Aims Unintentional nanoscale particles (UNP) are generated from usual work processes and thus exist since a long time and are more prevalent than the manufactured nanoscale particles. The objective of this study was to develop a job-exposure matrix, a useful tool to estimate prevalence of occupational exposure to UNP for epidemiologic studies. .

Methods Work-processes generating UNP and their associated chemical families have been identified through an extensive literature review and the knowledge of an expert’s panel in various domain such as industrial hygiene, toxicology, atmospheric physics and chemistry, epidemiology… These processes were associated to occupations extracted from the ISCO classification edition 1968. A probability and a frequency were assessed for each specific combination “occupation × work-process”. When an occupation was related to several work-processes, the final exposure assessment consisted in the highest probability of exposure and a weighted-frequency of exposure combining assessments from each related work-process. Exposure assessment for some specific occupations could differ according to industries and historical periods. Due to the few available measurement data, intensity could not be assessed at that time.

Results Over 50 work-processes generating UNP have been identified and were related with seven UNP chemical families: metal, mineral, carbon, wood, polymer, polycyclic aromatic hydrocarbon (PAH) and other organic. A little less than 50% occupational ISCO codes were unexposed, and 9%, 13% and 31% were possibly, probably and certainly exposed, respectively. Most of occupations were exposed to carbonaceous, PAHs UNP and then to metallic and mineral UNP.

Conclusions These results suggest that occupational exposure to UNP might be important at the workplace and might concern a wide variety of workers. In order to assess intensity of exposure, we are currently organising measurement campaigns in French and Canadian workplaces (ExproPNano program).