Overview of historical formaldehyde occupational exposure in China.

Objectives: Formaldehyde is a known human carcinogen related to leukemia and nasopharyngeal cancer. As China is the world's largest producer and consumer of formaldehyde, occupational exposure to formaldehyde may pose potential health risks to workers. We aimed to describe occupational exposure to formaldehyde over time in China.

Methods: Occupational formaldehyde exposure measurements were extracted from Chinese and English scientific publications as well as routine occupational hazard monitoring datasets. A weighted mean concentration was calculated by occupation and industry.

Results: We extracted over 20,447 individual measurements from 73 industries and 70 occupations during 1979 to 2023 across China. The majority of measurements (19%) were from the industry "Manufacture of veneer sheets and wood-based panels," with a pooled mean task-based concentration of 0.69 (0.02 to 4.98) mg/m3. Among occupations with over 200 individual measurements and a pooled weighted mean concentration of 0.5 mg/m3 or higher, "Metal moulders and coremakers" has the highest task-based concentration, at 1.40 (0.04 to 1.99) mg/m3. Formaldehyde exposure levels varied across occupations and changed over time. Before 1990, the overall pooled mean (range) task-based concentration was 1.60 (0.15 to 6.14) mg/m3, decreasing to 0.41 (0.00 to 12.0) mg/m3 from 2011 onward.

Conclusions: Occupational formaldehyde exposure in China has shown a declining trend over the past decades but remains high in certain occupations. Identifying high-risk industries and occupations can inform the development of targeted interventions and regulations to mitigate formaldehyde exposure. Furthermore, the presented exposure data can contribute to better exposure assessment in epidemiological investigations.