Rising leukemia rates in Thailand: the possible role of benzene and related compounds in cigarette smoke

Epidemiological studies suggest that cigarette smoking is associated with an increased risk of leukemia and that benzene and related compounds in cigarette smoke may contribute to this elevated risk. This report presents new findings on selected components of cigarette smoke (including benzene and 1,3-butadiene) from major brands of cigarettes sold in Thailand, which represent about 80% of market share. Tested were also two major and popular brands of U.S. cigarettes sold in Thailand, representing about 100% of market share. The cigarettes tested were filter and non-filter, and with high and 'low' tar and nicotine levels. The observed range for benzene, toluene and 1,3-butadiene were found in the range of 25.5-63.7, 36.4-79.8 and 44.6-78.7 microg/cigarette, respectively. The amount of acrolein ranged from 79.9-181 microg/cigarette and for isoprene from 313-694 microg/cigarette. Yields of these substances showed no correlation with tar deliveries in mainstream smoke. Consumption of tobacco products increased in Thailand since 1970. This study also showed increases in leukemia mortality rates in Thailand, and in the relative frequency of leukemia among incident cancers diagnosed at a large hospital in Bangkok. Exposure to benzene and related compounds in cigarette smoke may have contributed to these trends. Analytic epidemiological studies are needed on the relationship between these compounds in smoke from tobacco products used in Thailand. These preliminary findings support the need for voluntary and/or government-regulated reduction in smoke yields of benzene and related compounds in tobacco products, and for expanded smoking prevention and cessation efforts, in Thailand.