Results of sputum, cytology among workers exposed to vinyl chloride monomer and to poly(vinyl chloride).

The results of systematic cytological sputum examinations of 3,380 Italian VC-PVC industry workers and of 2,287 workers in other industries at different potential risk and chosen as control groups are reported. The results indicate an increase in cellular abnormalities and dysplasias in the epithelium of the respiratory tract among VC-PVC workers. These data are in line with experimental results showing that VC produces lung tumors in mice and with early epidemiological evidence among exposed workers.


Introduction
In 1975, it was decided to include the cytological examination of sputum in the protocol of systematic medical surveillance of the workers in all the Italian plastic factories exposed to vinyl chloride (VC) and poly(vinyl chloride) (PVC).
This program was co-sponsored by the Italian Federation of Unions of Chemical Workers (FULC) and by the Public Health Service of the Italian regions where the factories were located.
The decision to investigate cytologically all Italian VC-PVC industry workers was taken on the basis of the following facts: (1) the observation of a marked increase in the incidence of lung adenomas in mice exposed by inhalatory route, to a spectrum of doses of VC ranging from 10,000 down to 250 ppm (1-3); (2) the unusual finding of cellular abnormalities in a high portion of the lung adenomas of exposed mice (1-3); (3) the observation of frequent severe abnormalities (squamous dysplasia and atypical adenomatous hyperplasia) in the sputa of a small group of heavily exposed workers (3); (4) the report of some increase in lung carcinomas among workers from two VC-PVC factories (4); (5) the finding that the majority of lung carcinomas *Institute of Oncology and Tumor Center, Bologna, Italy. observed among exposed workers were not of a common histotype i.e., giant cell carcinomas (5).
A total of 3380 workers was examined. These workers have been and/or are exposed to the monomer and part of them also to PVC dust. For comparison 2287 workers in other industries at different potential risk were examined: namely, workers manufacturing PVC products, workers in chemical industries not dealing with plastics, metal workers, miners and workers in the chromium industry.
For each sputum examination four cytological slides were prepared. The smears were stained by the Papanicolaou technique.
The slides were screened and evaluated independently by the pathologists of the hospitals in the area where the factories were located, then by a trained cytologist in our institute. All abnormal smears were reviewed by the senior pathologist of October 1981   aOther than VC-PVC and chromium industries and not exposed to a known risk. bNot exposed to a known risk.  aOther than VC-PVC and chromium industries and not exposed to a known risk. bNot exposed to a known risk. the same institute. A joint critical reevaluation was carried out for those cases where there was not full agreement.
The same criteria of classification of the lesions and their distribution by classes were adopted by all pathologists.
Such criteria are based on our knowledge of the local cytological changes and of their sequence in the genesis of the various histotypes of pulmonary carcinomas ( Table 1).
The list of the most relevant changes correlated with environmental and occupational exposure, their distribution by classes following qualitative and quantitative parameters, and the code, are given in Table 2. This list takes into account not only cells from the pulmonary tree, but also cells from the upper respiratory tract and oral cavity.

Results
The number of valuable cases, the distribution of the cytological changes and the distribution of the results expressed by classes in the group of workers in the VC-PVC industries and in the control groups, are given in Tables 3 and 4. The incidence of dysplastic changes is particularly high in the plastics industry workers when compared to the other control groups, with the exception of chromium workers, which can be considered a positive control. The situation is well illustrated by the distribution of classes II-(III) and above (Table 5).
It may be stated that, in relation to the incidence of respiratory cell abnormalities, the workers in the VC-PVC industries can be placed halfway between chromium workers and other groups. A finding which deserves attention is the occurrence of atypical cells in the oral cavity and upper respiratory tract in 44 workers (17%) among VC-PVC workers ( Table 3).
The results were highly homogeneous in different factories, suggesting that variations in climate, which may affect the incidence of common pneumopathies, is not a determining factor.
The difference in the distribution of the pathological findings was not dependent on tobacco smoking.

Conclusions
The results presented are consistent with experimental data and early epidemiological evidence on the potential oncogenic effects of VC exposure on the lungs. Furthermore, our data suggest a possible oncogenic risk for the upper respiratory tract which should now be explored by proper epidemiological investigation.
Much remains to be done to clarify the part played by the monomer and by polymer dust in determining the observed cytological changes. Our data are now being re-examined, on the basis of the complete exposure history of single workers, to better establish the role played by PVC particles.