Document:

<PAGE>

                                                                  Exhibit 10.173

                                SECOND AMENDMENT
                             TO AND REAFFIRMATION OF
                    SUBORDINATION AND INTERCREDITOR AGREEMENT
                    -----------------------------------------

         THIS SECOND AMENDMENT TO AND REAFFIRMATION OF SUBORDINATION AND
INTERCREDITOR AGREEMENT (this "Amendment") is made effective as of the 30th day
of June, 2001 by APPLIED BIOSCIENCE INTERNATIONAL INC., a Delaware corporation
("ABI"), PPD UK HOLDINGS LIMITED, a private company incorporated in England and
Wales (collectively, the "Subordinate Creditors"), ENVIRON HOLDINGS, INC., a
Delaware corporation ("EHI"), ENVIRON INTERNATIONAL CORPORATION (formerly known
as APBI Environmental Sciences Group, Inc.), a Virginia corporation ("EIC") and
ENVIRON FACILITY SERVICES CORPORATION, a Virginia corporation ("EFSC", together
with EHI and EIC, collectively, the "Borrowers"), and FIRST UNION NATIONAL BANK,
a national banking association, its successors and assigns (the "Bank").

                                    RECITALS

         WHEREAS, the Bank has previously agreed, inter alia, to make a certain
                                                  ----- ----
term loan to EHI and EIC in the maximum outstanding principal amount of
$6,708,333.34 and a revolving credit loan to EHI and EIC in the maximum
outstanding principal amount of $3,500,000 pursuant to that certain Credit and
Security Agreement by and among EHI, EIC and the Bank dated March 30, 1999 as
amended by that certain First Amendment to Credit and Security Agreement dated
November __, 1999, that certain Second Amendment to Credit and Security
Agreement dated October 17, 2000 and that certain Third Amendment to Credit and
Security Agreement (the "FUNB Third Amendment") of even date herewith (as
hereafter amended, restated, modified or renewed from time to time, the "FUNB
Credit Agreement"); and

         WHEREAS, ABI has previously agreed, inter alia, to make a certain
                                             ----- ----
acquisition loan to EHI and EIC in the original principal amount of $18,000,000
pursuant to a Credit and Security Agreement by and among ABI, EHI and EIC dated
February 2, 1999, as amended by that certain Amendment No. 1 to Credit and
Security Agreement dated March 30, 1999, that certain Amendment No. 2 and
Restatement of Credit and Security Agreement dated November 24, 1999, that
certain Amendment No. 3 to Credit and Security Agreement dated October 17, 2000
and that certain Amendment No. 4 to Credit and Security Agreement (the "ABI
Fourth Amendment") of even date herewith (as hereafter amended, restated,
modified or renewed from time to time, the "ABI Credit Agreement"); and

         WHEREAS, the Borrowers' obligations under the FUNB Credit Agreement and
the other Credit Documents (as such term is defined in the FUNB Credit
Agreement, the "FUNB Credit Documents") are guaranteed by Environ UK Limited,
formerly Environmental Assessment Group Limited, a company limited by shares
organized under the laws of England and Wales ("EAGL") pursuant to the terms of
that certain Unconditional Guaranty dated November 24, 1999 (as thereafter
amended, modified and renewed from time to time, the "FUNB Guaranty"), and
secured by, among other things, that certain Mortgage Debenture from EAGL in
favor of the Bank dated November 24, 1999 (as thereafter amended, modified and
renewed from time to time, the "FUNB Mortgage Debenture"). The Borrowers'
obligations under the FUNB Credit

<PAGE>

Agreement and the other FUNB Credit Documents are also secured, by among other
things, that certain Pledge Agreement from EHI in favor of the Bank dated March
30, 1999, pursuant to which EHI pledged to the Bank all of the outstanding stock
of EAGL (as thereafter amended, modified and renewed from time to time, the
"FUNB U.K. Pledge Agreement"); and

         WHEREAS, the Borrowers' obligations under the ABI Credit Agreement and
the other Credit Documents (as such term is defined in the ABI Credit Agreement,
the "ABI Credit Documents") are guaranteed by EAGL pursuant to the terms of that
certain Unconditional Guaranty dated November 24, 1999 (as thereafter amended,
modified and renewed from time to time, the "ABI Guaranty"), and secured by,
among other things, that certain Mortgage Debenture from EAGL in favor of ABI
dated November 24, 1999 (as thereafter amended, modified and renewed from time
to time, the "ABI Mortgage Debenture"). The Borrowers' obligations under the ABI
Credit Agreement and the other ABI Credit Documents are also secured, by among
other things, that certain Pledge Agreement from EHI in favor of ABI dated March
30, 1999, pursuant to which EHI pledged to ABI all of the outstanding stock of
EAGL, subject to the terms of the FUNB U.K. Pledge Agreement (as thereafter
amended, modified and renewed from time to time, the "ABI U.K. Pledge
Agreement"); and

         WHEREAS, in order to avoid certain potential adverse tax consequences,
the Borrowers have requested that the Bank and the Subordinate Creditors (i)
release EAGL as a guarantor under the FUNB Guaranty and the ABI Guaranty, (ii)
release the Bank's and ABI's respective lien on any Collateral owned by EAGL and
created pursuant to the FUNB Mortgage Debenture and the ABI Mortgage Debenture,
and (iii) reduce the percentage of EAGL's outstanding stock pledged to the Bank
pursuant to the FUNB U.K. Pledge Agreement and pledged to ABI pursuant to the
ABI U.K. Pledge Agreement, in each case, from one hundred percent (100%) to
sixty-six percent (66%) (collectively, the "EAGL Release"); and

         WHEREAS, EHI has entered into that certain Share Purchase Agreement
dated as of June 29, 2001 (the "EFSC Stock Purchase Agreement") with Energy
Facility Services, Inc., a Texas corporation ("EFSI") to sell to EFSI all of the
outstanding shares of its subsidiary Environ Facility Services Corporation, a
Virginia corporation ("EFSC") (the "EFSC Sale") and has requested in connection
with the EFSC Sale that the Bank and the Subordinate Creditors (i) consent to
the EFSC Sale, (ii) release EFSC as a Borrower under the FUNB Credit Agreement,
the ABI Credit Agreement and all of the other FUNB Credit Documents and ABI
Credit Documents and release EFSC from any and all further liability under the
FUNB Credit Documents and under the ABI Credit Documents (iii) consent to the
accelerated payment of the purchase price in connection with the repurchase of
875 shares of Class A common stock and 1 share of Class B common stock of EHI
owned by Garland Faulk in accordance with the Shareholders' Agreement effective
as of February 1, 1999 among EHI and its shareholders, and (iv) release the
Bank's and the Subordinate Creditors' respective liens on any Collateral owned
by EFSC and created pursuant to the FUNB Credit Agreement, the ABI Credit
Agreement or any other FUNB Credit Document or ABI Credit Document
(collectively, the "EFSC Release"); and

         WHEREAS, in connection with the execution of the FUNB Credit Agreement,
the Subordinate Creditors, EHI, EIC and the Bank entered into that certain
Subordination and Intercreditor Agreement dated as of March 30, 1999, as amended
by that certain First

<PAGE>

Amendment to and Reaffirmation of Subordination and Intercreditor Agreement
dated as of October 17, 2000 (collectively, the "Agreement"); and

         WHEREAS, the Bank is not willing to consent to the EAGL Release or the
EFSC Release or enter into the FUNB Third Amendment unless the Subordinate
Creditors and the Borrowers each unconditionally reaffirm their obligations
under the Agreement as modified below and consent to such amendments; and

         WHEREAS, the Subordinate Creditors are not willing to consent to the
EAGL Release or the EFSC Release or enter into the ABI Fourth Amendment unless
the Bank and the Borrowers each unconditionally reaffirm their obligations under
the Agreement as modified below and consent to such amendments.

                                    AGREEMENT

         NOW THEREFORE, as an inducement for the Bank and the Subordinate
Creditors to consent to the EAGL Release, the EFSC Release, for the Bank to
enter into the Fourth Amendment, for ABI to enter into the ABI Fourth Amendment,
and for other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties do hereby agree as follows:

         1.   Capitalized terms used herein and not otherwise defined shall have
the meanings ascribed to them in the Agreement.

         2.   The Recitals set forth hereinabove are hereby incorporated by this
reference with the same force and effect as it fully set forth herein.

         3.   The parties hereto each acknowledge and agree that from and after
the effective date hereof (a) the term "Borrower" and "Borrowers" as used in the
Agreement shall not include EFSC, (b) the definitions of the terms "Bank Credit
Agreement," "Level 1 Senior Creditor Loan Documents" and "Senior Creditor Loan
Documents" set forth in the Agreement include the FUNB Third Amendment, a copy
or original of which has been received, reviewed and consented to by the
Subordinate Creditors and the Borrowers, (c) the definition of the term
"Subordinate Creditor Loan Documents" as set forth in the Agreement includes the
ABI Fourth Amendment, a copy or original of which has been received, reviewed
and consented to by the Bank and the Borrowers and (d) each party hereto
consents to the EAGL Release and the EFSC Release.

         4.   Each of the Subordinate Creditors and each of the Borrowers hereby
unconditionally reaffirm all of their respective obligations to Bank under the
Agreement.

         5.   The Borrowers each certify that each of the Borrowers has no
offsets, counterclaims or defenses to any of its obligations under the Agreement
as modified hereby.

         6.   The Bank and each of the Borrowers hereby unconditionally reaffirm
all of their respective obligations to the Subordinate Creditors under the
Agreement.

<PAGE>

         7.   From and after the effective date hereof, Schedule 2.01 and
Schedule 2.02 of the Agreement are hereby replaced in their entirety with
Schedule 2.01 and Schedule 2.02 attached hereto.

         8.   The Bank and the Subordinate Creditors each certify that the
representations and warranties contained in the Agreement and made by it or
them, respectively, remain true, correct and complete in all material respects
as of the date hereof with the same force and effect as if made on the date
hereof.

         9.   Except as modified hereby, the Agreement remains unmodified and in
full force and effect.

         10.  This Amendment may be executed in any number of duplicate
originals or counterparts, each of which duplicate original or counterpart shall
be deemed to be an original and all taken together shall constitute one and the
same instrument.

                      [Signatures follow on the next page]

<PAGE>

         IN WITNESS WHEREOF, the undersigned have executed and delivered this
Amendment as of the day and year first hereinabove written.

WITNESS:                                BANK:
                                        ----

                                        FIRST UNION NATIONAL BANK

____________________________            By: /s/ Monica Sevila         (SEAL)
                                            ------------------------
                                            Name: Monica Sevila
                                            Title: Vice President

                                        SUBORDINATE CREDITORS:
                                        ---------------------

                                        APPLIED BIOSCIENCE
                                        INTERNATIONAL INC.

/s/ B. Judd Hartman                      By: /s/ Fred B. Davenport, Jr. (SEAL)
----------------------------                --------------------------
                                            Name: Fred B. Davenport, Jr.
                                            Title: Vice President

                                        PPD UK HOLDINGS LIMITED

/s/ B. Judd Hartman                      By: /s/ Fred B. Davenport, Jr. (SEAL)
----------------------------                --------------------------
                                            Name: Fred B. Davenport, Jr.
                                            Title: Director

         Each Borrower signs this Agreement under seal at the requests of Senior
Creditor and Subordinate Creditors, to acknowledge that each Borrower consents
to the terms of the foregoing Amendment and covenants and agrees to be bound
thereby for the benefit of Senior Creditor and Subordinate Creditors.

                                        ENVIRON HOLDINGS, INC.

____________________________            By: /s/ Guy H. Lewis          (SEAL)
                                            ------------------------
                                            Name: Guy H. Lewis
                                            Title: Chief Financial Officer

<PAGE>

                                        ENVIRON INTERNATIONAL
                                        CORPORATION

____________________________            By: /s/ Guy H. Lewis          (SEAL)
                                            --------------------------
                                            Name: Guy H. Lewis
                                            Title: Chief Financial Officer

                                        ENVIRON FACILITY SERVICES
                                        CORPORATION

____________________________            By: /s/ Guy H. Lewis          (SEAL)
                                            --------------------------
                                            Name: Guy H. Lewis
                                            Title: Chief Financial Officer<PAGE>

                                                                  EXHIBIT 10.174

                AMENDMENT NO. 4 TO CREDIT AND SECURITY AGREEMENT
                ------------------------------------------------

         THIS AMENDMENT NO. 4 TO CREDIT AND SECURITY AGREEMENT (this
"Agreement") made effective as of the 30th day of June 2001, by and among
APPLIED BIOSCIENCE INTERNATIONAL INC., a Delaware corporation, its successors
and assigns ("Lender"), ENVIRON HOLDINGS, INC., a Delaware corporation ("EHI"),
ENVIRON INTERNATIONAL CORPORATION (formerly APBI Environmental Sciences Group,
Inc.), a Virginia corporation ("EIC", together with EHI, the "Original
Borrowers") and ENVIRON FACILITY SERVICES CORPORATION, a Virginia corporation
("EFSC", together with EHI and EIC, each a "Borrower", and collectively, the
"Borrowers").

                                    RECITALS
                                    --------

         A.    The Borrowers are parties to a certain Credit and Security
Agreement, along with the Lender dated February 2, 1999 (as thereafter amended,
modified and renewed from time to time, the "Credit Agreement"), pursuant to
which the Lender has agreed to make available certain credit facilities
consisting of (i) a revolving credit facility in the maximum principal amount of
Three Million Five Hundred Thousand Dollars ($3,500,000) (the "Revolving Credit
Facility") to provide working capital to the Original Borrowers, (ii) a term
loan (the "Term Loan") in the amount of Seven Million Dollars ($7,000,000) to be
used to pay a portion of the Purchase Price (as defined in the Credit
Agreement), (iii) letters of credit ("Letters of Credit") to be used for general
corporate purposes by the Original Borrowers, and (iv) an acquisition loan in
the amount of Eighteen Million Dollars ($18,000,000), also to pay a portion of
the Purchase price. As set forth in that certain Amendment No. 2 and Restatement
of Credit and Security Agreement dated November 24, 1999 by and among Lender and
the Original Borrowers, the Term Loan has been satisfied and the Lender has no
obligation to make any loans under the

<PAGE>

Revolving Credit Facility or to issue any Letters of Credit to or for the
benefit of the Original Borrowers under the Credit Agreement.

         B. The Borrowers' obligations under the Credit Agreement and the other
Credit Documents are guaranteed by Environ UK Limited, formerly Environmental
Assessment Group Limited, a company limited by shares organized under the laws
of England and Wales ("EAGL") pursuant to the terms of that certain
Unconditional Guaranty dated November 24, 1999 (as thereafter amended, modified
and renewed from time to time, the "Guaranty"), and secured by, among other
things, that certain Mortgage Debenture from EAGL in favor of the Lender dated
November 24, 1999 (as thereafter amended, modified and renewed from time to
time, the "Mortgage Debenture"). The Borrowers' obligations under the Credit
Agreement and the other Credit Documents are also secured, by among other
things, that certain Pledge Agreement from EHI in favor of the Lender dated
November 24, 1999, pursuant to which EHI pledged to the Lender all of the
outstanding stock of EAGL (as thereafter amended, modified and renewed from time
to time, the "U.K. Pledge Agreement").

         C. In order to avoid certain potential adverse tax consequences, the
Borrowers have requested that the Lender (i) release EAGL as a guarantor under
the Guaranty (ii) release the Lender's lien on any Collateral owned by EAGL and
created pursuant to the Mortgage Debenture, and (iii) reduce the percentage of
EAGL's outstanding stock pledged to the Lender pursuant to the U.K. Pledge
Agreement from one hundred percent (100%) to sixty-six percent (66%), and the
Lender has agreed on the condition, among others, that the Borrowers execute
this Agreement.

                                       -2-

<PAGE>

         D. EHI has entered into that certain Share Purchase Agreement (the
"EFSC Stock Purchase Agreement") with Energy Facility Services, Inc., a Texas
Corporation ("EFSI"), to sell to ESFI all of the outstanding shares of EFSC (the
"EFSC Sale") and has requested in connection with the EFSC Sale that the Lender
(i) consent to the EFSC Sale, (ii) release EFSC as a Borrower under the Credit
Agreement and all of the other Credit Documents and release EFSC from any and
all further liability under the Credit Documents, (iii) consent to the
accelerated payment of the purchase price in connection with the repurchase of
875 shares of Class A common stock and 1 share of Class B common stock of EHI
owned by Garland Faulk in accordance with the Shareholder Agreement (the "Faulk
Stock Repurchase"), and (iv) release the Lender's lien on any Collateral owned
by EFSC and created pursuant to the Credit Agreement or any other Credit
Document.

         NOW, THEREFORE, in consideration of the foregoing, and for other good
and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the Borrowers and the Lender do hereby agree as follows:

         1.  Recitals. The parties hereto acknowledge and agree that the above
             --------
Recitals are true and correct in all material respects and that the same are
incorporated herein and made a part hereof by reference.

         2.  Defined Terms.  Capitalized terms used herein and not otherwise
             -------------
defined shall have the meanings ascribed to them in the Credit Agreement.

         3.  Release of EAGL as Guarantor and Lender's Liens on Collateral of
             ----------------------------------------------------------------

EAGL. Subject to the terms of this Agreement, the Lender hereby (i) releases
----
EAGL as a Guarantor under the Guaranty, (ii) releases the Lender's Lien on any
Collateral owned by EAGL and

                                       -3-

<PAGE>

created pursuant to the Mortgage Debenture and agrees to promptly return the
Guaranty and the Mortgage Debenture (to the extent Lender has or may obtain such
instrument by employing commercially reasonable efforts) to the Borrowers,
provided, that the Borrowers shall be responsible for all of the Lender's fees
and expenses associated therewith, including, without limitation, the Lender's
reasonable attorney's fees, (iii) agrees that Lender's lien on the outstanding
shares of EAGL constituting Collateral shall be limited at all times to 66% of
the issued and outstanding shares of EAGL and (iv) releases and forever
discharges EAGL from any and all claims, demands, actions, causes of action,
rights of action, obligations, or liabilities of any nature whatsoever, at law
or in equity or by statute, known or unknown, which are related to the Guaranty
or the Mortgage Debenture.

         4. Release of EFSC and Lender's Liens on Collateral of EFSC. The Lender
            --------------------------------------------------------
hereby consents to the EFSC Sale and the Faulk Stock Repurchase, and subject to
the terms of this Agreement, hereby (i) releases EFSC as a Borrower under the
Credit Agreement and all of the other Credit Documents, (ii) releases the
Lender's Lien on any Collateral owned by EFSC and created pursuant to the Credit
Agreement and any other Credit Document and agrees to promptly execute and
deliver to the Borrowers, UCC-3's releasing the Lender's Lien on any of the
Collateral owned by EFSC, and (iii) releases and forever discharges EFSC from
any and all claims, demands, actions, causes of action, rights of action,
obligations, or liabilities of any nature whatsoever, at law or in equity or by
statute, known or unknown, which are related to any of the Credit Documents.

         5. Release of the Lender. (i) EFSC and its successors, assigns and
            ---------------------
anyone claiming under them, hereby release and forever discharge the Lender, its
parent, subsidiaries, affiliates, divisions, agents, attorneys, officers,
directors, employees, and each of their successors and

                                       -4-

<PAGE>

assigns, from any and all claims, demands, actions, causes of action, rights
of action, obligations, or liabilities of any nature whatsoever, at law or in
equity or by statute, known or unknown, which are related to the Credit
Documents and (ii) EAGL and its successors, assigns and anyone claiming under
them, hereby release and forever discharge the Lender, its parent, subsidiaries,
affiliates, divisions, agents, attorneys, officers, directors, employees, and
each of their successors and assigns, from any and all claims, demands, actions,
causes of action, rights of action, obligations, or liabilities of any nature
whatsoever, at law or in equity or by statute, known or unknown, which are
related to the Guaranty or the Mortgage Debenture.

         6. Definitions. From and after the effective date hereof, Section 1.07
            -----------
(Definitions) of the Credit Agreement shall be modified as follows:

                (i)   The definitions of "Guaranty Agreement" and "UK Credit
Documents" are hereby deleted in their entirety and all references in the Credit
Agreement to such terms shall be deleted in their entirety.

                (ii)  The definition of "Guarantor" is hereby deleted in its
entirety and all references in the Credit Agreement to "Guarantor" shall be
deemed to be a reference to "EAGL", except that all references to "Guarantor" in
the following provisions of the Credit Agreement shall be deleted in their
entirety: (a) the defined term "Seller Subordinated Obligations" in Section
1.07, (b) Sections 2D.03 and 2E.04(d), and (c) the introductory paragraph of
Article V.

                (iii) (a) The "Guarantor" or "EAGL" is hereby deleted from the
definition of "Obligors" with respect to (1) the defined term "Lock-Box" in
Section 1.07 and (2) Sections 2E.03(a)(v), 4.06, 4.12, 6.01(a), 6.01(b) and
6.02, and (b) with respect to Section 4.23,

                                       -5-

<PAGE>

the definition of "Obligors" is hereby deleted in its entirety and shall be
deemed to be a reference to the "Borrower Group". Except as otherwise
specifically set forth herein, each reference to the term "Obligors" in the
Credit Agreement shall hereafter be deemed to be a reference to each Borrower
and EAGL. Notwithstanding the inclusion of EAGL as an "Obligor" in certain
Sections of the Credit Agreement (including, without limitation, Sections
6.01(c), 6.04, 7.08, 7.10 and 7.14), it is understood and agreed that EAGL is
not a signatory to the Credit Agreement and EAGL shall not be construed to be a
pledgor or guarantor of the Obligations within the meaning of Section 956(d) of
the Code.

                (iv)  Clause (a) of the definition of "Permitted Investments" is
hereby amended and restated in its entirety as follows:

            (a) any Investment in any Person that is a Subsidiary of such
                Borrower (provided that total aggregate Investments in all such
                Persons may not exceed $6,000,000);

                (v)   (a) Each reference to the term "Borrower" with respect to
clauses (a), (b) and (d) only of the defined term "Permitted Indebtedness" shall
hereafter be deemed to be a reference to each Borrower and EAGL, and (b) each
reference to the term "Borrower" with respect to clauses (a) through (g) only of
the defined term "Permitted Investments" shall hereafter be deemed to be a
reference to each Borrower and EAGL.

         7. Conditions to All Revolving Credit. From and after the effective
date hereof, paragraph (b) of Section 2E.04 (Conditions to All Revolving Credit
Including the Initial Revolving Credit) is hereby deleted in its entirety, and,
all references with respect to an opinion of United Kingdom counsel for EAGL in
paragraph (c) of Section 2E.04 are hereby deleted in their entirety.

                                       -6-

<PAGE>

         8. Security Interest. From and after the effective date hereof, Section
            -----------------
4A.01(j) is hereby amended and restated in its entirety as follows:

            (a) All of each Borrower's "securities" (whether certificated or
                uncertificated), "security entitlements," "securities accounts,"
                " commodity contracts," "commodity accounts" and other
                "investment property" (as defined in Article 8A or Article 9 of
                the UCC, as the case may be) ("Investment Property").
                Notwithstanding anything provided herein to the contrary, the
                lien created herein shall be limited with respect to securities
                of EAGL to sixty-six percent (66%) of the shares of each class
                of issued and outstanding securities of EAGL;

         9. Conditions Precedent. This Agreement, other than Section 4 and
            --------------------
clause (i) of Section 5, shall become effective immediately upon the last to
occur of the following:

                (a) The Lender shall have received an Amended and Restated
Pledge Agreement (United Kingdom Stock) from EHI in favor of the Lender in such
form and substance as the Lender shall require;

                (b) Pursuant to Section 4.12 of the Credit Agreement, the Lender
shall have received payment of its reasonable attorneys' fees in connection with
the preparation, review, negotiation and execution of this Agreement and of all
other instruments, certificates and documents related hereto or executed in
connection herewith; and

                (c) The Lender shall received such other information,
instruments, opinions, documents, certificates and reports as the Lender may
deem necessary, each of which shall be satisfactory in form and substance to the
Lender.

         10. Conditions Precedent to Section 4 and Clause (i) of Section 5.
             -------------------------------------------------------------
Section 4 and clause (i) of Section 5 of this Agreement shall not be effective
until the Lender shall have received and reviewed to its satisfaction a fully
executed copy of the EFSC Stock Purchase

                                       -7-

<PAGE>

Agreement with all attached schedules and exhibits attached thereto and each
of the other conditions precedent in Section 9 shall have been satisfied.

         11. Counterparts. This Agreement may be executed in any number of
             ------------
duplicate originals or counterparts, each of which duplicate original or
counterpart shall be deemed to be an original and all taken together shall
constitute one and the same instrument.

         12. Credit Documents; Governing Law; Etc. This Agreement is one of the
             ------------------------------------
Credit Documents defined in the Credit Agreement and shall be governed and
construed in accordance with the laws of the Commonwealth of Virginia. The
headings and captions in this Agreement are for the convenience of the parties
only and are not a part of this Agreement.

         13. Acknowledgments. The Borrowers hereby confirm to the Lender the
             ---------------
enforceability and validity of each of the Credit Documents, as amended hereby.
In addition, the Borrowers hereby agree the execution and delivery of this
Agreement and the terms and provisions, covenants or agreements contained in
this Agreement shall not in any manner release, impair, lessen, modify, waive or
otherwise limit the liability and obligations of the Borrowers under the terms
of any of the Credit Documents, except as otherwise specifically set forth in
this Agreement. The Borrowers issue, ratify and confirm the representations,
warranties and covenants contained in the Credit Documents.

         14. Modifications. This Agreement may not be supplemented, changed,
             -------------
waived, discharged, terminated, modified or amended, except by written
instrument executed by the parties.

                                       -8-

<PAGE>

         15. Full Force and Effect. Except as expressly set forth above, the
             ---------------------
provisions of the Credit Agreement shall continue in full force and effect and
are hereby ratified and confirmed. A default under this Agreement shall be a
default under the Credit Agreement.

         16. Severability. Every provision of this Agreement is intended to be
             ------------
severable, and if any term or provision hereof shall be invalid, illegal or
unenforceable for any reason, the validity, legality and enforceability of the
remaining provisions hereof shall not be affected or impaired thereby, and any
invalidity, illegality or unenforceability in any jurisdiction shall not affect
the validity, legality or enforceability of any such term or provision in any
other jurisdiction.

         17. Effective Date. Notwithstanding the date on which this Agreement is
             --------------
executed,  the parties desire that the effective date of the amendments and
releases contained herein shall be June 30, 2001.

                         [SIGNATURES BEGIN ON NEXT PAGE]

                                       -9-

<PAGE>

         IN WITNESS WHEREOF the parties hereto have caused this Agreement to be
made effective as of the day and year first above written.

                                       LENDER:

WITNESS:                               APPLIED BIOSCIENCE INTERNATIONAL INC.

/s/B. Judd Hartman                     By:  /s/Fred B. Davenport, Jr.    (SEAL)
-------------------------                 -------------------------------
                                          Name:  Fred B. Davenport, Jr.
                                          Title:  Vice President

                                       BORROWERS:

                                       ENVIRON HOLDINGS, INC.,
                                       a Delaware corporation

__________________________             By:  /s/Guy H. Lewis              (SEAL)
                                          -------------------------------
                                          Name:  Guy H. Lewis
                                          Title: Chief Financial Officer

                                       ENVIRON INTERNATIONAL CORPORATION,
                                       a Virginia corporation

__________________________             By:  /s/Guy H. Lewis              (SEAL)
                                          -------------------------------
                                          Name:  Guy H. Lewis
                                          Title:  Chief Financial Officer

                                       ENVIRON FACILITY SERVICES CORPORATION,
                                       a Virginia corporation

__________________________             By:  /s/Guy H. Lewis              (SEAL)
                                          -------------------------------
                                          Name:  Guy H. Lewis
                                          Title:  Chief Financial Officer

                                      -10-

<PAGE>

                                            RELEASED GUARANTOR:

                                            ENVIRON UK LIMITED
                                            (formerly Environmental Assessment
                                            Group Limited), a company limited by
                                            shares organized under the laws of
                                            England and Wales

                                            By:  /s/Ian Bailey            (SEAL)
-------------------------------               ---------------------------
                                               Name: Ian Bailey
                                               Title: Director

                                      -11-

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00031-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00031-of-00352.parquet"}]]