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Health Impacts of Burning Tires in Cement Kilns

Ten years ago, Holcim applied to burn hazardous wastes at its cement plant near Headwaters State Park north of Three Forks. After years of public outcry, the application was withdrawn. Now Holcim is planning to seek a permit to burn scrap tires. Cement kilns are designed to make cement, not to be efficient waste incinerators. Burning scrap tires in cement kilns releases benzene and heavy metals and produces dioxins. These toxins are associated with a wide range of serious health problems including reproductive impairment, developmental delay and cancer. Burning tires also presents the potential for loss of productivity and reduced marketability of agricultural products in areas impacted by waste burning facilities. Until health studies are done on populations - of plants, wildlife, livestock, humans - impacted by waste burning cement kilns, the process can not be considered safe.

What makes up a tire?

Tires are composed of natural rubber from rubber trees, synthetic rubber made from petrochemical feedstocks, carbon black, extender oils, steel wire, up to 17 heavy metals, other petrochemicals and chlorine.
  • Synthetic rubber often contains the organic chemicals styrene and butadiene. Styrene, a benzene derivative, is a suspected human carcinogen.
  • Butadiene is known to cause cancer in laboratory animals and is a suspected human carcinogen. Studies show a strong association between leukemia and butadiene.
  • Extender oils contain benzene based compounds which cause cancer in laboratory animals. Crude oil contains heavy metals, including, but not limited to, lead, chromium, cadmium, and mercury.
  • A coal and tire chlorine content comparison showed that tires may contain as much as 2 to 5 times the chlorine level of western coal. The coal averaged a chlorine weight of .04% and tires showed a weight range of .07 to .2 percent. (CIWMBA, pg. 69).

Combustion Issues

Waste incinerators designed for that purpose are required to have afterburners or secondary combustion chambers to achieve the highest possible combustion efficiency. Cement kilns lack secondary chambers to assure complete destruction of wastes. "Upset" events, when a malfunction occurs in the cement making process, that result in uncontrolled emissions and possible large releases of particulate matter, are common.

Inadequate combustion can result in these chemicals being released into the air and lead to the creation of toxic byproducts. Byproducts of the incomplete combustion of benzene based compounds include dioxins, furans, PAH's (polyaromatic hydrocarbons), and PCB's (polychlorinated biphenyls), all recognized by health officials as causing cancer or reproductive toxicity. Incineration of chlorine and chlorinated compounds creates dioxins. Metals are not destroyed at any temperature, 100% are released into the air or concentrated into the cement product or the waste material of the process.


The term "dioxin" refers to a group of persistent, very toxic chemicals including dioxins, furans and some PCB's. Dioxin is a byproduct of industrial processes using chlorine. Recent EPA data ranks municipal waste incinerators, hazardous waste burning cement kilns, and medical waste incinerators as the leading sources of dioxin.

Dioxin released into the air can travel long distances in the atmosphere before settling onto soil, water and plants. It enters crops via the soil, from particles deposited on leaves, and by absorption of dioxin vapors from the air into the plant. Dioxin doesn't break down readily, but accumulates in the fatty tissues of animals consuming those plants, and concentrates in meat, eggs, and dairy products and consequently in humans. These toxins also biomagnify, which means that as dioxins move up the food chain, their concentrations are repeatedly multiplied. A study of biomagnification of low levels of dioxin from soil and feed into chickens showed levels of dioxins found in eggs and chickens tissues that were 10 to 200 fold greater than the soil concentrations. (Petras)

The EPA's 1994 Draft Reassessment of Dioxin concluded that there is no safe level of exposure to dioxin; even at extremely low levels a wide range of serious health effects are possible, including reproductive impairment, developmental injuries, and increased risk of diabetes.

Heavy Metals

Metals do not break down in the environment so they build steadily increasing concentrations in soil.

Metals taken up from the soil or deposited on plants from the air can contaminate crops. When cadmium levels in soil were increased by 50 parts per million, wheat yields declined 25%, with greater productivity damage as the cadmium levels increased. (Page) Metals bioaccumulate, moving from the environment into tissues of living beings where they build up over time. Low levels of lead can cause mental retardation, learning disabilities and stunted growth in children.


"...promoting burning waste tires in cement kilns cannot be supported by scientific evidence that it is safe to do so. It is likely that an increase in the use of waste tires as fuel will be damaging to the public's health and well being." *


CIWMB, California Integrated Waste Management Board, Tires as a Fuel Supplement: Feasibility Study. Sacramento, CA, 1992.
Page, A. et al. "Other Trace Metals" Impact of Heavy Metal Pollution on Plants. Volume 1:Effects of Trace Metals on Plant Function. N.Lepp, ed. London:Applied Science Publishers. 1980.
Petras,M.,et al. "Biotransfer and bioaccumulation of PCDD/PCDFs from soil; controlled exposure studies of chickens." Chemosphere 23:1731-1741. 1991.
*Dr. Seymour I. Schwartz, Professor, Environmental Science and Policy, University of California, Davis, in a letter to the California Integrated Waste Management Board, 1/21/1998

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