The aim of this study is to examine the association of exposure to air contaminants (PAH & VOC) emitted from the petrochemical industries, specific genetic polymorphisms (P4501A1 (MspI & exon 7) and GSTM1 & T1) of study subjects and their parents, and the risks of brain tumors and leukemia among children and youths in metropolitan Kaohsiung, southern Taiwan.