Environmental Factors and Exposure Time Windows Related to the Etiology of Acute Lymphoblastic Leukemia in Children

Abstract

Our objective in this chapter is to highlight recent advances and provide a perspective on the current understanding of the environmental factors related to the etiology of acute leukemia (AL) in children. Cancer is a major cause of infant mortality and is one of the main public health problems at a global level. AL is the most frequent type of cancer among children younger than 15 years of age. The causes of most forms of leukemia are unknown; only a few types of exposure have been established as risk factors. Nowadays, AL in children is considered to be the result of the interaction of different environmental factors with a genetic susceptibility to the disease. Environmental risk factors may play an important role in the development of childhood acute lymphoblastic leukemia (ALL). A “multi-stage” model for this disease has been proposed when the first “hit” occurs, possibly before conception or in the prenatal stage, and the second hit, called genetic susceptibility, occurs in the postnatal window through environmental exposure to a particular agent. We review the published studies of risk factors associated with the development of childhood ALL in recent years and identified these “windows of exposure” – preconception, prenatal, and postnatal – that may be critical to the development of the disease. The results are summarized in tables and discussed. Additionally, we discuss the use of ALL-associated fusion genes and genetic polymorphisms, together or separately, as indicators of ALL susceptibility and increased risk.