Does your work put you at risk for asthma?

Does what you do for a living increase your risk of asthma? About 11 million American workers may have occupational asthma. Recent studies have further highlighted the connection between occupation and the risk of asthma. Over 360 substances have been linked to the development of asthma with anywhere from 50% to 90% of cases due to aldehydes, animals, enzymes, flour, isocyanates, latex and persulphate salts.1

Because of their different mechanisms, inducing agents are generally classified as high-molecular, low-molecular weight or irritant. High molecular weight agents include animal and plant antigens, anthropods, mites, bio-aerosols, enzymes, latex and pharmaceutical product antigens. Low molecular weight agents include the reactive chemicals (aldehydes, amines, etc.), acrylates, epoxy chemicals and diisocyanates. Irritating agents include cleaning agents, wood and paper dusts, inorganic dusts and fumes, textile dust, metal working fluids, vehicle and motor exhaust and environmental tobacco smoke. Occupations that are at high risk for accidental peak exposure to irritants include firefighters, police officers, sheet metal workers, ore and metal furnace operators and welders.

A study2 published in Thorax showed that the type of job an individual has may increase the risk for developing asthma as an adult. The researchers found that one in six cases of asthma could be linked to the workplace. The development of adult asthma was clearly linked with 18 different occupations. The study involved 9488 British adults, born in 1958. Occupational histories were taken up to age 42. Lung function and atopy were also assessed. While one in four smoked tobacco by age 42, one in four also never held a job that increased the risk of asthma. The researchers calculated exposure to compounds known to cause occupational asthma. These included respiratory irritants, enzymes, flour, metal fumes, cleaning and disinfecting products, and textile production.

The study found exposure to agents and the likelihood of being diagnosed with a respiratory condition as follows:

  • subjects (8%) exposed to high-risk agents were 53% more likely to be diagnosed
  • subjects (28%) exposed to low-risk agents were 20% more likely to be diagnosed
  • the 34% exposed to both high- and low-risk agents were 34% more likely to be diagnosed.

Researchers also noted that the strongest link with adult asthma lay in occupations that involved cleaning or cleaning agents. While farmers led the list of 18 occupations, aircraft mechanics, typesetters, office and general cleaners, domestic helpers, laundry, and care workers were also on the list. The specific risk of developing asthma for certain occupations was listed in increasing order of risk as

  • Metal-working or jobs involving exposure to metal fumes – OR 1.45
  • Cleaning or disinfecting products – OR 1.67
  • Textile production – OR 1.71
  • Hairdressers – OR 1.88
  • Exposure to flour – OR 2.12
  • Exposure to enzymes – OR 2.32
  • Printers – OR 3.04
  • Farmers – OR 4.26

After accounting for all other factors including gender, smoking, social class at birth and childhood hay fever, the researchers found that 16% of adult-onset asthma was associated with the individuals’ occupations. Causality was not confirmed but an association was found to exist. In effect, the working environment, with its attendant respirable particles, may be the cause of inflammation in the lungs leading to occupational asthma.

A large, population-based study3 that involved five Northern European countries, showed that while both men and women exposed to cleaning agents were at risk for asthma, men had a significant increase in new-onset asthma and non-atopic men had a further increased risk. See table below.

Epoxy agents affected plumbers, pipe fitters and motor vehicle mechanics in particular, accounting for 90% of asthma cases.  It should be noted that these three occupations also accounted for 90% of jobs. Accidental peak exposure to irritants was also associated with new onset asthma. Persons at risk were welders, flame cutters, sheet metal workers, police officers and fire fighters.  

Among men, those at highest risk for new-onset asthma were spray painters followed by plumbers, cleaners, food and tobacco processing workers. For women the occupations with the highest risk of new-onset asthma included drivers, nurses, cleaners and hairdressers.

This study stratified data by gender and atopy. The risk for occupational asthma was calculated to be 14% for men and 7% for women. The researchers found that exposure to low molecular weight agents increased the risk of asthma for non-atopic individuals than atopic individuals.

Passive exposure to tobacco smoke in the workplace (as well as the home) is a risk factor for asthma. A study involving over 6000 individuals from 13 European countries found the risk for asthma induced at the workplace was also associated with cleaning work, solvents, irritants, pesticides and welding. Nursing posed a significant risk (OR 2.2). Asthma risk also increased with intense inhalation exposure to fire, mixing cleaning products or chemical spills (OR 3.3)4

To respond to the initial question, the answer is Yes. What you do does increase your risk for asthma depending on what and how much you are exposed to in the workplace. 2.7 million Americans have asthma that is caused by or exacerbated due to workplace conditions. The Behavioral Risk Factor Surveillance System (BRFSS) Asthma Call-back Survey that involved 33 states found that 48% of current asthma may be due to work and therefore preventable.5 With regard to the industry that had the highest prevalence in each state, Michigan ranked highest with health care support organizations at 21.5%; Massachussets’ information industry at 18% and Washington’s personal care and support services at 17.4%.6

Is the increased risk of asthma also associated with increased risk of exacerbations due to workplace exposures? Henneberger and colleagues7 examined data from 557 adults with asthma with reference to their workplace. They found that while almost 41% were exposed to asthma inducing agents at work, 29% had a severe exacerbation. With incidence or prevalence ratios shown below, the triggers for severe exacerbations included

  • 1.84 for environmental tobacco smoke
  • 2.53 for inorganic dusts among men
  • 1.97 for low molecular weight agents among women.

Another study8 indicated that the risk factors related to work provide a significant association to severe exacerbations of asthma. These include exposure to

  • problems with dampness and mold (OR 1.8)
  • organic dust (OR 1.7)
  • gas, fumes, mineral or any kind of dust (OR 1.7)
  • cold conditions (OR 1.7)
  • physically strenuous work (OR 1.6)
  • handling low molecular weight agents (OR 1.6)

Current smokers and women reported more exacerbations. Hence not only is the workplace environment likely to induce asthma but also to increase the severity of asthma exacerbations.

Abbreviation: OR odds ratio

References

  1. Vandenplas O. Occupational asthma: etiologies and risk factors. Allergy Asthma Immunol Res. 2011; 3: 157–67
  2. Ghosh RE, Cullinan P, et al. Asthma and occupation in the 1958 birth cohort. Thorax 2013;68:365-371 doi:10.1136/thoraxjnl-2012-202151
  3. Lillienberg L, Andersson E et al. Occupational exposure and new-onset asthma in a population-based study in Northern Europe (RHINE). Ann Occup Hyg. 2013 May;57(4):482-92. doi: 10.1093/annhyg/mes083.
  4. Kogevinas M, Zock JP, Jarvis D, et al. (2007) Exposure to substances in the workplace and new-onset asthma: an international prospective population-based study (ECRHS-II). Lancet; 370: 336–41.
  5. Knoeller GE, Mazurek JM, Moorman JE. Work-related asthma among adults with current asthma in 33 states and DC: evidence from the Asthma Call-Back Survey, 2006–2007. Public Health Rep 2011;126:603–11
  6. Dodd KE, Mazurek JM. Asthma among employed adults, by industry and occupation — 21 States, 2013. MMWR Morb Mortal Wkly Rep 2016;65:1325–1331. DOI: http://dx.doi.org/10.15585/mmwr.mm6547a1. Accessed December 30, 2016
  7. Henneberger PK, Liang X, et al. Occupational exposures associated with severe exacerbation of asthma.  Int J Tuberc Lung Dis. 2015 Feb;19(2):244-50. doi: 10.5588
  8. Kim JL, Henneberger PK et al. Impact of occupational exposures on exacerbation of asthma: a population-based asthma cohort study. BMC Pulm Med. 2016 Nov 15;16(1):148. doi:  10.1186/s12890-016-0306-1