Dioxin Sources in the United States

“Dioxin” is a term for a family of persistent chemicals (i.e., substances that do not break down chemically or break down very slowly) that are created through various natural and synthetic processes including incineration, forest fires, metal smelting, and certain industrial operations involving chlorine and other organic compounds. Because chlorine can be found almost everywhere on earth (e.g., in salt), dioxin will be formed when most things burn, including wood, food, garbage and vinyl.

Studies have shown that when burning is well controlled as it is in modern incinerators, very little dioxin is made or emitted. The amount of chlorine or vinyl going into the incinerator is not a reliable indicator of the amount of dioxin coming out. Rather, incinerator design and operation have far more important impacts. However, in uncontrolled burning (e.g., volcanoes, forest fires, old incinerators, backyard burn barrels and accidental building fires), dioxin can be formed in larger amounts.

The good news is that dioxin emissions and levels in the environment are declining, according to data from the U.S. Environmental Protection Agency. This has occurred even as production of vinyl has soared, proving that vinyl production and disposal are not significant contributors to dioxin levels.

EPA attributes declines in dioxin emissions to regulation as well as voluntary industry actions. According to EPA and other federal agencies:

  • "Dioxin levels in the environment have declined significantly since the 1970s, following EPA regulatory controls and industry actions. EPA’s best estimates of emissions from sources that can be reasonably quantified indicate that dioxin emissions in the United States decreased by about 80 percent between 1987 and 1995, primarily due to reductions in air emissions from municipal and medical waste incinerators, and substantial further declines continue to be documented." ("Dioxin: Summary of the Dioxin Reassessment Science," Information Sheet 1, U.S. EPA, June 12, 2000)
  • "As a result of EPA’s efforts, along with efforts by state government and private industry, known industrial emissions in the United States will be reduced by more than 90 percent from 1980 levels within the next year or so." ("Questions and Answers about Dioxin," Interagency Working Group on Dioxin, July 2000)

The table below shows trends in dioxin emissions from major sources. A number of industries (including several involved in producing building materials) are associated with emissions of dioxin. Even fireplaces (residential wood burning) contribute to dioxin. Fortunately, as the chart shows, most industries have reduced emissions. Today, the largest known human source of dioxin is backyard burning.
 


  

Dioxin Emission Sources Over Time (g-TEQ)1

Category

1987

% Total

1995

% Total

2002/4

% Total

Incineration of:

 

 

 

 

 

 

  • Municipal solid waste
  • 8,877

    77

    1,250

    71

    12

    32

  • Medical waste
  • 2,590

    22

    488

    27

    7

    18

  • Sewage sludge
  • 6

    0.05

    14

    0.84

    14

    39

  • Hazardous waste
  • 5

    0.04

    5

    0.33

    3

    9

    Total incineration

    11,478

    82

    1,758

    54

    37

    3

    Backyard barrel burning

    604

    4

    628

    19

    628

    56

    Metal smelting

    955

    6

    301

    9

    35

    3

    Cement kilns

    131

    0.94

    173

    5

    25

    2

    Land-appl'd sewage sludge

    76

    0.55

    76

    2

    76

    6

    Pulp & paper

    372

    2.67

    23

    0.71

    15

    1

    Coal-fired utilities

    50

    0.36

    60

    1

    60

    5

    Industrial wood burning

    26

    0.19

    27

    0.85

    27

    2

    Residential wood burning

    89

    0.64

    62

    1

    62

    5

    Diesel trucks

    27

    0.20

    35

    1

    35

    3

    Other

    137

    0.98

    103

    3

    100

    9

    TOTAL

    13,949

    100

    3,252

    100

    1,106

    100


    The quantities above are based on World Health Organization numbers reported in units of grams TEQ, which weighs dioxin according to the most toxic form; formatting by the Chlorine Chemistry Council

    Dioxin in building fires. It is impossible to prevent formation of small amounts of dioxin in an accidental building fire by avoiding the use of certain building materials. This is because of the omnipresence of chlorine in materials such as wood and synthetics. Moreover, all materials – synthetic and natural – when they burn emit hundreds of different chemicals, many of which are persistent and highly toxic. In a typical accidental fire, carbon monoxide and heat are recognized as the most serious threats. The best preventive action to take against accidental fires is to install smoke alarms and (particularly in commercial buildings) sprinklers to alert occupants and extinguish fires that do occur. Early detection and suppression save lives.

    Further preventive actions. The fact that dioxin can be produced naturally means that it will never be eliminated from the environment altogether. EPA and other agencies suggest that the best ways to help further reduce existing levels in the environment are to minimize uncontrolled and accidental burning (e.g., backyard burning, roadside leaf burning, landfill fires and other uncontrolled fires). As experience has shown, the combination of regulation and voluntary action by industry and individuals are key to preventing dioxin from becoming an environmental or public health problem.


    1US EPA (May, 2000 updated October 19, 2000). Inventory of Sources of Dioxin in the US.