There is an excess of hospitalization rates for acute exacerbation of COPD in Picardy compared to the national data. A first study realized in Picardy has shown a link between air quality and COPD. Nevertheless, the particles type is unknown and according to it, impact on COPD could be different. The investigator goal is to find a correlation between acute exacerbation of COPD consultation rate and daily ultra thin particles in Haut de France. The investigators will correlate the particles composition with daily acute exacerbation of COPD rate. All COPD patients with a diagnosis of acute exacerbation in emergency room in University Hospital of Amiens-Picardie and Lille, and Clinique de l'Europe between 01/01/2020 and 31/12/2020 will be included. For each patient, home and work address will be collected. The duration of 1 year was chosen to take into account seasonal variations. In parallel, a daily report of the rate of ozone, particles (PM2.5 and PM10), dioxide nitrogen but also odours and pollens will be done by ATMO Haut de France.

Inclusion Criteria:

• COPD patients with a diagnosis of acute exacerbation of COPD in the emergency room of Amiens and Lille centers
• Adults
• Patients able to express consent
• signed written informed consent form
• covered by national health insurance

Exclusion Criteria:

• patients non covered by national health insurance
• patients not able to express consent
• minors

All COPD patients with a diagnosis of acute exacerbation in emergency room in University Hospital of Amiens-Picardie and Lille, and Clinique de l'Europe between 01/01/2020 and 31/12/2020 will be included. Home and work address and spirometric data will be collected. Atmo Hauts-de-France will collect daily data on PM10, PM2,5, NO2 et O3 in Amiens and Lille metropoles. Odours and pollens will be collected too by ATMO Haut de France.