Introduction

Most known human chemical carcinogens were first identified in the work-place generally due to astute clinical observation following the tradition of Percival Pott (Historical introduction). By the early 1970s, most of the major occupational carcinogenic hazards known today had been recognized (McClure & MacMahon, 1980). Since then, although many industrial processes or compounds have been suspected to carry an elevated cancer risk and extensively studied, rarely has the evidence for humans been sufficient to implicate a previously unknown agent. The burden of occupational cancer in industrial states is generally considered as less than 6% (Wynder & Gori, 1977; Higginson & Muir, 1979; Doll & Peto, 1981) (Conclusions). Smaller estimates have been made in Finland (0.5%) (Hemminki & Vainio, 1984), Japan and other countries.

The period since World War II has seen major improvements in industrial hygienic practices in many countries, so that certain hazardous exposures should have been reduced. Thus, risk estimates made in the late 1970s largely reflect exposures prevalent in earlier decades and may be out of date. None the less, the problem of occupational cancer remains important especially in developing countries which offer a unique opportunity for control and prevention. Methodology and limitations in measuring the burden of occupational cancer are discussed in Banbury Report 9 (Peto & Schneiderman, 1981).