Urban or Rural Residence and Histologic Type Distribution in 21,000 Childhood Leukemia Deaths in the United States, 1950–59

Type-, age-, sex-, race-, year of death-, and urban-rural-specific leukemia mortality rates for 20,711 leukemia deaths in the entire United States for the years 1950–59 were compared with previous studies of childhood leukemia by histologic type and urban-rural residence. Among white children, urban rates exceeded rural rates, but among nonwhite children the reverse was true. Except for myelocytic leukemia, urban rates in whites appear to be increasing with the passage of time, but rural rates are declining. Data from the present study and from the studies reviewed suggest lymphocytic and myelocytic forms of the disease are distinct. A comparison of white and nonwhite mortality rates indicates that myelocytic leukemia has a common etiology in whites and nonwhites, but nonwhites are either not exposed to, or are protected against, agents causing lymphocytic leukemia.