solderers
metals, fluxes, (platinum salts, cobalt,
colophony)
platinum refineries, hard metal grinding,
electronic (soldering)
chloramine-T
janitorial work, cleaners
dyes
textile and dye manufacturing
persulphate
hairdresser
formaldehyde, glutaraldehyde
embalming, hospital workers
acrylates
adhesives handlers
drugs (e.g., antibiotics, psyllium)
pharmaceutical
manufacturing/packaging, health workers
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 1987–93 (p=0.001).
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.
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 1980-83

55-58 claims/year in 1988-90

19-20 claims/year by 1992-93
COMMON HIGH MOLECULAR WEIGHT AGENTS
CAUSING OCCUPATIONAL ASTHMA
Agents
Occupations at Risk
Plant-derived substances:
flour and grain dusts
bakers, millers
latex
health workers
enzymes
detergent making, detergent users,
pharmaceutical workers,
food processing,
meat tenderizer producer
gums
carpet makers,
pharmaceutical workers
COMMON HIGH MOLECULAR WEIGHT AGENTS
CAUSING OCCUPATIONAL ASTHMA - continued
Agents
Occupations at Risk
Animal-derived allergens:
laboratory animals
animal handlers, laboratory workers
crab/seafood
seafood processing
egg protein
egg production
grain mites, insects
silk workers
CAUSES OF OCCUPATIONAL SENSITIZATION 4
(examples)
Bakeries
wheat,
other cereals,
enzymes (e.g., fungal amylase)
Health care workers
natural rubber latex in gloves,
psyllium in laxatives,
penicillin-derived antibiotics, glutaraldehyde
Laboratories
animal proteins,
enzymes,
antibiotics,
other pharmaceutical products
Companies using or
making polyurethane foam
or spray paints
Diisocyanates
Electronic workers
colophony, amines, acrylic glues
Diagnosing Occupational Asthma:
Stepwise procedure:
(i)
Does the patient have asthma (variable airflow
limitation/bronchial hyperresponsiveness)?
(ii)
Is the asthma work-related?
(iii)
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
Diagnosis
FEV 1 post bronchodilator: 12% or more (ideally 15%)
(20% with repeated
measurements or after
corticosteroid treatment)
PEF: 20% or more postbronchodilator or after
repeated measurements
Methacholine test: PC20 < 8 mg/mL
(Juniper method)
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
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.
ADVANTAGES and DISADVANTAGES OF DIAGNOSTIC
METHODS for OCCUPATIONAL ASTHMA
Method
Advantages
Disadvantages
Questionnaire
Simple,
Sensitive
Low specificity
Immunologic testing
Simple,
Sensitive
Only for high-molecular- weight
and some low-molecular- weight
agents;
identifies sensitization,
not work disease;
many allergens not available
commercially
Bronchial
responsiveness to
methacholine or
histamine
Simple,
Sensitive
Not specific for occupational
asthma;
occupational asthma not ruled out
by a negative test
Measurement of FEV 1 Simple,
before or after work
Inexpensive
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)
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
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.
EXAMPLES OF OCCUPATIONAL DISEASES
chronic obstructive lung
cadmium
Infections:
human-to-human
animal to human
soil to human
tuberculosis
hantavirus
coccidiomycoses
granulomatous lung disease
beryllium
hypersensitivity pneumonitis
(allergic alveolitis)
organic dusts
pulmonary fibrosis
asbestos, silica
bronchogenic carcinoma
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
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
• Mouldy hay & straw
• Bird droppings &
feathers
• Water from
humidifiers & air
conditioners
• Wood Worker’s Lung
• Bark stripping; wood
pulp & chips
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
Hypersensitivity Pneumonitis
Treatment
• Stop exposure to the causative antigen
• Steroids
The End
EXAMPLES OF OCCUPATIONAL DISEASES - continued
Wood work
wood dusts (e.g., plicatic acid in red
cedar),
fungal spores,
phenol-formaldehyde resins,
formaldehyde in particle board
Metal work
complex platinum salts,
nickel,
cobalt,
chromium compounds
Working with plants, fish,
animals or insects
almost any plant, fish,
animal or insect protein with
airborne or skin exposure