With the generalized linear model and natural splines (ns), we examined the association between outdoor air pollutants and daily morbidity for diabetes and liver disease stratified by sexes and ages based on 4 years of daily data (2008-2011) in Tianjin, China. Season effects of air pollutants including particulate matter (PM), sulfur dioxide (SO2), and nitrogen dioxide (NO2) were also investigated. An increase of 10 μg/m(3) in a 2-day average concentrations of particulate matter with diameters of 10 μm or less (PM10), SO2, and NO2 corresponds to increases in diabetes morbidity of 0.39 % (95 % confidence interval (CI), -0.42-1.12), 0.15 % (95 % CI, -0.25-0.54), and 1.22 % (95 % CI, 0.51-2.96), respectively. As for liver morbidity, the increases were -0.84 % (95 % CI, -2.33-0.62), 0.90 % (95 % CI, 0.50-1.74), and 1.10 % (95 % CI, -2.58-4.78), respectively. The effects were stronger in the cool season than those in the warm season; females and the elderly were generally more vulnerable to outdoor air pollution. This study possesses scientific implications and instructional significance for local environmental standards and medical policymaking.