Silica particles as a possible aetiological factor of esophageal carcinoma in the Qassim region of Saudi Arabia; A pilot study.

Objective: To determine the causative relation between the high levels of silica content in local wheat and salt and the reported increased incidence of esophageal carcinoma in the Qassim region of Saudi Arabia.(14) Design: The wheat and natural salt produced in the Qassim province of Saudi Arabia are analyzed using the ''ash-weight-method'' in order to determine their content of silica. At the same time, the acid insoluble particles of silica isolated from esophageal squamous epithelium surrounding the tumor-bearing site are assessed using a filtration method for extraction. The particles are subsequently observed by a scanning electron microscope and the elements measured by an x-ray analyzer. The results obtained from the experimental and control specimens are tabulated and compared. Subjects: The resected esophageal segments of four Saudi patients who were diagnosed to have esophageal carcinoma and have been resident in the Qassim province formed test group number I (group I). Group II (the control tissue specimen) consisted of equal weight of mucosal samples obtained from four normal esophageal segments taken during necropsies performed in Riyadh Central Hospital. Results: The results of this retrospective pilot study showed that the wheat and natural salt produced in the Qassim province contain significantly higher levels of silica when compared with that of other countries like United Arab Emirates and Australia. 130 (6.5%), 74 (3.7%) and 34 mg (1.7%) of silica per 2000 mg of wheat respectively and 14 mg (0.12%) only of silica per 2000 mg of sample. A comparison between the mean values of the counts and weight of silica granules in carcinomatous esophageal specimens and that of control samples show a significant increase in the levels of silica in the resected esophageal segments, Table 1. Conclusions: This pilot study suggests a previously unconsidered possible aetiological relation between the significant silica contents in the wheat and salt and the increased reported incidence of oesophageal carcinoma among the local population of Qassim's province. It is possible that the putative sharp-edged silica particles cause repeated local injury during their passage down the esophagus and also during the time they spend buried in the mucosa. This repeated injury may lead to cellular proliferation and subsequent neoplastic change.