Varying data availability limits the representativeness of some of the indicators. We focused on creating estimates of mean measured levels as inputs for the indicators, in the absence of data that would support the development of valid exposure distributions in the Canadian population. Qualitative assessments of how well the data used represent the ‘average’ for Canadians for each substance/exposure pathway are provided with the results and summarized in Table 2. This approach is consistent with recommendations for screening-level assessments[35, 36]. More details on the basis for assigning data quality ranks (gap, very low, low, moderate and high) shown in the following results are available on the CAREX Canada website[37], as are documentation and citations for all data sources and levels used to calculate the LECRs reported here.