Exposure assessment to engineered nanomaterials within the French EpiNano program: inter-method reliability study

Objective: Inter-method reliability is a measure of the ability of two different methods which evaluate the same underlying exposure to yield similar results on the same subjects. In this study we compared an observational “EpiNano-method” developed for assessing exposure to nano-objects and their agglomerates and aggregates (NOAA) in workplaces within the framework of the French epidemiological surveillance program EpiNano with a more accurate but more expensive and time-consuming “Reference-method”.
Methods: EpiNano-method consists in an onsite visit of facilities and an observation of workstations where NOAA are present using a standardized tool, the Onsite technical logbook. Reference-method involved an onsite visit, interviews with operators and supervisors, analyzing results of available exposure measurements data, a debriefing meeting and an expert’s report to validate results through consensus. Seven workstations which synthesize and functionalize carbon nanotubes were assessed by Reference-method and by EpiNano-method implemented by three evaluators. All statistics were calculated based on pairwise comparisons of the evaluator’s respective results with the results from the Reference-method
Results: The prediction of exposure to NOAA using EpiNano-method exhibited substantial agreement with that of the reference method (Fleiss kappa=0.70, sensitivity=0.88, specificity=0.92). The best reliability of quantitative exposure scores was found for the EpiNano-method results of Evaluator #1, when comparing with the Reference-method (= 0.75). The correlation was positive but of moderate strength (= 0.57) for Evaluator #2 and negative for Evaluator #3. When comparing the semi-quantitative exposure potential variable almost perfect correlation was found; all but one workstation were classified in the first category corresponding to “Negligible to low” exposure potential.
Conclusion: This study allowed a first validation of the EpiNano-method. However, it should be confirmed by further comparison with more robust quantitative exposure measurement data, available for a larger workstation number, with more contrasting exposure conditions and various types of NOAA.