OBJECTIVES: The aims of this paper were (1) to analyze the prevalence of symptoms of post-traumatic stress disorder (S-PTSD) in a population of workers 1 year after an industrial disaster; and (2) to assess the role of factors of vulnerability such as the occupational impact of a disaster and economic conditions. METHODS: A cross-sectional survey assessing the relationships between socio-occupational category, impact on employment and S-PTSD was conducted by the self-administered impact of event scale-revised. RESULTS: The prevalence of S-PTSD in workers in the peripheral zone (<3 km around the explosion site) was 12% in men and 18% in women. Factors significantly associated with S-PTSD in men were non-managerial socio-occupational category: employees (ORa = 4.3; [2.3; 7.8]), factory workers/laborers (ORa = 3.7; [1.8; 7.6]), intermediate professions (ORa = 3.3; [1.9; 5.9]), and artisans (ORa = 3; [1.3; 7.7]); and layoff (ORa = 2.6; [1.5; 4.5]) or unusable workplace after the explosion (ORa = 1.8; [1.1; 2.8]). In women, factors significantly associated with S-PTSD were the socio-occupational categories of employees and factory workers (ORa = 2.2; [1.4; 3.5]), artisans (ORa = 2.7; [1.3; 5.7]) and intermediate professions, (ORa = 1.5; [1; 2.3]) and reporting of an occupational accident (ORa = 1.5; [1.1; 2.2]). CONCLUSION: Impact on the workplace and socioeconomic conditions were associated with S-PTSD. The epidemiological approach in disaster situations needs to be improved, particularly in the social and occupational dimension when economically active populations are involved. Vulnerable subgroups, defined by occupational impact and low socioeconomic category, should be taken into account.