Burning Plastics

Many plastics, particularly PVC when burned resuts in emissions of the deadly poison named dioxin.

Dioxin is a toxic organic chemical that contains chlorine and is produced when chlorine and hydrocarbons are heated at high temperatures.

To inhale dioxin or to be exposed any way to its fumes can cause many deadly results.

There are lots of them. Any carbon-based material produces hazardous products under most combustion conditions, mostly due to incomplete combustion. For instance, burning gasoline can produce carbon monoxide and hydrocarbons, burning charcoal can produce carbon monoxide, and burning methanol can produce formaldehyde.

Some types of plastic contain elements besides the standard carbon, hydrogen, and oxygen. Nylons contain nitrogen, and polyvinyl chloride contains, of course, chlorine. These constituents also find their way into the combustion products. Probably the particular component you have heard about most is TCDD, which is an abbreviation for the chemical name tetrachloro-dibenzo-dioxin. This compound contains four chlorine atoms, and is inevitably formed when polyvinyl chloride plastics are burned. (Complete combustion of PVC would yield only water, carbon dioxide, and hydrogen chloride; in practice, some incomplete combustion products such as TCDD are always formed, if at low levels.) TCDD is also formed when wood burns, because wood also contains small amounts of chlorine. Because of the much higher proportion of chlorine in PVC, however, it is the material leading to the highest levels of TCDD.

The toxicity of TCDD to animals is well-established. It is often considered to be the man-made compound most toxic to animals. Its toxicity to humans, however, is not as well-established. The only absolutely confirmed human health effect from exposure to TCDD is a skin rash called chloracne.  Other health effects are suspected. It is considered a carcinogen on the basis of animal studies. TCDD is also an unwanted by-product of the manufacture of the herbicides

2,4-D and 2,4,5-T. A manufacturing accident at a plant manufacturing these chemicals occurred near Sevesto, Italy in 1976 released an estimated 1-10 lb of TCDD into the surrounding countryside, killing many farm animals and causing chloracne. Since 2,4-D and 2,4,5-T were components of the defoliant “Agent Orange” used in Vietnam, many U.S. servicemen (and of course Vietnamese) were exposed to elevated levels of TCDD. TCDD is thus suspected as the cause of the symptoms attributed to “Agent Orange” exposure.

Richard E. Barrans Jr., Ph.D., PG Research Foundation, Darien, Illinois.
from “Ask a Scientist”

http://www.newton.dep.anl.gov/askasci/chem00/chem00031.htm

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Argonne National Laboratory, Division of Educational Programs, Harold Myron, Ph.D., Division Director.