Overview of historical occupational exposure to trichloroethylene in China.

Objectives: Trichloroethylene (TCE) is a carcinogen that has been causally linked to kidney cancer and possibly other cancer sites including the liver and lymphatic system. Its use in China has increased since the early 1990s due to the growing metal and electronic industries. We aimed to summarize the major sources of occupational exposure to TCE over time in China.

Methods: Occupational TCE exposure assessments were extracted from both the Chinese and English scientific literature, as well as from industrial hygiene surveys performed in Guangdong, Tianjin, and Hong Kong. Weighted mean concentrations were summarized by occupation and industry.

Results: We extracted over 12,412 measurements from 55 industries and 35 occupations across China since 1976, of which at least 201 were from case reports. More than half of the measurements were derived from 4 industries, including "manufacture of footwear" (29%), "manufacture of electronic components and boards" (17%), "manufacture of games and toys" (14%), and "manufacture of fabricated metal products, except machinery and equipment" (13%). Several occupations, including "electronic-equipment assemblers," "metal-, rubber-, and plastic-products assemblers," "metal finishing-, plating-, and coating-machine operators," "precision-instrument makers and repairers," "printing-machine operators," and "ore and metal furnace operators" were identified as having high risks of TCE exposure, with either pooled weighted mean task-based or full-shift concentrations over 150 mg/m3 over the years. TCE exposure levels varied across different occupations and changed over time. In 1990 and earlier, 1991 to 2000, the exposure levels were at their highest with pooled weighted mean task-based concentrations of 202.8 and 242.9 mg/m3, respectively. Subsequently, the level decreased to 118.7 mg/m3 from 2001 to 2010 before increasing again to 216.0 mg/m3 from 2011 onwards. This overall trend was also observed for "electronic-equipment assemblers" and "metal finishing-, plating-, and coating-machine operators." However, for "precision-instrument makers and repairers," the exposure levels consistently declined over the years.

Conclusions: Over the past few decades, degreasing-related occupations, such as "electronic-equipment assemblers" and "metal finishing-, plating-, and coating-machine operators" have been consistently identified as being at high risk of significant TCE exposure and continued to warrant attention. Identifying high-risk industries and occupations can inform the development of targeted interventions and regulations to mitigate TCE exposure. Furthermore, enhancing the quality and coverage of exposure measurement data in occupational settings will advance epidemiological investigations in occupational health.