
Harvey W. Rogers, M.S.and Betty C. Willis, M.S.
Division of Health Assessment and Consultation
Agency for Toxic Substances
and Disease Registry
Atlanta, Georgia 30333
February 1992
U.S. Department of Health and Human Services
Public Health
Service
Atlanta, Georgia
The Public Health Overview of Incineration as a Means to Destroy Hazardous Wastes is available through the U.S. Department of Commerce, National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161; telephone: (703)487-4650. The NTIS order number for this document is PB94-179835.
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Foreword by Robert Williams, Director, Division of Health Assessment and
Consultation
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Although this document deals with incineration of hazardous wastes, the reader is cautioned that ATSDR's acceptance of incineration of hazardous substances is contingent on consideration of all remedial alternatives for a site. That is, each remedial alternative, including incineration of hazardous wastes, must be evaluated for its potential to affect public health. Moreover, the selection of a particular remedial action at a site resides with federal and state regulatory agencies that must consider public health implications along with other risk management considerations.
Although ATSDR has public health authorities under both the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as amended, and the Resource Conservation and Recovery Act (RCRA), as amended, this document pertains only to incineration actions proposed or taken under CERCLA. Therefore, ATSDR's comments in this document pertain only to the temporarily-sited incinerators that are to be used to remediate sites under CERCLA.
Robert C. Williams, P.E., DEE
Director
Division of Health Assessment
and Consultation.
However, the better Agency staff understand the characteristics of a well-designed and properly operated hazardous waste incinerator, the better ATSDR can provide informed advice about public health implications. The purpose, therefore, of this document is to provide ATSDR staff an overview of the current engineering practices of incineration and their relationship to public health concerns regarding actual or potential contaminant releases associated with the technology.
ATSDR's Division of Health Assessment and Consultation maintains additional materials to help public health assessment personnel evaluate the public health implications of hazardous waste incineration. For a representation of the kinds of reference materials maintained by ATSDR, see the references used for this overview and the list of Environmental Protection Agency (EPA) guidance documents in Table 3.
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The EPA is responsible for selecting and implementing remedies for cleanup of Superfund National Priorities List (NPL) sites. EPA's selection of incineration as the remedy of choice for some sites has led to an increased number of requests to ATSDR for health information related to incineration. When selected as a site remedy, incineration should be conducted in a manner that protects human health.
ATSDR does not participate in the actual site remedy selection decision, or any engineering or monitoring decisions; however, it is ATSDR's responsibility to advise on the public health implications of the technology, as needed, when proposed for or used at NPL sites. Many of the requests for assistance ATSDR receives are related to the transportable incinerators used for site remediation. In response to such requests, it is ATSDR's policy to review site-specific design and operating detail sufficiently to assess actual and potential contaminant releases posed by the facility. That policy is consistent with the source evaluation phase of the ATSDR public health assessment protocol. Some of the information in this overview also may be applicable to other kinds of incinerators that public health assessors may be required to review, i.e., permanent municipal and medical waste incinerators; however, ATSDR staff are strongly cautioned against applying the findings in this paper to other than CERCLA incinerators.
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In addition to the potential health hazard to communities from air emissions of hazardous substances, the design and operation of an incinerator have implications for the workers at the facility. Inadequate work practices and poor industrial hygiene conditions at an incinerator have the potential to cause adverse health effects in workers.
In striving for hazardous waste incineration performance that protects both human health and the environment, EPA has established operating and performance standards based on research and trial burn data. The EPA hazardous waste incineration regulations are found in 40 CFR Part 264, Subpart O. The hazardous waste regulations developed under the Resource Conservation and Recovery Act (RCRA) are commonly called the RCRA regulations. The standards are designed to limit emissions of certain pollutants to EPA-specified acceptable levels. Emission standards have been set for particulates, hydrogen chloride, and principal organic hazard constituents (POHCs).
The EPA standards for particulates (0.08 grains per dry standard cubic foot corrected to 7% O2) and hydrogen chloride (4 pounds per hour or 99% removal) are generic and apply uniformly to all hazardous waste incinerators. EPA has also developed a number of guidance documents used by RCRA permit writers and by CERCLA staff to evaluate hazardous waste incinerators (See Table 3). Those documents specify how to apply the generic regulatory standards on a site-specific basis. The more recent guidance documents recommend limiting emissions of certain metals, products of incomplete combustion, and carbon monoxide. The public health assessor should obtain a copy of the operating conditions specified by CERCLA, as well as any amendments to those documents for the incinerator being evaluated. Those documents can be used to determine and evaluate the operating conditions and emission limits that have been applied to the incinerator during specific time periods.
The public and the regulatory community alike are concerned about PIC emissions, particularly because they are difficult to predict and, therefore, to regulate. In an attempt to address that concern, EPA researched the formation of PICs during test burns conducted at hazardous waste incinerators throughout the United States, and at incinerators used strictly for research. Testing was done under steady-state (normal) and upset operating conditions. Using test burn findings, EPA states that, if the incinerator is meeting the stack emission requirements, particularly the CO limit of 100 parts per million by volume, available field test data show that PIC emissions are limited to concentrations that do not pose unacceptable risks (4). That position is founded upon cancer-based health risk assessments for identified PICs. It should be noted that although research has not identified all PICs, and other potential health outcomes (non-cancer) have not been thoroughly evaluated, the evaluation of cancer risks typically results in allowable exposure levels much lower than would be allowed for non-cancer health outcomes. Because there is no recognized threshold exposure level for the cancer health outcome, even extraordinarily low exposures to carcinogenic substances are assumed to pose some risk of cancer. Only very low exposure levels are allowed by regulatory agencies in order to keep that risk at an acceptable level (usually either one cancer in a lifetime per 100,000 exposed individuals or one cancer in a lifetime per 1 million exposed individuals).
For organics of particular concern, or for inorganic contaminants such as metals, hydrogen chloride, or chlorine, emission limits can be formulated specifically for the incinerator and the geographic area of concern. The EPA guidance manuals recommend that such limits be based on anticipated stack releases of the particular contaminant (usually worst case), local meteorologic conditions, geographical site features, and proximity to local populations (4,5). It should be noted that such conditions have been included in RCRA guidance manuals only since the late 1980s. The public health assessor should review the CERCLA contracts, in effect at each facility to determine what the potential emissions may be.
The incinerator must be designed and operated in a manner that minimizes production of non-stack, fugitive emissions. That can be accomplished by ensuring proper seals at all system connections, maintaining negative gas pressures throughout the combustion gas flow path, and by limiting the waste feed to prevent excessive and rapid releases of volatile compounds. Careful attention must also be given to the design and operation of waste handling systems to minimize fugitive emissions. ATSDR public health assessors have found that excavation and handling of soils at some Superfund sites, and waste unloading and repackaging operations at some RCRA facilities, have been major sources of airborne contaminants that have resulted in exposure of workers and/or nearby residents.
Another critical part of the incinerator design is the pollution control system (9). Pollution control systems directly influence the levels and kinds of pollutants that are released and that can potentially reach the public. Most modern hazardous waste incinerators are designed with extensive air pollution removal systems. For example, a common pollution control system might include a system that cools or "quenches" gases produced by burning waste, followed by a system that reduces acid gas emissions, and ultimately followed by a particulate removal system such as fabric filters (baghouses), electrostatic precipitators, venturi scrubbers, and others.
Finally, current design of hazardous waste incinerators includes various safeguards, such as process monitoring devices (to monitor parameters such as temperature, air flow, and operating pressures); continuous emissions monitoring systems (to measure air emissions of carbon monoxide, gas flow rates, and possibly other combustion performance indicators); and automatic waste feed shutoff devices (AWFSOs). AWFSOs, as required by RCRA regulations (40 CFR 264.345(e)), automatically stop the waste feed to the incinerator when specified monitoring parameters exceed or fall below limits specified in the permit. The parameters that trigger the AWFSOs are established based on successful trial burns. AWFSOs are critical to ensuring that the incinerator cannot operate in an improper condition -- with attendant increased air emissions -- for extended periods of time (10).
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If, as in most cases involving mobile incinerators, the hazardous waste incinerator is used as a remedy for an on-site cleanup of a Superfund site, "no Federal, state, or local permit shall be required." That provision is made in the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (P.L. 96-510), as amended by the Superfund Amendments and Reauthorization Act of 1986 (P.L. 99-499). However, the CERCLA incinerator must comply with all the technical requirements that would be applied to a permitted hazardous waste incinerator. In other words, all technical requirements of a RCRA-regulated incinerator would apply to a Superfund remediation incinerator, except that a specific permit would not be issued for the Superfund incinerator. That provision was made to expedite remediation of this nation's Superfund sites by eliminating the very long period, sometimes several years, required to obtain permits for hazardous waste treatment. The Superfund program is still obligated to ensure that relevant provisions of the applicable laws or statutes are being met. This approach, as applied to CERCLA waste incinerators, is important to help ensure that certain regulatory provisions protective of public health are addressed even when the incinerator is not a RCRA-permitted facility.
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Similarly, wet wastes or process effluents should be stored in chemically compatible, leak-resistant containers. Storage areas for such liquid-bearing materials should have dikes or be designed to contain leakage. Processing of wastes, such as blending or shredding operations, may provide opportunities for aerosolization of contaminants. Such conditions should be adequately considered and waste-processing areas designed to minimize the potential exposure to workers on-site, as well as to people living or working nearby.
ATSDR believes one way to ensure that the system continues to operate in a manner consistent with operating conditions specified in the CERCLA contract, is for EPA to conduct frequent, random, unannounced facility inspections and to routinely provide the results to the public. Under some circumstances, permanent on-site inspectors might be advisable.
Another way to ensure continued satisfactory operation is to retest the incinerator periodically. This would be appropriate if the CERCLA incinerator operates at the site for an extended period of time, or there are other indications that it may not be operating properly.
Each time a CERCLA incinerator is relocated, ATSDR recommends that it be retested. A less rigorous trial burn may be appropriate if the incinerator successfully passed a full trial burn on similar wastes at another site.
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As reliance on incineration as a remediation technology increases, ATSDR will collaborate with EPA in a number of areas to further broaden the database used in regulatory decision-making and in evaluation of health implications associated with incinerator technology. Public health assessors are advised to contact the Division of Health Assessment and Consultation to get more information.
With careful attention to design and proper operation of the facility, significant quantities of hazardous waste can be reduced to smaller volumes of material that can be managed safely. With the vigilance of the regulatory community and the involved citizenry, the facility can operate as specified in the CERCLA operation and maintenance plan.
It is hoped that this overview provides public health assessment professionals with a general understanding of the key considerations and concerns related to hazardous waste incineration technology. As noted throughout this document, EPA plays a leading role in selecting or permitting, implementing, testing, and overseeing such technology. Most of the documentation needed by the public health assessor to evaluate a specific incinerator can be obtained from EPA. Table 2 contains a list of typical site-specific documents of interest to the public health assessor. In addition, Table 3 lists EPA guidance and resource documents that will be of assistance to the public health assessor. As a final caution, it must be remembered that each site is unique, and must be carefully evaluated individually and not by generic extrapolation of data from other sites or studies.
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DOCUMENT* |
RELEVANCE TO PUBLIC HEALTH ASSESSMENT |
| 1. Trial Burn Plan and Trial Burn Report | provides data on the typical and/or worst case emissions under specific operating conditions, for use in air pathway analysis |
| 2. QA/QC Plan and Sampling Plan | permits review of data collected to see that they are of adequate quality to assess the health impact on the community |
| 3. Remedial Design Plan or Engineering/Design Plan | permits review of containment and material flow provisions to assess the potential for releases to air, water and soil pathways; also permits review of process monitoring and safeguards against process upsets |
| 4. Site Health & Safety Plan; Contingency Plan | describes how emergency releases of contaminants are monitored and how the community is safeguarded |
| 5. Operation & Maintenance; Plan and Inspection; Schedules | specifies the routine checks of equipment, waste storage areas, etc., and calibration of monitoring equipment to minimize opportunity for process upset or unplanned hazardous material releases; useful in assessing the potential for releases. |
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2. Experience in incineration applicable to Superfund site remediation. Cincinnati, Ohio: EPA, Risk Reduction Engineering Laboratory, 1988; EPA publication no. EPA/625/9-88/008.
3. Oppelt ET. Incineration of hazardous waste: a critical review. Journal of the Air Pollution Control Association 1987;37(5):558-586.
4. Guidance on PIC controls for hazardous waste incinerators: volume V of the hazardous waste incineration guidance series. Washington, DC: EPA, Office of Solid Waste, 1989.
5. Guidance on metals and hydrogen chloride controls for hazardous waste incinerators: volume IV of the hazardous waste incineration guidance series. Washington, DC: EPA, Office of Solid Waste, 1989.
6. Bowser LR, Liberati MR. Upfront delisting of incinerator ash. In Proceedings of the 1989 Incineration Conference. Knoxville: 1989:8.2.1-8.2.6.
7. Carroll GJ, Oberacker DA. Characteristics of pilot- and full-scale hazardous waste incinerator ash. In Proceedings of the 1989 Incineration Conference. Knoxville: 1989:8.3.1-8.3.6.
8. Cheremisinoff P. Waste incineration pocket handbook. Northbrook IL: Pudvan Publishing Co., 1987:203.
9. Brunner CR. Incineration systems: selection and design. New York: Van Nostrand Reinhold Company, 1984:315-356.
10. Boomer BA, Trenholm AR. Common deficiencies in RCRA Part B incinerator applications. Journal of the Air Pollution Control Association 1987;37(3):275-277.
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