[Dioxin-l] RE: Dioxins: Natural or Manmade?

[pat.costner@dialb.greenpeace.org]


Greenpeace:  Pat Costner, May 1999

                   Dioxins:  Natural or Manmade?

In 1995, U.S. Environmental Protection Agency Science Advisory Board 
considered the question in its review of Anthropogenic (manmade) vs. 
Natural Sources of Dioxin and concluded:

    =93[T]he observation in the late 1970s that dioxins are produced 
    by the combustion of many common materials, including 
    municipal solid waste =85 led some scientists to suggest that 
    dioxins had been with us since =91the advent of fire=92 and that 
    dioxins could be produced by natural combustion (for example, 
    by forest fires). At that time, there were some suggestions that 
    observed levels of dioxins were primarily the result of coal 
    combustion or perhaps of wood burned in small stoves.=94 

    =93This speculation was largely refuted by sediment core studies, 
    both in the United States (primarily in the Great Lakes) and in 
    Europe, which indicated that environmental dioxin levels 
    increased significantly beginning about 1935-40 (see Volume II, 
    pages 3-92 to 3-94).  
    
    =93Since the advent of fire clearly predated this time, it can be 
    concluded that dioxins were largely anthropogenic and associated 
    with events taking place around 1935-40. What were these 
    events? Coal combustion could be ruled out because the 
    consumption of coal in the United States was essentially constant 
    from the turn of the century until about 1970; this record did not 
    agree with the sediment core data.  
    
This statement by the USEPA SAB then suggests what has changed. 
The major source of dioxin in the environment is not combustion by 
itself. The source, rather, is the production and combustion of certain 
man-made (anthropogenic) chlorine containing materials that first 
began circulating in large quantities in the period following 1930. 
    
    =93The explanation is likely to be the introduction of chlorinated 
    organic compounds (polyvinyl chloride and chlorinated pesticides 
    are but two examples) in the 1935-40 time-frame. Other sources 
    such as leaded gasoline (which commonly contained ethylene 
    dichloride and ethylene dibromide), diesel emissions, and PCBs 
    are also possibly significant contributors. 
    
    =93Although the details of dioxin formation are not yet quantitatively=
 
    understood, the introduction of these chlorinated products into 
    wastes that were combusted appears to be the most likely cause 
    of the increased dioxin deposition measured in sediments.=94

Source: U.S. Environmental Protection Agency Science Advisory 
Board, 1995. A Second Look at Dioxin: Science Advisory Board's 
review of the Draft Dioxin Exposure and Health Effects Reassessment 
Documents. EPA-SAB-EC-95-021, Washington, D.C., September 29, 
1995


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Pat Costner
Greenpeace
P.O. Box 548
 or 512 County Road 2663
Eureka Springs, Arkansas 72632
ph: 1 501 253 8440
fx: 1 501 253 5540
em: pat.costner@dialb.greenpeace.org
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