Objectives In 2014, the head of a elderly care facility (ECF) alerted the regional health authority for chronic irritative symptoms among office workers. Symptoms started in 2009 for 4 workers back in a newly rehabilitated building. From 2009 to 2014, the first analysis of indoor air quality lead to cleaning and disinfection of the air treatment plant. Furthermore no toxic compounds were identified in the materials used. In 2014, out of 21 office workers, 13 declared irritative symptoms, and the French national public health agency was called to carry out epidemiological investigations.

Methods In 2016, a regional group of experts in sanitary alerts in occupational health was involved as well as experts in air treatment, indoor air quality, building materials, and occupational medicine. Investigations were structured into 4 axes : clinical, epidemiological, environmental and psycho-sociological, all accepted by a local steering committee, except the psycho-sociological investigations.

Results Out of 130 workers of the ECF, 24 met the case definition. Among them, 18 worked in the newly rehabilitated building. Cases occurred regularly in this building from 2009 to 2016. Symptoms increasing with damp weather were: fatigue (89%), headache (83%) and multi-site irritations (35 to 88%). Medical consultations were reported by 12 workers. Underground springs existed under the building and water ingresses occurred after raining. Molds in high concentrations in indoor air (> 1000 UFC/m³) were identified in some offices. Ventilation systems followed reglementation. A surface disinfectant was withdrawn due to toxic compounds. Alcans disappeared when flooring was replaced in an office.

Conclusion This episode of sick building syndrom had an exceptional duration. Although former remediation measures were undertaken, the dampness of the environnment and symptoms of workers persisted. This suggests 2 possible ways of symptoms chronicization : hyper-sensibilisation of workers due to identified molds and/or psycho-sociological runaway (unfortunately not investigated).