Abstract

Background
Benzene is a group 1 carcinogen, and urinary trans, trans-muconic acid is a key biomarker of benzene exposure. Whether specific occupational groups in Korea have higher benzene body burdens beyond environmental levels has not been systematically evaluated using national biomonitoring data with smoking-adjusted biomarkers.
Methods
We pooled adult data from three cycles (3rd–5th) of the Korean National Environmental Health Survey (KoNEHS, 2015–2023; n = 10,786). Creatinine-adjusted urinary ttMA (UttMACr) was analyzed across nine occupation groups using complex-samples general linear models with nested covariates. Sampling weights were rescaled within each cycle to harmonize weight scales across waves. Smoking was controlled using questionnaire-based variables and five-level creatinine-adjusted urinary cotinine (COTCr). Variance decomposition quantified predictors' contributions, and sensitivity analyses included COTCr-stratified models and analyses limited to the economically active population.
Results
Population geometric mean UttMACr declined by 51% from the 3rd to 5th cycle, occupation remained a significant independent predictor after adjusting for temporal trends, smoking, demographic, and lifestyle covariates (ΔR² = 0.0018, p = 0.003). Cleaning/guard/elementary workers showed the highest elevation in the geometric mean ratio (GMR: 1.13; p < 0.001), followed by food/textile/other manufacturing (GMR: 1.12; p < 0.05) and chemical/metal/machinery manufacturing workers (GMR: 1.08; p < 0.05). COTCr-stratified analyses revealed occupation-specific patterns attenuated in pooled models: among participants with COTCr ≤ 1.0 μg/g creatinine, construction/mining (GMR: 1.62; p < 0.001) and agriculture/fishery (GMR: 1.41; p < 0.01) showed marked elevations.
Conclusions
Population UttMACr levels in Korea declined over time, but occupation-specific differences persisted after adjustment for trends, smoking, and sociodemographic factors. These findings suggest occupational benzene exposures may extend beyond traditionally recognized industrial settings and support more targeted biomonitoring, particularly for worker groups not routinely prioritized in current surveillance programs.

• Keywords: Benzene; Occupational exposure; Biological monitoring; ; trans,trans-muconic acid; Cotinine