[Federal Register Volume 61, Number 65 (Wednesday, April 3, 1996)]
[Notices]
[Pages 14773-14778]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-8008]
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ENVIRONMENTAL PROTECTION AGENCY
[OPPTS-42186A; FRL-5359-3]
Request for Proposals for Enforceable Consent Agreements; Dermal
Absorption Rate Testing of Eighty OSHA Chemicals; Solicitation of
Interested Parties; Text of Test Protocol
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice.
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SUMMARY: This notice addresses all manufacturers and processors of
eighty chemical substances of interest to the Occupational Safety and
Health Administration of the Department of Labor (OSHA) which were
designated for dermal absorption testing in the 31st, 32nd and 35th
Reports of the TSCA section 4 Interagency Testing Committee (ITC).
These persons are invited to submit to EPA proposals for enforceable
consent agreement (ECA) consideration for dermal absorption rate
testing of the 80 chemicals. The protocol set forth in this notice is
recommended as the test protocol for these proposals. In addition, EPA
is soliciting ``interested parties'' to participate in or monitor any
ECA negotiations initiated in response to this solicitation.
DATES: Written proposals for ECAs and written requests to be designated
an interested party must be received by July 2, 1996. EPA may extend
the deadline for receipt of testing proposals upon request and a
showing of good faith efforts on the part of potential submitters to
develop testing proposals by the deadline.
ADDRESSEES: Send written submissions, identified by the document
control number (OPPTS-42186A) (FRL-5359-3), in triplicate to: TSCA
Document Control Office (7407), Rm. ET-G099, Office of Pollution
Prevention and Toxics, U.S. Environmental Protection Agency, 401 M St.,
SW., Washington, DC 20460, Attn: TSCA section 4. The public record
supporting this action, including comments, is available for public
inspection from Noon to 4 p.m., Mondays through Fridays, except legal
holidays. The public record is located in the TSCA Nonconfidential
Information Center, Rm. NE-B607, U.S. Environmental Protection Agency,
401 M St., SW., Washington, DC 20460.
Persons submitting information any portion of which they believe is
entitled to treatment as confidential business information (CBI) by EPA
must assert a business confidentiality claim in accordance with 40 CFR
2.203(b) for each such portion. This claim must be made at the time
that the information is submitted to EPA. If a submitter does not
assert a confidentiality claim at the time of submission, EPA will
consider this waiver of any confidentiality claim, and the information
may be made available to the public by EPA without further notice to
the submitter.
Proposals may be submitted electronically by sending electronic
mail (e-mail) to: [email protected]. Proposals in electronic form
must be submitted as ASCII files and must avoid the use of special
characters and any form of encryption. Proposals will also be accepted
on disks in WordPerfect 5.1 (DOS) file format or ASCII file format. All
proposals in electronic form must be identified by docket number OPPTS-
42186A (FRL-5359-3). Information claimed as CBI should not be submitted
via e-mail. Proposals in electronic form may be filed on-line at many
Federal depository libraries. Additional information on submissions in
electronic form may be found in Unit VI of this notice.
FOR FURTHER INFORMATION CONTACT: Susan B. Hazen, Director,
Environmental Assistance Division (7408), Rm. ET-543B, Office of
Pollution Prevention and Toxics, U.S. Environmental Protection Agency,
401 M St., SW., Washington, DC 20460; telephone: (202) 554-1404; TDD:
(202) 554-0551; e-mail: TSCA-H[email protected]. For specific
information regarding this solicitation or related matters, contact
Roger A. Nelson, Project Manager, Chemical Testing and Information
Branch (7405), Rm. ET-729A, Office of Pollution Prevention and Toxics,
U.S. Environmental Protection Agency, 401 M St., SW., Washington, DC
20460; telephone: (202) 260-8163; e-mail: [email protected].
SUPPLEMENTARY INFORMATION:
I. Introduction
The ITC has reviewed 658 chemical substances that were presented to
the ITC by OSHA in 1991 (58 FR 26898, 26900, May 5, 1993 and 58 FR
38490,
[[Page 14774]]
38492-38493, July 16, 1993). OSHA requested the ITC to assess the
availability of dermal absorption data for these chemical substances
and to determine the need for further testing. (See 58 FR 26898, 26900,
May 5, 1993.) The ITC indicated that OSHA needs quantitative measures
of dermal absorption in order to evaluate the potential hazard of these
chemicals to workers (58 FR 38490, 38492, July 16, 1993).
In its 31st, 32nd, and 35th Reports to the EPA Administrator
(published at 58 FR 26898, May 5, 1993; 58 FR 38490, July 16, 1993; and
59 FR 67596, December 29, 1994, respectively) (FRL-4583-4, FRL-4630-2,
and FRL-4923-2, respectively), the ITC designated for dermal absorption
testing a total of 83 of the chemical substances nominated by OSHA.
These chemicals are listed in Table 1.--``Chemicals Designated by the
ITC for Dermal Absorption Testing'' in Unit II of this notice. After
reviewing additional information, in its 34th and 36th Reports
(published at 59 FR 35720, July 13, 1994 and 60 FR 42982, August 17,
1995, respectively) (FRL-4870-4 and FRL-4965-6, respectively), the ITC
withdrew the designation for three of the chemicals (noted in table 1
in Unit II of this notice). Eighty of the chemical substances nominated
by OSHA are thus currently designated by the ITC for dermal absorption
testing.
In the Federal Register notices containing the 31st, 32nd and 35th
ITC Reports, EPA solicited proposals for ECAs for dermal absorption
testing of the subject chemical substances. In the notices of the 31st,
32nd and 35th Reports, EPA referenced a proposed dermal absorption test
protocol for review by potential submitters in developing their
submissions (Ref. 1). Public comments on the protocol were received by
EPA and were entered into the docket for the 31st, 32nd, or 35th ITC
Report, as appropriate (docket nos. OPPTS-41038, OPPTS-41039, and
OPPTS-41042, respectively). In addition, the Chemical Manufacturers
Association (CMA) submitted a proposal outlining an alternative
protocol (Ref. 2). Scientists from EPA and a number of agencies
represented on the ITC (including OSHA) reviewed the public comments
and the CMA proposal. Based on this review, a protocol entitled
``Recommended Protocol for In Vitro Percutaneous Absorption Rate
Studies'' was developed, and is set forth in Unit V of this notice.
EPA received no proposals for ECAs for dermal absorption testing of
any of the subject chemical substances in response to the above-
mentioned solicitations. In today's notice, EPA is soliciting proposals
for ECAs which address the chemical substances listed in table 1 in
Unit II of this notice and through which dermal absorption rate data
would be developed to meet OSHA's needs.
II. Response to Submissions to EPA
A. Response to Public Comments on the ITC Reports
Comments were received on the 31st, 32nd and 35th ITC Reports and
were entered into the docket for the corresponding ITC Report. Comments
received on these ITC Reports addressing the proposed test protocol
were reviewed as part of the protocol development process, as discussed
in Unit I of this notice. EPA and the ITC have reviewed all other
comments received on these ITC Reports. The analysis of these comments
by EPA and the ITC follows.
In its comments on the 31st ITC Report, Mobil (Ref. 3) asserted
that acute dermal toxicity studies would be cheaper and faster than
skin penetration studies. EPA and the ITC believe that acute dermal
toxicity studies would not meet OSHA's needs since such studies would
not provide data on absorption rates.
BASF (Ref. 4) stated that it has been established that
tetrahydrofuran (32nd ITC Report) can be rapidly absorbed in lethal
amounts through the skin of rats and rabbits. OSHA needs data related
to the real measured rate of the absorption of tetrahydrofuran by the
skin. The needed data are not provided in the comment.
Aristech (Ref. 5) commented that there is no specific need to test
diphenylamine (32nd ITC Report) since this chemical is no different
from other regulated substances for which dermal penetration data are
not available. EPA and the ITC believe that such data are needed to
make determinations concerning the need to alert industrial hygienists,
employers, and workers to the potential adverse health effects of
dermal exposure to diphenylamine, as explained in Unit III of this
notice.
DuPont (32nd ITC Report) and the CMA Propylene Glycol Ethers Panel
(35th ITC Report) (Refs. 6 and 7, respectively) questioned how OSHA
planned to use these data. The uses to which the data will be put are
explained in Unit III of this notice. Dow (31st ITC Report) (Ref. 8)
questioned the appropriateness of the grouping of the subject chemical
substances for testing purposes. EPA believes that the identity of
testing needs (dermal absorption rate) for these eighty chemicals is
sufficient reason for grouping them together in one notice.
The CMA Ketones Panel (Ref. 9) commented on the request contained
in the Federal Register notice announcing the 31st ITC Report for a
testing consortium to develop ECAs for all designated chemicals. The
Panel expressed its belief that such a consortium would not be feasible
in light of the number of chemicals designated and the number of
companies that would have to participate in ECA negotiations. EPA
acknowledges that multiple ECAs may present a feasible approach. (See
Unit III of this notice).
Angus Chemicals submitted two dermal absorption studies (Refs. 10
and 11)--one on 1-nitropropane (31st ITC Report) and the other on 2-
nitropropane (32nd ITC Report). These studies were submitted by Angus
to support its claims that additional testing of these chemicals is not
needed. EPA and the ITC have ascertained that the submitted studies are
deficient because the recovered amounts (0.5%) of test material
rendered the studies inadequate to determine dermal absorption rates
for these chemicals.
DuPont (Ref. 6) submitted comments on 14 chemical substances in the
32nd ITC Report claiming that dermal toxicity data for these chemicals
(referenced in the comments) are available. EPA and the ITC have
determined that the references cited by DuPont do not address the issue
of dermal absorption rate.
The CMA Dinitrotoluenes Panel (32nd ITC Report) (Ref. 12) submitted
comments on 2,4-dinitrotoluene (2,4-DNT), including literature
describing studies of 2,6-DNT and technical grade DNT, a mixture of
2,4-DNT and 2,6-DNT. (The literature on 2,6-DNT was offered on the
basis that 2,6-DNT was an acceptable surrogate for 2,4-DNT.) The Panel
claimed that existing dermal absorption data are adequate for 2,4-DNT.
EPA and the ITC reviewed the literature and determined that since it
does not address dermal absorption rates, the literature is not
adequate to meet OSHA's data needs.
The CMA Propylene Glycol Ethers Panel (Ref. 13) commented that
dermal toxicity data already exist on dipropylene glycol methyl ether
(DPGME) (35th ITC Report). EPA and the ITC ascertained that no dermal
absorption rate studies were cited by CMA.
SOCMA (Ref. 14) questioned the designation of biphenyl (35th ITC
Report), stating that dermal exposure to biphenyl is limited and animal
studies indicate that biphenyl does not produce
[[Page 14775]]
adverse health effects following dermal application. EPA and the ITC
determined that none of the studies cited by SOCMA relate to dermal
absorption rate.
Union Carbide (Ref. 15) asserted that the ITC should not have
designated isophorone (35th ITC Report) for dermal absorption testing.
OSHA needs data related to the dermal absorption rate of isophorone.
These needed data are not provided in the comment.
B. Response to TSCA Section 8(d) Studies
EPA has screened the health and safety studies on the subject
chemical substances that have been submitted to the Agency pursuant to
section 8(d) of the Toxic Substances Control Act (TSCA). None of these
submitted studies was determined to be relevant to dermal absorption
rate.
Table 1.--Chemicals Designated by the ITC for Dermal Absorption Testing
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CAS No. Chemical Name
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31st ITC Report:
60-29-7................................. Ethyl ether
75-65-0................................. tert-Butyl alcohol
76-22-2................................. Camphor
78-92-2................................. sec-Butyl alcohol
79-20-9................................. Methyl acetate
97-77-8................................. Disulfiram
100-25-4................................ p-Dinitrobenzene
105-46-4................................ sec-Butyl acetate
106-42-3................................ p-Xylene
107-31-3................................ Methyl formate
107-66-4................................ Dibutyl phosphate
108-03-2................................ 1-Nitropropane
108-87-2................................ Methylcyclohexane
109-66-0................................ Pentane
110-83-8................................ Cyclohexene
111-84-2................................ Nonane
123-92-2................................ Isoamyl acetate
142-82-5................................ n-Heptane
287-92-3................................ Cyclopentane
532-27-4................................ a-Chloroaceto- phenone
540-88-5................................ tert-Butyl acetate
628-63-7................................ n-Amyl acetate
7631-90-5............................... Sodium bisulfite
7681-57-4............................... Sodium metabisulfite
32nd ITC Report:
61-82-5................................. Amitrole
74-96-4................................. Ethyl bromide
75-15-0................................. Carbon disulfide
75-25-2................................. Bromoform
75-34-3................................. 1,1-Dichloroethane
77-78-1................................. Dimethyl sulfate
79-46-9................................. 2-Nitropropane
80-62-6................................. Methyl methacrylate\1\
84-66-2................................. Diethyl phthalate\1\
88-72-2................................. o-Nitrotoluene
89-72-5................................. o-sec-Butylphenol
90-04-0................................. o-Anisidine
95-13-6................................. Indene
95-49-8................................. o-Chlorotoluene
99-65-0................................. m-Dinitrobenzene
100-00-5................................ p-Nitrochlorobenzene
100-01-6................................ p-Nitroaniline
100-44-7................................ Benzyl chloride
100-63-0................................ Phenylhydrazine
106-49-0................................ p-Toluidine
108-44-1................................ m-Toluidine
108-90-7................................ Chlorobenzene
109-99-9................................ Tetrahydrofuran
121-14-2................................ 2,4-Dinitrotoluene
122-39-4................................ Diphenylamine
126-99-8................................ beta-Chloroprene
150-76-5................................ p-Methoxyphenol
528-29-0................................ o-Dinitrobenzene
540-59-0................................ 1,2-Dichloroethylene
626-17-5................................ m-Phthalodinitrile
768-52-5................................ N-Isopropylaniline
1300-73-8............................... Xylidine
6423-43-4............................... Propylene glycol dinitrate
25013-15-4.............................. Vinyl toluene
35th ITC Report:
75-05-8................................. Acetonitrile
75-12-7................................. Formamide
75-35-4................................. Vinylidene chloride
77-73-6................................. Dicyclopentadiene
78-59-1................................. Isophorone
78-83-1................................. Isobutyl alcohol
78-87-5................................. Propylene dichloride
91-20-3................................. Naphthalene
92-52-4................................. Biphenyl
95-50-1................................. o-Dichlorobenzene
96-18-4................................. 1,2,3-trichloropropane
98-29-3................................. t-Butylcatechol
99-08-1................................. m-Nitrotoluene
99-99-0................................. p-Nitrotoluene
106-46-7................................ p-Dichlorobenzene
107-06-2................................ Ethylene dichloride
108-93-0................................ Cyclohexanol
108-94-1................................ Cyclohexanone\2\
110-12-3................................ Methyl isoamyl ketone
120-80-9................................ Catechol
121-69-7................................ Dimethylaniline
123-42-2................................ Diacetone alcohol
127-19-5................................ Dimethyl acetamide
542-92-7................................ Cyclopentadiene
34590-94-8.............................. Dipropylene glycol methyl
ether
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\1\ Removed by the ITC in its 34th Report.
\2\ Removed by the ITC in its 36th Report.
III. Request for Proposals
No proposals for ECAs for dermal absorption testing of any of the
subject chemical substances were received by EPA as a result of the
solicitations in the Federal Register notices containing the 31st, 32nd
and 35th ITC Reports. EPA has revised the test protocol and is now
seeking proposals that will provide for the development of dermal
absorption rate data on the eighty chemical substances listed in table
1 in Unit II of this notice. EPA has reason to believe that industry
now has an interest in proposing dermal absorption rate testing schemes
for at least some of these chemical substances.
EPA encourages submitters to work together to develop proposals for
ECAs that address all eighty subject chemical substances or significant
subsets thereof. The Agency, however, will also accept proposals for
ECAs providing for the testing of individual chemicals. All proposals
should set forth offers to test specific chemicals for the endpoint of
interest (dermal absorption rate); expressions of interest in ECA
negotiations do not, in and of themselves, constitute proposals.
The dermal absorption rate data obtained under this testing program
will be used to support development of OSHA's ``skin designations'' for
the subject chemical substances. Skin designations for specific
chemicals alert industrial hygienists, employers, and workers to
potential adverse health effects resulting from dermal exposure to
these chemicals in the workplace. OSHA assigns a skin designation to a
chemical if it determines that cutaneous exposure (through the skin,
eyes, and mucous membranes) to that chemical in the workplace
represents a potential significant contribution to overall workplace
exposure. Cutaneous exposure is a function of, among other things, the
rate of absorption of the chemical substance. One methodology under
consideration for developing and assigning skin designations is
discussed in Walker et al. (Ref. 17).
EPA has developed a protocol, set forth in Unit V of this notice,
that is recommended as the test protocol for all proposals for ECAs.
The Agency believes that testing conducted in accordance with the
protocol will provide data of use to OSHA, is consistent with EPA and
OSHA testing policies, and provides the most economical approach to
address a large number of diverse chemical substances. If a submitter
chooses not to use the recommended protocol but instead submits an
alternative protocol, an explanation should be given as to how this
alternative protocol will provide comparable data and achieve the same
goals as the recommended protocol.
IV. Solicitation of Interested Parties
Negotiations on ECAs for dermal absorption rate testing of the
subject chemical substances will be conducted pursuant to the
procedures described in 40 CFR 790.22. All persons who respond to this
notice on or before July 2, 1996 will be given the status of interested
parties and will be afforded an opportunity to monitor or participate
[[Page 14776]]
in the negotiations. All such persons should indicate the chemical
substance(s), by name and CAS number, in which they are interested.
Those persons who have already given notice in their response(s) to the
31st, 32nd, or 35th ITC Report that they wish to be designated
interested parties with regard to ECA negotiations on specific chemical
substances will be considered automatically to be interested parties on
such chemicals. Interested parties do not incur any obligation by being
so designated.
Upon making the appropriate findings under section 4 of the Toxic
Substances Control Act (TSCA), EPA has the authority to require dermal
absorption rate testing of some or all of these chemical substances
through formal rulemaking. If an ECA-based approach does not prove
viable, EPA will proceed with rulemaking to require industry to conduct
the needed testing.
V. Recommended Protocol for In Vitro Percutaneous Absorption Rate
Studies
A. Introduction
This recommended protocol was developed to provide percutaneous
absorption rate data for the Occupational Safety and Health
Administration (OSHA) chemicals designated in the 31st, 32nd and 35th
Reports (published at 58 FR 26898, May 5, 1993; 58 FR 38490, July 16,
1993; and 59 FR 67596, December 29, 1994, respectively) of the TSCA
section 4 Interagency Testing Committee (ITC), as modified by the 34th
and 36th ITC Reports (published at 59 FR 35720, July 13, 1994 and 60 FR
42982, August 17, 1995, respectively). The protocol was developed by a
group of scientists from agencies represented on the ITC (the Consumer
Product Safety Commission, the Department of Defense, EPA, the Food and
Drug Administration, the National Institute for Occupational Safety and
Health, and OSHA) based on the methods of Bronaugh and Collier (Ref.
16), and modified in response to comments.
The protocol outlines procedures for measuring a permeability
constant (Kp) and a short-term absorption rate for chemicals in liquid
form. Measurement of short-term absorption rates is only required when
a Kp cannot be obtained using the protocol described. For most
chemicals, a Kp is most useful in estimating skin permeation. However,
for harsh chemicals that may damage the skin more severely with
prolonged contact, a short-term absorption rate is more relevant. The
permeability constants and short-term absorption rates measured will be
used by OSHA to give more specific guidance to employers on whether a
chemical used in a particular process warrants changes in engineering
controls or use of personal protective equipment to reduce the hazard
of systemic toxicity after dermal absorption of the chemical.
OSHA expects that this would be accomplished by using a semi-
quantitative procedure such as estimating time required to absorb a
toxic dose compared to the inhalation permissible exposure limits (Ref.
17). It is not contemplated that the values developed using this
protocol would be used for quantitative risk assessment because of the
limitations of the methods used to collect the data and the variability
of individual exposure scenarios present in workplaces.
The protocol utilizes established in vitro diffusion cell
techniques which allow absorption studies to be conducted with human
skin. The in vitro method is chosen for practical considerations. It is
efficient in terms of labor and materials and can be easily performed
using a standard method by different laboratories. In vitro diffusion
cell studies are necessary for measuring a Kp.
Although maintaining the viability of skin more closely simulates
in vivo conditions, this protocol allows use of static diffusion cells
and cadaver skin. This protocol also requires the use of radiolabeled
chemicals unless it can be demonstrated that alternative, non-
radiolabeled methods provide sufficient sensitivity to detect the
parent chemical (and its major skin metabolites in those cases where
skin viability is maintained). The first five protocol parameters that
are discussed (choice of membrane, preparation of membrane, diffusion
cell design, testing hydrophobic chemicals and vehicle) are similar for
determination of either of the two percutaneous absorption values. In
contrast, the remaining two protocol parameters (i.e., dose and study
duration) are different for the two percutaneous absorption values.
B. Conduct of Test
1. Choice of Membrane
i. Skin selection. The most accurate absorption data for regulatory
concerns related to human health would be obtained with human skin.
Since this protocol allows use of the static cell, maintenance of
viability of skin is not necessary. Human cadaver skin is required for
these studies.
ii. Number of subjects. Data from a total of at least six samples
obtained from at least three human subjects should be averaged to allow
for biological variation between subjects. Replicates are not required.
The variability can be up to 5-fold in different samples of normal
human skin.
iii. Regional variability. Variability in skin permeation is well
known to occur in different anatomical regions. The trunk and the
extremities have reasonably similar barrier properties (less than 2-
fold differences). Enhanced absorption can be observed in regions of
the face (4-fold) and the scrotum (20-fold). Small differences in
regional absorption may not be significant compared to intersubject
variability. However, to minimize the variability in skin absorption
measurements, for these tests all samples of human skin shall be
obtained from the abdominal region of human subjects of known source
and disease state. The time elapsed between death and harvest of tissue
shall be reported.
iv. Validation of human skin barrier. Barrier properties of human
skin shall be pretested with a standard compound such as tritiated
water prior to conducting an experiment with the test chemical because
barrier alteration can result from surgery or topical scrubbing (Ref.
18).
2. Preparation of Membrane
Full thickness skin should not be used. Since absorbed chemicals
are taken up by blood vessels directly beneath the epidermis in vivo,
an in vitro study should use a membrane with most of the dermis
removed. This is particularly important for hydrophobic chemicals that
would diffuse slowly through the dermis. A suitable membrane shall be
prepared from fresh skin with a dermatome at a thickness of 200 to 500
mm. The microtomed skin samples can be stored frozen for up to two
weeks, if necessary, if they are frozen quickly and the barrier
properties of the samples are confirmed.
3. Diffusion Cell Design
Flow cells or static diffusion cells shall be used in these
studies. Flow cells are useful for maintaining the viability of the
skin (in the case that live skin is used) because nutrient media must
be continually replaced. Also, these cells are preferable for studies
requiring round-the-clock sampling since samples can be collected
automatically in a fraction collector. Flow cells of adequate design
will have only small exposed areas of skin for applying test chemicals
because the receptor volume must be small so that the cell contents can
be rapidly exchanged (Ref. 19). If flow cells are used, the draft ITC
protocol describing their use shall be followed. The draft
[[Page 14777]]
ITC protocol was first made publicly available with the 31st ITC
Report.
If static cells are used, the testing laboratory must verify that
there is not an increase in concentration of the test compound in the
receptor fluid that would change the penetration rate. Specifically,
the concentration difference across the membrane must not decrease by
more than 10% during the experiment. Concentration of the neat liquid
should be taken as the density of the compound.
4. Temperature
Skin shall be maintained at a physiological temperature which is
about 32 deg.C.
5. Testing Hydrophobic Test Chemicals
Chemicals with water solubility less than about 10 mg/L do not
freely partition from skin into aqueous receptor fluid. To increase the
water solubility of such hydrophobic chemicals, polyethoxyoleate (PEG
20 oleyl ether) shall be added to the receptor fluid at a concentration
of 6 percent. To ensure that an increase in concentration of the
chemical in the receptor fluid does not alter the penetration rate, the
concentration difference across the membrane must not decrease by more
than 10% during the experiment.
6. Vehicle
If the test chemical is a liquid at room temperature and does not
damage the skin during the determination of Kp, it shall be applied
neat. If the chemical cannot be applied neat because it is a solid at
room temperature or because it damages the skin when applied neat, it
should be dissolved in water. If the concentration of a hydrophobic
chemical in water is not high enough so that a steady-state absorption
can be obtained, the chemical shall be dissolved in isopropyl
myristate. In vitro percutaneous absorption experiments with other
vehicles of interest may be required for selected test chemicals in
order to meet the data needs of individual Federal agencies. A
sufficient volume of liquid shall be used to completely cover the skin
and provide the amount of test chemical needed as described in section
B.7. ``Dose'' of this protocol below. The volume should be sufficient
so that the skin surface remains covered by the vehicle during the
determination of Kp.
7. Dose
i. Permeability constant. An ``infinite dose'' of the test chemical
shall be applied to the skin to achieve the steady-state rate of
absorption necessary for calculation of a Kp. The actual concentration
required to give an undepletable reservoir on the surface of the skin
depends on the rate of penetration of the test chemical. Preliminary
studies may be necessary to determine this concentration. If necessary
to generate a reliable Kp, the diffusion cell tops should be covered
with a stopper or with Parafilm7 to prevent evaporation of the vehicle
or test chemical. If damage to the skin is likely due to the nature of
the test chemical, the skin barrier integrity shall be verified at the
end of the experiment by measuring the absorption of a standard
compound such as tritiated water (Ref. 18).
ii. Short-term absorption rates. Short-term absorption rates shall
be determined for those chemicals for which a Kp cannot be measured.
The dose of test chemical applied to the skin shall be sufficient to
completely cover the exposed skin surface. Four to six diffusion cells
shall be set up using skin from a single subject and two to three of
these will be terminated at 10 minutes and at 60 minutes. Skin
absorption at each sampling time is the sum of the receptor fluid
levels and the absorbed chemical that remains in the skin (Ref. 20).
Unabsorbed chemical is removed from the skin surface by washing gently
with soap and water. This experiment shall be repeated with skin from
two additional subjects. If necessary to generate reliable short-term
absorption rates, the diffusion cell tops should be covered with a
stopper or with Parafilm7 to prevent evaporation of the test chemical.
8. Study Duration
i. Permeability constant. The percutaneous absorption study shall
be performed until at least four absorption measurements are obtained
during the steady state absorption portion of the experiment. A
preliminary study may be useful to establish time points for sampling.
The required absorption measurements can be accomplished in an hour or
two with fast penetrating chemicals but can require 24 hours or longer
for slow-penetrating chemicals. Unabsorbed material need not be removed
from the surface of the skin.
ii. Short-term exposure rate. The test chemical shall be applied to
skin for at least durations of 10 and 60 minutes. At the end of the
study, the unabsorbed material shall be removed from the surface of the
skin with soap and water and the amount absorbed into the skin and
receptor fluid shall be determined (Ref. 20).
C. Expression of Results
1. Permeability Constant
The Kp shall be calculated by dividing the steady-state rate of
penetration (measured in g x hr-1 x cm-2) by the
concentration of test chemical (measured in g x cm-3)
applied to the skin. For example, if the steady-state rate is 1
g x hr-1 x cm-2 and the concentration applied to
the skin is 1000 g x cm-3, then the Kp value is
calculated to be 0.001 cm x hr-1.
2. Short-Term Exposure Rate
The rates of penetration (g x hr-1 x cm-2)
shall be determined from the total amount of test chemical found in the
receptor fluid and skin after the 10- and 60-minute exposures.
D. Recordkeeping and Reporting Requirements
In addition to compliance with TSCA Good Laboratory Practice (GLP)
Standards at 40 CFR part 792, the following specific information shall
be collected and reported:
1. Description of Test Systems and Test Methods
The report shall include where and when the test was performed, who
performed it, a good laboratory practice statement, and where the
records of the test are stored. All of this must be certified by the
signatures of the individuals performing the work and their
supervisors.
The source, identity and purity of the test chemical shall be
reported. The source, identity and handling of the test skin shall be
described. There shall be a detailed description of the test procedure
and all materials, devices used and doses tested. There shall be a
detailed description and illustration of flow cell design. There shall
be a description of the skin preparation method including measurements
of the skin membrane thickness.
The analytical techniques to be used including their accuracy,
precision and detection limits (in particular for non-radiolabelled
tests) shall be described and if a radiolabel is used, there shall be a
description of the radiolabel (e.g., type, location of and
radiochemical purity of the label).
All data collected in the course of the experiment must clearly be
identified as to dose and specimen. Derived values (means, permeability
coefficient, graphs, charts, etc.) are not sufficient.
2. Conduct of Study
Data shall be collected and reported on the following:
1. Monitoring of testing parameters.
[[Page 14778]]
2. Temperature of chamber.
3. Receptor fluid pH.
4. Barrier property validation.
5. Maintenance of glucose utilization (if using viable skin).
6. Analysis of receptor fluid for radioactivity or test chemical
and metabolites (if using viable skin).
3. Results
The permeability constant (Kp) or short-term absorption rate shall
be presented. In addition, all raw data from each individual diffusion
cell shall be maintained to support the calculations of permeability
constants and short-term exposure rates. When radiolabelled compounds
are used, a full balance of the radioactivity shall be presented,
including cell rinsings and stability of the test substance in the
donor compartment.
VI. Public Docket
A. Materials Contained in the Docket
EPA has established a docket for this action (to include paper
versions of comments in electronic form) under docket control number
OPPTS-42186A (FRL-5359-3). The public record is available for
inspection from Noon to 4 p.m., Mondays through Fridays, except legal
holidays, in the TSCA Nonconfidential Information Center, Rm. NE-B607,
U.S. Environmental Protection Agency, 401 M St., SW., Washington, DC
20460. Information claimed as CBI, while part of the record, is not
available for public review. The docket includes the following:
1. USEPA. Proposed Protocol for In Vitro Percutaneous Absorption
Studies. (May 5, 1993).
2. Chemical Manufacturers Association (CMA). Letter to Charles
M. Auer, USEPA. (October 21, 1994).
3. Mobil Oil Corporation. Comments on the 31st TSCA Interagency
Testing Committee Report. Submitted to the TSCA Docket Receipts
Office, USEPA. (July 6, 1993).
4. BASF Corporation. Comments on the 32nd TSCA Interagency
Testing Committee Report. Submitted to the TSCA Docket Receipts
Office, USEPA. (September 13, 1993).
5. Aristech Chemical Corporation. Comments on the 32nd TSCA
Interagency Testing Committee Report. Submitted to the TSCA Docket
Receipts Office, USEPA. (September 29, 1993).
6. DuPont. Comments on the 32nd TSCA Interagency Testing
Committee Report. Submitted to the TSCA Docket Receipts Office,
USEPA. (September 15, 1993).
7. The CMA Propylene Glycol Ethers Panel. Comments on the 35th
TSCA Interagency Testing Committee Report. Submitted to the TSCA
Nonconfidential Information Center, USEPA. (February 27, 1995).
8. The Dow Chemical Company. Comments on the 31st TSCA
Interagency Testing Committee Report. Submitted to the TSCA Docket
Receipts Office, USEPA. (June 3, 1993).
9. The CMA Ketones Panel. Comments on the 31st TSCA Interagency
Testing Committee Report. Submitted to the TSCA Docket Receipts
Office, USEPA. (July 2, 1993).
10. Angus Chemical Company. Letter from Allen F. Bollmeier, Jr.
to Roger Nelson, USEPA, enclosing study entitled: ``Skin Absorption
and Metabolism/Toxicokinetic Study of 14C-1-Nitropropane in
Female Rhesus Monkeys''. (June 16, 1993).
11. Angus Chemical Company. Letter from Allen F. Bollmeier, Jr.
to John D. Walker, ITC, enclosing study entitled: ``Skin Absorption
and Metabolism/Toxicokinetic Study of 14C-2-Nitropropane in
Female Rhesus Monkeys''. (June 21, 1993).
12. The CMA Dintrotoluenes Panel. Comments on the 32nd TSCA
Interagency Testing Committee Report. Submitted to the TSCA Docket
Receipts Office, USEPA. (September 30, 1993).
13. The CMA Propylene Glycol Ethers Panel. Comment letter on the
35th TSCA Interagency Testing Committee Report from Langley Spurlock
to Charles M. Auer, USEPA. (March 31, 1995).
14. Synthetic Organic Chemical Manufacturers Association, Inc.
(SOCMA). Comments on the 35th TSCA Interagency Testing Committee
Report. Submitted to the TSCA Nonconfidential Information Center,
USEPA. (January 30, 1995).
15. Union Carbide Corp. Comments on the 35th TSCA Interagency
Testing Committee Report. Submitted to the TSCA Nonconfidential
Information Center, USEPA. (February 24, 1995).
16. Bronaugh, R.L. and Collier, S.W. Protocol for In Vitro
Percutaneous Absorption Studies, in In Vitro Percutaneous
Absorption: Principles, Fundamentals, and Applications, (R.L.
Bronaugh and H.I. Maibach, Eds.), CRC Press, Boca Raton, 1991, pp.
237-241.
17. Walker, J.D., Whittaker, C. and McDougal, J.N. Role of the
TSCA Interagency Testing Committee in Meeting the U.S. Government's
Data Needs: Designating Chemicals for Percutaneous Absorption
Testing. In: F. Marzulli and H. Maibach (eds.) Dermatotoxicology.
Taylor Francis, Washington, DC. (In press).
18. Bronaugh, R.L., Stewart, R.F., and Simon, M. Methods for In
Vitro Percutaneous Absorption VII: Use of Excised Human Skin, J.
Pharm. Sci., vol. 75, pp. 1094-1097, 1986.
19. Bronaugh, R.L. and Stewart, R.F. Methods for In Vitro
Percutaneous Absorption Studies IV: The Flow-Through Diffusion Cell,
J. Pharm. Sci., vol. 74, pp. 64-67, 1985.
20. Bronaugh, R.L., Stewart, R.F., and Storm, J.E. Extent of
Cutaneous Metabolism during Percutaneous Absorption of Xenobiotics,
Toxicol. Appl. Pharmacol., vol. 99, pp. 534-543, 1989.
B. Submissions to the Docket in Electronic Form
Proposals in electronic form may be sent directly to EPA at:
[email protected]
Proposals in electronic form must be submitted as ASCII files and
must avoid the use of special characters and any form of encryption.
The official record of this action, as well as the public version,
will be maintained in paper form. Accordingly, EPA will transfer all
proposals received electronically into paper form as they are received
and will place the paper copies in the official record which will also
include all proposals submitted directly in writing. The official
record is the paper record maintained at the address in ``ADDRESSES''
at the beginning of this document.
Authority: 15 U.S.C. 2603.
Dated: March 26, 1996.
Charles M. Auer,
Director, Chemical Control Division, Office of Pollution Prevention and
Toxics.
[FR Doc. 96-8008 Filed 4-2-96; 8:45 am]
BILLING CODE 6560-50-F