Organochlorine contaminants in cetaceans: how to facilitate interpretation and avoid errors when comparing datasets

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Margaret M. Krahn
Gina M. Ylitalo
John E. Stein
Alex Aguilar
Asuncion Borrell


This paper reviews current scientific literature to provide information for avoiding errors commonly made in comparing and interpreting datasets from laboratories measuring organochlorine contaminants in cetaceans. Before making comparisons and interpretations using heterogeneous datasets (e.g. those from different laboratories or those from different methods in the same laboratory), it is essential to consider specific information about the animals sampled (e.g. age, sex, reproductive status, body condition and health status), sampling procedures (e.g. necropsy of subsistence, stranded or bycaught individuals; remote or surgical biopsy), methods for measuring and conventions for expressing analytical results for lipids and contaminants (e.g. percent lipid, percent dry weight, contaminant concentration units, totals of contaminant groups such as PCB congeners) and quality assurance performance. Reformatting should be carried out, as necessary, to unify the datasets (e.g. into like units and weight basis) and allow a critical evaluation of the data to be made. As part of the data interpretation, caveats or limits in the comparability of the datasets (based on quality assurance results) should be provided. In addition, the biological relevance of the data must be considered in interpreting the datasets.

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