Opium

Opium usage is common in many regions of Asia, including localities where there is a high incidence of esophageal cancer. Consumption is especially high in countries where alcohol is forbidden for religious reasons, and opium is used as a substitute. The crude opium is smoked, and the smoked residues remaining in the pipe (opium dross or sukhteh) and refined pyrolysis products (shireh) are eaten. The pipe scrapings are much less expensive than opium or shireh, and are therefore used mostly by the poorer people, who also have the higher incidence of esophageal cancer. In addition to being used for pleasure, opium is used for the treatment of disease, for insomnia, as a painkiller, and to quiet crying babies.

With reference to esophageal cancer, opium usage has been studied mainly in north-east Iran. Although the use of opium in Iran was made illegal in 1955, the fact that morphine metabolites were detected in the urine of 50% of the population over the age of 35 indicated that opium use continued to be very common in men and women in the areas studied (Joint Iran-IARC Study Group 1977).

Clinical studies of patients with esophageal cancer led to the suggestion that opium addiction was associated with the disease (Dowlatshahi et al. 1977). Black particles of burnt opium were often found in the esophageal mucosa of the patients. A Joint Iran-IARC Study Group (1977) also found evidence that the distribution of esophageal cancer in north-east Iran paralleled the use of opium.