Occupational asthma

Occupational asthma
Classification and external resources
MedlinePlus 000110
Patient UK Occupational asthma
MeSH D059366

Occupational asthma is an occupational lung disease and a type of asthma. Like other types of asthma, it is characterized by airway inflammation, reversible airways obstruction, and bronchospasm, but it is caused by something in the workplace environment.[1]

Symptoms include shortness of breath, tightness of the chest, nasal irritation, coughing and wheezing. The first person to use it in reference to a medical condition was Hippocrates, and he believed that tailors, anglers and metalworkers were more likely to be affected by the disease. Although much research has been done since, the inflammatory component of asthma was recognized only in the 1960s.

Hypersensitivity pneumonitis is a related condition, with many occupational examples (e.g. flock worker's lung, farmer's lung, and indium lung). However, although overlapping in many cases, hypersensitivity pneumonitis may be distinguished from occupational asthma in that it isn't restricted to only occupational exposure, and involves type III hypersensitivity and type IV hypersensitivity[2] rather than the type I hypersensitivity[3][4] of asthma. Also, unlike asthma, hypersensitivity pneumonitis targets lung alveoli rather than bronchi.[5]

Signs and symptoms

Less than five years of exposure or a single exposure to a high-concentration agent can result in symptoms. Coughing, wheezing, nasal irritation, shortness of breath, and chest tightness are the most common symptoms, all of which worsen after work and improve during time away from work. Pre-existing asthma can be exacerbated by similar agents.


Approximately 21% of the adults affected by asthma report an aggravation of their symptoms while at work and an improvement when away, which implies that they may be suffering from occupational asthma. In the United States, occupational asthma is the most common occupational lung disease.[6] Today, asthma affects as much as 15% of the Canadian population,[7] a statistic reflective of other developed countries, and has increased fourfold in the last 20 years. Various reasons can be identified for this increase, including increase environmental pollution, better diagnostic ability, and greater awareness.


Diagnosis of occupational asthma uses several techniques.[6]

A non-specific bronchial hyperreactivity test can be used to help diagnose occupational asthma. It involves testing with methacoline, after which the forced expiratory volume in 1 second (FEV1) of the patient is measured. This test is often used for measuring the intensity of a person's asthma and to confirm that the person needs to be treated for asthma.[6]

Other non specific tests could require the patient to run for a few minutes at a continuous pace. In this case, the individual’s peak expiratory flow rate (PEFR) is measured, showing how fast a person can exhale.[8] PEFR can also be measured at work to see if there is a difference from the PEFR in a controlled environment. Measuring PEFR at work is a highly reliable test for occupational asthma.

A skin prick test is usually performed on the inner forearm where a grid is marked and a drop of the allergens to be tested are placed on the arm in the grid. Once this has been done, the skin is pricked through the drop using a lancet. Reactions, if any, occur within 10 to 15 minutes and these results can then be analyzed.[9]

Immunoglobulin E is an antibody found in human blood and is effective against toxins. Since it can also trigger allergic reactions to specific allergens like pollen, the IgE test is performed to evaluate whether the subject is allergic to these substances.[6][10]

A spirometer is a device used to measure timed expired and inspired volumes, and can be used to help diagnose occupational asthma.[11]

Specific inhalation challenges test for reactions to substances found in the workplace. One method is a whole body sealed chamber where the patient is exposed to articles that are present in their workplace. This method has the advantage of being able to assess, albeit highly subjectively, ocular and nasal symptoms as well as a reduction in FEV1. Another test requires the patient to breathe aerosols of the suspected asthmagens through an oro-facial mask. These asthmagens are aerosolized using closed circuit chambers, and the quantities and concentrations administered are minute and extremely stable, to minimize the risk of exaggerated responses.

Prevention and treatment


Prevention of occupational asthma can be accomplished through better education of workers, management, unions and medical professionals. This will enable them to identify the risk factors and put in place preventive measures, including respiratory protection and exposure limits.[6]

Treatment and Recovery

Recovery is directly dependent on the duration and level of exposure to the causative agent. Depending on the severity of the case, the condition of the patient can improve dramatically during the first year after removal from exposure.

Three basic types of procedures are used for treating the affected workers: reducing a worker's exposure, removing a worker from the environment with the asthma-causing agent, and treatment with asthma medications.[6][12] Completely stopping exposure is more effective treatment than reducing exposure.[6] By reducing exposure, the probability of suffering another reaction is lowered. Methods of reducing exposure include transferring an affected worker to a position without the relevant asthmagen, use of respiratory protection, and engineering controls. In 1984 innovator David Cornell discovered and invented effective control equipment in the UK for the removal of many harmful workplace fumes. 'BOFA' extraction products are now found in over 100 countries worldwide.[13]

People affected by occupational asthma that occurred after a latency period, whether a few months or years, should be immediately removed from exposure to the causative agent. However, this can entail severe socio-economic consequences for the worker as well as the employer due to loss of job, unemployment, compensation issues, quasi-permanent medical expenditures, and hiring and re-training of new personnel. This can be mitigated by transferring the worker within a company.[6]

Medical and pharmacological treatment

Short-acting beta-agonists like salbutamol or terbutaline or long-acting beta-agonists like salmeterol and formoterol dilate airways which relieve the symptoms thus reducing the severity of the reaction. Some patients also use it just before work to avoid a drop in the FEV1.

Anti-inflammatory agents like corticosteroids, LKTRA or mast cell stabilizers can also be used depending on the severity of the case.

Occupations at risk

At present, over 400 workplace substances have been identified as having asthmagenic or allergenic properties.[14] Their existence and magnitude vary by region and industry and can include diisocyanates, acid anhydrides, plicatic acid, and platinum salts (all low molecular weight agents), and animal protein, enzymes, wheat, and latex (high-molecular weight agents).[1][6] For example, in France the industries most affected are bakeries and cake-shops, automobile industry and hairdressers,[15] whereas in Canada the principal cause is wood dust, followed by isocyanates. Furthermore, the most common cause of occupational asthma in the workplace are isocyanates.[16] Isocyanates are used in the production of motor vehicles.[16]

The occupations most at risk are: adhesive handlers (e.g. acrylate), animal handlers and veterinarians (animal proteins), bakers and millers (cereal grains), carpet makers (gums), electronics workers (soldering resin), forest workers, carpenters and cabinetmakers (wood dust), hairdressers (e.g. persulfate), health care workers (latex and chemicals such as glutaraldehyde), janitors and cleaning staff (e.g. chloramine-T), pharmaceutical workers (drugs, enzymes), seafood processors, shellac handlers (e.g. amines), solderers and refiners (metals), spray painters, insulation installers, plastics and foam industry workers (e.g. diisocyanates), textile workers (dyes) and users of plastics and epoxy resins (e.g. anhydrides)[17]

The following tables show occupations that are known to be at risk for occupational asthma, and main substances involved.[18]

Grains, flours, plants and gums

Occupation [18]

Agent [18]

Bakers, millers


Chemists, coffee bean baggers and handlers, gardeners, millers, oil industry workers, farmers

Castor beans

Cigarette factory workers

Tobacco dust

Drug manufacturers, mold makers in sweet factories, printers

Gum acacia

Farmers, grain handlers

Grain dust

Gum manufacturers, sweet makers

Gum tragacanth

Strawberry growers

Strawberry pollen

Tea sifters and packers

Tea dust

Tobacco farmers

Tobacco leaf

Woollen industry workers


Animals, insects and fungi

Occupation [18]

Agent [18]

Bird fanciers

Avian proteins

Cosmetic manufacturers



Moths, butterflies

Feather pluckers


Field contact workers


Fish bait breeders

Bee moths

Flour mill workers, bakers, farm workers, grain handlers

Grain storage mites, alternaria, aspergillus

Laboratory workers

Locusts, cockroaches, grain weevils, rats, mice, guinea pigs, rabbits

Mushroom cultivators

Mushroom spores

Oyster farmers

Sea pineapples (Hoya)

Pea sorters

Mexican bean weevils

Pigeon breeders


Poultry workers


Prawn processors


Silkworm sericulturers


Zoological museum curators



Occupation [18]

Agent [18]

Aircraft fitters


Aluminum cable solderers


Aluminum pot room workers


Autobody workers

Acrylates (resins, glues, sealants, adhesives)

Brewery workers


Chemical plant workers, pulp mill workers


Dye weighers

Levafix brilliant yellow, drimarene brilliant yellow and blue, cibachrome brilliant scarlet

Electronics workers


Epoxy resin manufacturers

Tetrachlorophthalic anhydride

Foundry mold makers

Furan-based resin binder systems

Fur dyers



Persulphate salts

Health care workers

Glutaraldehyde, latex

Laboratory workers, nurses, phenolic resin molders


Meat wrappers

Polyvinyl chloride vapour

Paint manufacturers, plastic molders, tool setters

Phthalic anhydride

Paint sprayers


Photographic workers, shellac manufacturers


Refrigeration industry workers



Polyether alcohol, polypropylene glycol

Isocyanates and metals

Occupation [18]

Agent [18]

Boat builders, foam manufacturers, office workers, plastics factory workers, refrigerator manufacturers, TDI manufacturers/users, printers, laminators, tinners, toy makers


Boiler cleaners, gas turbine cleaners


Car sprayers

Hexamethylene diisocyanate

Cement workers

Potassium dichromate

Chrome platers, chrome polishers

Sodium bichromate, chromic acid, potassium chromate

Nickel platers

Nickel sulphate

Platinum chemists

Chloroplatinic acid

Platinum refiners

Platinum salts

Polyurethane foam manufacturers, printers, laminators

Diphenylmethane diisocyanate

Rubber workers

Naphthalene diisocyanate

Tungsten carbide grinders



Stainless steel fumes

Drugs and enzymes

Occupation [18]

Agent [18]

Ampicillin manufacturers

Phenylglycine acid chloride

Detergent manufacturers

Bacillus subtilis

Enzyme manufacturers

Fungal alpha-amylase

Food technologists, laboratory workers



Gentian powder, flaviastase

Pharmaceutical workers

Methyldopa, salbutamol, dichloramine, piperazine dihydrochloride, spiramycin, penicillins, sulphathiazole, sulphonechloramides, chloramine-T, phosdrin, pancreatic extracts

Poultry workers

Amprolium hydrochloride

Process workers, plastic polymer production workers

Trypsin, bromelin


Occupation [18]

Agent [18]

Carpenters, timber millers, woodworkers

Western red cedar, cedar of Lebanon, iroko, California redwood, ramin, African zebrawood

Sawmill workers, pattern makers

Mansonia, oak, mahogany, abiruana

Wood finishers


Wood machinists


Society and culture


When a person is diagnosed with occupational asthma, it can result in serious socio-economic consequences not only for the workers but also for the employer and the healthcare system because the worker must change positions.[6] The probability of being re-employed is lower for those with occupational asthma compared to those with normal asthma. The employer not only pays compensation to the employee, but will also have to spend a considerable amount of time and energy and funds for hiring and training new personnel.[19][20] In the United States, it was estimated that the direct cost of occupational asthma in 1996 was $1.2 billion and the indirect cost $0.4 billion, for a total cost of $1.6 billion.[21]

See also

External links


  1. 1 2 "Asthma & Allergies". NIOSH. April 3, 2012.
  2. Mohr LC (September 2004). "Hypersensitivity pneumonitis". Curr Opin Pulm Med. 10 (5): 401–11. doi:10.1097/01.mcp.0000135675.95674.29. PMID 15316440.
  3. "Lecture 14: Hypersensitivity". Retrieved 2008-09-18.
  4. "Allergy & Asthma Disease Management Center: Ask the Expert". Retrieved 2008-09-18.
  5. Page 503 in: Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson (2007). Robbins Basic Pathology. Philadelphia: Saunders. ISBN 1-4160-2973-7. 8th edition.
  6. 1 2 3 4 5 6 7 8 9 10 de Groene, Gerda J.; Pal, Teake M.; Beach, Jeremy; Tarlo, Susan M.; Spreeuwers, Dick; Frings-Dresen, Monique Hw; Mattioli, Stefano; Verbeek, Jos H. (2011). "Workplace interventions for treatment of occupational asthma". The Cochrane Database of Systematic Reviews (5): CD006308. doi:10.1002/14651858.CD006308.pub3. ISSN 1469-493X. PMID 21563151.
  7. C-Health: Asthma in Canada(2007)
  8. Milton DK, Solomon GM, Rosiello RA, Herrick RF (January 1998). "Risk and incidence of asthma attributable to occupational exposure among HMO members". Am. J. Ind. Med. 33 (1): 1–10. doi:10.1002/(SICI)1097-0274(199801)33:1<1::AID-AJIM1>3.0.CO;2-2. PMID 9408523.
  9. Kroczyńska-Bednarek J, Grzelewska-Rzymowska I, Tymińska K (March 1997). "[Nonspecific bronchial hyperreactivity in patients with seasonal bronchial asthma observed through two consecutive years]". Pol. Arch. Med. Wewn. (in Polish). 97 (3): 216–23. PMID 9333767.
  10. Allergy Society of South Africa. The Skin Prick Test. Toerien A,Potter P C, Buys C
  11. Specific Test Key To Determine Whether Or Not Allergy Symptoms Are Really Allergy-Related
  12. Diagnosis and Management of Work-Related Asthma. Evidence Report/Technology Assessment number 129. Beach J, Rowe B, Blitz S, Crumley E, Hooton N, Russell K, Spooner C
  13. http://www.bofa.co.uk/history.asp
  14. (T78) Occupational Asthma : Table of agents, products and substances which can cause asthma
  15. Ameille J, Pauli G, Calastreng-Crinquand A, et al. (February 2003). "Reported incidence of occupational asthma in France, 1996–99: the ONAP programme". Occup Environ Med. 60 (2): 136–41. doi:10.1136/oem.60.2.136. PMC 1740458Freely accessible. PMID 12554842.
  16. 1 2 Chan-Yeung, Moira; Malo, Jean-Luc (1995-07-13). "Occupational Asthma". New England Journal of Medicine. 333 (2): 107–112. doi:10.1056/NEJM199507133330207. ISSN 0028-4793. PMID 7777015.
  17. MayoClinic --> Occupational asthma May 23, 2009
  18. 1 2 3 4 5 6 7 8 9 10 11 12 13 Unless else specified in boxes, then reference is: Canadian Centre for Occupational Health and Safety (CCOHS) (a federal government site) > OSH Answers > Diseases, Disorders & Injuries > Asthma Document last updated on February 8, 2005
  19. MedlinePlus Medical Encyclopedia: Peak expiratory flow rate
  20. Dewitte JD, Chan-Yeung M, Malo JL (May 1994). "Medicolegal and compensation aspects of occupational asthma". Eur. Respir. J. 7 (5): 969–80. PMID 8050556.
  21. Leigh JP, Romano PS, Schenker MB, Kreiss K (January 2002). "Costs of occupational COPD and asthma". Chest. 121 (1): 264–72. doi:10.1378/chest.121.1.264. PMID 11796461.
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