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                                                                  EXHIBIT 10.160

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

     THIS FIRST AMENDMENT TO AND REAFFIRMATION OF SUBORDINATION AND
INTERCREDITOR AGREEMENT (this "Amendment") is made and executed as of the 17th
day of October, 2000 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 (the "New Borrower", 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
(the "Term Loan") and a revolving credit loan to EHI and EIC in the maximum
outstanding principal amount of $3,500,000 (the "Revolving Loan", together with
the Term Loan, the "Loans") 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 (the "First
Amendment") dated November, 1999 and as further amended pursuant to that certain
Second Amendment to Credit and Security Agreement (the "Second Amendment") of
even date herewith (as hereafter amended, restated, modified or renewed from
time to time, the "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 (the "ABI First Amendment"), that
certain Amendment No. 2 and Restatement of Credit and Security Agreement dated
November 24, 1999 (the "ABI Second Amendment") and that certain Amendment No. 3
to Credit and Security Agreement (the "ABI Third Amendment") of even date
herewith (said Credit Agreement, as heretofore and hereafter amended, restated,
modified or renewed from time to time, the "ABI Credit Agreement"); and

     WHEREAS, pursuant to a plan of corporate restructuring approved by EIC's
Board of Directors, EIC has created a separate legal entity for its facilities
group in the form of the New Borrower and has transferred all of its assets
related to the facilities group to the New Borrower pursuant to that certain
Asset Purchase Agreement dated January 1, 2000 by and between EIC and the New
Borrower (the "Facilities Group Spin Off") and the Borrowers have requested that
the Bank consent to the Facilities Group Spin Off, and the Bank has consented
upon the conditions, among others, that the New Borrower be added as a co-
borrower under the Credit Agreement, the Restated Revolving Note (as defined in
the Second Amendment) and the
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Restated Term Note (as defined in the Second Amendment) pursuant to the Second
Amendment and that the parties hereto execute this Amendment; and

     WHEREAS, the Borrowers have requested that the Subordinate Creditors
consent to the Facilities Group Spin Off, and the Subordinate Creditors have
consented upon the conditions, among others, that the New Borrower be added as a
co-borrower under the ABI Credit Agreement and the Seller Note (as defined in
the ABI Credit Agreement) pursuant to the ABI Third Amendment and that the
parties hereto execute this Amendment; and

     WHEREAS, in connection with the execution of the Credit Agreement, the
Subordinate Creditors, EHI, EIC and the Bank entered into that certain
Subordination and Intercreditor Agreement dated as of March 30, 1999
(collectively, the "Agreement"); and

     WHEREAS, the Bank is not willing to consent to the Facilities Group Spin
Off or enter into the Second 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
Facilities Group Spin Off or enter into the ABI Third 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 Facilities Group Spin Off, for the Bank to enter into the
Second Amendment, for ABI to enter into the ABI Third 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 (a) the term
"Borrower" and "Borrowers" as used in the Agreement shall include the New
Borrower, (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 First Amendment, the Second Amendment, the Restated
Revolving Note and the Restated Term Note and any other respective amendments of
each of said documents being executed and delivered simultaneously herewith in
connection with the Second Amendment, copies or originals of which have been
received and reviewed by the Subordinate Creditors and the Borrowers, and (c)
the definition of the term "Subordinate Creditor Loan Documents" as set forth in
the Agreement includes the ABI First Amendment, the ABI Second Amendment, the
ABI Third Amendment, the Restated Seller Note

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(as defined in the ABI Third Amendment) and any other respective amendments of
each of said documents being executed and delivered simultaneously herewith in
connection with the ABI Third Amendment, copies or originals of which have been
received and reviewed by the Bank and the Borrowers.

     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 the representations and warranties
contained in the Agreement 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 and 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.

     7.   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.

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

     9.   Contemporaneously herewith, EIC has delivered to Senior Creditor the
original promissory note evidencing the purchase price for the assets conveyed
to the New Borrower in furtherance of the Facilities Group Spin Off (the "New
Borrower Note").  The New Borrower Note will be held by the Senior Creditor as
Collateral in accordance with the terms of the Senior Creditor Loan Documents.
After payment in full of the Level I Senior Creditor Obligations, Senior
Creditor shall deliver forthwith the New Borrower Note to the Subordinate
Creditor to be held by the Subordinate Creditor as Collateral in accordance with
the terms of the Subordinate Creditor Loan Documents.

                      [Signatures follow on the next page]

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     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


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


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

                                               APPLIED BIOSCIENCE
                                               INTERNATIONAL INC.


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


                                               PPD UK HOLDINGS


 /s/ Joanne Teague                      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.


 /s/ Margaret Breyer                    By: /s/ Joseph Highland           (SEAL)
------------------------------              ------------------------------
                                            Name:  Joseph Highland
                                            Title: Chairman, Chief Executive
                                                   Officer & Secretary

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                                            ENVIRON INTERNATIONAL CORPORATION


 /s/ Margaret Breyer                    By: /s/ Joseph Highland           (SEAL)
------------------------------              ------------------------------
                                            Name:  Joseph Highland
                                            Title: Chairman, Chief Executive
                                                   Officer & Secretary



                                            ENVIRON FACILITY SERVICES
                                            CORPORATION


 /s/ Margaret Breyer                    By: /s/ Joseph Highland           (SEAL)
------------------------------              ------------------------------
                                            Name:  Joseph Highland
                                            Title: Chairman, Chief Executive
                                                   Officer & Secretary

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