LEA Advisory #46--November 6, 1997

Evaluation of Employee Health Risk from Open Tire Burning

To All Local Enforcement Agencies:

Site-Specific Health and Safety Report

Purpose

The Board recognizes that there are times when an employee, in performing field duties, may inadvertently be exposed to potentially hazardous environments associated with tire burning. It is Board policy to provide a safe and healthful working environment for all of its employees. LEAs and staff working within the Permitting and Enforcement Division may provide technical assistance in response to a tire fire. The intent of this document is to provide guidance to prevent and or protect them from unsafe conditions. To predict the exact conditions, emissions, and potential exposure to open burning of tires is extremely difficult due to variability of site conditions. This document is a compilation of available information through literature review, known tire fire data, and other available information.

Introduction

It has been estimated that over 29.5 million tires are generated each year in California, of which 21 million are considered waste tires. Only about one-half of one percent by weight of the total municipal solid waste stream consists of tires. However, their shape, size, and physical and chemical properties present an unusually challenging disposal problem.

In the past few years, many landfills have refused to accept tires because they present not only a disposal problem (statute prohibited the disposal of whole tires after 1993 in permitted solid waste disposal sites) but health-related problems. Facilities disposing of tires have increased their fees, resulting in the creation of tire stockpiles and illegal dumps. When improperly managed, these stockpiles present a significant risk to the environment and public health. The risks arise from the potential for fires and the potential to become a breeding ground for insects, especially mosquitoes.

Tires are highly combustible. Even when densely piled, there can be enough oxygen supply for combustion. Tire fires are most often started by arson, and generate a large amount of heat, which makes them extremely difficult to extinguish. Some tire fires have continued to burn for months. An example is the Rhinehart tire fire in Winchester, Virginia, which burned for nearly nine months. This uncontrolled burning of tire piles produces smoke and toxic air pollutants, including benzene and polycyclic aromatic hydrocarbons (PAH). The intense heat leads to the generation of pyrolytic oil that mixes with extinguishing material, contaminating surrounding soils, surface waters, and groundwater.ⁱ

General Information

Tires are a mixture of vulcanized or cross-linked polymers, carbon black, dispersing oil, sulfur, synthetic fibers, pigments, processing chemicals, and steel or fiberglass. Tire manufacturers use a variety of formulation recipes when producing tires. For specific information on the processing and manufacturing of tires refer to the Board’s report Effects of Waste Tires, Waste Tire Facilities, and Waste Tire Projects on the Environment. The following table lists a typical tire composition.

Typical Tire Composition: Passenger Tire Recipe

An automobile tire weighs about 20 pounds, with a diameter ranging from 18-30 inches. In addition to rubber, a tire contains some steel in the bead and some rayon or steel in the belt. An average tire is produced from about 2.5 gallons of petroleum, making it a good source of heat energy. Shredded or chipped tires, without their steel belts, have an energy content ranging from 14,000 to 15,000 Btu per pound. Coal has an energy content of 8,000 to 12,000 Btu per pound.

Process

When tires are burned, the rank smell can probably be attributed to sulfur-bearing compounds. The carbon black used in the vulcanization of rubber is the source of most of the dark particulate matter. "As a tire burns, two distinct types of burning appear to occur, during which emissions will differ. These burn patterns correspond to the materials in the tread layers and the belt layers of the tires." (CTC,1989, page 3) Tire combustion occurs at a temperature range of approximately 100 (remote from the flame) to 2000 (at the flame front) degrees centigrade (° C). Ideal burn conditions would include adequate time for mixing of fuel and air, high temperatures, and complete mixing between the fuel and air. The fire burn rate can be affected by the material size. Shredded tires will burn at a much lower rate than chunk tires. Small-scale simulation of open burning of tires found the gaps between the tire material provides a pathway for oxygen transport and appears to be the controlling mechanism for sustaining the combustion process.

Thermal degradation and oxidation of tires is a function of the process conditions applied, cross-linkage, and how the rubber is cured. Degradation below 250° C produces an oily tar. Gaseous C1-C5 hydrocarbons (methane, ethane, isopropene, butadiene, propane) are produced at temperatures typically between 250° -450° C. As the reaction proceeds, various primary products formed in the initial fragmentation will be rapidly converted into secondary products. Several aromatic and cyclic compounds by means of the Diels-Alder reaction are also produced.

It has been shown that open burning, regardless of feed stock or fuel, results in greater mutagenic emission factors than does controlled combustion provided by incinerators, boilers, cement kilns, or other combustion devices. Chunk tires produce higher burn rates and more potent organic emissions than do shredded tires. The mutagenic emission factor for the open burning of tires was 3-4 orders of magnitude greater than that for the combustion of oil, coal, or wood in a utility boiler.

Airborne Emissions

All tire fires may vary and the exact emissions and concentrations cannot be predicted. There are many factors that influence the emissions produced while the fire is burning. Some of these factors include the amount of fuel, fire temperature, meterologic conditions, topography of the area, etc. In most cases airborne emissions found will include volatile organics, semivolatile organics (including polycyclic aromatic hydrocarbons [PAH]), carbon monoxide, and particulate matter, which includes metals.

In 1983, the National Institute of Occupational Safety and Health (NIOSH) evaluated a fire containing approximately 5 million tires. This fire, called the Rhinehart Tire Fire, covered a 4-acre site and created a black plume of smoke approximately 3,000 feet high and 30-50 miles long. The NIOSH evaluation showed no acute hazard for employees performing containment and cleanup operations. Airborne monitoring of the plume indicated the presence of carbon monoxide (50-100 ppm), PAH (58-6802 ng/m³), metals (all below 2 ug/m³ except lead, zinc, and iron), total organic compounds (0.73-0.81 mg/m³ ), and nitrosamine (below laboratory detection limits). (See report for more specific emission data information.) The potential for excessive inhalation exposure to PAHs and carbon monoxide and dermal absorption of heavy metals, primarily zinc and lead, were reported as exposure concerns.

Volatile organic emissions were detected during the 16-acre Panoche Tire Fire, which burned 3-5 million tires within a steep-sided box canyon. Benzene concentrations did not exceed OSHA and NIOSH allowable exposure levels when sampled on two different days at a location 50 feet downwind of the fire. Measured benzene levels ranged from .43-.50 mg/m³. Airborne emission sampling also detected, not significantly, PAHs, metals, and semivolatile organics (see report for more specific emission data information). These concentrations did not exceed regulatory allowable exposure levels. Sampling points were 50 feet downwind, 50 feet upwind and west and east of the visual smoke plume. Subsequent industrial hygiene monitoring of Board personnel many weeks after the fire had been extinguished indicated no employee overexposure. Sampling results indicated no detectable hydrocarbons or heavy metals dust (zinc, cadmium, chromium, and lead). The breathing zone samples were taken during site supervision and the soil sampling process. Air monitoring results of employees performing remediation activities, specifically scraping burn residues from the canyon walls onto the floor, showed the presence of nuisance particulate (.51-11 mg/m³ ), zinc (<0.002-11 mg/m³ ), and PAHs below their detection limits (See report for more specific emission data information).

In a controlled burn chamber simulating open burning of scrap tires, a U.S. EPA report estimated emissions of semivolatile organics ranged from 10 to 50 g/kg of tire material burned. It is likely that emissions measured during this study characterize an actual fire, but the similarity of actual gaseous concentrations and estimated emissions may not be representative. The predominant emission products identified were monoaromatic and polyaromatic hydrocarbons. The presence of benzo(a)pyrene in particulate extracts is notable because of the compound’s carcinogenicity. High emissions of other compounds, particularly benzene, with concentrations often exceeding 1 ppm, may pose a significant health risk. Zinc and lead in gaseous particulate was also verified and quantified. (See paper for more specific emission data information.)

Examination and characterization experiments measuring emissions from combustion of scrap tire material were performed in a rotary kiln incinerator simulator. These experiments allowed controlled combustion where feed rates, temperatures, and oxygen concentrations could be controlled and varied. Results indicated that, if burned in a steady-state mode, tire-derived fuel combustion will result in very low emissions of carbon monoxide, total hydrocarbons, volatile and semivolatile organics, and metal aerosols. (See paper for more specific emission data information.)

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) were measured in ambient air during a burning tire fire. Concentrations of PCDDs and PCDFs in ambient air, converted to toxicity equivalents (TEQ) by application of the International Toxicity Equivalency Factors showed sites one kilometer (km) downwind of the fire were an order of magnitude higher than at three kms downwind. Steer, et.al. reported that measurement of volatile organic compounds (VOC) and polycyclic aromatic hydrocarbons (PAH) measured both in the plume and downwind of the source showed no PCDDs or PCDFs.

Potential Environmental Contamination

Uncontrolled open tire burning poses potential environmental effects by contamination of the soil, and ground and surface water. The two fire by-products, which pose a major concern, are the generation of pyrolytic oil and ash.

Because of the starved-air conditions and the intense heat generated by an uncontrolled tire fire, pyrolytic reactions occur, producing a free-flowing, oily tar. This pyrolytic oil product consists of naphthalenes, anthracene, benzenes, thiazoles, amines, ethyl benzene, toluene, and other hydrocarbons. Also included are metals such as cadmium, chromium, nickel and zinc. This pyrolytic oil material can contaminate soil, and ground and surface water surrounding the site. Maximum production of the pyrolytic oil material occurs at about 200ºC and exhibits properties similar to heating oil. In a field-scale gasification reactor it was found that a greater portion of pyrolytic oil was produced at the beginning of the process. Water applied to tire fires often increases the production of pyrolytic oil and provides a method of transport for the oils to move off site and accelerate contamination of soils and water.

Analyses of ash produced as a by-product of tire fires typically show the presence of heavy metals. High concentrations of metals such as lead, cadmium, and zinc are not uncommon. Fly ash has been shown to be rich in zinc, probably due to the fact that zinc is found in the curing agent during tire manufacturing.

Laboratory analysis of soil samples taken from a tire fire in Bakersfield indicated the total concentration of zinc exceeded the total threshold limit concentration (TTLC) [7800 mg/kg and 15800 mg/kg]. The TTLC for zinc is 5,000 mg/kg. Zinc concentrations at the Panoche Waste Tire Site were also found to be extremely high (32,800-156,000 mg/kg). Background zinc soil concentrations for the site averaged 64 mg/kg while underlying soil beneath the ash concentrations ranged from 74 to 179 mg/kg. At the Rhinehart Tire Site elevated levels of zinc were identified in surface water samples and on site soils. A comparison of zinc levels in background sediments (93 ppm) with the highest zinc level found on the site (2880 ppm) showed a significant increase. (See reports for more specific emission data information.)

The fire at a used tire facility near Hagersville in Ontario, Canada was monitored by the Ontario Ministry of Environment and Energy (MOEE) for impacts on the site and surrounding environment. Soil samples collected during the fire did not show elevated PCDD or PCDF concentrations. However, low concentrations of both compounds were detected in vegetation collected at 100 meters and 200 meters from the site. PCDD and PCDF concentrations in the foliage decreased with time but was still detectable for at least 200 days after the fire started.

Potential Health Hazards

To evaluate worker protection at tire fires, two cases must be considered: potential exposure while the fire is burning and potential exposure after the fire is out. This evaluation considers what activities will be performed at the site and what substances are present. A decision as to whether a health hazard exists is based on comparing emissions estimates with established safe levels for those compounds. Based upon available information, the following chemical hazards are of occupational concern.

While the fire is still burning, the smoke plume may contain hazardous substances that should not be inhaled or allowed to contact the skin. The two substances for which excessive exposure risk exists are believed to be polycyclic aromatic hydrocarbons and carbon monoxide.

Polycyclic aromatic hydrocarbons (PAH) are a class of compounds consisting of various arrangements and substitutions of multiple benzene rings. PAHs result mainly from the incomplete combustion or high-temperature treatment of coal-derived materials. Since there are no published exposure limits to PAHs, coal tar pitch volatile exposure values are used. The coal tar pitch volatile (CTPV) is a "benzene-soluble" fraction of total particulates that generally contains substances that have carcinogenic potential. Epidemiological studies of the cancer mortality rates among those workers that have high PAH exposure show an association with increased mortality from lung cancer.

Benzene compounds may be produced as part of the thermal breakdown and reformation of molecules in the cooling process. Benzene may cause adverse health effects through inhalation, ingestion, or dermal contact. Acute exposure symptoms include dizziness, euphoria, giddiness, headache, nausea, weakness, drowsiness, respiratory irritation, pulmonary edema, and pneumonia. Benzene can also cause irritation to the skin, eyes, and mucous membranes.

Allowable Employee Exposure Levels

Carbon monoxide (CO) is an odorless, colorless, and tasteless gas usually resulting from incomplete combustion. When inhaled, carbon monoxide combines with hemoglobin to form carboxyhemoglobin, which interferes with the oxygen-carrying capacity of blood, resulting in a state of tissue hypoxia. Typical signs and symptoms of acute CO poisoning are headache, dizziness, drowsiness, nausea, vomiting, collapse, coma, and death. The amount of carboxyhemoglobin formed is dependent on concentration and duration of exposure, ambient temperature, health, and metabolism of the individual.

Other substances that pose a lesser exposure risk include metals and solvent vapors. Airborne exposure to these substances in the plume may pose a health hazard. Employee exposures to solvent vapors, except for benzene, have been shown to be well below established exposure limits. Organic compounds typically found and of potential concern include toluene, xylene, ethyl benzene, and styrene. Aromatic hydrocarbons typically cause central nervous system depression or other effects, and, depending on the compound, hepatic, renal, or bone marrow disorders.

The presence of heavy metal compounds in the ash materials may also present a health hazard concern. High concentrations of zinc, lead, or arsenic have been found in sample analysis. Metals affect multiple organ systems, and the targets for toxicity are specific biochemical processes and/or membranes of cells and organs. Dermal or skin contact with contaminated materials should be avoided for these compounds. The metals act as primary irritants by removing the surface film, disturbing the water-holding quality of the cells, and injuring the membrane structure of the epidermal cells

Exposure Control Measures

There are a number of hazards or potential hazards associated with open burning of tires for field personnel outlined above. Control measures used are based upon the nature of the harmful substance, its routes of exposure, and what job activities will be performed at the site. To prevent potential exposure and to control exposure to hazards, the measures listed below shall be considered.

• Conduct preplanning to identify safety precautions prior to responding to a site or performing field activities.
• Avoid being in close proximity to the fire.
• Always select a safe place to observe.
• Do not touch or attempt to collect samples of soil, burn ash, or debris of any kind without appropriate personal protective equipment.
• Select personal protective equipment based on the hazards that will be encountered while at the site. Consult with the Health and Safety Officer and/or program staff.
• Use proper respiratory equipment to prevent inhalation of airborne hazards when appropriate.
• Never put notebooks or other equipment down in contaminated areas.
• Avoid the smoke plume. Stand upwind and out of the smoke plume area.
• Avoid ash, dust clouds, runoff, pyrolytic oils, tarry substances.
• Avoid walking in the burn site waste.
• Observe site conditions and wind direction.
• Keep vehicles away and upwind of all hazards and avoid contaminating the interior of vehicles.
• Avoid hand or body contact with contaminated materials or any contaminated surfaces.
• Avoid touching eyes, nose, or mouth with or without gloved hands.
• Decontaminate when leaving the site; wash hands and face.
• No eating, drinking, or smoking at the site, except in designated areas.
• Seal all nonreusable contaminated materials generated during the field activity and dispose of them on site. Contaminated reusable equipment should be bagged and returned to the field shop for decontamination.

Conclusion

There are potential health hazards associated with open tire burning. Tire combustion poses an inhalation and dermal exposure risk for employees at the site. Airborne emission information, especially in the smoke plume, has shown the presence of high concentrations of carbon monoxide and polycyclic aromatic hydrocarbons (PAH). Heavy metals contamination of zinc and lead may present a dermal problem. Prior to performing field activities, Board staff should consult with the Health and Safety Officer and/or program staff. The information provided in this document is intended to supplement the information provided in the Board’s Field Health and Safety Program (Policy 1095-003).

If you have any questions please contact Diane Kihara at (916) 341-6392.

Sincerely,

Original signed by:

Deputy Director
Permitting and Enforcement Division

Publication #232-97-019

The intent of the advisories is to provide guidance to Local Enforcement Agencies (LEA) in performing their duties. Guidance, for this purpose, is defined as providing explanation of the Board’s regulations and statutes.

Unless included by reference in the LEA's Enforcement Program Plan (EPP), advisories are not enforceable in the same manner as regulations because they have not been adopted through the formal rulemaking process (see Government Code sections 11340.5 and 11342.6). Advisories do not take precedence over statute or regulation.