CAT and childhood onset asthma: Discuss the correlation between single nucleotide polymorphisms (SNPs) of the Glutathione s-transferase Pi-1 (GSTP1), Catalase (CAT), Heme oxygenase-1 (HMOX1), and Homo sapiens epoxide hydrolase 1 (EPHX1) genes and the risk of childhood asthma in Fuzhou.