Abstract:
Introduction: Transit workers in the United States face a host of occupational health hazards including chronic exposure to physical, chemical, and psychosocial agents. A systematic review of 187 studies identified that all workers suffering hazardous occupational noise exposure can cause permanent auditory threshold shifts, though the evidence for elevated risk among railway workers is mixed, with some studies showing minimal or no increased loss relative to reference populations. Respiratory illness is a recognized occupational concern for transit workers, driven in part by elevated exposures to airborne pollutants in enclosed and high-density transit environments. Measured concentrations of fine particulate matter (PM₂.₅) inside buses and subways, coupled with inadequate ventilation or filtration, contribute to inflammation and increased risk of chronic respiratory conditions, and musculoskeletal disorders driven by static postures and vibration.1,2,3,4,5 These exposures may contribute to a higher prevalence of hypertension, diabetes, and mental health conditions among transit employees compared to the general workforce.6 Despite the severity and persistence of these conditions, occupational health surveillance and regulatory prioritization in the transit sector remain fragmented and underdeveloped.6,7,8 Efforts to quantify these burdens are further complicated by systemic underreporting, definitional inconsistencies, and jurisdictional barriers to case recognition.8,9,10 This thesis explores these gaps by examining national Occupational Safety and Health Administration’s (OSHA’s) Injury Tracking Application (ITA) data from 2016–202311, with analyses by agency size, North American Industry Classification System (NAICS) classification12, and geographic context. The ITA dataset offers establishment-level detail enabling trend analysis by agency characteristics. The findings aim to inform targeted policy responses and advance data-driven protections for transit workers across the country.Our hypothesis is that OSHA-reportable rates of hearing loss, poisonings, respiratory disorders, skin disorders, days away from work, other illnesses, deaths, and total illness, differ significantly over time and by agency subgroup, particularly size and geographic classification. This will be evaluated through: Aim 1: Assess temporal trends in illness rates across the study period (2016–2023). Aim 1A: Identify statistically significant differences between individual years. Aim 1B: Examine whether respiratory illness rates increased during the COVID-19 pandemic (2020–2021). Aim 2: Compare illness rates across transit agency subgroups. Aim 2A: Assess statistically significant differences in illness rates by establishment (agency) size classification. Methods: A retrospective descriptive study design was applied using OSHA’s ITA data by NAICS codes 4851 for urban transit systems and 4852 for interurban and rural bus transportation and establishment level information such as, total hours worked at the agency in the previous year, agency size, and geographic location. The ITA is composed of OSHA-reportable cases, which include any work-related fatality, loss of consciousness, days away from work, restricted duty, job transfer, or injuries and illnesses requiring medical treatment beyond first aid. Also included are diagnosed cases of cancer, chronic irreversible diseases, fractured bones or teeth, punctured eardrums, and cases meeting specific recording criteria such as needlestick injuries, medical removal, hearing loss, tuberculosis, and work-related Covid-19 reported as respiratory conditions.13 Rates were calculated per full-time equivalent (FTE) employees to normalize across agency size based on hours worked. Variables such as geographic region, agency size, and transit classification based on NAICS codes for urban transit vs. interurban and rural bus transportation, were incorporated into the analysis. Analytical methods included Mann-Kendall trend tests to assess changes in illness and injury rates from 2016 to 2023. Year-to-year differences were evaluated using Kruskal-Wallis tests, and one-way ANOVA was used to compare rates across pandemic periods. Linear regression models were applied to examine associations between illness rates and agency-level characteristics such as size, region, and NAICS classification. A hierarchical clustering method was used to normalize and merge establishment records across years by grouping similar company names and addresses, improving consistency in longitudinal analysis. Results: OSHA-reportable illness and injury rates in U.S. transit agencies remained largely stable between 2016 and 2023, with no apparent trends observed. While respiratory conditions and poisonings showed increases in 2021 and 2022 respectively, these increases were not statistically significance. Only injury rates varied significantly by year, spiking in 2021, though these were not statistically significant after adjustment. Linear regression models, excluding state-level predictors, identified agency size was a modest but statistically significant predictor of hearing loss (β = 0.0925, 95% CI [0.0667, 0.1183]), though the overall model fit was poor (adjusted R² = 0.026). Conclusion: This thesis presents a national, retrospective multi-year assessment of OSHA-reportable illness and injury trends among reporting U.S. transit employers from 2016 to 2023. While rates remained generally stable over the study period, the ability to predict illness and injury patterns based on agency-level characteristics captured in ITA data was limited. This limitation likely reflects the narrow scope of available variables, which exclude key factors such as worker demographics, job classifications, and exposure conditions. These limitations emphasize the need for improved occupational health surveillance in both urban and rural transit sectors. A more robust and integrated surveillance system would better equip health and safety practitioners to identify patterns early and implement preventive strategies. Future research should incorporate workers’ compensation records, Federal Transit Administration (FTA) datasets, and proactive hazard monitoring, with a focus on high-risk roles and standardized reporting practices.