Study on the Influence of Climatic and Environmental Factors on Respiratory Diseases in Sanya, Hainan Province, China.

Inclusion Criteria: * 50-80 years-old migratory people with asthma, allergic rhinitis, COPD or atopic dermatitis from northern China; * 3-12 years-old children in Sanya; * Agree to participate this study. Exclusion Criteria: * Disagree to participate this study; * Having other respiratory diseases which can influence airflow, such as lung cancer, tuberculosis, pneumonia, bronchiectasis, etc; * Inability to understand the study procedures or inability/reluctance to answer questionnaire judged by the investigator.