[Federal Register Volume 86, Number 54 (Tuesday, March 23, 2021)]
[Notices]
[Pages 15476-15477]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-05380]


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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-ORD-2020-0564; FRL 10020-77-ORD]


Multiple-Path Particle Dosimetry (MPPD) Model Software (MPPD EPA 
2021 v.1.01) With Technical Support Documentation and User's Guide 
(External Review Draft)

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice; request for public comment.

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SUMMARY: The Environmental Protection Agency (EPA) is announcing an 
external expert peer review and public comment for the EPA Multiple-
Path Particle Dosimetry (MPPD) Model Software (MPPD EPA 2021 v. 1.01) 
and its associated ``Technical Support Documentation and User's Guide 
(External Review Draft)'' ([EPA/600/R-20/406]). The document was 
prepared by the Center for Public Health and Environmental Assessment 
(CPHEA) within EPA's Office of Research and Development (ORD), with 
contributions from Applied Research Associates, Inc., and Fred J. 
Miller, LLC. EPA is releasing this draft model software version and 
associated document to seek review by external experts and the public. 
This external review draft document and model software (MPPD EPA 2021 
v. 1.01) are not final and do not represent, and should not be 
construed to represent, any final Agency policy or views. When revising 
the document and the model software, EPA will consider any peer or 
public comments submitted during the public comment period specified in 
this document.

DATES: The 30-day public comment period begins March 23, 2021 and ends 
April 22, 2021. Comments must be received on or before April 22, 2021.

ADDRESSES: The EPA Multiple-Path Particle Dosimetry (MPPD) Model 
Software (MPPD EPA 2021 v. 1.01) and its associated ``Technical Support 
Documentation and User's Guide'' (External Review Draft)'' will be 
available from the contractor managing the external peer review, 
Eastern Research Group, Inc. (ERG). To obtain a copy of the external 
review draft or the associated MPPD software (EPA 2021 v. 1.01), 
contact ERG at email: [email protected] with the Subject line: MPPD 
EPA 2021 Peer Review; Phone: 781-674-7362.

FOR FURTHER INFORMATION CONTACT: For information on the public comment 
period, contact the ORD Docket at the EPA Headquarters Docket Center;

[[Page 15477]]

phone: 202-566-1752; fax: 202-566-9744; or email: [email protected]. 
For technical information, contact Annie M. Jarabek; phone: 919-637-
6016; or email: [email protected].

SUPPLEMENTARY INFORMATION:

I. Information About the Document and MPPD Model Software

    The EPA is undertaking an external peer review of an EPA version of 
the Multiple-Path Particle Dosimetry (MPPD) model (MPPD EPA 2021 v. 
1.01) and its software, together with an EPA Technical Support 
Documentation and User's Guide. The EPA introduced formal dosimetry 
modeling into its derivation procedures for risk assessment of inhaled 
materials with its 1994 document entitled ``Methods for Derivation of 
Inhalation Reference Concentrations (RfCs) and Application of 
Inhalation Dosimetry'' (US EPA, 1994). These methods relied upon the 
Regional Deposited Dose Ratio (RDDR) model and underwent two expert 
technical panel and two expert Science Advisory Board (SAB) reviews 
prior to finalization. The dosimetry adjustments were also subsequently 
incorporated into the Agency's guidelines for carcinogen risk 
assessment (US EPA, 2005).
    The EPA RDDR model was an empirical model fit to a unique set of 
experimental data from inhalation studies across five laboratory animal 
species commonly used in testing for regulatory risk assessment as well 
as for humans. The model provided predictions of inhaled deposited dose 
in various regions of the respiratory tract, including the 
extrathoracic (ET), tracheobronchial (TB), pulmonary (PU), thoracic (TB 
+ PU) or total respiratory tract (TOTAL).
    However, since 1994, mechanistic modeling of inhalation dosimetry 
for particles has matured. The MPPD model and its software include many 
modernized features, with some dose metric predictions now based on 
mechanistic descriptions instead of empirical fitting, the ability to 
address a wider range of particle size, providing prediction of 
retained mass for some species, and including some different test 
species.
    The EPA is convening this external peer review to evaluate the MPPD 
model. The model results provide dosimetry adjustment of inhalation 
exposures for the following purposes: Interspecies extrapolation, 
evaluation of intra-human variability, informing experimental design, 
and in vitro to in vivo (IVIVE) extrapolation.
    The EPA Multiple-Path Particle Dosimetry (MPPD) Model Software 
(MPPD EPA 2021 v. 1.01) and its associated ``Technical Support 
Documentation and User's Guide (External Review Draft)'' will be 
discussed at a virtual external expert peer review meeting, which will 
be open to the public. In addition to the opportunity to submit written 
comments during the public comment period announced in this notice, the 
public will have an opportunity to make brief oral comments during the 
virtual expert peer panel meeting. For more information about the peer 
review meeting, including information about how to register, please 
visit: https://projects.erg.com/conferences/peerreview/register-mppd.html.

II. How To Submit Technical Comments to the Docket at 
www.regulations.gov

    Out of an abundance of caution for members of the public and our 
staff, the EPA Docket Center and Reading Room are closed to the public, 
with appointment only, to reduce the risk of transmitting COVID-19. Our 
Docket Center staff will continue to provide remote customer service 
via email, phone, and webform. We encourage the public to submit 
comments via the web at https://www.regulations.gov/ or via email at 
[email protected], as there may be a delay in processing mail and 
faxes. Hand deliveries and couriers may be received by scheduled 
appointment only. For further information on EPA Docket Center services 
and the current status, please visit https://www.epa.gov/dockets.
    Submit your materials identified by Docket ID No. EPA-HQ-ORD-2020-
0564 by one of the following methods:
     www.regulations.gov: Follow the online instructions for 
submitting comments.
     Email: [email protected].
     Fax: 202-566-9744.
     Mail: Office of Research and Development (ORD) Docket 
(Mail Code: 28221T), U.S. Environmental Protection Agency, 1200 
Pennsylvania Ave. NW, Washington, DC 20460. The phone number is 202-
566-1752.
     Hand Delivery: The ORD Docket is located in EPA's 
Headquarters Docket Center, Room 3334 EPA West Building, 1301 
Constitution Ave. NW, Washington, DC. If you provide materials by mail 
or hand delivery, please submit three copies of these materials. For 
attachments, provide an index, number pages consecutively with the 
materials, and submit an unbound original and three copies.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-ORD-
2020-0564. Please ensure that your comments are submitted within the 
specified comment period. Comments received after the closing date will 
be marked ``late,'' and may only be considered if time permits. It is 
EPA's policy to include all materials it receives in the public docket 
without change and to make the materials available online at 
www.regulations.gov, including any personal information provided, 
unless materials include information claimed to be Confidential 
Business Information (CBI) or other information whose disclosure is 
restricted by statute. Do not submit information that you consider to 
be CBI or otherwise protected through www.regulations.gov or email. The 
www.regulations.gov website is an ``anonymous access'' system, which 
means EPA will not know your identity or contact information unless you 
provide it in the body of your comment. If you send an email directly 
to EPA without going through www.regulations.gov, your email address 
will be automatically captured and included as part of the materials 
that are placed in the public docket and made available on the 
internet. If you submit electronic materials, EPA recommends that you 
include your name and other contact information in the body of your 
materials and with any disk or CD-ROM you submit. If EPA cannot read 
your materials due to technical difficulties and cannot contact you for 
clarification, EPA may not be able to consider the materials you 
submit. Electronic files should avoid the use of special characters, 
any form of encryption, and be free of any defects or viruses. For 
additional information about EPA's public docket, visit EPA's Docket 
Center homepage at www.epa.gov/epahome/dockets.htm.
    Docket: Documents in the docket are listed in the 
www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other materials, 
such as copyrighted material, are publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in www.regulations.gov or in hard copy at the ORD Docket in EPA's 
Headquarters Docket Center.

    Authority: Pub. L. 94-475; Environmental Research, Development, 
and Demonstration Authorization Act of 1976.

    Dated: February 18, 2021.
Vanessa Holt,
Acting Director, Center for Public Health and Environmental Assessment 
(CPHEA).
[FR Doc. 2021-05380 Filed 3-22-21; 8:45 am]
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