Chongqin and Other Chinese Plants
A study evaluated lung cancer and mesothelioma in a cohort of workers in an asbestos plant in Chongqin, China. Dust analysis indicated that a "virtually pure form of chrysotile asbestos" (i.e., the concentration of amphiboles was reportedly below the limit of detection at that particular laboratory) was used extensively throughout the plant obtained from two mines in the Sichuan province (Yano et al., 2001; Tossavainen et al., 2001). However, the authors' conclusion that there was no detectable amphibole contamination rests solely on an unpublished analysis performed by a colleague in Japan in 2000 of four commercial samples from those mines and referenced in the paper as a personal communication. The plant in Chongqin opened in 1939 and expanded operations in 1958. The geometric mean of asbestos fiber exposures was reported in 1999 to be 12.6 f/ml, and the authors presumed that they were higher in the past as handling practices have improved over time. Two cases of pathologically confirmed mesothelioma, 1 pleural and the other peritoneal, were diagnosed among this cohort. The latencies were 13.8 and 21.8 years, respectively, which would be unusually short time periods for the induction of mesothelioma (Weill et al., 2004). Amphibole contamination of chrysotile particularly with tremolite and anthophyllite is known to exist throughout China, including in Sichuan province, which is where the plant studied by Yano et al. (2001) exclusively obtained chrysotile asbestos. Reviews of studies on asbestos in China point out the diagnostic problems as well as the presence of amphiboles in that country (Tossavainen et al., 2001; Cai et al., 2001; Herman and Crump, 2003, p. 3-3). A mortality study for a plant in Qingdao of 530 workers using Chinese and Canadian chrysotile (and thus tremolite contamination presumably) does not report any mesotheliomas without specifically stating an absence of cases (Pang et al., 1997). Conclusions of the studies from China are difficult to draw not only due to the low number of cases (some with short latency), probable amphibole contamination of asbestos exposures, lack of complete occupational histories for the cases, incomplete or unconfirmed outcomes data, and lack of lung fiber analyses, but also due to written language barriers such as lack of translations from Chinese to English, mismatching and misnumbering of references, lack of peer-review publication, and limited data in summary tables (Cai et al., 2001; Li et al., 2004).