While the health impacts of environmental air pollution on the general population are well established, its effects on occupational groups remain less understood. Outdoor workers are exposed to higher levels of environmental air pollution due to the nature of their work, especially in the context of frequent wildfire smoke events and global climate change. The American Thoracic Society convened an international interdisciplinary team of experts to assess the current impact of occupational air pollution exposure on worker health and to develop research recommendations and action plans to assess, mitigate, and regulate occupational air pollution exposure.
On November 1, Maeve G MacMurdo, a communications representative of the American Thoracic Society, published a paper in the Annals of the American Thoracic Society titled “Occupational Exposure to Ambient Air Pollution: At-Risk Worker Groups, Regulatory and Research Needs An Official American Thoracic Society Workshop Report.”
The workshop report indicates that, based on findings from studies on the general population, occupational exposure to air pollution may lead to serious health risks. Outdoor workers, due to longer exposure times and increased ventilation and metabolic rates from physical labor, may have higher cumulative exposure doses and could bear a heavier health burden related to air pollution than the general population. Health impacts range from exacerbation of short-term symptoms and decreased quality of life to the occurrence and progression of long-term chronic diseases, including negative effects on the respiratory, cardiovascular, reproductive, and nervous systems. According to estimates from the International Labour Organization, approximately 860,000 outdoor worker deaths globally are related to air pollution, a figure that may be underestimated.
Occupational exposure to air pollution has significant economic impacts. Studies show that exposure to high concentrations of PM2.5 increases absenteeism, particularly among workers who need to care for young children and the elderly. Air pollution also directly affects the productivity of on-site workers by reducing their physiological reserves and increasing symptoms. Observational studies confirm that improvements in air quality can enhance productivity; for example, agricultural workers in California’s Central Valley exposed to relatively low levels of ozone (about 40 ppb) experienced significant declines in productivity, and indoor pear packing workers reduced their packing numbers as outdoor PM2.5 levels increased. Model analyses indicate that improving air quality can yield substantial economic benefits; for instance, improvements in environmental PM10 levels in Spain from 2005 to 2014 may have reduced the loss of 5.6 million workdays, saving approximately 500 million euros.
Estimates of the number of workers exposed to occupational hazards in the U.S. show that over 20 million outdoor workers face risks from occupational environmental air pollution. About 65.3% of these workers are concentrated in three major occupational categories: construction and extraction, installation, maintenance and repair, and transportation and material moving. Racial and ethnic minorities are overrepresented in the exposed worker population. Additionally, an estimated 1.5 million workers in agriculture, fishing, and forestry, along with a large number of uncounted agricultural workers, warehouse, and manufacturing workers, may have their exposure risks underestimated.
The workshop identified high-risk worker groups, assessing their risks based on a matrix of exposure levels and social/legal marginalization. Agricultural workers are classified as a very high-risk group due to work exposure and legal and social marginalization (e.g., most are undocumented immigrants, face language barriers, and are excluded from some protections under federal labor laws). Construction and transportation workers face dual exposure to environmental pollutants and specific occupational pollutants (such as volatile organic compounds, traffic-related air pollution, silica, and nitrogen dioxide), resulting in the highest workplace mortality rates. Wildfire firefighters are exposed to high concentrations of air pollutants for extended periods, and their unique work patterns (long hours of intense labor in remote locations) pose challenges for the use of respiratory protective equipment. Existing studies have primarily focused on wildfire firefighters, indicating that exposure to wildfire smoke can lead to acute and potentially long-term cardiovascular and respiratory impacts, but results are inconsistent, and research on other outdoor worker groups is lacking.
In terms of worker protection measures, there are currently no federal standards in the U.S. for protecting against occupational air pollution exposure. However, California, Washington, and Oregon have established local regulations regarding exposure to wildfire smoke, which draw on the U.S. Environmental Protection Agency’s Air Quality Index (AQI) to set thresholds for PM2.5 concentrations that trigger exposure mitigation actions. These regulations recommend engineering controls (such as providing clean air shelters), administrative controls (such as adjusting work locations, times, and intensities), and the use of respiratory protective equipment based on exposure control hierarchy principles. A draft report from the National Institute for Occupational Safety and Health titled “Exposure to Wildfire Smoke for Agricultural Workers and Other Outdoor Workers” also proposes a similar tiered decision-making framework based on AQI. However, the implementation of these measures faces challenges, including insufficient AQI monitoring networks in rural areas, accuracy issues with low-cost sensors, difficulties in implementing administrative controls for time-sensitive work (such as agricultural harvesting), and practical barriers to using respiratory protective equipment (such as the need for fit testing for N95 masks, potential increased heat discomfort, and costs). Powered air-purifying respirators may address some issues, but they are currently expensive and their durability remains to be validated.
The workshop proposed policy and research priorities. On the policy front, there is an urgent need to establish federal standards to protect workers, especially immigrant and seasonal workers; expand the coverage of air monitoring networks, particularly in rural and workplace settings; conduct worker education and training; and incorporate medical monitoring into potential regulations. In terms of research, more epidemiological studies are needed targeting specific worker groups (such as agricultural workers, construction workers, wildfire firefighters, transportation workers, and warehouse workers) to assess their acute and chronic health impacts, interactions with co-exposures (such as heat), and how structural social factors (such as poverty, language barriers, immigration status, and lack of health insurance) exacerbate risks. Additionally, the effectiveness of existing state-level regulations needs to be evaluated, and improved exposure monitoring technologies, cost-effective respiratory protection technologies, and research combining engineering development, human factors interventions, and worker participatory assessments should be developed.
Occupational exposure to environmental air pollution poses a significant threat to the health of many American workers, and this issue is expected to worsen with climate change and increasing wildfire smoke events. Existing evidence strongly supports the urgent need for policy action to protect worker health, while concurrently advancing research to fill knowledge gaps, assess the effectiveness of interventions, and provide a basis for establishing national protective standards.