A new tool to support the protection of workers’ health: development and application of an innovative analytical method for biomonitoring occupational exposure to formaldehyde

Formaldehyde (FA) is a widely used industrial chemical and a ubiquitous environmental contaminant, for which biological monitoring remains challenging due to its high reactivity and substantial endogenous background. In the present study, a sensitive and selective analytical method based on headspace solid-phase microextraction with on-fiber derivatization (HS-SPME) coupled to gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed and applied for the determination of urinary FA. Direct on-fiber derivatization using O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) was optimized to ensure quantitative derivatization, reproducibility, and minimal sample handling. The method was validated in terms of linearity, sensitivity, precision, and robustness, demonstrating suitability for trace-level FA determination in complex biological matrices. The applicability of the method was evaluated in an occupational biomonitoring campaign involving 124 subjects, including workers occupationally exposed to FA (healthcare personnel, laboratory staff, and firefighters) and non-exposed administrative employees. Urinary FA concentrations showed wide inter-individual variability and substantial overlap between exposed and non-exposed groups, particularly at low exposure levels. Stratified analyses indicated associations with sex and smoking habits, while age and body mass index showed no clear influence. Overall, the results highlight both the analytical reliability of the proposed HS-SPME GC-MS/MS approach and the biological complexity of urinary FA as an exposure biomarker.