Does Occupational Silica Exposure or Silicosis Cause Lung Cancer?

Abstract

The International Agency for Research on Cancer's (IARC) assessment of silica as a probable human carcinogen rested on three evidentiary bases: (a) positive experimental rat model of pulmonary carcinogenesis via inhalation and injection; (b) elevated cancer (mostly lung) among silica-exposed workers; and (c) elevated pulmonary cancer risk among workers with extant silicosis, often diagnosed and recorded in conjunction with compensation registers (IARC, 1987). IARC indicated that the following epidemiology issues were of concern to the scientists on the Monograph writing committee 10 years ago. (1) Absence of dose-response findings; (2) Lack of adjustment for smoking; (3) Lack of adjustment for other possible confounding factors (i.e. radon, polycyclic aromatic hydrocarbons, arsenic); and (4) Diagnostic bias of lung cancer among compensated silicotics. For these reasons, the evidence among humans was judged to be limited.