How did the 2003 CDC report the “limit of detection” for dioxins?
Each individual blood sample that CDC analyzed for dioxins and furans had a unique limit of detection. That is because the volume of blood available for analysis was slightly different for each individual in the NHANES. For each chemical, CDC reported the average amount, the standard deviation, and the maximum value of the detection limit in a series of tables. As a matter of policy, for chemicals that were detected at the limits of detection, CDC decided not to report information in its selected percentile tables if any individual limit of detection exceeded the percentile estimate. Thus, in the Second National Exposure Report CDC reported ‘below the limit of detection’ for most of the dioxin-like chemicals. 7. Why did CDC pool (combine) individuals’ blood samples for measuring dioxins for the 2005 report? For the 2001-2002 sampling years, the CDC strove to report levels above the limit of detection-that is, to report actual levels rather than reporting almost all “non-detects.” To do
