World Day for Safety and Health at Work 2013

Case Study: Bile duct cancer in printing plants in Japan

Workers, who had worked in a small-scale proof-printing plant (around 70 workers) in Osaka, Japan, were found to have bile duct cancer. Between March 2012 and February 2013, a total of sixteen male workers and formerly employed workers sent their occupational cancer claims to the local inspection office. All of them started working in the plant in the 1980s and 1990s, and were aged between 20 and 49 at the onset of the cancer. Only around 30 workers had regularly worked in the proof-printing room and thus the rate of the cancer was unusually high.

The printing room used large quantities of 1,2-dichloropropane and dichloromethane from 1991 – 2006 and from 1991 – 1996, respectively. The workers were exposed to these chlorohydrocarbons which had been used as the ink remover. Proof-printing is a kind of test printing to ensure the printing quality, and the plant printed small numbers of sample sheets before their customers ordered thousands of sheets from other printing companies. This is why the workers frequently cleaned rollers, blankets or rubber-made printing devices of the proof-printing machines using the chlorohydrocarbons before printing the next sample sheets.

The printing room was in the basement and there were no windows and no effective ventilation systems. Compounding the situation was the fact that the air was internally circulated to maintain the room temperature and humidity for printing. Workers were not provided with adequate respiratory protection. There were no occupational health officers who should have been appointed according to the OSH Act of Japan.

The medical expert group who reviewed the cases concluded that bile duct cancer could be developed after long-term exposure to high concentrations of dichloromethane and or 1,2-dichloropropane and that it was highly probable that the cancer cases of the sixteen workers was caused by long-term exposure to these chemicals. The sixteen workers were duly notified of this and advised that they were to be compensated as suffering from an occupational disease.

Other cases in printing plants in Japan

The Ministry carried out intensive inspections on 561 printing plants with the cleaning process throughout Japan in June 2012 and announced additional cases of bile duct cancer from different provinces. As of 28 February 2013, the total number of claims submitted to the Ministry as bile duct cancer in printing plants is 64, including the 16 cases in the Osaka plant. The Ministry is further to complete a survey of 18,000 printing plants throughout Japan to ensure the compliance of the regulations through local labour offices.

Lessons learned
1. Reporting: The onset of the first bile duct cancer case in the proof-printing plant was in 1996 followed by the second case in 1997 and the third in 1999. Some workers suspected that the cleaning agents being used might be the cause and asked employers to take proper action. But this did not happen. If these early cases were reported to the government, some of the later cases could have been prevented.

2. Working environment: The plant did not have effective ventilation systems, and this, along with the numbers of workers involved in the cleaning process served to increase the concentration of hydrocarbons in the atmosphere resulting in higher exposures. Improved control measures, including, for example substitution of the chemical, local exhaust ventilation should have reduced the risk of the disease.

3. Information supply and scientific research: Scientific information on human carcinogenicity of hydrocarbons was also limited. Some hydrocarbons were known to cause liver cancer in experimental animals, but there was no clear conclusion on the human carcinogenicity.

4. Law compliance: The plant did not have occupational health personnel required by the OSH Law. If it had one, there could have had an active OSH committee and risk assessment activities, which could reduce the risk, or at least lead to earlier detection and reporting of the disease.

Ministry of Health, Labour and Welfare, Japan
Occupational Biliary Cancer: Cases in Japan, May 2014 (in Japanese) (in Japanese)