Benzene and leukemia.

Dear Editors: Although there were numerous case reports showing the possible role of benzene in the development of leu-kemia, the first epidemiologic study on this problem appeared in 1974 (1). From 1967 to September 1973,26 patients with leukemia were investigated among 28,500 shoe, slipper, and handbag workers chronically exposed to benzene in Istanbul, Turkey. Seventeen of them were studied at the Second Internal Clinic of Is-tanbul Medical School (1). The remaining nine leuke-mic workers were investigated in the hospitals in Is-tanbul, five at the First Internal Clinic of Istanbul Medical School, three at the Therapeutic Clinic of Cer-rahpasa Medical School, and one at the Hematology Department of the same faculty (1). The incidence of leukemia among these shoe workers was 13/100,000, which is a markedly and statistically significant increase over that for leukemia in general population. In 1974 the number of leukemic shoe workers in Istanbul increased to 31 (2). Thus, the incidence of leukemia among them was 13.59/100,000. The peak incidence of leukemia among shoe workers in Istanbul occurred in 1973. The number of leukemic shoe workers in Istan-bul started to decrease following the prohibition and discontinuation of the use of benzene from 1969 onward (3). The working conditions were not good, and their shops were usually small, not hygienic, and poorly ventilated. The concentration of benzene was found to reach a maximum of 150 to 650 ppm when adhesives containing benzene were in use. The benzene levels in 98 adhesives and thinners available between 1970 and 1972 in Istanbul were determined by gas chromatography and ranged between 9% and 88% (4). In their paper "Review and Update ofLeukemia Risk Potentially Associated with Occupational Exposure to Benzene" in Environmental Health Perspectives, Volume 82, Brett et al. (5) considered these estimations unsatisfactory because they supposed the shoeworkers might have been exposed to volatile hydrocarbons in addition to benzene, curing agents, dyes, and other chemicals used in the shoe industry. Other than ben-zene and toluene, no other material including curing agents and dyes was used in shoe workplaces during the period 1960 to 1974. Only occasionally was shoe varnish used. But this material did not evaporate. In Turkey, until recent years, toluene and benzene available in the market were obtained from the coke plants. As is well-known, benzene, toluene, and xylene produced in the coke plants contain other homologs of aromatic hydrocarbons. According to Brett et al. (5), our exposure data …