USING RASCH ANALYSIS TO VALIDATE A MEASURE OF CHRONIC EXPOUSURE TO MERCURY IN ARTISANAL GOLD MINERS IN COLOMBIA

INTRODUCTION:  Mercury has been used worldwide for artisanal miners in the process of extracting gold by amalgamation. Validated questionnaires are the only available measurement tool when biomarkers of chronic exposure are absent; currently, there are not available biomarkers to measure the chronic exposure to mercury. Our objective was to design and validate a questionnaire to measure the chronic exposure to mercury in artisanal gold mining population.

METHODS:  Diagnostic technology assessment with design and validation of an questionnaire. The questionnaire was developed taking into account the dynamics of the mercury use in the mining districts, then it was administered to 124 participants who work as artisanal gold miners. Rasch analysis of the questionnaire items were conducted using WINSTEPS.

RESULTS:  Using the construct validation we developed a questionnaire with 11 items.  The variance explained by the questionnaire was 83.2% and first contrast of unexplained variance was 1.9%, which suggests unidimensionality. The separation index was 1.51 for persons and 6.5 for items; the reliability was 0.56 for persons and 0.99 for items. Appropriated adjustment to the model was demonstrated by the outfit values.

CONCLUSIONS:  This is the first validated questionnaire with unidimensional measurement of mercury exposure in minning settings. Further research is needed to develop unidimensional measurement questionnaires for other environmental and occupational exposures for which biomarkers are not available.