[Effects of chromium compounds on the respiratory system. 5. Long term inhalation of chromic acid mist in electroplating by C57BL female mice and recapitulation of our experimental studies].

Long term inhalation of CrO3 mist by C57BL mice The effects of the chromic acid mist used in electroplating on the respiratory system of C57BL mice (female; n = 43) were examined histopathologically after exposure for 12 months to the mist (1.81 mgCr/m3-120 min, twice a week). Among the 23 mice sacrificed at 12 months after the first exposure, three cases of perforation in the nasal septs, a case of proliferative change of the tracheal epithelium, nine cases of emphysema and four of adenomatous metaplasia of the lungs were observed on antopsy. Among the 20 mice which were sacrificed six months after the last exposure, the same changes as the 12-month exposure group were also observed in the nasal septum, trachea and lungs, but papillomas observed in the nasal epithelia of six mice and adenoma in the lung of a mouse were new findings not seen in the 12-month exposure group. These results suggest that, in view of the low incidence of spontaneous lung tumor in C57BL mice, inhalation of chromic acid mist in electroplating might be a risk factor of lung cancer. Additionally, the occurrence of papillomas in the nasal epithelium demonstrates the need of directing attention to the possible development of cancer of the upper respiratory tract in chromium electroplating workers. Recapitulation on our experimental studies Upon completion of our five reports on the effects of chromium compounds on the respiratory system, a recapitulation of our experimental studies was made and compared with the findings of a number of reports on chromium. It was experimentally and epidemiologically confirmed that hexavalent chromium compounds act as carcinogens and cause specific biological effects on the respiratory system. These characteristics of hexavalent compounds might be attributable to the strong oxidizing potency and/or high permeability through the cell membrane. Furthermore, hexavalent compounds might be entirely different in biological action from trivalent compounds which are chemically most stable.