[Federal Register Volume 61, Number 153 (Wednesday, August 7, 1996)]
[Proposed Rules]
[Pages 41111-41114]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-20108]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 260, 261, 262, 264, 268, 269 and 271

[FRL-5548-3]


Requirements for Management of Hazardous Contaminated Media 
(HWIR-media); Proposed Rule--Correction Notice and Notice of Data 
Availability

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; Correction and notice of data availability.

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SUMMARY: Since publication of the proposed rule ``Requirements for 
Management of Hazardous Contaminated Media (HWIR-media)'' (61 FR 18780 
(April 29, 1996)), the Agency has become aware of four areas that 
should be clarified in the proposed rule. First, in the Appendices to 
Part 269, EPA is correcting the equations used to calculate the soil 
screening levels for inhalation of soil contaminants that are presented 
on page 18855 of the notice. These equations, as printed in the 
proposal, included a volatilization factor term that is not necessary. 
Second, also in the Appendices to Part 269, Exhibits 1, 2 and 3 
appearing on pages 18855 and 18859 were mis-formatted. As a result,

[[Page 41112]]

the acronyms, spelled out words, and the values associated with both 
were not lined up properly. Some commenters have stated that this has 
made it difficult to determine what assumptions were used in the 
equations to set the proposed Bright Line concentrations. Third, EPA is 
clarifying the sources for the assumptions listed in Exhibits 1, 2, and 
3. Fourth and finally, commenters observed that EPA did not explain how 
the groundwater Bright Line concentrations for dioxins and furans were 
developed. EPA stated in the proposal that the Bright Line 
concentrations were developed by using the risk values in IRIS or HEAST 
for each constituent; however, not all the dioxins and furans which had 
proposed Bright Line values for groundwater have risk values in IRIS or 
HEAST.1 EPA is providing the information in today's notice to help 
commenters to better understand this proposal.

    \1\ U.S. EPA. 1996. Integrated Risk Information System (IRIS). 
Online Office of Health and Environmental Assessment, National 
Center for Environmental Assessment, Cincinnati, Ohio. U.S. EPA. 
1995a. Health Effects Assessment Summary Table. Annual Update with 
Supplements. FY-1995. Office of Research and Development, Office of 
Health and Environmental Assessment, National Center for 
Environmental Assessment, Cincinnati, Ohio. ECAO-CIN-821.
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DATES: The comment period on the proposed rule for Requirements for 
Management of Hazardous Contaminated Media (61 FR 18780) ends on August 
28, 1996.

ADDRESSES: Commenters on the HWIR-media proposal must send an original 
and two copies of their comments referencing Docket Number F-96-MHWP-
FFFFF to: (1) If using regular US Postal Service mail: RCRA Docket 
Information Center, Office of Solid Waste (5305W), U.S. Environmental 
Protection Agency Headquarters (EPA, HQ), 401 M Street, SW., 
Washington, DC 20460, or (2) if using special delivery, such as 
overnight express service: RCRA Docket Information Center (RIC), 
Crystal Gateway One, 1235 Jefferson Davis Highway, First Floor, 
Arlington, VA 22202. For other information regarding submitting 
comments electronically or viewing the comments received and supporting 
information, please refer to the proposed rule (61 FR 17870 (April 29, 
1996)). The RCRA Information Center is located at Crystal Gateway One, 
1235 Jefferson Davis Highway, First Floor, Arlington Virginia and is 
open for public inspection and copying of supporting information for 
RCRA rules from 9 am to 4 pm Monday through Friday, except for Federal 
holidays. The public must make an appointment to view docket materials 
by calling (703) 603-9230. The public may copy a maximum of 100 pages 
from any regulatory document at no cost. Additional copies cost $0.15 
per page.

FOR FURTHER INFORMATION: For general information, call the RCRA Hotline 
at 1-800-424-9346 or TDD 1-800-553-7672 (hearing impaired). Callers 
within the Washington Metropolitan Area must dial 703-412-9810 or TDD 
703-412-3323 (hearing impaired). The RCRA Hotline is open Monday-
Friday, 9 a.m. to 6 p.m., Eastern Standard Time. For more detailed 
information on specific aspects of the HWIR-media rulemaking, contact 
Carolyn L. Hoskinson, Office of Solid Waste (5303W), U.S. Environmental 
Protection Agency, 401 M Street, S.W., Washington, DC 20460, phone 
(703) 308-8626.

SUPPLEMENTARY INFORMATION: On April 29, 1996, EPA proposed Requirements 
for Management of Hazardous Contaminated Media (HWIR-media). See 61 FR 
18780. The following are corrections to the proposed rulemaking.

Appendices to Part 269

    The equations presented on page 18855 to calculate the soil 
screening levels for inhalation of soil contaminants included a 
volatilization factor (VF) term that is not necessary. The corrected 
equations are presented here.
    For cancer health effects:
    [GRAPHIC] [TIFF OMITTED] TP07AU96.008
    
    For non-cancer health effects:
    [GRAPHIC] [TIFF OMITTED] TP07AU96.009
    
    Exhibit 1 on page 18855 was mis-formatted and should have appeared 
as follows:

                               Exhibit 1.--Exposure Assumptions Used to Calculate Soil Inhalation Soil Screening Levels *                               
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                                                                    Cancer                                                Non-cancer                    
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SSL = soil screening level..............  Calculated (mg/kg).......................................  Calculated (mg/kg).                                
TR = target excess lifetime cancer risk.  10-6.....................................................                                                     
THQ = target hazard quotient............  .........................................................  1.                                                 
AT = averaging time.....................  70 years.................................................  30 years.                                          
URF = inhalation unit risk factor.......  Constituent specific (ug/m\3\)-1.........................                                                     
RfC = inhalation reference concentration  .........................................................  Constituent specific (mg/m\3\).                    
EF = exposure frequency.................  350 days/yr..............................................  350 days/yr.                                       
ED = exposure duration..................  30 years.................................................  30 years.                                          

[[Page 41113]]

                                                                                                                                                        
PEF = particulate emission factor.......  1.32x10\9\ m\3\/kg.......................................  1.32x10\9\ m\3\/kg.                                
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* These exposure assumptions are presented in the Superfund Soil Screening Guidance: User's Guide, U.S. EPA, Office of Solid Waste and Emergency        
  Response, 9355.4-23, EPA/540/R-96/018, April 1996; Soil Screening Guidance: Technical Background Document, U.S. EPA, Office of Solid Waste and        
  Emergency Response, 9355.4-17A, EPA/540/R-95/128, PB96-963502, May 1996, and were originally presented in Risk Assessment Guidance for Superfund,     
  Volume 1, Human Health Evaluation Manual, (Part A), EPA/540/1-89/002, 1989 and in the Supplemental Guidance to Volume 1: ``Standard Default Exposure  
  Factors,'' EPA Office of Solid Waste and Emergency Response Directive 9285.6-03, National Technical Information Service (NTIS) PB91-921314.           


    Exhibit 2 on page 18855 was mis-formatted and should have appeared 
as follows:

                                Exhibit 2.--Exposure Assumptions Used to Calculate Soil Ingestion Soil Screening Levels*                                
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                                                                 Cancer                                                  Non-cancer                     
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SSL = soil screening level...........  Calculated (mg/kg)........................................  Calculated (mg/kg).                                  
TR=target excess lifetime cancer risk  10-6......................................................                                                       
THQ=target hazard quotient...........  ..........................................................  1.                                                   
AT=averaging time....................  70 years..................................................  6 years.                                             
BW=body weight.......................  ..........................................................  15 kg.                                               
SF=oral slope factor.................  Constituent specific (mg/kg-day)-1........................                                                       
RfD=oral reference dose..............  ..........................................................  Constituent specific (mg/kg-day).                    
IF=age-adjusted soil ingestion factor  114 mg-yr/kg-day..........................................                                                       
IR=soil ingestion rate...............  ..........................................................  200 mg/day.                                          
EF=exposure frequency................  350 days..................................................  350 days/yr.                                         
ED=exposure duration.................  ..........................................................  6 years.                                             
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* These exposure assumptions are presented in the Superfund Soil Screening Guidance: User's Guide, U.S. EPA, Office of Solid Waste and Emergency        
  Response, 9355.4-23, EPA/540/R-96/018, April 1996; Soil Screening Guidance: Technical Background Document, U.S. EPA, Office of Solid Waste and        
  Emergency Response, 9355.4-17A, EPA/540/R-95/128, PB96-963502, May 1996, and were originally presented in Risk Assessment Guidance for Superfund,     
  Volume 1, Human Health Evaluation Manual, (Part A), EPA/540/1-89/002, 1989 and in the Supplemental Guidance to Volume 1: ``Standard Default Exposure  
  Factors,'' EPA Office of Solid Waste and Emergency Response Directive 9285.6-03. National Technical Information Service (NTIS) PB91-921314.           

    Exhibit 3 on page 18859 was mis-formatted and should have appeared 
as follows:

                                Exhibit 3.--Exposure Assumptions Used to Calculate HWIR-Media Ground Water Bright Lines *                               
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                                                                 Cancer                                                  Non-cancer                     
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C=constituent concentration in         Calculated (mg/l).........................................  Calculated (mg/l).                                   
 groundwater.                                                                                                                                           
TR=target excess lifetime cancer risk  10-3......................................................                                                       
AT=averaging time....................  70 years..................................................  30 years.                                            
BW=body weight.......................  70 kg.....................................................  70 kg.                                               
SF=oral cancer slope factor..........  Constituent specific (mg/kg/day)-1........................                                                       
RfD=oral reference dose..............  ..........................................................  Constituent specific (mg/kg/day).                    
IR=groundwater ingestion rate........  2 liters/day..............................................  2 liters/day.                                        
EF=exposure frequency................  350 days/year.............................................  350 days/year.                                       
ED=exposure duration.................  30 years..................................................  30 years.                                            
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* These exposure assumptions are presented Risk Assessment Guidance for Superfund, Volume 1, Human Health Evaluation Manual, (Part A), EPA/540/1-89/002,
  1989 and in the Supplemental Guidance to Volume 1: ``Standard Default Exposure Factors,'' EPA Office of Solid Waste and Emergency Response Directive  
  9285.6-03. National Technical Information Service (NTIS) PB91-921314.                                                                                 

    Oral cancer slope factors and oral reference doses were taken from 
IRIS or HEAST.
    In this notice, EPA is clarifying the assumptions used to calculate 
the HWIR-Media bright-line levels. The exposure assumptions are 
intended to represent an estimate of the reasonable maximum exposure 
(RME) for a particular exposure scenario. The goal of RME is to combine 
upper-bound and mid-range exposure factors so that the result 
represents an exposure scenario that is both protective and reasonable, 
but not the worst possible case. In general, exposure factors for 
ingestion rate, exposure frequency, and exposure duration are upper-
bound estimates, while the body weight estimate represents an average 
value. A discussion of the choice of upper-bound versus mid-range 
exposure factor estimates is presented in Human Health Evaluation 
Manual, Supplemental Guidance: Standard Default Exposure Factors, EPA 
Office of Solid Waste and Emergency Response Directive 9285.6-03. 
National Technical Information Service (NTIS) PB91-921314.

[[Page 41114]]

Calculation of Groundwater Bright Lines for Dioxins and Furans

    Polychlorinated dibenzodioxins (PCDDs) and polychlorinated 
dibenzofurans (PCDFs) are halogenated aromatic hydrocarbons with 
similar physical and chemical properties. The most widely studied of 
these compounds is 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8,-TCDD). 
In fact, among dioxins and furans, it is the only compound for which 
toxicity benchmarks have been established by EPA. An oral cancer slope 
factor of 1.6E+5 (mg/kg/day)-1 was used to calculate the groundwater 
Bright Line concentration for this compound.2 Toxicity benchmarks 
(e.g., cancer slope factor) were developed for other dioxins and furans 
by applying a scaling factor to the CSF for 2,3,7,8-TCDD. These scaling 
factors, known as toxicity equivalency factor (TEF) values, are 
estimates of the toxicity of dioxin-like compounds relative to 2,3,7,8-
TCDD, which is assigned a TEF of 1. The TEF procedure was developed 
under the auspices of the North Atlantic Treaty Organization's 
Committee on Challenges of Modern Society (NATO/CCMS) to promote 
international consistency in addressing contamination involving CDDs 
and CDFs.3 EPA has adopted the TEFs as an interim procedure for 
assessing the risks associated with exposures to complex mixtures of 
CDDs and CDFs.4 The following table presents the TEFs for dioxins 
and furans as well as the calculated CSFs that were used to calculate 
the proposed HWIR-media Bright Line concentrations.
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    \2\ This toxicity benchmark is presented in the Health Effects 
Assessment Summary Tables (HEAST). A slope factor of 1.6E+5 (mg/kg/
day)-1 was used to calculate the groundwater Bright Line 
concentration level for 2,3,7,8-TCDD (and, through the TEFs, for the 
other dioxins and furans). However, the 1995 updates to the HEAST 
list a cancer slope factor of 1.5E+5 for 2,3,7,8-TCDD. See Health 
Effects Assessment Summary Tables, May 1995, EPA/540/R-95/036, 
National Technical Information Service, PB95-921199. EPA discussed 
on page 18801 of the proposal that ``the Agency's understanding of 
risk assessment * * * is always developing'' and that ``almost as 
soon as risk-based numbers are published, they can become 
outdated.'' EPA requested comment in the proposal on page 18801 on 
alternatives to keep the Bright line concentrations up-to-date.
    \3\ North Atlantic Treaty Organization, Committee on Challenges 
of Modern Society (NATO-CCMS) Report number 176, ``International 
Toxicity Equivalency Factor (I-TEF) Method of Risk Assessment for 
Complex Mixtures of dioxins and Related Compounds,'' and NATO/CCMS 
Report Number 178, ``Scientific Basis for the Development of 
International Toxicity Equivalency (I-TEF) Factor Method of Risk 
Assessment for Complex Mixtures of dioxins and Related Compounds.''
    \4\ See ``Interim Procedures for Establishing Risks Associated 
with Exposures to Mixtures of Chlorinated Dibenzo-p-dioxins and 
Dibenzofurans (CDDs and CDFs), and 1989 Update,'' U.S. Environmental 
Protection Agency, Risk Assessment Forum, EPA/625/3-89/016. National 
Technical Information Service, Springfield, VA, PB90-145756.

                         Toxicity Equivalency Factors and Calculated Toxicity Benchmarks                        
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                                                       Published CSF (from                 Calculated CSF (mg/kg-
     Compound CAS number           Compound name      HEAST) (mg/kg-day) -1       TEF             day) -1       
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1746-01-6....................  2,3,7,8-TCDDDioxin...  1.6E+5...............         1      1.6E+5               
51207-31-9...................  2,3,7,8-TCDFuran.....  NA...................         0.1    1.6E+04              
57117-31-4...................  2,3,4,7,8-PeCDFuran..  NA...................         0.5    7.8E+04              
99999-01-0...................  2,3,7,8-PeCDdioxins..  NA...................         0.5    7.8E+04              
99999-04-0...................  1,2,3,7,8-PeCDfurans.  NA...................         0.05   7.8E+03              
99999-02-0...................  2,3,7,8-HxCDdioxins..  NA...................         0.1    1.6E+04              
99999-05-0...................  2,3,7,8-HxCDfurans...  NA...................         0.1    1.6E+04              
99999-03-0...................  2,3,7,8-HpCDdioxins..  NA...................         0.01   1.6E+03              
99999-06-0...................  2,3,7,8-HpCDfurans...  NA...................         0.01   1.6E+03              
3268-87-9....................  OCDDioxin............  NA...................         0.001  1.6E+02              
99999-07-0...................  OCDFuran.............  NA...................         0.001  1.6E+02              
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    EPA only set Bright Line concentrations for constituents for which 
EPA had sufficient information to do the necessary calculations to 
determine the Bright Line. For constituents that do not have Bright 
Line values, EPA proposed that the overseeing agency would use 
appropriate, available information to make contained-in determinations. 
EPA decided to use the approach described above to calculate Bright 
Line concentrations for dioxins and furans even though they did not 
have risk values in HEAST because it is a widely accepted practice to 
use the TEFs.

    Dated: August 1, 1996.
Elliott P. Laws,
Assistant Administrator, Office of Solid Waste and Emergency Response.
[FR Doc. 96-20108 Filed 8-6-96; 8:45 am]
BILLING CODE 6560-50-P