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ObjectiveTo determine whether there is an ongoing risk of developing bladder cancer in a previously studied cohort of workers exposed to both benzidine and dichlorobenzidine or dichlorobenzidine only in the last benzidine manufacturing plant in the USA.MethodsWorkers (n=488) were identified from the quarterly 941 forms the employer was required to submit to the Social Security Administration from 1960 to 1977. Exposures were assigned based on dates worked and known benzidine/dichlorobenzidine production schedules. Incidence, vital status and cause of death were determined through 2014. Analyses were restricted to white men.ResultsBladder cancer incidence and mortality were significantly increased (25 incident cases, standardised incidence ratio (SIR) 2.19, 95% CI 1.42 to 3.23, and 5 deaths, standardised mortality ratio (SMR) 3.79, 95% CI 1.23 to 8.84). There were significant increases in incidence and mortality in those exposed to both benzidine and dichlorobenzidine (SIR 3.11, 95% CI 1.97 to 4.67, SMR 4.10, 95% CI 1.12 to 10.50), but not among workers exposed to dichlorobenzidine only (two incident cases, SIR 0.89, 95% CI 0.11 to 3.23 and one death, SMR 2.90, 95% CI 0.07 to 16.15). Bladder cancer incidence and mortality were increased in individuals with >20 years since last exposure with >5 years worked (six observed, SIR 5.94, 95% CI 2.18 to 12.92 and two deaths, SMR 7.93, 95% CI 0.96 to 28.65).ConclusionsIncidence and mortality due to bladder cancer increased among workers exposed to benzidine but not among workers exposed only to dichlorobenzidine. The risk of incidence and death from bladder cancer remain elevated more than 20 years after last exposure to benzidine in those who worked >5 years.

Blastomycosis is a rare, potentially fatal fungal infection caused by inhalation of Blastomyces spores, typically acquired outdoors in the midwestern and eastern United States. In 2023, the largest recorded U.S. blastomycosis outbreak occurred among workers at a paper mill in Michigan's Upper Peninsula. Few data exist on occupational risk factors or indoor exposure to Blastomyces, limiting prevention efforts. We assessed workplace environments and conditions associated with blastomycosis risk through a cross-sectional medical survey and environmental sampling. During April 22-28, 2023, we conducted a voluntary medical survey, including a work and health questionnaire and urine antigen testing, for 603 workers out of approximately 1,000 at the mill. We compared worker characteristics, work locations, and environmental exposures by blastomycosis case status and modeled disease risk using Poisson regression. We tested 533 environmental samples of outdoor soil, indoor surface dust, and raw materials for Blastomyces using polymerase chain reaction and culture-based methods. Twenty percent of workers were classified as blastomycosis cases based on positive urine antigen testing during the survey, self-reported provider diagnoses, or confirmed or probable case status reported by state or local health departments. Prevalence was highest among workers in paper machine line #1 (27%) and maintenance areas (25%). Adjusted analyses indicated a 40% [Prevalence Ratio (PR): 1.40; 95% confidence interval (CI): 1.00, 1.95] and 53% (PR: 1.53; 95% CI: 1.04, 2.25) higher risk for workers in these locations, respectively, compared to workers working elsewhere. Working in both locations doubled blastomycosis risk. Daily exposure to indoor pooling water was associated with a nearly two-fold higher prevalence of blastomycosis (PR: 1.79; 95% CI: 1.25, 2.57). All indoor and outdoor environmental samples were negative for Blastomyces. Blastomycosis was associated with specific indoor work locations and environmental conditions, suggesting the potential for occupational exposure to Blastomyces in indoor industrial settings. These findings may guide future outbreak investigations and occupational prevention strategies.

Tracheal mucus accumulation is a significant problem in racehorses, as its presence in sufficient quantities negatively affects racing performance. The cause is likely multifactorial in nature, but the stable environment has been implicated as one risk factor, as it has been shown that some healthy horses brought into the stable from pasture experience airway inflammation. The purpose of my work was to describe the range of concentrations of airborne particulate matter within the stable, and factors that influence its presence. I hypothesized that tracheal mucus accumulations result, at least in part, from exposure to particulate matter (PM) in size ranges (less than 10 and less than 2.5 microns in diameter) determined to be important in human respiratory disease. I hypothesized that ambient particle concentration and personal particulate exposure varies with season, stable, stall location within a stable, and activity level, and correlates in an exposure-dependent manner with established measures of inflammatory airway disease (IAD). Using direct-reading instruments that measure particulate concentrations, I demonstrated that dusts present in the breathing zone of horses during routine stable activities (cleaning, feeding, and riding) contained concentrations of PM10 and PM2.5 that would be considered unacceptable in industrial environments, but that consistent use of easy to implement dust-suppression techniques more than adequately reduced exposures. Investigations in stables at a Midwestern Thoroughbred racetrack, again using direct-reading instruments, revealed significant variations in ambient PM10 and PM2.5 concentrations by season (month), time of day, stable, and certain stalls within stables. PM was lowest during months following periods of wet weather and highest after periods of hot dry weather. Early morning PM concentrations, when feeding, cleaning, and training activities occur, were highest in comparison to mid-day and afternoon concentrations when activity was minimal. Enclosed stables with few sources of natural dilution ventilation experienced the highest concentrations of PM as compared to the open-aired stables designed for maximum ventilation. Stalls located in either high-traffic areas or areas devoid of natural dilution ventilation contained ambient PM concentrations significantly higher than adjacent stalls. The presence of tracheal mucus was significantly associated with ambient PM concentrations, and overall prevalence was highest during months and in stables and stalls where ambient PM concentrations were the greatest. Personal particulate exposure monitoring (PM10) in horses both with and without tracheal mucus suggests that personal idiosyncratic activities did not influence personal exposures to the same degree as ambient PM; furthermore, overall prevalence of tracheal mucus shows a striking association to personal PM exposures that likely reflects ambient concentrations (e.g. monthly variations in PM). If this is true, then implementation of dust suppression techniques within stables should significantly reduce the overall prevalence of significant quantities of tracheal mucus. Percent neutrophils present in tracheal wash samples did not correlate with the presence of tracheal mucus, and I therefore suggest that its use in diagnosing LAD be reconsidered, as endoscopic examination scoring of tracheal mucus is easy to perform, and likely the most accurate predictor of airway disease sufficient to affect performance.

Hypersensitivity Pneumonitis (HP) is an interstitial lung disease caused by an immune response to the inhalation of antigens. Since only a small proportion of individuals exposed to HP-related antigens develop the disease, a genetic variation may play a role in disease development. In this small-scale study, 24 patients diagnosed with HP were matched with control group who shared the patient’s environment and were exposed to the same HP-associated antigens. Logistic regression was employed to identify Single-Nucleotide Polymorphisms (SNPs) associated with HP. Next genes associated with HP were identified using sequence kernel association test (SKAT) analysis. Last, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Oncology (GO) enrichment analysis were employed to find HP signaling pathways using SNPs coded on genes and on non-coding genes, respectively. Given the small sample size, no single SNPs or genes were identified to be significantly associated with HP after adjustment for multiple testing. After P-value adjustment, the KEGG and GO pathway enrichment analysis identified 11 and 20 significant pathways respectively using SNPs coded on genes. Among these pathways, Cell cycle, Proteasome and Base excision repair had previously reported to be associated with lung function. This is the first GWAS study identifying genetic factors associated with HP. Although no significant associations at SNPs/gene level were identified, there were significant pathways that are identified associated with HP which need further investigation in large cohorts.