Genes and the environment: their impact on children's health.

Because the human population is biologically diverse and genetically heterogeneous, it is not surprising that differences in susceptibility to disease among individuals with or without exposure to environmental agents exist. Individuals vary greatly in their susceptibility to disease. This is true of adults and children. The etiologies of many diseases of childhood are due to a combination of factors, including genetic susceptibility and environmental exposures during vulnerable periods of development. Genes regulate cellular growth and development, DNA replication and repair, the metabolism of endogenous agents in the body, and the metabolism and excretion of exogenous agents that the body comes in contact with in the environment. This regulation varies over the life span, contributing to the cellular consequences of the environmental exposures. This paper summarizes the contributions of genetics in understanding the etiology of environmentally induced diseases in children. The use of biomarkers of genetic susceptibility in the study of these diseases will be discussed. Future research needs for expanding our knowledge of the interactions between genetic and environmental components of childhood diseases will be presented.