EST on the Dioxin Reassessment

[charlie.cray@green2.greenpeace.org]

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Original-TO:      dioxin-l@essential.org
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Thought all would be interested to hear what EST is saying about the status of
the EPA's Dioxin Reassessment:
 
Source:  Johnson, J. News/Government:  Dioxin assessment revi-
sions unlikely to change conclusions.  Environ. Sci. & Technol. 
30 (12): 528A (1996)
 
   Clearer documentation, greater transparency, more detail, but 
   little substantive change are expected in the conclusions of 
   the EPA dioxin risk reassessment currently undergoing 
   revisions.  According to interviews with EPA and other scien-
   tists in and out of the federal government who are on the 
   rewriting team, many of the conclusions in the original risk 
   assessment remain:  Dioxin is a probable human carcinogen, and 
   some cancer and noncancer effects are being seen at or near 
   current body burden levels in humans.
 
   The team is preparing a clearer, better referenced document 
   that is expected to be released in February to the EPA Science 
   Advisory Board (SAB), the body whose criticism triggered the 
   current effort to revise parts of the 2000-page, nine-chapter 
   assessment.  Last year, SAB called for EPA to rewrite sections 
   on dose-response and risk characterization.  If EPA makes the 
   February date, it will mark a milestone in the five-year 
   review (ES&T, August 1995, p. 338A).
 
   As of early November, the dose-response revisions were com-
   plete  but the writing team had bogged down on key risk char-
   acterization sections on  cancer, toxic equivalency 
   factors,and immunotoxicity.  The team has reached agreement on 
   these sections, but team members who are responsible for 
   writing them have been stretched too thin to complete the job, 
   scientists said.  
 
   Generally, the revised sections include new and better data 
   supporting the use of toxic equivalent factors and body  
   burden levels rather than daily intake as a dose metric.  The 
   revised sections will also reflect more studies showing a very 
   small margin of exposure for dioxin.  Regulators usually seek 
   a difference of at least 100-fold between exposure and observ-
   able effects, EPA officials said, but studies and other data 
   are turning up no margin for some subtle effects from dioxin.
 
   Researchers said the new risk characterization section will be 
   a more transparent document with clearer references to 
   supporting sections in the main risk assessment and will be 
   easier for risk managers to use -- a chief SAB criticism.  
   However, they also noted that the long delays caused by re-
   viewing the rewriting mean that the report's underlying data 
   are becoming dated; risk assessment chapters were first peer 
   reviewed in 1992.  Meanwhile the agency has moved ahead to 
   propose new dioxin control regulations for incineration, which 
   are a major dioxin source, without a final assessment of health 
   impacts.
 
 

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