Document:

THIS  NOTE  HAS  BEEN ACQUIRED FOR INVESTMENT AND  HAS  NOT  BEEN
REGISTERED   UNDER  THE  SECURITIES  ACT  OF  1933,  AS   AMENDED
("SECURITIES ACT"), IN RELIANCE ON AN EXCEPTION CONTAINED IN  THE
SECURITIES ACT.  THIS NOTE MAY ONLY BE TRANSFERRED PURSUANT TO AN
EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT AND ANY
APPLICABLE STATE SECURITIES LAWS UNLESS THERE IS FURNISHED TO THE
BUYER  AN  OPINION OF COUNSEL OR OTHER EVIDENCE  SATISFACTORY  TO
BUYER TO THE EFFECT THAT SUCH REGISTRATION IS NOT REQUIRED.  THIS
NOTE IS SUBJECT TO THE TERMS AND CONDITIONS OF THAT CERTAIN STOCK
PURCHASE AGREEMENT DATED MAY 16, 2000 BETWEEN THE MAKER  AND  THE
PAYEE  OF  THIS  NOTE, AS AMENDED BY THE FIRST AMENDMENT  TO  THE
STOCK PURCHASE AGREEMENT BETWEEN MAKER AND PAYEE

$3,500,000                                        Denver,
                                                  Colorado
                                                  August 31, 2000

                         PROMISSORY NOTE

     1.   FOR VALUE RECEIVED, the undersigned, Perma-Fix Environmental
Services, Inc. a Delaware corporation ("Maker"), hereby  promises
to  pay  to  the  order  of Waste Management  Holdings,  Inc.,  a
Delaware corporation, its successors and assigns,  ("Holder") the
principal sum of three million five hundred thousand U.S. dollars
($3,500,000), with interest thereon from and including  the  date
hereof at the rate hereinafter set forth.

     The  principal amount of $3,500,000 shall be due and payable
on August 31, 2005 (the "Maturity Date").

     2.   Interest.  The rate of interest payable hereunder shall be
seven percent (7%) per annum.  Interest shall be computed on  the
basis  of  a  year of 365 or 366 days, as applicable, and  actual
number  of  days  elapsed.  Interest shall  be  due  and  payable
annually on each anniversary date hereof

     3.    Default Interest.  The amount of all principal and (to
the  extent permitted by then applicable law) all interest  which
is  not  paid  when  due  (whether  as  set  forth  above  or  by
acceleration)  shall  bear interest, from the  time  such  amount
becomes  due until payment of the amount in default  is  paid  in
full,  at  rate which is equal to the lesser of thirteen  percent
(13%)  per  annum, or the maximum rate of interest  permitted  by
then applicable law.

<PAGE>
     4.   Payments.  Maker shall make any payments hereunder to Holder
at the address set forth below or such other address as Holder
shall designate in writing addressed to Maker.  All payments
hereunder shall first be applied to unpaid accrued interest and
the balance, if any, to principal.  If, however, the Holder has
incurred costs and expenses of collection, as described below, in
enforcing this Note, such payments shall first be applied
thereto.

     5.    Prepayment.   Maker  may prepay the  principal  amount
outstanding  under this Note in whole or in part at any  time  or
from  time  to  time  without penalty,  notice,  or  bonus.   All
prepayments  received shall be applied first in  satisfaction  of
any  accrued  but unpaid interest and then against all  remaining
principal.

     6.   Costs of Collection.  Should the indebtedness represented by
this Note or any part thereof be enforced or collected at law or
in equity or through any bankruptcy, receivership, probate, or
other court proceedings, or if this Note is placed in the hands
of attorneys for collection after default, Maker agrees to pay to
Holder, in addition to the principal and interest due and payable
hereon and to the full extent permitted by law, all reasonable
attorneys' fees and costs of collection

     7.    Setoff.  This note is subject to setoff  as  set
forth  in  the Stock Purchase Agreement between Maker and  Holder
dated May 16, 2000.

     8.    Events of and Remedies for Default.  The occurrence of
any of the following events shall constitute a default under this
Note:

          (a)  default in the payment of any interest or principal
               installment when due of the Maker to Holder under this Note and
               such is not cured within ten(10) days from the date of such
               default;

          (b)  termination of existence, suspension or discontinuance of
               business, or business failure  of or by Maker;

          (c)  issuance of any injunction, restraining or other order with
               respect to any material aspect of the business of Maker, or levy
               on or attachment of any funds or other property, real or
               personal, of Maker, if, in each case, the same has a material
               effect on the ability of Maker to make payments under this Note
               and the same is not dismissed, discharged, released, satisfied or
               vacated within a period of thirty (30) days;

          (d)  appointment of a receiver, trustee, custodian or similar
               official, for Maker;

          (e)  conveyance of  substantially all of the assets of the Maker
               to a trust mortgagee or liquidating agent or assignment for the
               benefit of creditors by Maker;

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<PAGE>
          (f)  commencement of any proceeding under any law of any
               jurisdiction, now or hereafter in force, relating to bankruptcy,
               dissolution, or reorganization, to the relief of debtors  by or
               against Maker, if such proceeding is involuntary and is not set
               aside within ninety (90) days from the filing of such involuntary
               proceeding or immediately if such proceeding is voluntary;

Upon  any  default  described in paragraph (f) above,  this  Note
shall  automatically become due and payable, in each case without
notice  or demand. In addition, the Holders shall have all  other
rights and remedies under the laws as then in effect in Delaware,
and  may proceed with any remedy provided for thereby or in  this
Note.

     9.    Waivers.   Maker, to the fullest extent  permitted  by
applicable  law,  expressly waives presentment, protest,  demand,
notice  of  dishonor, or default and all exemptions in connection
with  delivery, acceptance, performance, default, or  enforcement
of  or  under this Note or any guaranty of this Note.  No renewal
or  extension  of  this  Note, no release  or  surrender  of  any
collateral  or  other security for this Note or any  guaranty  of
this  Note,  no  release of any person, primarily or  secondarily
liable on this Note (including any Maker, indorser or guarantor),
no  delay  in  the  enforcement of payment of this  Note  or  any
guaranty of this Note, and no delay or omission in exercising any
right or power under this Note or any guaranty of this Note shall
affect the liability of any Maker, indorser or guarantor of  this
Note.  Maker and each indorser and each guarantor of this Note or
of the indebtedness hereby represented agree to pay to Holder, on
demand,  all costs and expenses of collection, including, without
limitation,  reasonable  attorneys'  fees  and  legal   expenses,
incurred  by  Holder  in  enforcing this  Note,  whether  or  not
litigation  is commenced.  No failure by Holder to  exercise,  or
delay  by the Holder in exercising, any right or remedy hereunder
shall operate as a waiver thereof or of any other right or remedy
and  no  single or partial exercise of any right or remedy  shall
preclude  any other or further exercise thereof or of  any  other
right  or remedy.  Acceptance by Holder of any payment after  the
maturity of this Note has been accelerated shall not constitute a
waiver of such acceleration.

     10.  Notices.  All notices, requests, demands, consents, and
other  communications which are required or may  be  given  under
this  Note (collectively, the "Notices") shall be in writing  and
shall  be  given  either  (a)  by  personal  delivery  against  a
receipted  copy,  (b)  by  facsimile to the  following  facsimile
numbers,  or  (c) by certified or registered United States  mail,
return  receipt  requested,  postage prepaid,  to  the  following
addresses:

          (i)  If to Holder, to:
          Waste Management Holdings, Inc
          1001 Fannin
          Suite 4000
          Houston, TX 77002
          Facsimile No.:  713- 209-9711

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<PAGE>
          With a copy to:

          William A. Jeffry, Esq.
          Burns, Figa & Will, P.C.
          6400 S. Fiddlers Green Circle
          Suite 1030
          Engelwood, CO 80111
          Facsimile No.:  303-796-2777

          (ii) If to Maker to:
          Dr. Louis F. Centofanti, President
          Perma-Fix Environmental Services, Inc.
          1940 Northwest 67th Place
          Gainesville, FL 32653
          Facsimile No.:

          With a copy to:

          Irwin H. Steinhorn, Esq.
          Conners & Winters, A Professional Corporation
          One Leadership Square
          211 North Robinson
          Suite 1700
          Oklahoma City, OK 73102
          Facsimile No.:  405-232-2695

or  to such other address or notice party of which written notice
in accordance with the provisions hereof shall have been provided
by  such  party.   Notices  may  only  be  given  in  the  manner
hereinabove described and shall be deemed received when given  in
such manner.

     11.   Governing  Law.  This Note shall be  governed  by  and
construed  in accordance with the laws of the State of  Delaware,
without giving effect to conflict of laws principles.

     12.  Section Headings, Construction.  The headings of sections or
paragraphs  in  this Note are provided for convenience  only  and
will  not  affect its construction or interpretation.  All  words
used  in  this  Note will be construed to be of  such  gender  or
number, as the circumstances require.  Unless otherwise expressly
provided,  the word "including" (i) does not limit the  preceding
words  or  terms  and  (ii)  is to be  ascribed  a  non-exclusive
meaning.

     13.  Time of Essence.  With regard to all dates and time periods
set forth or referred to in this Note, time is of the essence.

     Dated on the date first set forth above.

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<PAGE>
                              MAKER:

                              Perma-Fix Environmental Services, Inc

                              By:  /s/ Louis Centofanti
                                 __________________________________
                                     Dr. Louis F. Centofanti
                                     President

                                 5Non-Recourse
                       Guaranty of Payment
                               Of
                         Promissory Note

WHEREAS, Waste Management Holdings, Inc., ("WM") has been
requested to accept a $2,500,000 Promissory Note in lieu of a
certain amount of cash from Perma-Fix Environmental Services,
Inc.("Debtor"), in connection with the closing of the Stock
Purchase Agreement between WM and Debtor dated May 16, 2000 as
amended by First Amendment to Stock Purchase Agreement dated
August 31, 2000.  Said Promissory Note in the principal sum of
two million five hundred thousand dollars ($2,500,000.00), dated
August 31, 2000 ("Promissory Note"), together with interest
thereon at the rate of 11.25 percent per annum and secured by
this Guaranty.

WHEREAS, WM has declined to accept the Promissory Note unless
said Promissory Note shall be guaranteed on a non-recourse basis
by Diversified Scientific Services, Inc., a Tennessee corporation
("Guarantor") and unless such guaranty shall be secured by
certain assets of Guarantor.

NOW, THEREFORE, in consideration of WM's promise to accept the
Promissory Note, and for other valuable consideration received,
Guarantor hereby unconditionally and irrevocably guarantees
pursuant to the terms of this Agreement, WM., its successors and
assigns, the prompt and full repayment of the principal sum owing
on said Promissory Note, and all interest accrued and to accrue
thereon in accordance with its terms, except that Guarantor shall
be liable for the outstanding principal on said Note, together
with only so much of the interest owing thereon that would not
exceed the lawful rate for individual borrowers applicable at the
time the Note was made.

The Guarantor does hereby guarantee and become a surety, without
personal liability, to WM for the prompt satisfaction when due,
whether by acceleration or otherwise, of Debtor's obligations
under the Promissory Note subject to the terms of this Guaranty.

The Guarantor agrees that if Debtor's obligations under the
Promissory Note are not satisfied when due, either at maturity or
by acceleration or otherwise, the Guarantor shall upon demand by
WM forthwith satisfy such indebtedness of the Debtor to the
extent and only to the extent of the Collateral pledged pursuant
to this Guaranty shall satisfy Guarantor's obligations hereunder,
and provided that this Guaranty is non-recourse to the Guarantor
hereunder and is limited to the proceeds derived from the public
sale of the Collateral by Guarantor acting in good faith to
achieve the highest possible sales price for the Collateral or at
the sole election of WM, by surrendering the Collateral to WM.
If the Collateral is sold at a public sale the costs and expenses
of such sale shall be borne by Guarantor..  The Guarantor shall
not be liable for any deficiency which may remain under the
Promissory Note or otherwise upon the public sale of the
Collateral.

<PAGE>
A separate cause of action may be brought and prosecuted against
the Guarantor without the necessity of joining the Debtor or
previously proceeding or exhausting any other remedy against the
Debtor or any other person who might have become liable for the
indebtedness by assumption thereof or of realizing upon any
security then held by noteholder to secure such indebtedness.

The Guarantor hereby specifically waives any and all defenses to
any action or proceeding brought to enforce this Guaranty or any
part of this Guaranty either at law or in equity, except the
single defense that the sum claimed has actually been paid to the
holder of the Promissory Note.  Without limiting the foregoing in
anywise but merely by way of illustration, Guarantor specifically
waives any and all technical, dilatory or nonmeritorious
defenses, and any defense predicated upon and including but not
limited to:

     1)   Change or modification of the Promissory Note.
     2)   Indulgence or forbearance in enforcement of any term of
          either the Promissory Note or any other instrument securing
          affecting or modifying said Note or any term for the repayment of
          the indebtedness it evidences.
     3)   Change of ownership of any of the assets securing this
          Guaranty.
     4)   A release of all or any part of the security, whether for
          valuable consideration or otherwise.
     5)   Acquiring additional security
     6)   Substitution of different security in exchange or exchanges
          for part or parts of the original security.
     7)   The fact that there may be persons other than the Guarantor,
          solvent and responsible for the payment of the indebtedness.

The Guarantor hereby assigns and grants to WM a continuing
general lien on, and security interest in, all of Guarantor's
right, title and interest in, and to the collateral described in
Schedule 1 attached hereto and hereby made a part of this
Guaranty (the "Collateral")to secure the payment and performance
of all of Guarantor's obligations under this Guaranty.

The Guarantor hereby represents, warrants and covenants, and for
so long as this Guaranty is in effect shall be deemed to
continuously represent, warrant and covenant, that:
The Guarantor is the owner of the Collateral and, except for the
first priority security interest granted by Guarantor to WM
pursuant hereto, and the second lien and security interest in and
to the Collateral granted by the Guarantor to its lender, the
Collateral and each part thereof is free and clear from, and is
not subject to, any security interest, mortgage, pledge, lien,
levy for taxes or other assessment, interest, charge, adverse
claim or other encumbrance, including any financing statement or
other document file din any public office (collectively, the
"encumbrances"); and Guarantor shall keep and maintain the
Collateral, and each part thereof, in good condition, ordinary
wear and tear excepted;

Notwithstanding the above, if any portion of the Collateral was
in the possession of Guarantor at the time of the Closing of the
transaction contemplated by the Stock Purchase Agreement, and
such Collateral is not owned by the Guarantor or is subject to a
lien or security interest in breach of WM's representations,
warranties or covenants contained in the Stock Purchase
Agreement, then such shall not be a breach of this Agreement.

                                2
<PAGE>
     (a)  The Guarantor shall, at its sole cost and expense, defend
          its right, title and interest in and to the Collateral, and
          defend the Collateral against any claims of infringement and all
          other claims or demands of any other party and all other
          liabilities of any nature whatsoever;

     (b)  The Collateral is personalty and the Guarantor shall not,
          except with the prior written consent of WM, affix the Collateral
          to real estate in such a manner as to cause the Collateral to
          become a fixture, as such term is defined in Section 9-313 of the
          Uniform Commercial Code of Tennessee or to become part of real
          estate; if the Collateral is or in the opinion of WM may become a
          fixture or part of any real estate, the Guarantor shall give WM a
          written waiver by the record owner of such real estate of all
          interest in the Collateral and a written subordination by any
          person who has a lien on such real estate which is or may be
          superior to the security interest created by this Agreement;

     (c)  The Guarantor shall, at its expense, maintain the Collateral
          and every part thereof in good operating condition and shall not
          permit anything to be done or any condition to exist that may
          impair the value of the Collateral, ordinary wear and tear
          excepted;

     (d)  The Guarantor shall at all times and at its expense keep the
          Collateral fully insured against risks of loss or physical damage
          by collision, upset, fire (including so-called extended
          coverage), theft and other casualties as WM may reasonably
          require, losses in all cases to be payable to WM and the
          Guarantor as their interests may appear; all policies of
          insurance shall provide for at least ten days' prior written
          notice of cancellation to WM; the Guarantor shall promptly
          furnish WM with certificates of insurance or other evidence
          satisfactory to WM as to compliance with the provisions of this
          Section; the Guarantor further agrees that, in the event it shall
          fail to pay the premium on any such insurance; WM may do so and
          the Guarantor shall promptly reimburse WM for such expense.

     (e)  The Guarantor shall duly and promptly pay and discharge, or
          cause to be paid and discharged, (i) all taxes, assessments and
          governmental charges or levy upon or against it or its profits,
          income, properties or assets and when such became due, except
          Guarantor may contest such in good-faith, (ii) all lawful claims,
          for labor, materials, supplies, or services, becomes a lien or
          charge upon the Collateral, unless and to the extent only that
          the same are being diligently contested in good faith by
          appropriate proceedings and appropriate reserves therefore have
          been established in accordance with generally accepted accounting
          principles consistently applied;

     (f)  The Collateral, or any part thereof, will not be sold,
          assigned, conveyed, transferred, disposed of or become subjected
          to any subsequent interest of any party, created or suffered by
          the Guarantor, voluntarily or involuntarily, except as expressly
          authorized in writing by WM, except in the ordinary course of
          business or to replace such because of damage or obsolence of
          such, provided, however that such replacement of the Collateral
          or any part thereof shall have a fair market value equal to or in
          excess of the Collateral replaced, that Guarantor provide WM

                                 3
<PAGE>
          written notice of the replacement within ten days thereof and
          htat the property replacing the Collateral be deemed substituted
          for the original Collateral and subject to this Guaranty;

     (g)  The Guarantor, at its sole cost and expense, shall duly
          execute, deliver and file, or cause to be duly executed,
          delivered or filed, financing, continuation or termination
          statements, certificates of title for endorsement with respect to
          the security interested created by this Agreement and such other
          instruments and documents as WM may request, and do and cause to
          be done such acts and things as WM may at any time reasonably
          request in order to enforce, perfect and protect its security
          interest in the Collateral as herein provided and its rights and
          remedies with respect to the Collateral;

     (h)  No other Obligation shall be released, discharged, or
          impaired in any manner or to any extent if:  (i) WM renews,
          extends, modifies, changes or waives the time of payment and/or
          the manner, place or terms of payment of all or any part of any
          obligation secured hereby or any renewal thereof; or (ii) WM
          makes any exchange, release, substitution, addition, surrender,
          settlement or compromise with WM subordinates an obligation or
          the Collateral, or both, to any other indebtedness of the
          Guarantor or security therefore, or both, which may exist at any
          time hereafter and no right of WM shall be impaired by any of the
          foregoiung, including its right to declare a subsequent default
          of the Promissory Note, this right bring deemed a continuing one;

     (i)  The Guarantor shall promptly notify WM of any act, condition
          or event which, with the giving of notice or lapse of time, or
          both, would constitute an Event of Default hereunder, including
          the existence of any material litigation, arbitration or other
          legal proceedings involving or affecting the collateral; and
          The liability hereunder assumed shall not be affected by the
          acceptance of any settlement or composition by Guarantor either
          in liquidation, readjustment, receivership, bankruptcy or
          otherwise, except only to the extent that such settlement has
          resulted in actual payment of a part of the indebtedness, and
          then only to that extent.

WM shall not be required to give notice to Guarantor of any
failure or omission on the part of Guarantor to meet any payment
sooner than at the time payment hereunder is demanded, and
Guarantor expressly waives any other notice.

The undersigned Guarantor hereby agrees to waive any rights of
subrogation of WM or any beneficiary of the Guaranty until such
time as WM or the beneficiary has received payment under the
aforementioned Note.

Nothing contained in this Guaranty shall be construed as obliging
Guarantor in anywise to be responsible for interest in excess of
what would be lawful for Guarantor to pay under the
circumstances.

This instrument is to be construed as a continuing, binding,
absolute, and unconditional guaranty that shall remain in full
force and effect as written until actual payment of said

                               4
<PAGE>
Promissory Note, both principal and interest, or until terminated
by agreement between the Guarantor and the holder of this
guaranty.  To the extent permitted by law, Guarantor shall pay
all reasonable attorney fees and other costs and expenses
incurred by WM in the event that WM shall be obliged to resort to
the courts or require the services of an attorney to collect
hereunder or to protect or preserve the Collateral.

If any part of this guaranty agreement shall not be valid under
the laws or the state or jurisdiction where the premises
encumbered by the mortgage that secures the Promissory Note
concerning which this guaranty has been issued is located, such
part shall be rendered inoperative, but the remainder of this
guaranty shall be enforced.

Wherever the name of WM appears, the rights and authority granted
WM shall inure to the benefit of its successors and assigns
(whether such statement follows WM's title or not), and the
agreement contained herein by Guarantor shall bind the successors
and assigns of Guarantor.

IN WITNESS WHEREOF the Guarantor has executed this guaranty on
this 31st day of August, 2000.

DIVERSIFIED SCIENTIFIC SERVICES,
INC.

By: /s/ Robert G. Simpson
    _____________________________

Title:  President
      ____________________________

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