Radiographic Evidence of Asbestos Disease in ...

Ann. occup. Hyg., Vol. 46, Supplement 1, pp. 154–156, 2002 © 2002 British Occupational Hygiene Society Published by Oxford University Press DOI: 10.1093/annhyg/mef667

Radiographic Evidence of Asbestos Disease in Chinese Factory Workers A. L. FRANK1*, L. LI2, W. CAO2, Z. PANG3, Z. ZHANG3 and H. ZHANG3 1The

University of Texas Health Center at Tyler, 11937 US Highway 271, Tyler, TX 75708, USA; Medical University, Department of Epidemiology, 38 Xue Yuan Road, Beijing 100083, PR China; 3Qingdao Centers for Disease Control, 175 Shandong Road, Qingdao 266033, PR China 2Beijing

In three asbestos-utilizing factories in the People’s Republic of China, two use chrysotile exclusively while one uses small amounts of crocidolite. Among the workers—the majority of whom are women—all the traditional asbestos-related diseases are found, including fibrosis, lung cancer and mesothelioma. This study reports on the extent of radiographic changes seen in these three factories. Difficulties and shortcomings of conducting such research in China are reviewed.

for the evaluation of pneumoconioses, but rather an indigenous Chinese system is used instead. Undertaking asbestos-related research in China has several serious drawbacks compared to similar undertakings in North America, Europe or other Westernized countries. Until recently, the equipment available for high-quality radiographs was not widely available and radiographic techniques were generally not up to traditional Western experiences. Tissue confirmation of clinical diagnoses is much less frequently carried out in China, and the level of experience of most pathologists with these problems is not considerable. Records of all types are not maintained as in Western medical settings, and it is not at all unusual for there to be destruction of medical records, including X-rays and tissue specimens, at the time of death, which is usually followed by cremation. There are also many fewer physicians, of all types, experienced in occupational lung diseases than would be found elsewhere. Notwithstanding these difficulties, one publication based on part of this study population has already appeared, a work examining lung cancer cases at one factory (Pang et al., 1997). That study documented that six of seven cases of lung cancer in one factory were seen among female workers, all of whom had been non-smokers, and all of whom had been exposed only to chrysotile fibers. The other case was in a smoking male. The rate of lung cancer in this plant was noted to be far higher than expected among the age- and sex-matched population of Qingdao. This paper looks at a broader range of asbestos-exposed workers and examines the X-ray findings associated

INTRODUCTION

Asbestos-related diseases have been well documented for some one hundred years, and work in England in the 1930s (Merewether and Price, 1930) clearly documented many of the basic principles well appreciated today, including the dose–response relationship, latency, no apparent difference by sex, the disease-causing ability of both serpentine and amphibole fiber types, the wide range of products that can cause disease, and perhaps most significantly, but little heeded, the preventability of disease caused by asbestos. The rationale for studying disease patterns caused by asbestos in China came from several areas of consideration. In some settings only one fiber type, chrysotile, was used and little has been published about exposure to this fiber alone. Secondly, most publications, especially of working populations in North America or Europe, deal primarily, if not exclusively, with male workers, while assessment of Chinese factory workers allowed for the evaluation of a workforce with considerable numbers of women. There is a potential to study any possible interrelationship between asbestos and tuberculosis, as has been documented for silica and tuberculosis, given the high prevalence of tuberculosis in China. Also, in China the International Labor Organization (ILO) classification system of radiographs is not utilized *Author to whom correspondence should be addressed. Fax: +1-903-877-5902; e-mail: [email protected]

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Keywords: asbestos; asbestosis; chrysotile; cancer; radiology

Radiographic evidence of asbestos disease in Chinese factory workers

with such exposure, the rates of asbestosis and describes these patterns among a large number of female workers. Workers traditionally spend their whole working lifetime at one factory, often at the same job, and housing, health and retirement benefits are tied to the factory, including lifetime medical care. In China, most men smoke, few women do. FACTORIES STUDIED

At a second factory in Qingdao (Qingdao 2), opened in 1966, asbestos construction products were manufactured, including asbestos brick, pipe and corrugated board. By the mid-1990s some 1200 workers were employed, one-third of whom were female. The vast majority of fiber used was chrysotile, mostly Chinese with small amounts of Canadian fiber, and it was said to be the only factory in China to use crocidolite. About 2% of the yearly 4000 tons of asbestos utilized was said to be South African crocidolite. Fiber levels had come down over time, having been in the hundreds of fibers/cm3 when these plants first opened, to generally single digits by the mid-1990s. Taken together, these factories represent the facilities in China that use the largest amounts of asbestos. There is a great economic disincentive to making the diagnosis of asbestosis since when this diagnosis is made the worker is immediately retired, but all salary and benefits for the worker and their family are maintained. An X-ray review was undertaken, with all available films reviewed. X-rays had been taken on an irregular basis over the years, generally when funds for such an undertaking were available at the factory in Shenyang, or at the local public health department in Qingdao. Not every worker had a film. For each worker for whom there were X-rays the most recent set of films was read and if totally negative no further films were evaluated. If the most recent films were thought to be positive, then a retrospective review of films was undertaken to determine when the film had first become abnormal. Initial readings were made using the ILO scale, but all films were then read with the Chinese system. One reader (A.L.F.) evaluated all films. RESULTS

Together, from these three factories, some 1694 sets of X-rays were read. A positive film had parenchymal and/or pleural changes consistent with asbestos exposure by use of the ILO classification, with 1/0 or higher being considered abnormal. From the Shenyang factory some 1264 sets of films were evaluated from 714 males and 550 females. Of the males, 642 smoked, 64 did not, and for eight the smoking status was unknown. Among the females 25 were smokers, 521 non-smokers, and for four the smoking status was unknown. At Qingdao 1, 317 sets of films were evaluated, 75 from males and 242 from females. Again, most males smoked (51 versus 21) while most females did not (234 versus 8). At Qingdao 2, 113 sets of X-rays were reviewed with 17 males (7 smokers, 10 non-smokers) and 96 females (80 non-smokers, 16 smokers). From these X-rays, 57 of 714 males in Shenyang (8%) were found to be positive, with 85% of these


Three factories in two cities were studied. In Shenyang, an industrial city (population 10 million) in the north of China, a factory said to be the third or fourth largest user of asbestos in China was studied. This factory uses only Chinese chrysotile (~2500– 3000 tons/yr) to make rope, textiles, brake pads and rubberized asbestos-containing products. The plant opened in 1952; the medical director in the 1990s had worked there since 1956, and from that time forward had maintained personal, handwritten records of all workers. In 1993 there were some 1600 employees, about one-half women, and in this group various diseases had been diagnosed. Utilizing the Chinese classification system, there were said to be 180 cases of asbestosis seen between 1958 and 1992, with the period of exposure ranging from 6 to 38 yr. Of these 180, ~15%, or some 24 individuals, had died of cancer, primarily lung cancer; a similar number had died of respiratory insufficiency, and about the same number from other causes. Among these 180 there had been one tissue-verified mesothelioma, with a suggestion of a second in this worker population. Overall, there appeared to be more deaths in this worker population than among other Shenyang residents, and the average age at time of death was ~10 yr younger than the general population, based upon cityspecific data. Over the years, only ~50% of air tests met the Chinese standard of 2 fibers/cm3, and levels in the past were thought to be higher than more recent ones. Over time there was an institution of dust suppression, as well as a prohibition of taking home work clothes, a rule instituted in 1982. In the coastal town of Qingdao, about 500 miles south of Beijing, two asbestos factory populations were investigated. At one factory (Qingdao 1), opened in 1950, only chrysotile fiber, primarily Chinese but with small amounts of Canadian and Zimbabwean (formerly Rhodesian) chrysotile, has been used to make brake linings, with a second product, fireman’s textile cloth, being added in 1988. This factory, located in a densely populated residential area, by the mid-1990s employed about 2200 workers, of whom 700 had retired when the factory population was studied. Of the 1557 active workers, some 117 had been identified, by Chinese criteria, to have asbestosis. Seventy percent of all workers were female.

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being smokers. Twelve of the 550 females were positive (2.2%), with only one smoker. In Qingdao 1, 13.3% of males and 6.2% of females were positive. At Qingdao 2, the percentages were 23.5% of males and 19.8% of females. Most cases were found among workers in their fifties or sixties, with only 17 total cases in workers in their forties. There were few workers in their seventies and eighties, but some positive cases were found in these age groups as well. No data are available at this time regarding rates of tuberculosis compared to the ILO classification. Tuberculosis rates, in general, are higher than levels found in the USA or Europe, with ~15% prevalence in this population. No cancers were found on these X-rays. A comparison of the ILO and Chinese evaluation systems will be published subsequently. The Chinese system appears to over-read positive cases. DISCUSSION

CONCLUSION

Exposure just to chrysotile, among both men and women, in Chinese factories leads to the development of the usual range of disease among such workers, including benign asbestosis and various asbestos-related malignancies. Acknowledgement—Funding for this research came from internal funds of the academic institution involved. No corporate or grant support was received to carry out this work.

REFERENCES Merewether ERA, Price CW. (1930) Report on effects of asbestos dust on the lungs and dust suppression in the asbestos industry. London: HM Stationery Office. Pang Z, Zhang Z, Wang Y, Zhang H. (1997) Mortality from a Chinese asbestos plant: overall cancer mortality. Am J Ind Med; 32: 442–4.


These data reveal a pattern of asbestos-related disease, specifically asbestosis, not unlike the experience in the West. Although many men smoke, women as a rule do not, but still many develop asbestosis, but at rates somewhat lower than among males. This may be due to a number of factors, including specific job assignments and smoking status. The carcinogenic potential of Chinese asbestos in the Qingdao factories has been previously reviewed (Pang et al., 1997). Fiber levels in these plants are reviewed in that paper, and in the past were very high. Clearly, since most, and at some factories all, asbestos used has been chrysotile, this fiber itself clearly has the ability to produce not only asbestosrelated cancers, but traditional asbestosis.

Clearly, because of the patterns of employment, health oversight, and medical record and specimen retention, what is presented here cannot be thought of as a comprehensive picture. It is quite likely that any workers who died of cancer or from asbestosis, or any other cause, would no longer have their X-rays available for analysis. This would lead to an underestimate of the true disease pattern in these groups of workers. Workers, especially after retirement, may well have been lost to follow-up. Nevertheless, as was documented in 1930, women are at risk, both for asbestosis and lung cancer, and future analyses may well document different patterns of cancer mortality in women. Such additional data analyses can be anticipated in the future.