Formaldehyde exposure risk assessment among fiberboard furniture manufacturing workers in Thailand: Comparison of TIS 2012 and EPA IRIS standards

Abstract

Formaldehyde exposure in medium-density fiberboard furniture manufacturing is an important occupational health concern because formaldehyde-containing resins can release hazardous airborne emissions during production processes. The aim of this study was to evaluate and compare formaldehyde exposure risks among furniture manufacturing workers using the Thai Industrial Standard (TIS) 2012 semi-quantitative model and the United States Environmental Protection Agency Integrated Risk Information System (EPA IRIS) quantitative model, and to examine the concordance between the two frameworks. A cross-sectional study was conducted among 439 workers from ten departments in a medium-density fiberboard furniture factory in Chachoengsao Province, Thailand. Work characteristics and health symptoms were collected using structured questionnaires. Full-shift personal air sampling was performed in accordance with the National Institute for Occupational Safety and Health Method 5700, and samples were analyzed by high-performance liquid chromatography. Risk characterization was conducted using TIS 2012 based on exposure rating × health effect rating, while EPA IRIS was applied to estimate non-cancer risk using the hazard quotient and lifetime cancer risk using the inhalation unit risk. Non-cancer and lifetime cancer risks were assessed using HQ and inhalation unit risk. The mean formaldehyde concentration was 5.47 mg/m³ (0.70–11.55 mg/m³), peaking in the Clearing department (11.55 mg/m³). TIS 2012 classified 80% of departments as very high risk, compared with 50% under the EPA IRIS HQ model. The EPA IRIS model showed hazard quotients ranging from 6.59 to 87.99 and lifetime cancer risks ranging from 7.72×10⁻³ to 1.27×10⁻¹, all exceeding the acceptable cancer risk threshold of 1×10⁻⁶. Concordance between the two models was 73%, with discrepancies observed in the Edging and Drilling departments. All departments had unacceptable cancer risks, indicating the need for immediate exposure-control measures. Integrating semi-quantitative and quantitative assessment frameworks is essential for comprehensive occupational risk management. Departments identified as very high risk by both models require urgent control measures and inclusion of cancer-risk assessment in routine occupational health surveillance.