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Dibasic Esters : In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin Laboratory Project ID: DuPont 5295 TESTGUIDELINES: OECD Guideline for the Testing of Chemicals ( Draft Guideline 428), Skin Absorption: in vitro Method ( 20015)

AUTHOR: William J. Fasano, Sr., B. S.

STUDYCOMPLETEDON: March 24,2003 SPONSOR: Dibasic Esters Group 1100 New York Avenue, N. W., Suite 1090 Washington, D. C. 20005 PERFORMINGLABORATORY: E. I. du Pont de Nemours and Company Haskell Laboratory for Health and Environmental Sciences Elkton Road, P. O. Box 50 Newark, Delaware 19714 0050 WORKREQUESTNUMBER: 13395 SERVICE CODENUMBER: 1377 Page 1 of41 OPPT 2002 0009 0009 Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 GOOD LABORATORY PRACTICE COMPLIANCE STATEMENT This study was conducted in compliance with U. S. EPA TSCA ( 40CFR part 792) Good Laboratory Practice Standards except for the item documented below. The item listed does not impact the validity of the study.

The test substances were characterized by the sponsor prior to the initiation of this study. AIthough the characterizations were not performed under Good Laboratory Practice Standards, the accuracy of the data is considered sufficient for the purposes of this study.

Study Director: 2q MA SL 2003 Willw J. Eano, Sr., B. S. Date Research Toxicologist n Dibasic Esters: In Vitro Dermal Permeability   i Coefficients ( Kp) in Rat and Human Skin DuPont 5295 QUALITY ASSURANCE STATEMENT Haskell Sample Number( s):

24296,25333,24300,24301 Dates of Inspections:

Protocol: August 30,2002 Conduct: August 30,2002; November 1,2002 Records, Reports: January 27,28,30,31,2003; February 3,4,2003 Dates Findings Reported to:

Study Director: November 1,2002; February 4,2003 Management: November 1,2002; February 24,2003 Reported by: c 2qtf. fkl. 2~~ 3 Joseph C. Hamill Date Staff Quality Assurance Auditor  3 Director: r

Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 CERTIFICATION We, the undersigned, declare that this report provides an accurateevaluation of data obtained from this study.

Approved by: Zcf Misk Lou3 Gary W. Jepson, Ph. D. Date Principal Research Toxicologist and Manager Approved by:

Issued by Study Matthew S. BogdanfG, Ph. D.# A@ V.. Research Manager and Director L5 d Willia . Fasano, Sr., B. S. ResGrch Toxicologist  42q M~ zd0.3 Date 29 frlA+ 2003 Date Dibasic Esters: In Vitro Dermal Permeability . Coefficients( Kp) in Rat and Human Skin DuPont 5295 TABLE OF CONTENTS Page GOOD LABORATORY PRACTICE COMPLIANCE STATEMENT .................................. 2 QUALITY ASSURANCE STATEMENT................................................................................... 3 CERTIFICATION ........................................................................................................................ 4 LIST OF TABLES ........................................................................................................................ 7 LIST OF FIGURES ...................................................................................................................... 7 LIST OF APPENDICES............................................................................................................... 7 STUDY INFORMATION............................................................................................................. 8 STUDY PERSONNEL................................................................................................................ 11 SUMMARY.................................................................................................................................. 12 INTRODUCTION ....................................................................................................................... 14 MATERIALS AND METHODS ............................................................................................... 14 A. Regulatory Test Guidelines ............................................................................................... 14 B . Test Substances................................................................................................................. 15 C. Analytical Reference Standard.......................................................................................... 15 D. Test System ....................................................................................................................... 16 1. Rat Skin ....................................................................................................................... 16 2. Human Skin................................................................................................................. 17 E. Test Solution Information ................................................................................................. 17 1. Formulation ................................................................................................................. 17 2. Administration and Concentration .............................................................................. 17 F. Exposure Groups ............................................................................................................... 17 G. Preparation of Skin Membranes ........................................................................................ 17 1 . Rat Skin ....................................................................................................................... 17 2. Human Skin................................................................................................................. 18 H. In VitroFlow Through Diffusion Cells ............................................................................ 18 I. Assessment of Membrane Integrity and Membrane Equilibration.................................... 18 J . In Vitro Percutaneous Penetration ..................................................................................... 19 K. Sample Analysis ................................................................................................................ 19 L. Data Evaluation ................................................................................................................. 20 M. Statistical Analyses............................................................................................................ 20  5 Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 RESULTS AND DISCUSSION ................................................................................................. 21 A. Permeability parameters for individual DBE homologues................................................ 21 B. Permeability parameters for the DBE homologues in the 1: 3: 1 ( DMS: DMG: DMA) blend................................................................................................. 21. C. Comparison of permeability coefficient ( Kp) data within a species ................................. 22 CONCLUSIONS......................................................................................................................... 22 RECORDS AND SAMPLE STORAGE ................................................................................... 23 REFERENCES............................................................................................................................ 23 TABLES....................................................................................................................................... 24 FIGURES ..................................................................................................................................... 28 APPENDICES ............................................................................................................................. 34  6 , Dibasic Esters: In Vitro Dermal Permeability , Coefficients ( Kp) in Rat and Human Skin DuPont 5295 LIST OF TABLES Page 1. Permeability parameters for individual DBE homologues...................................................... 26 2. Permeability parameters for DBE homologues in the 1: 3: 1blend ( DMS: DMG: DMA)......... 27 LIST OF FIGURES Page 1. Individual DBE homologues comparison of permeability coefficients ( Kp) for rat and human skin........................................................................................................................ 30 2. DBE 1: 3: 1 @ MS: DMG: DMA) blend  comparison of permeability coefficients ( Kp) for rat and human skin............................................................................................................. 31 3. A comparison of permeability coefficients.( Kp) for the individual DBE homologues and the homologues in the 1: 3: 1 @ MS: DMG: DMA) blend for rat skin ................................ 32 4. A comparison of permeability coefficients ( Kp) for the individual DBE homologues and the homologues in the 1: 3: 1 ( DMS: DMG: DMA) blend for human skin ......................... 33 LIST OF APPENDICES Page A. Permeability parameters for the individual DBE homologues  individual data for DMS, DMG, and DMA when applied to rat and human skin................................................. 36 B. Permeability parameters for the individual DBE homologues in the 1: 3: 1 ( DMS: DMG: DMA) blend  individual data for DMS, DMG, and DMA when applied to rat and human skin .............................................................................................................. 39  7  Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin STUDY INFORMATION Test Substance 1:

9th CollectiveNomenclature: Butanedioic acid, dimethyl ester SynonvmsKodes: Dimethyl succinate DBE 4 DMS F124347A ( Lot No.)

Haskell Number: 25333 CAS Registry Number: 106 65 0 DuPont 5295 Composition: 99.2% Dimethyl succinate @ MS DBE4)

Known Impurities: 0.2 wt% Dimethyl glutarate ( DMG DBE5) 0.03 wt% Water Phvsical Characteristics: Colorless liquid Test Substance 2:

9th Collective Nomenclature: Pentanedioicacid, dimethy1ester SvnonvmsKodes: Dimethyl glutarate DBE 5 DMG 0 Dimethyl Glutarate ( DMG) H931363 A ( Lot NO.)

Haskell Number: 24300 CAS Repistry Number: 1119 40 0 Composition: 99.61% Dimethyl glutarate ( DMG DBE5) by gas chromatography ( GC)

Known Impurities: 0.085% Dimethyl adipate @ MA DBEG) by GC 0.163% Dimethyl succinate OMS DBE4) by GC 2.8ppm HCN Physical Characteristics: Colorless liquid r). Dibasic Esters: In VitroDermal Permeability , Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Test Substance 3:

9th Collective Nomenclature: Hexanedioic acid, dimethyl ester SvnonvmdCodes:

0 e e e 0 e 0 Dimethyl adipate DBE 6 DMA Adipic acid, dimethyl ester Dimethyl hexanedioate Methyl adipate Dibasic ester 6 J806339 A ( Lot NO.)

Haskell Number: 24301 CAS Registry Number: 627 93 0 Composition: 98.824%

Known Imuurities: 0.607% 4.8ppm Dimethyl adipate @ MA DBE6) by GC Dimethyl glutarate ( DMG DBE5) by GC HCN Physical Characteristics: Colorless Iiquid Test Substance 4:

Substance Tested: DBE Synonyms/ Codes: 0 Aliphatic dibasic esters  DBE Dibasic ester Dibasic ester mixture 0 18077336 ( Lot NO.)

Haskell Number: 24296 CAS Registry Number: 1119 40 0 Dimethyl glutarate 627 93 0 Dimethyl adipate 106 65 0 Dimethyl succinate Composition: 58.92% Dimethyl glutarate ( DMG DBES) by GC 2 1.92% Dimethyl adipate ( DMA DBE6) by GC 18.76% Dimethyl succinate ( DMS DBE4) by GC  9 Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Known Impurities: 0.09% MEOH 4.8ppm HCN Phvsical Characteristics: Colorless liquid Sponsor: Dibasic Esters Group 1100 New York Avenue, N. W., Suite 1090 Washington, DC 20005 Study InitiatedCompleted: July 26,2002 / ( see report cover page)

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Dibasic Esters: In Vitro Dermal Permeability , Coefficients ( Kp) in Rat and Human Skin DuPont 5295 STUDY PERSONIWL Study Director: William J. Fasano, Sr., B. S. Management: Matthew S. Bogdanffy, Ph. D., D. A. B. T. Gary W. Jepson, Ph. D. Primary Technician: LaRue A. Manning, B. A. Analytical Associate: Julia N. Wang, Ph. D.

Toxicology Report Preparation: Lisa G. Burchfield, A. A. Management: Nancy S. Selzer, M. S.

Laboratory Veterinarian: Thomas W. Mayer, D. V. M., A. C. L. A. M. William Singleton, D. V. M., A. C. L. A. M.

 11  Dibasic Esters: In Vim Dermal Permeability Coefficients ( Kp) in Rat and HumanSkin DuPont 5295 SUMMARY The in vitro dermal kinetic parameters of penetration rate, lag time, and permeabilitycoefficient ( Kp) were determined for rat and human skin for the refined individual Dibasic Ester @ BE) homologuesDimethyl Succinate( DMS), Dimethyl Glutarate ( DMG), and Dimethyl Adipate ( DMA), and for the homologues in a 1: 3: 1 ( DMS: DMG: DMA) blend. Split thicknessrat skin and human epidermal membranes were mounted in a flow through diffusion cell system which was maintained at 32 ° C. Skin specimens were equilibrated with a 0.9% saline receptor fluid and integrityconfirmed by electricalresistance. Following specimen selection and replacement of the saline receptor fluid with 1: 1 ( v/ v) ethano1: water maintained at a flow rate of approximately 2 mUh, an infinite dose ( 150 pL) of the test solvent was applied to the epidermal surface of 6 skin replicatesper species. Under occlusive conditions, receptor chambereffluent samples were collected hourly for each replicate until 6 hours post application. Quantitative analysis of receptor fluid samples for the DBE homologue of interest was performed using a liquid chromatograph coupled to a mass spectrometeroperating in multiple reaction mode.

Following application of the individual dibasic ester homologues DMS, DMG, and DMA to rat and human skin, the penetration rates for each homologue were comparable within a species and ranged from 3131.8 to 4542.4 pg/ cm2/ hfor rat skin and from 79.5 to 113.0 pg/ cm2/ hfor human skin. In contrast, when the DBE blend containingDMS, DMG, and DMA in a nominal ratio of 1: 3: 1 ( v/ v) was applied to rat skin, the penetration rate for DMS ( 571.7 pg/ cm2/ h), DMG ( 1571 pg/ cm2/ h), and DMA ( 507.0 pg/ cm2/ h) was slower compared to the penetration rates observed when the individual homologues were applied alone as a single solvent system. The rate of DMG Penetration from the blend was approximately3 fold fastercompared to DMS and DMA, owing to its concentration as penetration is passive and concentration dependent.

As was observed for rat skin, the penetration rate for DMG through human skin from the homologue blend ( 108.7 pg/ cm2/ h) was faster compared to DMS ( 24.2 pg/ cm2/ h) and DMA ( 16.3 pg/ cm*/ h). With the exception of DMG, the penetration rates for DMS and DMA were slower as measured from the blended solvent system compared to the penetration rates observed when each homologue was applied alone to human skin.

Overall, and exclusive of whether the DBE homologue was applied alone or as part of the blended formulation, lag times, a measure of the time required for the DBE homologue to cross the skin and appear in the receptor fluid, were shorter for rat skin ( 20.15 hours) than for human skin ( 10.64 hours).

The permeability coefficients( Kp), whether the DBE homologue was applied alone or as part of the 1: 3: 1 blend, were comparablefor each homologue within a species and higher for rat skin compared to human skin. The Kp values for rat and human skin ranged from 2.12 x to 4.18 x lo" cdh and from 6.81 x to 1.69 x respectively.

The results from these in vitro dermal kinetic experiments show that DMS, DMG, and DMA penetrated through rat skin faster and with a shorter lag time than was observed for human skin.

 12 Dibasic Esters: In VitroDermal Permeability . Coefficients ( Kp) in Rat and Human Skin DuPont 5295 The data also show that the permeability coefficient was comparable for each dibasic ester homologue within a species and exclusiveof whether the DBE of interest was applied alone as a single solvent system or as part of the 1: 3: 1 ( DMS: DMG: DMA) blend.

The permeability coefficient, which serves to describe the movement or flux of a chemical through skin and principally the stratum corneum, normalized for concentrationand expressed as a depth of diffusion per unit of time, provides a basis for comparisonwith other industrial solvents and is useful in estimating absorbed dose following dermal exposure.

 13 Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 INTRODUCTION Dibasic Esters ( DBEs) are used in degreasing and paint stripping operations and as a replacement for traditional aromatic solvents. The DBEs are identified as Dimethyl Succinate ( DMS), Dimethyl Glutarate ( DMG), and Dimethyl Adipate @ MA). Based on the potential for dermal exposure to DBEs, comparative in vitro dermal kinetic data in rat and human skin was requested by the sponsor in order to comply with an EPA issued consent order pursuant to TSCA section 4.

This study was designed to determine a permeability coefficient ( Kp) for each DBE homologue alone, and for each homologue in a 1: 3: 1 v/ v blended formulation of DMS: DMG: DMA. The data generated in this study can be used in evaluating dermal exposure to DBEs.

A permeability coefficient ( Kp), which is a conservative measure of penetration since it is determined with an infinite application of the solvent and under steady state penetration, is useful for predicting absorbed dose in vivo using the following equation:

Q = Kp * A * C * ( T Z)

Where Q is the amount of the homologue absorbed ( mg), Kp is the permeability coefficient ( crdh), A is the skin exposure area ( cm2), C is the concentration of the homologue in the solution, whether applied alone or in the 1: 3: 1 ( DMS: DMG: DMA) v/ v blend ( mg/ mL), Tis the exposure time ( hours), and Tis the lag time, or time required for the solvent to cross the skin barrier and reach the systemic circulation.'')

Kp values are primarily a function of the octanol water partition coefficient, molecular weight, molecular volume, and thickness of the stratum corneum. Considered the rate limiting barrier to penetration, the sfraturncumeurn is the outermost layer of skin and is composed of vertically stacked, polyhedral comeocytes surrounded by a matrix of lipid enriched membranes.'*)

In addition to performing exposure assessments for the individual DBE homologues alone and in the blend, Kp values are useful for making comparisons to existing Kp data for various industrial solvents.

MATERIALS AND METHODS A. Regulatory Test Guidelines This study was not designed to meet any specific regulatory guideline requirement. However, there are guidelines on percutaneous absorption from the Organization for Economic Co operation and Development ( OECD), which provides information on the practical use of the in vitro dermal absorption meth~ d.'~'

 14 Dibasic Esters: In Vitro Dermal Permeability . Coefficients ( Kp) in Rat and Human Skin DuPont 5295 B. Test Substances The test substances, DMS, DMG, DMA, and a 1: 3: 1 ( v/ v) blend of DMS: DMG: DMA were supplied by the sponsor and assigned unique Haskell Laboratory Numbers upon receipt. Available information on the purity, composition, contaminants, synonyms, basic physical properties, hazards, and hazardous material classification( s) was provided by the sponsor and documented in the study records. The samples were stored at room temperature.

General Information and Structures Dimethyl succinate @ MS) 0 Molecular Weight: 146 0 II CASRN: 106 65 0   I1 0

Haskell# 25333 0 Dimethyl glutarate ( DMG) Molecular Weight: 160 O\ CASRN: 1119 40 0 0 0 HaskeIl# 24300 Dimethyl adipate ( DMA) 0 Molecular Weight: 174 CASRN: 627 93 0 1,

Haskell# 24301 0 The 1: 3: 1 ( v/ v) blend of DMS: DMG: DMA was assigned Haskell# 24296.

Dibasic esters are clear liquids at room temperature, with high boiling points, low vapor pressures, and low solubility in water, but are generally soluble in alcohols.

C. Analytical Reference Standard Reference standards of DMS, DMG, and DMA were purchased from Sigma Aldrich Corporation ( St. Louis, MO) and had a chemical purity of 98%. The standards were assigned Haskell Laboratory Numbers 22703 239 ( DMS), 22703 240 ( DMG), and 22703 241 ( DMA) and were stored at room temperature. The reference standards served to confirm the identity of each DBE in the test substances and the concentration of DBEs in receptor fluid samples. Dibasic Esters: In Vitro Dermal Permeability CoeMicients ( Kp) in Rat and Human Skin DuPont 5295 D. Test System 1. RatSkin Skin used was from male rats of the Sprague Dawleystrain, Crl: CD@( SD) IGSBR, 6 8 weeks of age. Rats were supplied by Charles River Laboratories, Inc., Raleigh, North Carolina.

Animal Husbandry Upon arrival at Haskell Laboratory, animals were removed from shipping cartons and housed in appropriate cages, according to Standard Operating ProceduresLAOO3 P unless specified in the study records. Animals were maintained under quarantine for at least 6 days unless approved otherwise by the site veterinarian, had 3 recorded weight gains and no abnormalities detected. After the quarantine period, rats were selected for study.

Animal rooms are targeted at a temperatureof 23 21 ° C and a relative humidity of 40 60%. Animal rooms are artificially illuminated ( fluorescent light) on an approximate 12 hour lighvdark cycle.

All animals were provided tap water ad libitum and fed PMI Nutrition International, Inc. Certified Rodent LabDiet@ 5002 ad libitum during the quarantine period.

Animal Health Monitoring As specified in the Haskell Laboratory animal health and environmental monitoring program, the following procedures are performed periodically to ensure that contaminant levels are below those that would be expected to impact the scientific integrity of the study:

Water samples are analyzed for total bacterial counts, and the presence of coliforms, lead, and other contaminants.

Feed samples are analyzed for total bacterial, spore, and fungal counts.

Samples from freshly washed cages and cage racks are analyzed to ensure adequate sanitation by the cagewashers.

Certified animal feed is used, guaranteed by the manufacturerto meet specifiednutritional requirements and not to exceed stated maximum concentrationsof key contaminants, including specified heavy metals, aflatoxin, chlorinated hydrocarbons, and organophosphates. The presence of these contaminants below the maximum concentration stated by the manufacturer would not be expected to impact the integrity of the study,

The animal health and environmental monitoring program is administeredby the attending laboratoryanimal veterinarian. Evaluation of these data did not indicate any conditions that affected the validity of the study.

 16 Dibasic Esters: In Vitro Dermal Permeability . Coefficients( Kp) in Rat and Human Skin DuPont 5295 2. Human Skin Samples of human skin ( lateral thigh), harvested postmortem, was supplied by the International Institute for the Advancement of Medicine ( Jessup, PA). The skin samples were stored frozen at approximately  20 ° C until prepared for use. The source and identity of the skin samples ( sex and approximate age of donor) were documented in the study records.

E. Test Solution Information 1. Formulation The test substances were applied as received.

2. Administration and Concentration The test substances were applied to each test skin as a single, infinite dose of 150 pL.

The concentration of each individual homologue alone and in the blend @ g/ mL) wasbased on data supplied by the sponsor.

F. Exposure Groups The following exposure groups were used to determine the in vitro dermal permeability coefficients ( Kp) in rat and human skin, when applied either as a pure solvent, or when incorporated into a blended formulation.

Species Test Group DBE Test Solution Number of Skin Preparations Rat A B C D Human E F G H DMS DMG DMA 1: 3: 1 ( DMS: DMG: DMA) blend DMS DMG DMA 1: 3: 1 ( DMS: DMG: DMA) blend 6 6 6 6 G. Preparationof Skin Membranes 1. RatSkin Following quarantine, rats were euthanized by carbon dioxide asphyxiation and the fur from the dorsal region was carefully shaved using clippers. Any animals showing obvious abrasion within the region of the test skin area were considered unsuitable and discarded. The shaved area was excised, held briefly on wet ice, and frozen at approximately  20 ° Cuntil processed.

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I Dibasic Esters: In VitroDermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Samples of skin were removed from storage, thawed at room temperature, then dermatomed to approximately 450 pm. The skin sample was then placed onto an aluminum pan, identified using the Haskell animal number, and stored refrigerated at approximately0 10 ° C until readied for use.

2. Human Skin Samples of human skin, which were stored frozen, were allowed to thaw at room temperature, and any extraneous tissue was removed ( e. g., subcutaneousfat). The skin section was then immersed in approximately60 ° C water for approximately50 seconds, removed, and the epidermis peeled off the dermis. Each membrane was floated onto an aluminum pan and the excess water allowed to drain away. Each membrane was given a unique identifying number and stored refrigerated at approximately0 10 ° C until readied for use.

H. In Vitro Flow Through Diffusion Cells An automated flow throughdiffusion cell system ( PermeGear, Inc., Bethlehem, PA) was used in this study. The skin membrane was mounted, dermal side down, onto the top of the receptor chamber. The donor chamber ( top) was then placed over the skin section, clamped in place, and fluid pumped under the skin section. The in vitro cells have an exposure area of 0.64 cm2.

I. Assessment of Membrane Integrity and Membrane Equilibration The integrity of each membrane was assessed by measurement of electrical resistanceprior to application of test substance.")

Membranes were removed from refrigeration storage and hydrated in 0.9% saline. Following hydration, the membrane was mounted onto the top of the receptor chamber and the donor chamber clamped in place. Physiologic saline ( 0.9%) was then pumped through the system at a rate of approximately 2 mUh, and the membrane equilibrated in the test system for approximately 30 minutes. During equilibration, the water jacketed cells were maintained at approximately 32OC using a recirculating water bath system. Followingequilibration, a resistance measurement of each skin membrane was taken using a Tinsley 6401 Databridge ( H. Tinsley and Company, Croydon, Surrey, England).

Membranes with a resistance of 26 kS2 ( rat) and 217 kSZ ( human) were considered intact and retained for use on study. Membranes not meeting these criteria were replaced, and electrical resistance confirmed followingequilibration. This procedure was followed until a minimum of 6 skin preparationsrepresented by at least 2 individuals per species per formulation was achieved.

Following electrical resistance measurement, the saline in the donor chamber was removed and discarded. The rate of flow of saline through the receptor chamber was maintained at approximately 2 Wh, and the in vitro cells held overnight without occlusion of the donor chamber, prior to test solution application.

18ri Dibasic Esters: In Vim Dermal Permeability * Coefficients ( Kp) in Rat and Human Skin DuPont 5295 J. In Vitro Percutaneous Penetration Following overnight equilibration, the saline receptor fluid was discarded and replaced with 1: 1 ethano1: water ( vh) and the flow rate increased for a period of time sufficient to purge the system of saline. Following this, the flow rate was adjusted to approximately2 mUhand the system equilibrated for approximatelyone hour prior to application of the test solution.

The test solution ( 150 pL) was then applied to the skin surface, via the donor chamber, and the donor chamber occluded with tape for the duration of the exposure period.

Following dose application, samples of receptor fluid were collected at 1,2,3,4,5, and 6 hours for all skin preparations. Samples not immediatelyprocessed for analysis were stored frozen at 5 10 ° C.

K. Sample Analysis Quantitativeanalysis of receptor fluid samples, along with reference standards, was performed using a Waters Alliance@ 2790 Liquid Chromatograph( LC) coupled to a Micromass Quattro microTM tandem quadrapole mass spectrometer( MS) equipped with a MASSLYNX data acquisition system ( Micromass Inc., Manchester, UK).

LC Conditions: Column: HP Zorbax RxC8,2.1 x 150 mm. 5pm particles Column temperature: 20 ° C Injection volume: 5 PL Solvent A 10mM formic acid in water Solvent B: Acetonitrile Gradient: Time A B 0 80 20 5.00 30 70 6.00 30 70 6.10 80 20 Flow rate: 0.450mUmin MS Conditions: Ionization mode: Electrospray positive ( ES+) Capiilary voltage: 3.20 kV Cone voltage 25.8 V Extractor voltage: 4.20 V Source temperature: 100 ° C Cone temperature: 20 ° C Desolvation temperature: 250 ° C Cone gas flow: 84L/ Hr ( nitrogen) Desolvation gas flow: 668UHr ( nitrogen) Collision energy: 4eV Collision gas: Argon Mode: Multiple Reaction Monitoring( MRM) ( a) 147.07> 114.93for DMS ( b) 161.05 > 128.92for DMG ( c) 175.07> 142.94for DMA  19 Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 L. Data Evaluation The cumulative amount of test material penetrating the membrane and appearing in the receptor fluid at each sampling time point, divided by the exposure area ( 0.64 cm2) was plotted versus time ( hours) on a linear scale. The linear portion of this plot, containing a minimum of three data points, represents steady state penetration. The slope of this portion of the line was the test material flux ( e. g., pg/ cm%).

Lag time, a measure of the amount of time required for a chemical to penetrate through the skin membrane and enter the receptor fluid, was determined by back extrapolation of the steady state penetration line with the x axis.

The permeability coefficient ( Kp) was calculated by dividing the flux at steady statepenetration ( e. g., pg/ crn2/ h) by the concentration of the applied dose ( e. g., pg/ cm3).

M. Statistical Analyses Group data was represented at Mean . c SD. The statistical significance of the Kp results was assessed by the Student s T test using Microcalm OriginTM, version 7.0 ( OriginLab Corporation, Northampton, MA). A p value of 50.05 was considered significant.

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I Dibasic Esters: In Vitro Dermal Permeability . CoeEcients ( Kp) in Rat and Human Skin DuPont 5295 RESULTS AND DISCUSSION A. Permeability parameters for individual DBE homologues ( Table 1, Figure 1)

Key observations of mean data:

Following application of the individual DBE homologues ( DMS, DMG, and DMA), the penetration rates for each homologue were comparable within a species and ranged from 3131.8 to 4542.4 pg/ cm2/ hfor rat skin and from 79.5 to 113.0 pg/ cm2/ hfor human skin.

At steady state, the penetration rates were noted to be faster through rat skin compared to human skin for each individual DBE homologue.

Lag times, a measure of the amount time required for the DBE homologue to cross the skin, were ~ 0.0 1 hours and 0.26 0.64 hours for rat and human skin, respectively.

Permeability coefficient ( Kp) values ( penetration rate data normalized for the applied concentration of the DBE homologue) for rat and human skin ranged from 2.98 x to 4.18 x lo  cdh and from 7.56 x lo  to 1.02 x respectively. The individual DBE homologues penetrated through rat skin 34.2 to 43.9 fold faster than through human skin.

B. Permeability parameters for the DBE homologues in the 1: 3: 1 ( DMS: DMG: DMA) blend ( Table 2, Figure 2)

Key observationsof mean data:

Following application of the DBE blend to rat skin, the penetration rate for DMG ( 1571. O pg/ cm2/ h) was approximately 3 fold faster than the rate observed for DMS ( 571.7 pg/ cm*/ h) and DMA ( 507.0 pg/ cm2/ h).

As was observed for rat skin, the penetration rate for DMG through human skin ( 108.7 pg/ cm2/ h) was faster compared to the rate observed for DMS ( 24.2 pg/ cm2/ h) and DMA ( 16.3 pg/ cmZ/ h).

At steady state, the penetration rates for each DBE homologue from the 1: 3: 1 blend were noted to be faster through rat skin compared to human skin.

The rate of penetration for the DBE homologues from the 1: 3: 1 blend were slower compared to rates observed following application of the individual dibasic ester homologues alone ( with the exception of DMG for human skin).

Lag times, a measure of the amount time required for the DBE homologue to cross the skin, were 0.12 to 0.15 hours and 0.09 to 0.28 hours for rat and human skin, respectively. Diba6ic Esters: In Vitro Dermal Permeability   Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Permeability coefficient ( Kp) values ( penetration rate data normalized for the applied concentration of the DBE homologue) for rat and human skin ranged from 2.12 x to 2.79 x cdh and from 6.81 x lo  to 1.69 x lo4 cdh, respectively. The DBE homologues penetrated through rat skin 14.5 to 31.1 fold faster than through human skin.

C. Comparison of permeability coefficient ( Kp) data within a species ( Figures 3 4)

Whether the dibasic ester of interest was applied alone as a single solvent system or as part of the 1: 3: 1 @ MS: DMG: DMA) blend, the permeability coefficients for DMS, DMG, and DMA were comparable within a species and were higher for rat skin compared to human skin.

CONCLUSIONS Following application of the individual dibasic ester homologues DMS, DMG, and DMA to rat and human skin, the penetration rates for each homologue were comparable within a species and ranged from 3131.8 to 4542.4 pg/ cm2/ hfor rat skin and from 79.5 to 113.0 pg/ cm*/ hfor human skin. In contrast, when the DBE blend containing DMS, DMG, and DMA in a nominal ratio of 1: 3: 1 ( v/ v) was applied to rat skin, the penetration rate for DMS ( 571.7 pg/ cm2/ h), DMG ( 1571 pglcm lh), and DMA ( 507.0 pg/ cm*/ h) was slower compared to the penetration rates observed when the individual homologues were applied alone as a single solvent system. The rate of DMG penetration from the blend was approximately 3 fold faster compared to DMS and DMA, owing to its concentration as penetration is passive and concentration dependent.

As was observed for rat skin, the penetration rate for DMG through human skin from the homologue blend ( 108.7 pg/ cm2/ h) was faster compared to DMS ( 24.2 pg/ cm2/ h) and DMA ( 16.3 pg/ cm2/ h). With the exception of DMG, the penetration rates for DMS and DMA were slower as measured from the blended solvent system compared to the penetration rates observed when each homologue was applied alone to human skin.

Overall, and exclusive of whether the DBE homologue was applied alone or as part of the blended formulation, lag times, a measure of the time required for the DBE homologue to cross the skin and appear in the receptor fluid, were shorter for rat skin ( SO. 15 hours) than for human skin ( 50.64 hours).

The permeability coefficients ( Kp), whether the DBE homologue was applied alone or as part of the 1: 3: 1 blend, were comparable for each homologue within a species and higher for rat skin compared to human skin. The Kp values for rat and human skin ranged from 2.12 x to 4.18 x lo3 cdh and from 6.81 x to 1.69 x respectively.

The results from these in vitro dermal kinetic experiments show that DMS, DMG, and DMA penetrated through rat skin faster and with a shorter lag time than was observed for human skin. The data also show that the permeability coefficient was comparable for each dibasic ester homologue within a species and exclusive of whether the DBE of interest was applied alone as a single solvent system or as part of the 1: 3: 1 ( DMS: DMG: DMA) blend.

 22  Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 The permeability coefficient, which serves to describe the movement or flux of a chemical through skin and principally the stratum corneunt, normalized for concentration and expressed as a depth of diffusion per unit of time, provides a basis for comparison with other industrial solvents and is useful in estimating absorbed dose followingdermal exposure.

RECORDS AND SAMPLE STORAGE All data and records for analytical characterizationsconducted by the sponsor will be archived by the sponsor. Laboratory specific or site specific raw data, such as personnel files and equipment records will be retained by the facility where the work was done.

A sample of each test substance will be collected for archive purposes and retained at HaskelI Laboratory, Newark, Delaware. Specimens ( if applicable), raw data, and the final report will be retained at Haskell Laboratory, Newark, Delaware, or at Iron Mountain Records Management, Wilmington, Delaware.

REFERENCES 1. Roberts MS and Walters KA ( 1998). The RelationshipBetween Structure and Barrier Function of Skin. In: Dermal Absorption and Toxicity Assessment, Vol91, Edited by MS Roberts and KA Walters, pp 1 42. Marcel Dekker, Inc., New York, NY.

2. Potts RO and Guy RH ( 1994). Drug Transport Across the Skin and the Attainment of Steady StateFlux. Proceedings of the International Symposium on ControlledRelease of Bioactive Materials 21, 162 163.

3. OECD Guideline for the Testing of Chemicals ( Draft Guideline 428), Skin Absorption: in vitro Method ( 2002).

4. Fasano WJ, Manning LA, and Green JW( 2002). Rapid Integrity Assessmentof Rat and Human Epidermal Membranes for In Vitro Dermal Regulatory Testing: Correlation of Electrical Resistance with Tritiated Water Permeability. Toxicology In Vitro 16,731 740.

 23  Dibasic Esters: In Vim DermaI Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 TABLES  24 Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 TABLES EXPLANATORY NOTES ABBREVIATIONS:

DBE dibasic esters DMS dimethyl succinate DMG dimethyl glutarate DMA dimethyl adipate h hour( s) SD standard deviation Dibasic Esters: in Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Table 1: Permeability parameters for individual DBE homologues Rat DMS DMG DMA Mean SD Mean SD Mean SD Penetration rate ( pg/ cm h/ h) 3859.3 1750.6 4542.4 235I .4 3131.8 1414.1 Lag time ( h)  0.40 1.51  2.79 3.34  1.12 2.04 Permeability coefficient, KP ( cmW 3.47x IO3 1.57x lo3* 4.18x IO  2.16x IO3* 2.98x lo3 1.34x lW3*

Human DMS DMG DMA Mean SD Mean SD Mean SD Penetration rate ( pg/ cm*/ h) 113.0 39.1 103.5 44.0 79.5 35.6 Lag time ( h) 0.26 0.48 0.64 0.22 0.60 0.40 Permeability coefficient. KP ( c&) 1.02 ioJ 3.52 9.53 4.05 7.56 10 ~ 3.39 Ratio: Rat Kp f Human Kp 34.2 43.9 39.4 * Kp values within a species were not statistically different from one another ( p > 0.05). Kp values for each homologue between species were statistically different from one another ( p < 0.05).

 26 Dibasic Esters: In Vitro Dermal Permeability  Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Table 2: Permeability parameters for DBE homologues in the 1: 3: 1 blend @ MS: DMG: DMA)

Penetration rate ( clglcm2/ h)

. Lagtime ( h)

Permeability coefficient, KP ( c&)

Penetration rate ( ps/ cmz/ h)

Lag time ( h)

Permeability coefficient, KP ( Ch)

Ratio: Rat Kp I Human Kp Rat DMS DMG DMA Mean SD Mean SD Mean SD 571.7 203.0 1571.0 541.0 507.0 205.0 0.15 0.47 0.12 0.44 0.12 0.53 2.79x lW3 9.91x lo4* 2.44x 8.41 x IO+ 2.12 103 8.56 104*

Human DMS DMG DMA Mean SD Mean SD Mean SD 24.2 14.3 108.7 59.6 16.3 7.73 0.28 0.35 0.09 0.22 0.28 0.34 1.18x 10' 6.99x lUs* 1.69x 10* 9.27x lo"* 6.81x lo5 3.23x lo'*

23.6 14.5 31.1 * Kp values within a species were not statistically different from one another ( p> 0.05). Kp values for each homologue between species were statistically different from one another ( p c0.05).

 27 Dibasic Esters: In Vitro Dermal Permeability Coefficients ( KD) in Rat and Human Skin DuPont 5295 FIGURES  28  Dibaiic Esters: In VitroDermal Permeability   Coefficients ( Kp) in Rat and Human Skin DuPont 5295 EXPLANATORY NOTES ABBREVIATIONS:

DBE dibasic esters DMS dimethyl succinate DMG dimethyl glutarate DMA dimethyl adipate  29 Dibasic Esters: In VitroDermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Figure 1: Individual DBE homologues comparison of permeability coefficients ( Kp) for rat and human skin 7. OOE 03 6.00E 03 T 5.00E 03 4. O0E 03 0 Y 2 3.00E 03 2.00E 03 1.00E 03 O. OOE+ OO DMS DMG DMA

30il i . Dibasic Esters: In Vitro Dermal Permeability . Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Figure 2: DBE 1: 3: 1 ( DMS: DMG: DMA) blend  comparison of permeability coefficients 2.50E 03 Ih 2 2.00E

03c 1 0Rat v 69Humany" 150E 03 t 5.00E 04 DMS DMG DMA  31  a.

Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Figure 3: A comparison of permeability coefficients ( Kp) for the individual DBE homologues and the homologues in the 1: 3: 1 ( DMS: DMG: DMA) blend for rat skin 7.00E 03 6. OOE 03 5.00E 03 4.00E 03 5 v 6 @ 3. OOE 03 2. OOE 03 1.00E 03 O. OOE+ OO I l r IT I 0 Individual DMS DMG DM4 Kp values were not statistically different from one another ( p > 0.05)

 32

I/ I Dibasic Esters: In Vitro Dermal Permeability . Coefficients( Kp) in Rat and Human Skin DuPont 5295 Figure 4: A comparison of permeability coefficients ( Kp) for the individual DBE homologues and the homologues in the 1: 3: 1 @ MS: DMG: DMA) blend for human skin  2.5OE 04 2.00E 04 A f 0Individual v 1.50E 04 2 1.00E 04 5.00E 05 0.00E+ 00 DMS DMG DMA Kp values were not statistically different from one another ( p > 0.05)

 33

P Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin DuPont 5295 APPENDICES  34  , . i . Dibasic Esters: In Vitro Dermal Permeability . Coefficients ( Kp) in Rat and Human Skin DuPont 5295 APPENDICES EXPLANATORY NOTES ABBREVIATIONS:

DBE dibasic esters DMS dimethyl succinate DMG dimethyl glutarate DMA dimethyl adipate h hour( s) SD standard deviation  3s  1'

Dibasic Esters: Zn Vitro Dermal Permeability Coefficients( Kp) in Rat and Human Skin DuPont 5295 Appendix A Permeability parameters for the individual DBE homologues  individual data for DMS, DMG, and DMA when applied to rat and human skin  36 I Dibasic Esters: In Vitro Dermal Permeability Coefficients( Kp) in Rat and Human Skin Protocol group Species Test Material Cell ID cell 1 cell 2 cell 3 cell 5 cell 6 cell 7 Protocolgroup Species Test Material Cell ID cell 8 cell 9 cell 11 cell 12 cell 13 cell 14 Protocolgroup Species Test Material Cell ID cell 1 cell 3 cell 4 cell 5 cell 6 cell 7 DMS Specimen ID 659693 659694 659695 659697 659693 659694 Mean SD DMG Specimen ID 659693 659696 659693 659694 659695 659696 Mean SD DMA Specimen ID 659693 659694 659694 659693 659697 659696 Mean SD Penetrationrate ( ug/ cm2/ h) 1719.5 6169.1 5236.5 3579.8 2078.6 4372.7 3859.3 1750.6 Penetration rate ( ug/ cm2/ h) 1943.6 8136.2 1972.4 5030.6 4565.0 5606.6 4542.4 2351.4 Penetration rate ( ug/ cm2/ h) 1577.8 2603.0 4124.6 1509.0 4S36.0 4440.6 3131.8 1414.1 DuPont S295 KP Lag time ( crnlh) ( h) 1.55E 03 0.17 5.55 E 03 0.69 4.71 E 03  2.64 3.22E 03  1.95 1.87E 03 0.35 3.93E 03 0.97 3.47E 03  0.40 1.57E 03 1.51 KP Lag time ( cmlh) ( h) 1.79E 03 0.23 7.49503  5.74 1.82E 03 0.17 4.63E 03 0.35 4.20E 03  6.15 5.16E 03  5.62 4.18E 03  2.79 2.16E 03 3.34 KP Lagtime ( cm/ h) ( h) 1.50E 03 0.18 2.48E 03 0.71 3.92 E 03  2.42 1.44E 03 0.44 4.31 E 03  1.07 4.22E 03  4.55 2.98E 03  1.12 1.34E 03 2.04  37  Dibasic Esters: In VimDermal Permeability Coefficients ( Kp) in Rat and Human Skin  r

Test Material Cell ID cell 1 cell 2 cell 3 cell 5 cell 6 cell 7 Protocolgroup Test Material Cell ID cell 8 cell 9 cell 11 cell 12 cell 13 cell 14 DMS 1 Specimen ID HCMT 24A HCFT 25A HCFT 26A HCFT 28A HCMT 24A HCFT 25A Mean SD Specimen ID HCFTP6A HCMT 27A HCMT 24A HCFT 25A HCFT 26A HCMT 27A Mean so Penetration rate ( ug/ cm2/ h) 86.9 104.1 175.5 136.7 63.9 110.7 113.0 39.1 Penetration rate ( ug/ cm2/ h) 109.6 69.2 3024.6 85.5 177.2 76.1 103.5 44.0 DuPont 5295 KP Lag time ( cm/ h) ( h) 7.82E 05  0.56 9.36E 05 0.34 1.58E 04 0.76 1.23E 04 0.04 5.75E 05 0.31 9.96E 05 0.68 1.02E 04 0.26 3.52E 05 0.48 KP Lag time ( cm/ h) ( h) 1.01E 04 0.61 6.36E 05 0.78 2.78E 03  4.21 7.86E 05 0.35 1.63E 04 0.92 7.01E 05 0.52 9.53E 05 0.64 4.05E 05 0.22 Note: Cell 11 excluded from calculations of mean and SD as it was not representative Protocolgroup Test Material Penetration rate KP Lagtime Cell ID cell 1 cell 2 cell 3 cell 4 cell 6 cell 7 Specimen ID HCMT 24A HCFT 25A HCFT 26A HCMT 27A HCFT 25A HCFT 26A Mean SD ( ug/ cm*/ h) ( cmh) ( h) 69.5 6.61E 05 0.27 56.7 5.39E 05 0.65 115.5 1.1OE 04 0.38 116.6 1.11E 04 1.36 26.0 2.47E 05 0.40 93.1 8.85E 05 0.52 79.5 7.56E 05 0.60 35.6 3.39E 05 0.40  38  Dibasic Esters: In VitroDermal Permeability ~

Coefficients ( Kp) in Rat and Human Skin DuPont 5295 Appendix B Permeability parameters for the individual DBE homologues in the 1: 3: 1 ( DMS: DMG: DMA) blend  individual data for DMS, DMG, and DMA when applied to rat and human skin  39 Dibasic Esters: In Vitro Dermal Permeability Coefficients ( Kp) in Rat and Human Skin Protocol group Species Test Material Cell ID cell 8 cell 9 cell 10 cell 11 cell 13 cell 14 Protocol group Species Test Material Cell ID cell 8 cell 9 cell 10 cell 11 cell 13 cell 14 Protocol group Species Test Material Cell ID cell 8 cell 9 cell 10 cell 11 cell 13 cell 14 DMS Specimen ID 659693 659694 659693 659694 659696 659694 Mean SD DMG Specimen IO 659693 659694 659693 659694 659696 659694 Mean SD DMA Specimen ID 659693 659694 659693 659694 659696 659694 Mean SD Penetration rate ( ug/ cm*/ h) 358.9 865.2 326.8 604.6 588.2 686.8 571.7 203.0 Penetration rate ( ug/ cm2/ h) 1055.1 2323.7 846.0 1620.6 1733.0 1847.5 1571. O 541. O Penetration rate ( ug/ cm2h) 305.9 813.8 248.6 531.2 567.7 574.4 507.0 205.0 DuPont 5295 KP Lag time ( cmh) ( h) 1.75E 03 0.23 4.22E 03  0.37 1.59E 03 0.66 2.95E 03 0.10 2.87E 03 '  0.39 3.35E 03 0.68 2.79E 03 0.15 9.91E 04 0.47 KP Lagtime !

( cmh) ( h) 1.64E 03 0.24 t:

3.61E 03  0.38 1.31E 03 0.56 2.52E 03 0.08 2.69E 03  0.38 2.87E 03 0.62 2.44E 03 0.12 8.41E 04 0.44 KP Lag time

( Cmlh) ( h) 1.28E 03 0.29 3.40E 03  0.54 1.04E 03 0.52 2.22E 03 0.1 1 2.37E 03  0.45 2.40E 03 0.79 2.1 2E 03 0.12 8.56E 04 0.53  40 Protocol group Test Material Dibqsic Esters: In VitroDermal Permeability Coefficients ( Kp) in Rat and Human Skin Protocolgroup Test Material Cell ID Specimen ID cell 8 HCMT 27 A cell 10 HCFT 25A cell 11 HCFT 26A cell 12 HCMT 27A cell 13 HCFT 28A cell 14 HCFT 25A Mean SD Protocol group Test Material Cell ID Specimen ID cell 8 HCMT 27 A cell 10 HCFT 25A cell 11 HCFT 26A cell 12 HCMT 27A cell 13 HCFT 28A cell 14 HCFT 25A Mean SD Protocolgroup Species=] s peciesl 1 Cell ID Specimen ID cell 8 HCMT 27 A cell 10 HCFT 25A cell 11 HCFT 26A cell 12 HCMT 27A cell 13 HCFT 28A cell 14 HCFT 25A Mean SD Penetration rate ( ug/ cm2/ h) 25.2 15.1 34.9 11.8 46.7 11.4 24.2 14.3

Penetration rate ( ug/ cm2/ h) 129.7 37.1 145.7 56.5 196.2 87.2 108.7 59.6 Penetrationrate ( ug/ cm2/ h) 18.8 9.92 21.3 10.9 28.1 8.73 16.3 7.73 DuPont 5295 KP Lag time ( cm/ h) ( h) 1.23E 04 0.60 7.39E 05 0.18 1.70E 04 0.50 5.74 E 05 0.62 2,28504 '  0.25 5.55E 05 0.04 1. I 8E 04 0.28 6.99 E 05 0.35 KP Lag time ( cmlh) ( h) 2.02 E 04 0.24 5.76E 05 0.26 2.26E 04 0.19 8.78 E 05 0.25 3.05E 04  0.24 1.35E 04  0.13 1.69E 04 0.09 9.27E 05 0.22 KP Lag time ( cm/ h) ( h) 7.86E 05 0.58 4.14E 05 0.22 8.92 E 05 0.50 4.55E 05 0.51 1.17E 04  0.32 3.65 E 05 0.21 6.81 E 05 0.28 3.23E 05 0.34  41


 1 III. HOW TO IDENTIFY SOURCES " SUBJECT TO BART"

Once you have compiled your list of BART eligible sources,

you need to determine whether ( 1) to make BART determinations for all of them or ( 2) to consider exempting some of them from BART because they may not cause or contribute to any visibility impairment in a Class I area. If you decide to make BART determinations for all the BART eligible sources on your list ( i. e., that all of them should be " subject to BART"), you should make those determinations by applying the five statutory factors discussed in Section IV below.

On the other hand, you may want to conduct further analysis to determine whether and the degree to which a particular BARTeligible source or group of sources contributes to visibility impairment in nearby Class I areas. If your analysis, or analysis submitted by the source, shows that an individual source or group of sources ( or certain pollutants from those sources)

cannot reasonably be anticipated to cause or contribute to any visibility impairment in a Class I area, then you do not need to make BART determinations for that source or group of sources ( or for certain pollutants from those sources). In such a case, the source is not " subject to BART" and you do not need to apply the five statutory factors to make a BART determination.

This section briefly discusses the factors you should consider in deciding whether to make BART determinations for all 2 your BART eligible sources. It then discusses several approaches that you can use to exempt sources from BART even though they are BART eligible.

A. What Factors Should I Consider in Deciding Whether All BARTEligible Sources Should be Subject to BART?

States have considerable discretion in making BART determinations and in determining which sources should be subject to BART. In exercising this discretion, you may want to consider all your state's air quality planning needs, including the need to meet the national ambient air quality standards ( NAAQS) for ozone and PM2.5. The pollutants that are primarily responsible for visibility impairment ( SO2, NOX, and PM) are also the primary contributors to PM2.5 nonattainment. In addition, NOX is an ozone precursor that, in most areas, needs to be controlled during the ozone season to reduce the formation of ground level ozone. You may not want to invest significant resources in conducting visibility analysis for individual BART eligible sources if your state is likely to control SO2, NOX, or PM from those same sources in order to meet its attainment needs.

On the other hand, if there are not PM2.5 or ozone nonattainment areas in your state or in nearby states, then you may want to consider various approaches that would allow you to determine that your BART eligible sources cannot reasonably be anticipated to contribute to visibility impairment in any Class I 3 area. In particular, if most of your sources are relatively small NOX only sources that are located relatively far away from Class I areas, you should consider the approaches discussed below that would allow you to find that individual sources or groups of sources are not subject to BART.

B. What Steps Do I Follow to Determine Whether A Source or Group of Sources Cause or Contribute to Visibility Impairment for Purposes of BART?

1. How Do I Establish a Threshold?

One of the first steps in determining whether sources cause or contribute to visibility impairment for purposes of BART is to establish a threshold ( measured in deciviews) against which to measure the visibility impact of one or more sources. A single source that is responsible for a 1.0 deciview change or more should be considered to " cause" visibility impairment; a source that causes less than a 1.0 deciview change can still contribute to visibility impairment and thus be subject to BART.

Because of varying circumstances affecting different Class I areas, the appropriate threshold for determining whether a source " contributes to any visibility impairment" for the purposes of BART may reasonably differ across States. As a general matter,

any threshold that you use should not be higher than 0.5 deciviews, and could be as low as 0.1 deciviews or less.

In setting a threshold for " contribution," you should 1 We expect that regional planning organizations will have modeling information that identifies sources affecting visibility in individual class I areas, and the magnitude of their impacts.

4 consider the number of emissions sources affecting the Class I areas at issue and the magnitude of the individual sources'

impacts. 1 In general, a larger number of sources causing impacts in a class I area would warrant a lower contribution threshold.

Depending on the circumstances and number of sources affecting a Class I area and their modeled impacts, you should consider a threshold captures the BART eligible sources responsible for the vast majority of the total visibility impacts from such sources,

while still excluding other sources with relatively small impacts.

2. What Pollutants Do I Need to Consider?

You must look at SO2, NOx, and PM10 and PM2.5 emissions in determining whether sources cause or contribute to visibility impairment. Consistent with the approach for identifying your BART eligible sources, you do not need to consider less than de minimis emissions of these pollutants from a source.

As explained in Section II, you must use your best judgement to determine whether VOC or ammonia emissions are likely to have an impact on visibility in an area. In addition, you may use PM10 as an indicator for particulate matter in determining whether a source is BART eligible. In determining whether a 5 source contributes to visibility impairment, however, you should distinguish between the fine and coarse particle components of direct particulate emissions. Although both fine and coarse particulate matter contribute to visibility impairment, the longrange transport of fine particles is of particular concern in the formation of regional haze. Air quality modeling results used in the BART determination will provide a more accurate prediction of a source's impact on visibility if the inputs into the model account for the relative particle size of any directly emitted particulate matter ( i. e. PM10 vs. PM2.5).

3. What Kind of Modeling Should I Conduct to Determine Which Sources and Pollutants Need Not Be Subject to BART?

This section presents several options for determining that certain sources need not be subject to BART. These options rely on different modeling and/ or emissions analysis approaches. They are provided for your guidance. You may also use other reasonable approaches for analyzing the visibility impacts of an individual source or group of sources.

Option 1: Individual Source Attribution Approach ( Dispersion Modeling)

You can use dispersion modeling to determine that an individual source cannot reasonably be anticipated to cause or contribute to visibility impairment in a Class I area and thus is not subject to BART. You can conduct this modeling yourself or 2 In determining whether sources of particulate matter are subject to BART, you should try to estimate the PM2.5 fraction of direct particulate emissions as correctly as possible. This is because, as discussed in section II. A. 3. above, long range transport of fine particles is of particular concern in the formation of regional haze, and because we believe that air quality modeling results will be more meaningful if your inputs account for the relative particle size of directly emitted particulate matter ( e. g. PM10 vs. PM2.5).

3 The model code and its documentation are available at no cost for download from http:// www. epa. gov/ scram001/ tt22. htm# calpuff.

6 allow the submission of modeling from an outside expert. Under this option, you can analyze an individual source's impact on visibility as a result of its emissions of SO2, NOx and direct particulate matter emissions ( PM10 and PM2.5) 2 Dispersion modeling cannot currently be used to estimate the predicted impacts on visibility from an individual source's emissions of VOC or ammonia. You may use a more qualitative assessment to determine on a case by case basis which sources of VOC or ammonia emissions may be likely to impair visibility and should therefore be subject to BART review, as explained in section II. A. 3. above.

You can use CALPUFF3, or another EPA approved model, to predict the visibility impacts from a single source at a Class I area. CALPUFF is the best regulatory modeling application currently available for predicting a single source's contribution to visibility impairment and is currently the only EPA approved model for use in estimating single source pollutant 4 The Guideline on Air Quality Models addresses the regulatory application of air quality models for assessing criteria pollutants under the CAA, and describes further the procedures for using the CALPUFF model, as well as for obtaining approval for the use of other, nonguideline models.

7 concentrations resulting from the long range transport of primary pollutants. 4 It can also be used for some other purposes, such as the visibility assessments addressed in today's rule, to account for the chemical transformation of SO2 and NOx.

There are several steps for making an individual source attribution using a dispersion model:

a. Submit a modeling protocol to EPA.

If you are doing the modeling, you should submit a modeling protocol to EPA in advance so that any issues can be discussed before you run the models. Similarly, if you are allowing the source owner or operator to do the modeling, it should prepare and submit a modeling protocol in advance to assure that relevant technical issues are addressed up front.

Some critical items to include in the protocol are the meteorological and terrain data that will be used, as well as the source specific information ( stack height, temperature, exit velocity, elevation, and emission rates of applicable pollutants), and receptor data from appropriate Class I areas.

We recommend following EPA's Interagency Workgroup on Air Quality Modeling ( IWAQM) Phase 2 Summary Report and Recommendations for 5 Interagency Workgroup on Air Quality Modelig ( IWAQM) Phase 2 Summary Report and Recommendations for Modeling Long Range Transport Impacts, U. S. Environmental Protection Agency, EPA 454/ R 98 019, December 1998.

8 Modeling Long Range Transport Impacts5 for parameter settings and meteorological data inputs. You may use other settings from those in IWAQM, but you should identify these settings and explain your selection of these settings.

One important element of the protocol is in establishing the receptors that will be used in the model. The receptors that you use should be located in the nearest Class I area with sufficient density to identify the maximum impact of the source. ( In general, one kilometer spacing should be used.) For other Class I areas in relatively close proximity to a BART eligible source,

you may model a few strategic receptors to determine whether impacts at those areas may be greater than at the nearest Class I area. For example, you might chose to locate receptors at these areas at the closest point to the source, at the highest and lowest elevation in the Class I area, at the IMPROVE monitor, and at the approximate expected plume release height. If the highest modeled impacts are observed at the nearest Class I area, you may choose not to analyze the other Class I areas any further, as additional analyses might be unwarranted. In any event, a full field of receptors should be modeled for the Class I area with the highest impact. 9 You should bear in mind that some receptors within the relevant Class I area may be less than 50 km from the source while other receptors within that same Class I area may be greater than 50 km from the same source. As indicated by the Guideline on Air Quality Models, this situation may call for the use of two different modeling approaches for the same Class I area and source, depending upon the State's chosen method for modeling sources less than 50 km. In situations where you are assessing visibility impacts for source receptor distances less than 50 km, you should use expert modeling judgment in determining visibility impacts, giving consideration to both CALPUFF and other EPA approved methods.

b. Run the model in accordance with the accepted protocol and compare the predicted visibility impacts with your threshold for " contribution."

You should calculate daily visibility values for each receptor as the change in deciviews compared against natural visibility conditions. You can use EPA's " Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule," EPA 454/ B 03 005 ( September 2003) in making this calculation. To determine whether a source may reasonably be anticipated to cause or contribute to visibility impairment at Class I area, you then compare the impacts predicted by the model against the threshold that you have selected. 10 In making this comparison, you should note that the modeling approach we recommend includes several features that likely understate the potential visibility impacts of the source being modeled. The emissions estimates used in the models are intended to reflect steady state operating conditions during periods of high capacity utilization. We do not generally recommend that emissions reflecting periods of start up, shutdown, and malfunction be used, as such emission rates could produce higher than normal impacts than would be typical of most facilities. In addition, the monthly average relative humidity is used, rather than the daily average humidity   an approach that effectively lowers the peak values in daily model averages.

For these reasons, if you use the modeling approach we recommend, you should compare your " contribution" threshold against either the maximum daily value or the 99th percentile of values. Comparing values to the 99th percentile of values effectively excludes approximately 4 days per year, or 18 20 days in any 5 year period, with the worst visibility. Such an approach affords added protection against the possibility that poor visibility might be caused by unusual meteorology and thus,

in our view, represents a reasonable lower bound for comparison.

If the maximum daily visibility value or the 99th percentile value from your modeling is less than your threshold, then you may conclude that the source does not contribute to visibility 11 impairment and is not subject to BART.

You may wish to use another reasonable approach, such as use of the maximum 24 hr potential emission rate of the source and more realistic assumptions regarding meteorology ( e. g. daily relative humidity values rather than a 30 day average), comparing results to some other value than the maximum 24 hour visibility value or 99th percentile. If so, you must consult with EPA,

providing specific facts supporting any alternative approach.

Option 2: Use of Model Plants to Exempt Individual Sources with Common Characteristics.

Under this option, analysis of model plants could be used to exempt certain BART eligible sources that share specific characteristics. It may be most useful to use this type of analysis to identify the types of small sources that do not cause or contribute to visibility impairment for purposes of BART, and thus should not be subject to a BART review. Due to the unique characteristics of different Class I areas, you should use special care to ensure that the criteria you develop are appropriate for all applicable cases.

In carrying out this approach, you could use modeling analyses of representative plants to sort specific sources with important common characteristics. Based on these analyses, you may find that certain types of sources are reasonably anticipated to cause or contribute to visibility impairment. You 6 [ insert reference to Mark's docket memo]

12 could then choose to categorically require those types of sources to undergo a BART determination. Conversely, you may find based on representative plant analyses that certain types of sources are clearly not reasonably anticipated to cause or contribute to visibility impairment. To do this, you should conduct your own modeling to establish emission levels and distances from Class I areas on which you can rely to exempt sources with those characteristics. For example, based on your modeling you might choose to exempt all NOx only sources that emit less than a certain amount per year ( such as 500 tons), and which are located a certain distance from a Class I area ( such as 100 kilometers).

You could then choose to categorically exempt such sources from BART. In designing your analyses, you should ensure that all sources of that type would not contribute any more to visibility impairment than the modeled representative facility. In doing such, you should also consider the number of sources with these characteristics contributing to visibility impairment in your State.

Our analyses of visibility impacts from model plants provide a useful example of the type of analyses that might be used to exempt categories of sources from BART. 6 In our analysis, we developed model plants ( EGUs and non EGUs), with representative plume and stack characteristics, for use in considering the 13 visibility impact from emission sources of different sizes and compositions at distances of 50, 100 and 200 kilometers from two hypothetical Class I areas ( one in the East and one in the West).

Since the plume and stack characteristics of these model plants were developed considering the broad range of sources within the EGU and non EGU categories, they do not necessarily represent any specific plant in the United States. However, the results of these analyses may be instructive in the development of an exemption process for any Class I area.

In our analyses, for example, a larger EGU in the eastern domain ( see Run # 9 in the example runs where the SO2 emission rate is 30,000 TPY and NOx is 10,000 TPY) would almost certainly contribute to visibility impairment and should be subject to BART. On the other hand, a representative EGU in the east or west with much lower SO2 emission rates ( well controlled for SO2 for example) may suggest that similar EGUs could be exempt from BART. You should note that the model plants in our analyses that represented industrial boilers or other BART eligible source categories with similar emission profiles to EGUs, in some instances, have comparable or higher visibility impacts than the EGUs ( especially for closer distances to the Class I area  see Runs # 12 and # 13). This may be due to relatively lower stack heights and flow rates.

In a manner similar to these analysis and using information 14 from model plant runs that take into account local, regional, and other relevant factors ( such as meteorology, sulfur dioxide,

nitrogen dioxide, and ammonia), you could compare your sources to the model plants, make appropriate adjustments to account for small differences in emissions and stack parameters, and construct an attribution process to apply to your BART eligible sources. Any State wishing to pursue this approach should discuss it, along with a proposed protocol for modeling, with your appropriate Regional Office before undertaking the exercise.

In preparing our hypothetical examples, we have made a number of assumptions and exercised certain modeling choices;

some of these have a tendency to lend conservatism to the results, overstating the likely impacts, while others may understate the modeling results. On balance, when all of these factors are considered, we believe that our examples reflect realistic treatments of the situations being modeled.

Option 3: Cumulative Modeling to Show that No sources in a State are subject to BART You may also submit to EPA a demonstration, based on an analysis of overall visibility impacts, that the sum of all emissions from BART eligible sources in your State do not cause or contribute to any visibility impairment in a Class I area and thus no source should be subject to BART. You may do this on a pollutant by pollutant basis or for all visibility impairing 15 pollutants to determine if emissions from these sources contribute to visibility impairment.

For example, emissions of SO2 from your BART eligible sources may clearly cause or contribute to visibility impairment,

while direct emissions of PM2.5 from these sources may not contribute to impairment. If you can make such a demonstration,

then you may reasonably conclude that none of your BART eligible sources are subject to BART for a particular pollutant or pollutants. As noted above, your demonstration should take into account the interactions among pollutants and their resulting impacts on visibility before making any pollutant specific determinations.

Analyses may be conducted using several alternative modeling approaches. First, you may use the CALPUFF or another EPAapproved model as described in Option 1 to evaluate the impacts of individual sources on downwind Class I areas, aggregating those impacts to determine the collective contribution of all BART eligible sources to visibility impairment. You may also use a photochemical grid model. As a general matter, the larger the number of sources being modeled, the more appropriate it may be to use a photochemical grid model. However, because such models are significantly less sensitive than dispersion models to the contributions of one or a few sources, as well as to the interactions among sources that are widely distributed 16 geographically, if you wish to use a grid model, you should consult with the appropriate EPA Regional Office to develop an appropriate modeling protocol.


[Federal Register Volume 77, Number 18 (Friday, January 27, 2012)]
[Rules and Regulations]
[Pages 4219-4220]
[FR Doc No: 2012-1830]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 121

[Docket No. FAA-2011-1343; Amdt. No. 121-358]

FAA-Approved Portable Oxygen Concentrators; Technical Amendment

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; technical amendment.

-----------------------------------------------------------------------

SUMMARY: The FAA is amending regulations relating to operating rules
for FAA approved portable oxygen concentrators (POC) onboard aircraft.
This document updates the names of two manufacturers of approved POCs
listed in the Special Federal Aviation Regulation (SFAR).

DATES: Effective January 27, 2012.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning
this action, contact DK Deaderick, Air Transportation Division, AFS-
200, Federal Aviation Administration, 800 Independence Avenue SW.,
Washington, DC 20591; telephone:<PHONE_NUMBER>; email:
<EMAIL_ADDRESS>For legal questions concerning this action,
contact Alex Zektser, AGC-220, Office of Chief Counsel, Regulations
Division, Federal Aviation Administration, 800 Independence Avenue SW.,
Washington, DC 20591; telephone<PHONE_NUMBER>; email:
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Background

    On July 12, 2005, the FAA published SFAR 106, ``Use of Certain
Portable Oxygen Concentrator Devices Onboard Aircraft'' (70 FR 40156).
SFAR 106 permits passengers to carry on and use certain small portable
oxygen concentrators (POCs) on board aircraft if the operator ensures
compliance with conditions specified in the SFAR. Some of the devices
determined acceptable for use in SFAR 106 are Delphi Medical Systems'
RS-00400 (added to the SFAR in 74 FR 2351) and International Biophysics
Corporation's LifeChoice (added to the SFAR in 75 FR 739).
    As a result of business changes that took place after SFAR 106 was
published, the LifeChoice POC is now manufactured by Inova Labs, Inc.
and not by the International Biophysics Corporation. Similarly, the RS-
00400 POC is now manufactured by Oxus, Inc. and not by Delphi Medical
Systems.
    The two companies currently manufacturing these POCs have
petitioned the FAA to amend SFAR 106, Section 2 and section 3(a), of
Title 14, Code of Federal Regulations (14 CFR). This amendment would
update section 2 and section 3(a) of SFAR 106 with the names of the
current manufacturers of the LifeChoice and RS-00400 POCs.

Technical Amendment

    LifeChoice and RS-00400 are still the same products that were
originally approved in SFAR 106--only the names of their manufacturers
have changed. As such, this technical amendment makes two revisions to
the final rule. First, the language in SFAR 106 section 2 and section
3(a) is revised to refer to LifeChoice as being manufactured by Inova
Labs. Second, the reference to the RS-00400 POC is revised to refer to
this device as being manufactured by Oxus, Inc.
    Because the changes in this technical amendment result in no
substantive change, we find good cause exists under 5 U.S.C. 553(d)(3)
to make the amendment effective in less than 30 days.

List of Subjects in 14 CFR Part 121

    Air carriers, Aircraft, Airmen, Aviation safety, Charter flights,
Safety, Transportation, Air taxis.

The Amendment

    In consideration of the foregoing, the Federal Aviation
Administration amends chapter 1 of title 14, Code of Federal
Regulations as follows:

PART 121--OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL
OPERATIONS

0
1. The authority citation for part 121 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 40119, 41706, 44101, 44701-
44702, 44705, 44709-44711, 44713, 44716-44717, 44722, 46105.

0
2. Amend SFAR 106 by revising sections 2 and 3(a) introductory text to
read as follows:

Special Federal Aviation Regulation 106--Rules for Use of Portable
Oxygen Concentrator Systems On Board Aircraft

* * * * *
    Section 2. Definitions--For the purposes of this SFAR the following
definitions apply: Portable Oxygen Concentrator: Means the AirSep
FreeStyle, AirSep LifeStyle, DeVilbiss Healthcare iGo, Inogen One,
Inogen One G2, Invacare XPO2, Invacare Solo2, Inova Labs LifeChoice,
Oxlife Independence Oxygen Concentrator, Oxus, Inc. RS-00400,
Respironics EverGo, and SeQual Eclipse Portable Oxygen Concentrator
medical device units as long as those medical device units: (1) Do not
contain hazardous materials as determined by the Pipeline and Hazardous
Materials Safety Administration; (2) are also regulated by the Food and
Drug Administration; and (3) assist a user of medical oxygen under a
doctor's care. These units perform by separating oxygen from nitrogen
and other gases contained in ambient air and dispensing it in
concentrated form to the user.
    (a) No person may use and no aircraft operator may allow the use of
any portable oxygen concentrator device, except the AirSep FreeStyle,
AirSep LifeStyle, DeVilbiss Healthcare iGo, Inogen One, Inogen One G2,
Invacare XPO2, Invacare Solo2, Inova Labs LifeChoice, Oxlife
Independence Oxygen Concentrator, Oxus, Inc. RS-00400, Respironics
EverGo, and SeQual Eclipse Portable Oxygen Concentrator units. These
units may be carried on and used by a passenger on board an aircraft
provided the aircraft operator ensures that the following conditions
are satisfied:
* * * * *

    Issued in Washington, DC, on January 20, 2012.
Pamela Hamilton-Powell,
Director, Office of Rulemaking.
[FR Doc. 2012-1830 Filed 1-26-12; 8:45 am]
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[Federal Register: June 4, 2008 (Volume 73, Number 108)]
[Proposed Rules]
[Page 31780-31782]
[DOCID:fr04jn08-8]

=======================================================================
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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0609; Directorate Identifier 2008-SW-24-AD]
RIN 2120-AA64

Airworthiness Directives; Sikorsky Aircraft Corporation Model S-
76A, S-76B, and S-76C Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: This document proposes adopting a new airworthiness directive
(AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-76A, S-76B,
and S-76C helicopters. The AD would require an initial and recurring
inspections of the tail rotor vertical stabilizer aft spar assembly
(aft spar assembly) for a crack, loose or working fasteners, and
corrosion, and, if any are found, further inspections of the vertical
stabilizer forward spar assembly (forward spar assembly). Repairing or
replacing any unairworthy part before further flight would also be
required. The action would also require a recurring track-and-balance
of the tail rotor. Finally, the proposed AD would require installing a
vertical stabilizer modification kit, which would be terminating action
for the requirements of the AD. This proposal is prompted by 26 reports
of fatigue cracks in the aft spar assembly web and outer caps. The
actions specified by the proposed AD are intended to detect and correct
an unbalanced or out-of-track tail rotor, which could lead to increased
vibrations, a fatigue crack, loss of a portion of the vertical
stabilizer and subsequent loss of control of the helicopter.

DATES: Comments must be received on or before August 4, 2008.

ADDRESSES: Use one of the following addresses to submit comments on
this proposed AD:
     Federal eRulemaking Portal: Go to http://
www.regulations.gov. Follow the instructions for submitting comments.
     Fax:<PHONE_NUMBER>.
     Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue, SE., Washington, DC 20590.
     Hand Delivery: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays.
    You may get the service information identified in this proposed AD
from Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical
Support, Mailstop s581a, 6900 Main Street, Stratford, Connecticut
06614, phone<PHONE_NUMBER>, e-mail address<EMAIL_ADDRESS>
FOR FURTHER INFORMATION CONTACT: Richard Noll, Aviation Safety
Engineer, Boston Aircraft Certification Office, 12 New England
Executive Park, Burlington, MA 01803, telephone<PHONE_NUMBER>, fax
(781) 238-7170.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to submit any written data, views, or arguments
regarding this proposed AD. Send your comments to the address listed
under the caption ADDRESSES. Include the docket number ``FAA-2008-0609,
Directorate Identifier 2008-SW-24-AD'' at the beginning of your
comments. We specifically invite comments on the overall regulatory,
economic, environmental, and energy aspects of the proposed AD. We will
consider all comments received by the closing date and may amend the
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://
www.regulations.gov, including any personal information you provide. We

will also post a report summarizing each substantive verbal contact
with FAA personnel concerning this proposed rulemaking. Using the
search function of the docket Web site, you can find and read the
comments to any of our dockets, and if provided, the name of the
individual who sent or signed the comment. You may review the DOT's
complete Privacy Act Statement in the Federal Register published on
April 11, 2000 (65 FR 19477).

Examining the Docket

    You may examine the docket that contains the proposed AD, any
comments, and other information in person at the Docket Operations
office between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays. The Docket Operations office (telephone<PHONE_NUMBER>) is
located in Room W12-140 on the ground floor of the West Building at the
street address stated in the ADDRESSES section. Comments will be
available in the AD docket shortly after receipt.

Discussion

    This document proposes adopting a new AD for Sikorsky Model S-76A,
S-76B, and S-76C helicopters with any of the following part-numbered
aft spar assemblies installed:

------------------------------------------------------------------------
                                                       Aft spar assembly
                  Helicopter model                         part No.
------------------------------------------------------------------------
S-76A...............................................     76201-05002-114
                                                         76201-05002-115
S-76B and S-76C.....................................     76201-05002-047
                                                         76201-05002-048
                                                         76201-25002-041
                                                         76201-25002-044
                                                         76201-25002-045
                                                         76201-25002-046
------------------------------------------------------------------------

    For any aft spar assembly having 1,000 or more hours time-in-
service (TIS), the AD would require, initially and then at intervals
not to exceed 50 hours TIS, inspecting the aft spar assembly for a
crack, a loose or working fastener, or corrosion. If a crack, a loose
or working fastener, or corrosion is found, repairing or replacing any
unairworthy parts and inspecting the forward spar assembly would be
required before further flight. If that inspection reveals a crack, a
loose or working fastener, or corrosion in the forward spar assembly,
then the damage would have to be repaired or the parts would need to be
replaced with airworthy parts before further flight. The AD would also
require a track-and-balance of the tail rotor within 30 days and
thereafter at intervals not to exceed 200 hours TIS. The AD would also
require, on or before December 31, 2010, installing a vertical
stabilizer modification kit, part number (P/N) 76070-20562, 76070-
20563, or 76070-20564, which would be terminating action for the
requirements of the AD.
    This proposal is prompted by 26 reports of fatigue cracks in the
aft spar assembly web and outer caps since February 1998. The actions
specified in this proposed AD are intended to detect and correct an
unbalanced or out-of-track tail rotor, which could lead to increased
vibrations, a fatigue crack, loss of a portion of the vertical
stabilizer and subsequent loss of control of the helicopter.
    We have reviewed the following service information:
     Sikorsky Alert Service Bulletin (ASB) No. 76-55-20A,
Revision A, dated November 11, 2003, that applies to Sikorsky Model S-
76A and Model S-76C helicopters and describes procedures for a one-time
inspection of the vertical stabilizer aft spar assembly for cracks,
loose or working fasteners, and/or corrosion, and if necessary an
inspection of the forward spar assembly.
     ASB No. 76-65-58A, Revision A, dated November 11, 2003,
that applies to all Sikorsky Model S-76 serial numbered helicopters up
to and including 760526 and describes procedures for an initial
enhanced tail rotor balance check.
    This proposal would differ from those ASBs in that the inspections
described in ASB No. 76-55-20A would be required for the Model S-76B
helicopters as well as for the Model S-76A and Model S-76C helicopters.
Also, the proposed AD would require repetitive inspections of the aft
spar assembly and the forward spar assembly, if necessary, and
repetitive tail rotor track-and-balance inspections, whereas the two
ASBs specify only a one-time tail rotor balance check and an aft spar
assembly inspection and, if necessary, a one-time forward spar assembly
inspection.
    This unsafe condition is likely to exist or develop on other
helicopters of the same type designs. Therefore, the proposed AD would
require, for any spar assembly that has 1,000 or more hours TIS, within
30 days and thereafter at intervals not to exceed 50 hours TIS,
inspecting the aft spar assembly, and if you find a crack, a loose or
working fastener, or corrosion, inspecting the forward spar assembly
before further flight and replacing or repairing any unairworthy part
with an airworthy part before further flight.
    The AD would also require, within 30 days and thereafter at
intervals not to exceed 200 hours TIS, inspecting the tail rotor track-
and-balance. Accomplishing the tail rotor track-and-balance inspection
would involve both a pilot and mechanic. The pilot's function would be
to operate the helicopter to a ``light on wheels'' state--almost to the
point of takeoff, and the mechanic would accomplish the vibration
measurements. Also, the AD would require, on or before December 31,
2010, installing a vertical stabilizer modification kit, P/N 76070-
20562, 76070-20563, or 76070-20564, which would be terminating action
for the requirements of the AD. The inspections and repairs or
replacements, if necessary, would have to be accomplished in accordance
with specified portions of the ASBs previously described.
    We estimate that this proposed AD would affect 216 helicopters of
U.S. registry. We also estimate that the inspections for a crack, a
loose or working fastener, or corrosion would take approximately 7 work
hours per helicopter to accomplish; the tail rotor track-and-balance
inspections and adjustments would take approximately 10 work hours per
helicopter; and installing the vertical stabilizer modification kit
would take approximately 120 hours, at an average labor rate of $80 per
work hour. The vertical stabilizer modification kit would cost
approximately $4,250. Based on these figures, we estimate the total
cost impact of this AD on U.S. operators would be $4,961,520, assuming
that, on each helicopter, 12 spar assembly inspections would be done
($1,451,520), that 3 tail rotor track-and-balance inspections would be
done ($518,400), that no spar assembly would need to be repaired or
replaced, and that the vertical stabilizer modification is done.

Regulatory Findings

    We have determined that this proposed AD would not have federalism
implications under Executive Order 13132. Additionally, this proposed
AD would not have a substantial direct effect on the States, on the
relationship between the national Government and the States, or on the
distribution of power and responsibilities among the various levels of
government.
    For the reasons discussed above, I certify that the proposed
regulation:
    1. Is not a ``significant regulatory action'' under Executive Order
12866;
    2. Is not a ``significant rule'' under the DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979); and
    3. Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

    We prepared a draft economic evaluation of the estimated costs to
comply with this proposed AD. See the AD docket to examine the draft
economic evaluation.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, Section 106, describes the
authority of the FAA Administrator. Subtitle VII, Aviation Programs,
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701, ``General
requirements.'' Under that section, Congress charges the FAA with
promoting safe flight of civil aircraft in air commerce by prescribing
regulations for practices, methods, and procedures the Administrator
finds necessary for safety in air commerce. This regulation is within
the scope of that authority because it addresses an unsafe condition
that is likely to exist or develop on products identified in this
rulemaking action.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration proposes to amend
part 39 of the Federal Aviation Regulations (14 CFR part 39) as
follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec.  39.13  [Amended]

    2. Section 39.13 is amended by adding a new airworthiness directive
to read as follows:

Sikorsky Aircraft Corporation: Docket No. FAA-2008-0609; Directorate
Identifier 2008-SW-24-AD.

    Applicability: Model S-76A, S-76B, and S-76C helicopters with
any of the following part-numbered vertical stabilizer aft spars
assemblies having 1,000 or more hours time-in-service (TIS)
installed, certificated in any category.

------------------------------------------------------------------------
                                                           Vertical
                                                        stabilizer aft
                  Helicopter model                    spar assembly part
                                                              No.
------------------------------------------------------------------------
S-76A...............................................     76201-05002-114
                                                         76201-05002-115
S-76B and S-76C.....................................     76201-05002-047
                                                         76201-05002-048
                                                         76201-25002-041
                                                         76201-25002-044
                                                         76201-25002-045
                                                         76201-25002-046
------------------------------------------------------------------------

    Compliance: Required as indicated.
    To detect and correct an unbalanced or out-of-track tail rotor,
which could lead to increased vibrations a fatigue crack, loss of a
portion of the vertical stabilizer, and subsequent loss of control
of the helicopter, accomplish the following:
    (a) Within 30 days, unless accomplished previously, and
thereafter at intervals not to exceed 50 hours TIS, inspect the
vertical stabilizer aft spar assembly (aft spar assembly) for a
crack, a loose or working fastener, or corrosion in accordance with
the Accomplishment Instructions, paragraph 3.A., in Sikorsky Alert
Service Bulletin (ASB) No. 76-55-20A, Revision A, dated November 11,
2003 (No. 76-55-20A). For purposes of this AD, ASB No 76-55-20A
pertains to Model S-76B helicopters as well as Model S-76A and S-76C
helicopters.
    (1) If a crack, a loose or working fastener, or corrosion is
found in the aft spar assembly, before further flight:
    (i) Repair or replace any unairworthy parts and
    (ii) Inspect the vertical stabilizer forward spar assembly
(forward spar assembly) for a crack, a loose or working fastener, or
corrosion in accordance with the Accomplishment Instructions,
paragraph 3.B., in ASB No. 76-55-20A. Contacting the manufacturer is
not required by this AD.
    (2) If a crack, a loose or working fastener, or corrosion is
found in the forward spar assembly, repair in accordance with the
applicable maintenance manual or replace with airworthy parts before
further flight.
    (b) Within 30 days, unless accomplished previously, and
thereafter at intervals not to exceed 200 hours TIS, track-and-
balance the tail rotor in accordance with the Accomplishment
Instructions, paragraph 3.A., in ASB No. 76-65-58A, dated November
11, 2003.

    Note 1: Although the ASB specifies only an initial inspection of
the aft spar assembly and a track-and-balance of the tail rotor,
this AD requires inspecting the aft spar assembly and track-and-
balancing the tail rotor repetitively.

    Note 2: The track-and-balancing of the tail rotor that is
required by paragraph (b) of this AD involves both a pilot and
mechanic. The pilot's function is to operate the helicopter to a
``light on wheels'' state--almost to the point of takeoff. The
mechanic is needed to accomplish the vibration measurements.

    (c) On or before December 31, 2010, install a vertical
stabilizer modification kit, part number 76070-20562, 76070-20563,
or 76070-20564. Installing the vertical stabilizer modification kit
is terminating action for the requirements of this AD.
    (d) To request a different method of compliance or a different
compliance time for this AD, follow the procedures in 14 CFR 39.19.
Contact the Manager, Boston Aircraft Certification Office, Engine
and Propeller Directorate, ATTN: Richard Noll, Aviation Safety
Engineer, FAA, 12 New England Executive Park, Burlington, MA 01803,
telephone<PHONE_NUMBER>, fax<PHONE_NUMBER>, for information about
previously approved alternative methods of compliance.

    Issued in Fort Worth, Texas, on May 22, 2008.
David A. Downey,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. E8-12414 Filed 6-3-08; 8:45 am]

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