United States Environmental NESHAP: Final Standards for July 2000
Protection Agency Hazardous Air Pollutants for http://www.epa.gov
Hazardous Waste Combustors;
Final Rule
Office of Solid Waste (5305W)
Hazardous Waste Combustion (HWC) National
Emission Standards for Hazardous Air Pollutants >* ^^fe t>
(NESHAP) Final Rule Fact Sheet: |
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RESOURCE CONSERVATION AND RECOVERY
ACT SITE-SPECIFIC RISK ASSESSMENT
POLICY FOR HAZARDOUS WASTE COMBUSTION FACILITIES
EPA promulgated Maximum Achievable Control Technology (MACT) standards, also catted the National Emission Standards for
Hazardous Air Pollutants (NESHAP), for hazardous waste burning incinerators, cement kilns, and lightweight aggregate kilns
(64 FR 52828, September 30, 1999). These standards are promulgated under joint authority of the Clean Air Act (CAA) and
Resource Conservation and Recovery Act (RCRA). This fact sheet summarizes, for the convenience of all interested stakeholders,
regulators, and industry, the RCRA Site-Specific Risk Assessment Policy for hazardous waste combustion facilities as articulated
in thepreambk to the final MACT standards. This fact sheet does not provide guidance on risk assessment methodology or
articulate new policy.
Background
Sections 3004(a) and (q) of the Resource Conservation and Recovery Act (RCRA) require EPA to
develop national standards for hazardous waste combustion facilities that are protective of human health
and the environment. In addition, section 3005(c)(3) of RCRA, which we commonly refer to as the
"omnibus authority" or "omnibus provision," gives EPA both the authority and responsibility to include
additional terms and conditions in each RCRA facility permit, as necessary, to protect human health and
the environment.
In 1981 and 1991, respectively, we issued RCRA combustion standards for incinerators (40 CFR part
264, subpart O) and boilers and industrial furnaces (40 CFR part 266, subpart H). Since that time,
however, additional information became available which suggested that the standards may not have fully
addressed the potential risk to humans from indirect exposures. Indirect exposures can occur as a
result of contact with contaminated soil, plants, water or food. Because of our concern regarding
indirect exposures, we strongly recommended in the 1994 Hazardous Waste Minimization and
Combustion Strategy that site-specific risk assessments (SSRA) be conducted for each combustion
facility seeking a RCRA permit. Permitting authorities could then use the results of the SSRAs to
RCRA Site-Specific Risk Assessment Policy For Hazardous Waste Combustion Facilities Fact Sheet - Page 1
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determine, on a case-by-case basis, whether the operation of the combustors in accordance with the
standards would be protective of human health and the environment. In those cases where a RCRA
permitting authority identified a potentially significant risk, it could invoke the "omnibus authority" and
augment the RCRA permit with additional conditions to those required under 40 CFR part 264 and
part 266.
On September 30, 1999, we revised and updated our national standards for incinerators, cement kilns
and light-weight aggregate kilns (64 FR 52828). We based the revised standards on the Maximum
Achievable Control Technology (MACT) approach required under the Clean Air Act (CAA). This
approach represented the maximum degree of hazardous air pollution reduction achievable through
currently available emission control technologies.
Since the MACT standards are technology-based, we performed a national risk assessment to
determine if they satisfied the RCRA mandate to protect human health and the environment. This
national assessment was a multimedia, multipathway analysis addressing both human health and
ecological risk. The assessment was predicated on the assumption that sources whose emissions are
currently above the MACT standards will reduce their emissions to MACT levels and that sources
whose emissions currently are below the standards will maintain their emissions at current levels. Based
on this national assessment, we determined that sources complying with the MACT standards
generally are not anticipated to pose an unacceptable risk to human health and the environment under
RCRA. Thus, we concluded that the technology-based MACT standards met the protectiveness
requirement of RCRA sections 3004(a) and (q).
Although comprehensive, the national risk assessment did contain several uncertainties and limitations.
As a result, we could not conclude that the MACT standards would be protective of human health and
the environment in all cases, i.e., that it would never be necessary to include additional permit conditions
in a specific facility's permit pursuant to the omnibus provision of §3005(c)(3). For example, the
national risk assessment did not include an evaluation of the potential risk posed by nondioxin products
of incomplete combustion. In addition, the uncertainties associated with the mercury portion of the
assessment were significant and limited the use of the analysis for drawing quantitative conclusions
regarding the risk associated with the mercury MACT standard. Finally, the national risk assessment
utilized generalized assumptions which may not be reflective of unique, site-specific considerations.1
Thus, in some cases an SSRA may be necessary to confirm whether operation of a particular
hazardous waste combustor in accordance with the MACT standards will be protective of human
health and the environment under RCRA.
human health and ecological combustion risk assessment guidance documents referenced
at the end of this fact sheet contain our current recommendations of the methodology and assumptions
that you should consider when conducting hazardous waste combustion SSRAs.
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Revised Policy
As explained above, in the 1994 Hazardous Waste Minimization and Combustion Strategy we
strongly recommended that an SSRA be considered for each combustion facility seeking a RCRA
permit. In the preamble to the final hazardous waste combustion MACT standards, we articulated a
revised policy for incinerators, cement kilns and light-weight aggregate kilns. Under the revised policy,
we are recommending that permitting authorities evaluate the need for an SSRA on a case-by-case
basis.
If an SSRA does demonstrate that operation in accordance with the MACT standards may not be
protective of human health and the environment, permitting authorities may require additional conditions
in the RCRA permit, pursuant to the omnibus authority. As with the original policy, permitting
authorities must provide the justification for any omnibus-based permit conditions in the facility's
administrative record. For hazardous waste combustors not subject to the September 1999 MACT
standards, we continue to recommend that SSRAs be conducted as part of the RCRA permitting
process.
For More Information
HWC NESHAP Final Rule - Final Standards for Hazardous Air Pollutants for Hazardous
Waste Combustors (64 FR 52828, September 30, 1999). See Part Three, Section IV: How Is
RCRA 's Site-Specific Risk Assessment Decision Process Impacted by this Rule ? Internet Address:
HWC NESHAP Background Document: Human Health and Ecological Risk Assessment
Support to the Development of Technical Standards for Emissions from Combustion Units
Burning Hazardous Wastes. July 1999. EPAF-1999-RC2F-S0014 and S0015. Internet Address:
Combustion Strategy: Strategy for Hazardous Waste Minimization and Combustion. November
1994. Internet Address: hktejj//w3vs.,.ejia^^
Human Health Combustion Risk Assessment Guidance: Human Health Risk Assessment
Protocol for Hazardous Waste Combustion Facilities, Volumes I - III. July 1998. EPA530-D-98-
001 A, B, and C. Internet Address: httr^^w^Bv.^ejajIQX/^
Ecological Combustion Risk Assessment Guidance: Screening Level Ecological Risk
Assessment Protocol for Hazardous Waste Combustion Facilities, Volumes I - III. November
1999. EPA530-D-99-001 A, B, and C. Internet Address:
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