Reliability and Relative Validity of Fish Consumption Data Obtained in an Exposure Assessment Study among Montreal-Area Sportfishers

A two-season exercise was undertaken in 29 high-level sportfish consumers to evaluate the reliability and accuracy of study instruments. Fishers were invited to participate after completing the main study interview (Time 1) in fall 1995 or winter 1996. Over a 4-week period, they provided a nonconsecutive 7-day weighed food record, kept a fish consumption calendar, and responded to a shortened version of the Time 1 instrument at the end of this period (Time 2). A second blood sample (at Time 2) was analyzed for whole blood mercury (Hg) and the omega-3 fatty acids eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) in plasma and erythrocytes. Identical questions were compared in the Time 1 and Time 2 instruments. Reported sportfish consumption assessed by the different instruments was subjected to nutrient analysis. Three estimates of exposure to the target substances were derived from the dietary intake estimates and correlated with their respective Time 2 plasma (EPA, DHA) or blood (Hg) values, and with a kinetically derived interval-specific plasma/blood uptake value. Remarkable similarities were observed for the data derived from like questions in the Time 1 and 2 questionnaires in both seasons. However, frank discrepancies between some portion size estimates and measured values may signal cause for concern. The strongest correlations between the Time 2 plasma DHA and EPA, and blood Hg, and the three exposure indices emerged between estimates of retrospective DHA intake and DHA fish calendar values and their corresponding Time 2 plasma levels, and for Hg estimated both retrospectively and from the fish consumption calendar and correlated with Time 2 blood Hg, especially in the winter 1996 dataset. Overall, the results suggest that the main study instrument provides a reliable and relatively accurate indication of sportfishers' fishing practices, species selection, and sportfish consumption habits.