Onset and remission of eczema at pre-school age in relation to prenatal and postnatal air pollution and home environment across China.

We investigated associations between prenatal and postnatal environmental factors and onset and remission of preschool childhood eczema across China. The study population was preschoolers in randomized day care centers in seven cities (N = 39,782). Data on eczema and prenatal and postnatal indoor and outdoor environment were obtained from a cross-sectional questionnaire sent to parents or other guardians. Reports on eczema in the first 2 years and in the past year was used to retrospectively calculate onset and remission (changes of reported eczema). Prenatal and postnatal outdoor temperature, NO and PM were modelled from official air pollution data. Associations were estimated by two-level logistic regression. Calculated onset rate was 3.2%/y and remission rate 29.2%/y. Exposure to NO during pregnancy was associated with onset of eczema, similarly for all trimesters. Postnatal PM and NO were related to decreased remission. Postnatal outdoor temperature was associated with onset of eczema. Pre-natal and current redecoration or buying new furniture, and perinatal as well as current dampness and indoor mould, were associated with increased onset and decreased remission. Cockroaches in current home was another indoor risk factors. Prenatal exposure to farm environment and large family size were all negatively associated with eczema. In conclusion, a warmer climate and prenatal NO can be associated with increased onset of eczema in Chinese preschoolers. Postnatal PM and NO can be associated with reduced remission. Perinatal and current dampness, indoor mould and cockroaches may increase onset and decrease remission. Exposure to chemical emissions from indoor materials after first year of life may increase onset. Prenatal exposure to farm environment and large family size could be protective.