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08/23/05 CDC Dioxin "Background" ranges for humans not exposed to dioxin in question

David Linhardt, a Chemical Engineer formerly employed by Dow,  has just released an analysis of the data and methods used by the CDC, Dow, and the MDEQ to calculate the so called "background blood serum levels" of dioxin  in non-exposed populations.  Could the data be flawed?   Visit his web site for more information: www.dioxinspin.com , the new report can be found on the Flawed Science page, volume 4.


Dow Chemical and Michigan Department of Community Heath studies of dioxin blood serum levels in Midland area residents and Dow employees reference a ATSDR-CDC study, Patterson, et al, 2004, that provides an estimate of background blood serum levels in 588 U.S. citizens supposedly not exposed to dioxins other than in their diet or in an environment distant from known sources of dioxins. 

However, Patterson, failed to exclude four unusually high serum levels and, as a result, the reported ranges of dioxin levels by age group are much greater than if only the 584 more normal levels were used.  As a result, some of the dioxin serum studies being carried out in Michigan erroneously report that ranges of serum levels being found are "lower than" or "are consistent" with US background levels.

In addition, the Dow and MDCH studies determined dioxin serum levels in the test subjects in 2004 and 2005.  However, Patterson was based on serum levels measured in 1996, 1997 and 2001.  The Dow and MDCH studies failed to adjust the Patterson serum levels to 2004/2005 levels which would be reduced through biological degradation.

A conclusion from his report:

Adjustment of the Patterson findings to 2005 and exclusion of the four abnormally high
dioxin serum levels indicates that Tittabwassee River residents have dioxin blood serum
levels that are higher than the estimated U.S. background serum levels. While the
maximum serum levels found in the PEI are not appreciably different than the maximum
levels found in the U.S. population, the minimum levels found are significantly higher.
The increase in the lower range of serum levels indicates a greater exposure to dioxins
of an extended period of time.

8/24/05 CDC blood dioxin background levels follow-up

"I discussed the four abnormal serum levels with Dr. Patterson. He indicated that he was not aware of any reason to exclude them from the study. He offered two possible reasons why the four levels were so high.

1. The four subjects eliminate dioxins from their systems at rate much slower than the average US population.
2. Prior exposure to high levels of dioxins had occurred but the four subjects were not aware of the exposure.
After some thought, I believe that there might be a third possibility. All the test subjects were questioned about dioxin exposure and only those that indicated no prior high level exposure were included in the study. Study members were told that they would be informed as to their own dioxin levels. A less than honest subject -- interested in knowing his/her own serum level -- might indicate no exposure if only to obtain info on personal serum levels without spending $3000.

A resampling of the four subjects five years later should be able to verify if biological half-lives are normal or abnormal.

The issue still remains that four abnormal serum levels have had a profound effect on the background ranges being reported by the CDC. In addition, as we have already seen, subsequent researchers are using the CDC background levels per se without any comment that some maximum age group ranges were based on a single sample.

I'm somewhat surprised that the CDC issued the study without a discussion of the impact of the four serums -- one might think that someone in CDC management felt that very wide ranges in background levels might have a calming effect on dioxin exposed citizens. "

Dave Linhardt, www.dioxinspin.com

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