In early 2017, the Regional Unit of Public Health France was solicited for recurring symptoms, mostly irritations and headaches, affecting employees of a 400 people administration office. These symptoms had emerged with the relocation in a new building completely renovated that was characterized by low consumption mode and cumulative new working conditions (open space, reorganization of services). These events led to the evacuation of the building because of non-compliant indoor air analyzes. In order to identify the origin of this episode, surveys were conducted by a multidisciplinary group (epidemiology, occupational health, environment, socio-anthropology) following the recommendations of the National Public Health Agency for the management of unexplained collective syndromes.

In this study, three health components were investigated: the environment, the epidemiological context and the psychosocial context. Environmental expertise was conducted on indoor air quality, ventilation, acoustics and lighting. A retrospective cohort epidemiological survey was set up among the employees to characterize the health events in terms of people's time and working conditions (noise, lighting, open space…). Finally, an assessment of the psychosocial context was carried out on the basis of interviews with volunteer employees and through the development of a chronogram of events that occurred in recent months.

Environmental expertise has revealed a poor ventilation system that may have degraded the quality of indoor air, insufficient thermal comfort, acoustic discomfort and lighting problems. As a result, 78% of employees were symptomatic within 6 months (from October 2016 to April 2017), with a higher attack rate among women (85% vs. 68%, P=0.009) and 89% of people with multiple episodes of symptoms. Individuals presented a variety of symptoms with a higher incidence of headache (58%), asthenia (56%) and eye stinging (42%). For more than 70% of them, the symptoms disappeared when they left the building and for more than 30% when they opened the windows. The occupational doctor registered 28 recognitions of occupational accidents. Problems related to the building (light, noise, ventilation, odors) were more often felt by the symptomatic people. In total, 71% of people were dissatisfied with the work in open-space, the main inconveniences mentioned being: difficulty of concentration, noise and lack of confidentiality. The interviews of the psychosocial component put forward various elements that could have favored the epidemic phenomenon, such as the disruption of the organization of work, a damaged and impersonal work environment or communication problems with management.

The various investigations led to the identification of many symptomatic people, although we cannot exclude some biases of information and selection, and allowed us characterizing these events as sick building syndrome. The occurrence of various and non-specific symptoms having the particularity of disappearing at the exit of the building, the large number of recurrent cases and the higher attack rate in women are characteristic of these episodes. There are also triggers at the environmental level such as insufficient ventilation and noise- or lighting-related annoyances. The new organization of work in open-space was also a particularly contributory factor. Recommendations on the technical points but also on the working conditions were developed in consultation with the management and will require a mid-term evaluation.