Asthma, a chronic respiratory disease, is a major public health concern, affecting millions of people worldwide (1,2). In 2021, an estimated 20 million US adults had current asthma, with 41% of them reporting one or more asthma attacks in the past 12 months (2). Asthma is characterized by inflammation and narrowing of the airways, leading to symptoms such as wheezing, coughing, chest tightness, and shortness of breath (1). During 2011–2016, an estimated (average annual) 11 million US adults who were working at any time in the previous 12 months reported having current asthma (3). Among them, an estimated 44.7% reported an asthma attack and 9.9% had an asthma-related emergency room (ER) visit (3). Asthma prevalence varied across industries and occupations, with over 8% among workers in the healthcare and social assistance, and education services industries (3,4). Additionally, half of the workers with asthma in the hospital industry and education services, reported an asthma attack/episode (3,4). Asthma significantly impacts workers’ health, affecting their ability to perform job duties (4–7). Furthermore, workplace exposures to environmental risk factors can trigger asthma and asthma attacks (1,4).

Work-related asthma (WRA) includes both occupational asthma (new-onset asthma caused by workplace exposures) and work-exacerbated asthma (preexisting asthma that is made worse by workplace exposures) (1,8,9). Among workers with asthma, an estimated 6.9% reported that their asthma was associated with their job (10). Workers with WRA may experience reduced income due to absenteeism, fewer work hours, or lower wages (11). Vandenplas et al. reported the estimated average annual lost income attributed to WRA was approximately $4,000 to $6,000 in 2003 (11). Additionally, asthma is associated with a significant health and economic burden. During 2011–2015, an estimated 8 million US workers had at least one asthma-related medical event (i.e. inpatient visit, prescribed drug, physician office visit, ER visit, or hospital stay) (12). The total average annual medical cost associated with these events was estimated at $7 billion ($901 per-person) in 2017-US dollar value (12). Managing asthma effectively is essential not only for individual well-being but also for maintaining a productive workforce and reducing economic burden.

Workplace exposures can significantly impact worker health, especially among workers with asthma. Workers in certain industries and occupations have high asthma prevalence, asthma attack rates or ER visits, and may also be exposed to potential asthma triggers (3–5,7). For example, healthcare workers have high asthma prevalence and are exposed to asthma triggers including cleaning and disinfecting agents, latex proteins from gloves, aerosolized medications, and allergens, which have been associated with new onset asthma (4,5). Approximately, 23%–49% of adults with asthma report occupational exposures to various hazards (13). Adults exposed to vapors, dust, fumes, dampness, mold, and strenuous job conditions have significantly higher odds of severe asthma exacerbations (13). In a previous study examining the risk of developing or worsening asthma based on the level of asthma trigger exposures, authors reported that workers in the high risk occupations were 60% more likely to report asthma during their working life, and were four times more likely to report asthma and three times more likely to report new asthma diagnosis (14). Higher risk occupations included in the study were healthcare support, health aides, nurses, cooks, bartenders, entertainers, artists, personal care services, mechanics, machinists, and protective services (14).

The association between workplace exposures and asthma is complex. Findings from previous studies reporting on the proportion of adult asthma that might be associated with work varied based on the methodology used, population samples, and other factors (8,9,15,16). Blanc et al. identified and reviewed nine longitudinal population-based studies estimating incident asthma prevalence and occupational risk factors (8). The authors reported that 16.0% (pooled population attributable fraction across all studies; range 7%–44% of all adult asthma cases are associated with work-related factors (8). The occupational contribution to the burden of asthma using self-reported physician diagnosis asthma data from seven population-based studies was estimated at 19% (15). Groenewold et al. estimated that 11%–26% of incident asthma cases are attributable to occupational exposures among US adults aged ≥20 years (17). Using the Behavioral Risk Factor Surveillance System (BRFSS) Asthma Call-Back Survey data from 31 U.S. states and the District of Columbia, Dodd et al. reported 13.9% of ever-employed adults with current asthma had WRA during 2012–2014 (17). Limited information is available on asthma cases attributable to employment among currently working adults based on their industry and occupation. Continued surveillance for early identification and management of asthma cases among workers, is essential for minimizing its impact on worker health and well-being. The current study (1) estimates the prevalence of current asthma, asthma-related episodes/attacks and ER visits among US working adults employed in the 12 months prior to the survey, and (2) identifies the proportion of asthma cases attributable to employment by industry and occupation.

The estimated average annual prevalence of current asthma, asthma attacks/episodes and asthma-related ER visits among employed persons aged ≥18 years during 2020–2021, by selected demographic characteristics, physical and mental health status, and industry and occupation was assessed. Estimated frequencies, standard errors, and prevalence rates with 95% confidence intervals (CIs) were calculated. To assess the association between current asthma and specific sociodemographic characteristics, industry, and occupation, multivariable logistic regression was used. Adjusted prevalence ratios (PRs) were calculated using the predicted marginal risk ratio method. The variables age, sex, education, and insurance status were identified as confounders and adjusted in the multivariable regression models. The final model was assessed for collinearity among the covariates. Given the cross-sectional study design, PRs were calculated instead of odds ratios (ORs) because ORs may overestimate prevalence when the disease outcome is common and may not accurately represent the excess fraction of cases attributable to the exposure (20). PRs directly relate to prevalence and accurately represent the excess fraction of cases attributable to the exposure of interest (20). Population attributable fractions (PAFs) for asthma among all workers, were estimated by industry and occupation groups (21). The PAF or fraction of cases with asthma that are associated with employment by industry and occupation was calculated using the following equation (15,21): PAF=∑i=1KPci(PRi−1)PRi where k is the number of industry or occupation groups (21 and 23 groups, respectively).

Pci is the asthma cases/total cases, cases represent the estimated number of asthma cases in the ith industry or occupation group, and total cases represent the total estimated number of asthma cases summed across in the ith industry group/ith occupation group. PRi is the adjusted PR for current asthma estimated for the ith industry/occupation. Attributable cases (ACs) were calculated using the following equation (21): AC=Ni*Pi(PRi−1)/PRi where Ni is the estimated number of US working adults in the ith industry or occupation group; and Pi is the estimated current asthma prevalence in the ith industry or occupation. No cases were attributed to industries/occupations where PR≤1.

In the current analysis, the information industry and computer and mathematical occupation groups were selected as reference categories based on current asthma prevalence. Previous study (4) findings indicate that during 2011–2016, current asthma prevalence among workers in both (6.6% and 5.8%, respectively) these groups were lower than the national average (6.8%) (4). In addition, both computer and mathematical occupation and information industry typically involve indoor work environments or office-based tasks and interactions with clients, with minimal exposure to respiratory irritants (21,22).

In a study by Calvert et al. (22) 5% of workers in the “computer and the mathematical occupation” and 14% of workers in the information industry self-reported vapor, dust, gas, and fumes (VGDF) exposures, which was significantly lower than the national average (25% self-reported VDGF exposures in the longest held job.

During 2020–2021, an estimated 12.7 million US workers had current asthma. Among workers with asthma, approximately, half experienced an asthma attack/episode in the past 12 months and 1 in 12 had an asthma-related ER visit. The estimated current asthma prevalence among workers has increased from 6.8% (11 million workers) during 2011–2016 (3) to 7.5% (12.7 million) in 2020–2021. However, the current study findings indicate that the prevalence of asthma attack/episode and asthma-related ER visits among workers with current asthma have declined (from 44% to 40% and 9.9% to 8.6%, respectively). The lower prevalence of asthma attack/episode and asthma-related ER visits among workers during 2020–2021 may be partially explained by changes in the work arrangements from workplace to telework/remote work (i.e. working at home offices) during the Coronavirus Disease 2019 (COVID-19) pandemic, likely resulting in lower frequency of occupational exposures (23). Also, during the early COVID-19 pandemic due to concerns of potential exposure to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) there was a 42% overall decline in ER visits, and persons with asthma might have avoided ER in-person visits and utilized virtual visits and triage help lines instead (22). Similar to the previous findings, workers aged 18–24 years, females, non-Hispanic AIAN, those with insurance, workers living below the federal poverty level, who reported poor physical health, and those with depression were significantly more likely to report current asthma (3,5,24,25).

Higher prevalence of asthma attacks and ER visits among workers in certain industries and occupations has been associated with various factors, including presence of potential exposures/controls, number of workers employed in each industry or occupation and workplace environment (3,26,27). Nearly, half of the workers with asthma in arts, design, entertainment, sports, and media occupation reported an asthma episode/attack and could have been associated with work-place exposures (including irritant chemicals, dusts, physical exertion, etc.) (14,25). In addition, an estimated 19% of workers with asthma in the accommodation and food services industry reported an ER Visits. Workplace exposures, second hand smoke, stress and poor ventilation or exhaust systems have been associated with chronic respiratory symptoms (3,26–29). For example, a Taiwanese study found that in a bakery with no ventilation there was an increased concentration of inhalable flour dust in the oven and baking areas compared with a bakery with a local exhaust ventilation (30). Furthermore, an estimated 30% of all workers in the accommodation and food services industry used some form of tobacco (31). Cigarette smoke is a common trigger for asthma. Both smoking and secondhand smoke exposures can irritate the airways, leading to airway narrowing and exacerbations of asthma symptoms (28,32). Long-term exposure and asthma symptoms can lead to serious implications on disease progression into chronic respiratory illnesses, which might subsequently cause poor quality of life, disability, increase in work lost days, and reduce productivity (9,30).

Current findings indicate that, an estimated 9.2%–12.2% of all current asthma cases were associated with employment by industry and occupation. The overall proportions of asthma cases attributable to employment by industry were lower than those for the occupation. This can be partially explained by reference groups selected to assess workplace risk factors, and the fact that the industry group can include workers from several occupations and some of the occupations with increased risk for asthma may not be represented by the industry categories with increased risk. The highest number of asthma cases associated with employment by occupations were in the office and administrative support, followed by sales and related, and education training and library occupations and by industry, retail trade, administrative & support and waste management & remediation services and management of companies and healthcare and social assistance industry. Workers in these industries and occupations often are exposed to environmental indoor allergens, cleaning agents, aerosolized medications (e.g., pentamidine, ribavirin), anesthetic agents, glutaraldehyde, enzymes, latex, metal dusts, adhesives, dyes, wood dusts, indoor dampness, mold, among others (25–27,33), all of which have been associated with WRA.

Identifying and minimizing exposure to these triggers is important for managing asthma effectively (14,34). In addition, high asthma prevalence among workers in certain industries and occupations underscores the importance of implementation of targeted interventions, including improved access to healthcare and asthma management resources, as well as addressing underlying social determinants of health that may contribute to asthma disparities. Workers have the right to a safe workplace, free of known hazards such as triggers that can cause or exacerbate asthma (34,35). This can be achieved by reducing or eliminating exposure to WRA triggers; substituting agents causing asthma triggers with less harmful products and materials, implementation of engineering controls (e.g. isolating or enclosing processes or improve ventilation) and implementation of appropriate administrative controls (including smoke free policies), work practices, policies, worker training and personal protective equipment use (14,29,30,33–35).

The current study has several key strengths. First, it utilizes NHIS data, which is a nationally representative sample with a large sample size, enhancing its generalizability to the working population. Second, it provides the most recent national estimates on prevalence and burden of asthma among working adults, and also provides the proportion of asthma cases associated with employment by industry and occupation. Lastly, the standardized industry and occupational classification used in the study ensures consistency and comparability when assessing asthma among working adults. However, the findings in this report are subject to some limitations. First, NHIS data are self-reported and may be subject to recall bias. The asthma data were not validated by pulmonary function tests, medical records review or follow-up with health-care providers. However, previous studies have found self-report of adult asthma to be reliable compared with reviews of medical records (36).Only adults who were employed at some time in the past 12 months were included in this study. Workers with severe asthma might have left employment because of workplace exposures that might have exacerbated their asthma and could not be included in this study. Moreover, the industry and occupation might not accurately identify workers’ industry and occupation where exposures might have occurred. The asthma attributable cases calculated varied by industry and occupation and can be sensitive to the choice of reference group. An industry group can include workers from several occupations. Therefore, it is also possible that some of the occupation groups with higher PRs may not represent the industry categories with increased risk. Additionally, sample size in certain groups was small for some groups resulting in unreliable estimates. Finally, lack of detailed information on asthma episodes/attack events was not available, therefore, it was not possible to determine their association with work.