Proved carninogen : silicic acid dust

by Akihiko Kataoka
Kansai Occupational Safety and Health Center
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Pneumoconiosis develops after mineral or vegetable dusts deposited in the pulmonary tissue fibrose them. Recently World Health Organization (WHO) has initiated its pneumoconiosis elimination campaign because the category of occupational diseases still now remain the most important of all the occupational diseases in the world despite of high likelihood of eliminating them.

Pneumoconiosis is a pathological condition, but also causes various illnesses including pulmonary tuberculosis, bronchitis and pneumothorax. Lung cancer is also among them. In the Japanese pneumoconiosis compensation scheme, only the severest category, referred to as administrative class IV, is covered by compensation benefits. Yet, victims with less severe pneumoconiosis can be covered with equivalent benefits if they are officially deemed to suffer from statutory complications. Pneumoconiosis victims with lung cancer can be exceptionally compensated for only when they are classified into the administrative class IV. The official reason for this limitative approach is that pneumoconiosis may deter detection of lung cancer or make it difficult to treat it. The Japanese Government has not yet recognized the causal relationship between lung cancer and pneumoconiosis. Several pneumoconiosis victims have brought their lung cancer cases to the court, claiming that the existing narrow compensation scheme for lung cancer be groundless and unfair. In this context, International Agency of Research on Cancer (IARC) classified the silicic acid dust (crystalline silica), a common causative substance of pneumoconiosis, into the Group 1 (substance carcinogenic to humans) in late 1997. IARC, affiliated with WHO is the most prestigious institute on cancer in the world.

The high incidence of lung cancer in silicosis victims, reported long before, was also referred to in favor of this decision. Now many different NGOs, victims groups and lawyers have been continuing movements toward widening the existing compensation scheme for lung cancer-complicated pneumoconiosis victims. The Japanese government and court have not yet decided to extend the coverage for these victims.

The high frequency of lung cancer in pneumoconiosis victims began to raise attention in late 1970s, when better medical services were provided for them. Before then, prevalence of severe victims and poor medical services had prevented lung cancer from developing because the victims had died of pneumoconiosis before developing lung cancer. Now that the carcinogenecity of crystalline silica has been scientifically proved, the compensation criteria should be revised in favor of victims and at the same time more effective preventive measures should be implemented. We have no exhaustive information about the response to the IARC decision in other countries, but we know that South Korean authorities have started to revise the certification criteria recently. In US, the National Toxicity Program (NTP) is certain to revise the carcinogenecity rank of crystalline silica upward. Here in Japan, the Japanese Industrial Health Association began to investigate the possibility of revising the carcinogenecity for crystalline silica in the context of the IARC decision. UK authorities had established new certification criteria for lung cancer-complicated pneumonociosis victims before the IARC decision.

Pneumoconiosis remains one of the most important occupational diseases to be tackled jointly by NGOs and researchers all over the world. In these efforts, the carcinogenecity of crystalline silica has surely a pivotal role, and our desire is to promote the information exchange beyond the country borders.

For more information, visit the following Web sites

JOSHRC NEWSLETTER No.19 (July, 1999)

Japan Occupational Safety and Health Resource Center (JOSHRC)
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