Glossary of Terms
Solid Waste Management
Farming Environmental Management
US EPA Dioxin Reassessment
Dioxin Measurement Units
Baghouses vs Precipitators
US EPA Dioxin Reassessment
by John W. Norton, P.E., B.C.E.E.
1. Background/Purpose of the 1994 USEPA Dioxin Reassessment
The objectives of the reassessment were to review and compile knowledge about:
Dioxins and related substances have been the subject of a great deal of study, but there is still great uncertainty regarding many issues including where they come from and what effects they have on people. There is also a great deal of misinformation which occurs due to misunderstanding or misinterpretation of the available information. Studies which have been done frequently do not provide conclusive evidence of where dioxins came from, how much people were exposed to, or what the detectable health effects were or are.
- the formation and sources of dioxin,
- the presence of dioxin in the environment,
- the degree of exposure which people have to dioxin, and
- the potential health effects dioxin may have on people.,
Therefore, many assumptions are necessary in developing theories.
2. Major Findings, Theories, Assumptions
- Dioxins are ubiquitous at extremely low levels.
The reassessment includes discussion of data indicating dioxin and related substances are present in the environment at comparable levels in both industrialized nations and remote rural areas.
Estimates of current levels in humans in the United States and Europe are comparable -- on the order of 30 parts per Trillion (Trillion = 1,000,000,000)
For purposes of perspective one part per trillion is comparable to one second out of 32,000 years or 1 square inch in 400 square miles.
There are also indications that dioxin levels in the environment have been rising since 1920 but reached a peak in the late 1970's and have been declining since then.
- There are many sources of dioxin:
Health Effects are Uncertain:
- Diesel exhaust
- Waste combustion
- Wood burning
- Cement kilns
- Coal combustion
- Pulp and Paper Mills
- Metal Smelting
- Chemical manufacturing
Health effects studies provide a great deal of conflicting and inconclusive findings as to actual health effects of dioxin. However, the nature of its various effects on biologic processes appears in some studies potentially significant enough to justify minimizing dioxin releases to the extent feasible.
3. Ramifications to Municipal Solid Waste Management
Society has to do something with the garbage it produces, every day. Everything has to be someplace.
4. Health Risks
- Landfills have health risks including emissions of dioxins and related compounds
- Recycling has risks (pulp and paper process, metal smelting, etc.)
- Composting has risks; it also releases dioxins and related compounds.
- Transportation of solid waste even moderate distances in diesel trucks causes substantial dioxin emissions to be released.
- There is no risk free alternative.
Municipal Waste Combustors present health risks well below one in one million based on assessments done in Europe and Japan.
5. What Conclusions Can Be Drawn from This Dioxin Risk Assessment Information?
There are many uncertainties and unknowns relative to the potential health effects of dioxin exposure at low levels, although it seems reasonably prudent to reduce manmade emissions where feasible.
It is not possible to eliminate exposure to dioxin since it is produced by many sources throughout the environment.
Eliminating all manmade dioxin emissions would not make any real difference in the overall health risk or exposure since other sources of dioxins will continue to exist.