United States
                    Environmental Protection
                    Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
                    Research and Development
EPA/600/SR-92/187    October 1992
\yEPA        Project  Summary
                     Pollution  Prevention Opportunity
                     Assessment:  Histology
                     Laboratory  Xylene  Use
                     Fort  Carson, Colorado

                    George Wahl, Deana Stamm, Jeffery Driver, and Joe Bob Cravens
                      One of the primary ongoing programs
                    for promotion and encouragement of
                    pollution prevention research is a co-
                    operative  program  between the U.S.
                    Environmental Protection Agency (EPA)
                    and the Federal  community at large.
                    EPA's Waste Reduction Evaluations at
                    Federal Sites (WREAFS) Program sup-
                    ports  pollution prevention research
                    through joint assessments of problem-
                    atic areas at selected sites. The three
                    primary objectives of the WREAFS
                    Program are to 1) conduct waste mini-
                    mization assessments and case stud-
                    ies; 2) conduct research and demon-
                    stration projects jointly with other Fed-
                    eral activities; and 3) provide technol-
                    ogy and information transfer of pollu-
                    tion prevention results.
                      A Pollution Prevention  Opportunity
                    Assessment of a community hospital
                    undertook an evaluation of xylene and
                    ethanol waste streams generated as the
                    result of tissue processing and staining
                    in the hospital's  histology laboratory,
                    and methanol waste pollutions from the
                    hematology laboratory.
                      Feasibility analyses for  solvent re-
                    covery, materials substitution, and vol-
                    ume reduction also considered both
                    technical and economic factors. These
                    analyses  allowed an  "economic  of
                    scale" to  be constructed  to illustrate
                    the net savings and payback periods
                    for these options when implemented in
                    histology laboratories of varying work
                    loads (i.e., tissue sample throughputs).
                      This Project Summary was developed
                    by EPA's Risk Reduction Engineering
                    Laboratory, Cincinnati, OH, to announce
key findings  of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).

Introduction
  To promote  pollution prevention activi-
ties in accordance with the national policy
objectives established under the  1984
Hazardous and Solid Waste Amendments
to  the Resource Conservation and Re-
covery Act of 1976 (RCRA), the Risk Re-
duction Engineering Laboratory (RREL) of
the EPA's Office of  Research and Devel-
opment  is supporting the Waste Reduc-
tion  Evaluations   at Federal  Sites
(WREAFS) Program. This program con-
sists of  a series of projects for pollution
prevention conducted cooperatively by
EPA and various parts of the Department
of  Defense, Department of Energy, and
other Federal  agencies. The WREAFS
Program focuses on pollution prevention
research opportunities and technical as-
sessments at Federal sites. The present
project focused on a pollution prevention
opportunity assessment conducted at the
Fort Carson Evans Community Hospital
(ECH) Histology Laboratory in Colorado
Springs, CO.
  Results of the pollution prevention op-
portunity assessment conducted at the
histology laboratory identified two pollution
prevention opportunities involving materi-
als used for tissue  processing and slide
staining.  The third  opportunity that was
investigated was volume  reduction. At
ECH, however, this option  had  been
implemented by installing and utilizing au-
tomatic tissue and staining processors, so
                                                                    Printed on Recycled Pd

-------
 the cost savings associated  with volume
 reduction had already been  realized and
 are no longer available.

 Pollution Prevention
 Opportunities
   The pollution prevention opportunity as-
 sessment was  initiated by developing an
 inventory of the wastes generated at the
 ECH. Although the waste stream includes
 small quantities of various chemicals, xy-
 lene, ethanol, and methanol are the most
 significant wastes, with respect to volume,
 and require disposal as hazardous waste.
   The Pathology  Department (which in-
 cludes the histology  laboratory) at ECH
 disposes of approximately 150, 250, and
 240 L (40, 66, and 63 gal) per yr of xy-
 lene, ethanol, and methanol,  respectively.
 The principal operations  involving these
 solvents include human tissue processing
 and slide staining  for histologic and cyto-
 logic evaluations to support clinical diag-
 noses. The current method of disposal is
 through a local contractor who transports
 and incinerates the solvent waste. Chemi-
 cal  Waste  Management,  located  in
 Henderson, CO, is currently  under con-
 tract  for this purpose.  Disposal costs is
 approximately $160/55-gal drum,  includ-
 ing transportation. The generation of these
 solvent  wastes  involve the following spe-
 cific processes.

 Tissue Processing
   One solvent  reservoir of xylene  with a
 volume  of 1.5  L  and two reservoirs  of
 ethanol with  volumes of  3.5  and  0.7  L,
 respectively,  are used  in  the  automatic
 tissue processing equipment. The  xylene
 and ethanol baths  used during tissue pro-
 cessing are discarded and replaced  with
 fresh solvent on a weekly basis. The dis-
 carded solvents are currently placed in a
 hazardous waste storage container.  During
 this  procedure,  the  solvents  are  mixed
 (the three chemicals from both the histol-
 ogy and  hematology  laboratories are not
 segregated but  "pooled"  (mixed)  in the
 same drum and disposed together) in 55-
 gal drums with  significant  volumes of
 methanol from the hematology laboratory
 for eventual transport by a contractor for
 disposal.

 Slide Staining
   Two solvent reservoirs  of xylene, both
 with  volumes of  0.7 L, and one reservoir
of ethanol with a volume of 0.7 L are used
 in the automatic staining equipment. The
 ethanol  used  during slide  staining of his-
tologic or cytologic specimens is changed
on  a weekly basis.  Of  the  two  xylene
 reservoirs (baths), the first reservoir is dis-
 carded;  the  second  reservoir  is rotated
 forward; and a fresh  xylene reservoir re-
 places  the  reservoir  that is rotated for-
 ward. This is done on a weekly basis. In
 the  hematology  laboratory, methanol  is
 used for slide staining and other purposes.
   It is important  to note that for the pur-
 poses of implementing any solvent recov-
 ery option, it would be necessary to keep
 these solvents separate to maximize their
 recovery and  reuse.  The hematology
 laboratory's methanol waste can  be kept
 separate  from  the histology laboratory's
 xylene and ethanol waste. Because cross-
 contamination of  the  xylene and ethanol
 baths occur during tissue processing and
 slide staining, therefore, mixing of xylene
 and ethanol  will always occur in the pro-
 cess of tissue preparation for microscopic
 examination.
   Two  pollution prevention options were
 identified and evaluated  for xylene and
 ethanol waste generated  as the result of
 tissue  processing and  slide staining ac-
 tivities in the histology laboratory solvent
 substitution  and solvent recovery. These
 options were also evaluated for methanol
 waste  resulting from staining procedures
 performed in the  hematology  laboratory.
 The technical details of these options are
 discussed in the full  report summarized
 here.

 Solvent Substitution
   Example   xylene  substitutes  include
 Clear-Rite 3®*, Americlear®, Histosolv X®,
 and Mediclear II®.  Adequate discussions of
 the toxicological profiles of these substi-
 tutes are not available to be able to com-
 pare their toxicity and  safety to that  of
 xylene.  A review  of the  Material Safety
 Data Sheets  shows that the primary haz-
 ardous constituent of the chemical substi-
 tutes are aliphatic petroleum distillates,
 which are classified as a D001 (Flammable
 Liquid) hazardous waste for disposal pur-
 poses. Before disposal into the sanitary
 sewer, the local wastewater treatment au-
 thority  would need to  be consulted for
 either discharge  approval, or  permitting,
 or both.  Sanitary sewer districts often  grant
 permission  for  such  discharges for
 nonbioaccumulative wastes that are  in di-
 lute, or low-volume solutions, or both.
  When  selecting  a substitute, a number
 of criteria must be considered. These  in-
clude toxicity, physicochemical character-
 istics, compatibility with  other materials,
 performance, availability,  recycling re-
quirements,  disposal  requirements, and
cost.
 Mention of trade names or commercial products does
 not constitute endorsement or recommendation for
 use.
   The ECH has initiated an evaluation of
 available xylene substitutes.  Preliminary
 results with vendor's substitutes indicated
 a preference for continuing to use xylene.
 The primary reason is related to xylene's
 ability to provide maximum paraffin infil-
 tration  of tissues resulting  in greater
 specimen  visibility  and, thus, enhanced
 microscopic  examination.  Further,  some
 of the available substitutes have a citrus
 odor that  was undesirable to laboratory
 staff, and the staff believed the substitutes
 did not provide equal or better specimen
 visibility. The use of vacuum hoods could,
 however, eliminate  the undesirable odors.
 Xylene  substitutes  are used in both open
 and closed processors  and  have  been
 reported to be nondrying to skin, leave no
 oily  residue  for faster  and  easier slide
 cleaning, and allow for complete paraffin
 infiltration rendering tissues less brittle than
 xylenes. Further information is required,
 however,  with respect  to  the potential
 hazards and safe use conditions of xylene
 substitutes.
   Methanol substitutes for use in the he-
 matology laboratory were not identified.
 Since methanol waste mixed with xylene
 and ethanol is difficult to separate by dis-
 tillation, ECH should implement a program
 to keep methanol waste separate.

 Solvent Recovery
   Clinical laboratories in general, and his-
 tology laboratories  in  particular, have a
 large demand  for organic solvents. The
 ECH  laboratory is no exception. The his-
 tology department is a major consumer of
 xylene and ethanol. In addition, the hema-
 tology laboratory uses  a significant vol-
 ume of methanol. One method for mini-
 mizing the amount  of these solvents is to
 recover the solvents with the use of distil-
 lation techniques.  The  histology labora-
 tory  at  ECH has  been  considering this
 option as a possible means of pollution
 prevention. The initial investment cost of
 a  sophisticated distillation  system  can
 usually  be recovered in  a reasonable
 amount of time (e.g., 1 yr because less
 solvent is needed and disposed costs are
 reduced).
  The ECH laboratory mixes xylene, etha-
 nol, and  methanol wastes for ease of dis-
 posal. The only  method to effectively sepa-
 rate these  chemicals onsite is by distilla-
tion. In distillation, substances are heated
to their boiling temperatures when the sub-
stance with the lowest boiling point is va-
porized.  This vapor rises  into the  con-
densing portion of the distillation column
where it reverts back to its liquid state and
is  removed from the column. Efficiencies
for separating compounds in mixtures have
been achieved  by using mechanisms de-

-------
signed to continuously mix the vapor and
liquid phases  during  the  distillation  pro-
cess. With these mechanisms, the vapor
becomes increasingly enriched  with the
higher boiling  compound,  and essentially
complete separations  can  be achieved.
  Two different  solvent  recovery tech-
niques have been developed to  enhance
the efficiency  of solvent separation. One
method available for distillation of labora-
tory  solvents  (spinning band distillation)
uses  a motor-driven  Teflon band  in the
distillation  column.  Another method uti-
lizes  an  atomized  plate  technique.  Al-
though these distillation methods offer ef-
ficient separation, pure ethanol cannot be
separated and recovered from xylene and
ethanol mixtures. In fact,  even if ethanol
could be kept completely free of xylene
contamination during tissue processing and
slide  staining, the  ability of an  alcohol
recovery  system to produce a virgin grade
(95% +) alcohol depends on the system's
ability to  deal with the azeotropic link be-
tween alcohol  and water  (see number 2
below for explanation  of the source of the
water) as well  as on effective alcohol re-
covery operational procedures. Effective
operational procedures have been recom-
mended as follows:
 (1) Either  ethanol or methanol  (recom-
    mended   by  the  tissue processor
    manufacturer) should  be used  be-
    cause of their low  azeotrope to water;
 (2) All alcohol containers should be filled
    at the  end of each shift; discard the
    contents of the flush  container  (nor-
    mally 70% alcohol) following the for-
    malin container; the alcohol in all re-
    maining containers is  put into a stor-
    age vessel to be reclaimed later;
 (3) The last alcohol container is normally
    absolute; it should continue to be re-
    placed with absolute alcohol; this will
    be the only "make-up" solvent neces-
    sary  to purchase;
 (4) The  alcohol reclaimed using distilla-
    tion methods normally has a  purity of
    95%  or greater; this  alcohol should
    be used in  the containers between
    the flush container and the absolute
    container;  there will  be enough re-
    claimed 95% + alcohol left over after
    filling the  middle  containers to be
    blended to 70% purity for the flush
    container.
 Economic Feasibility Analysis
   The economic feasibility evaluation in-
 cludes a preliminary cost analysis of both
 capital and operating costs. For this study,
 capital costs include  estimates of equip-
 ment and materials. The operating  costs
 include estimates of disposal fees and
 raw materials.  Not included were  insur-
 ance and  liabilities  costs  because  they
 were undetermined  and  utility  use and
 labor costs because they were consid-
 ered  relatively unchanged. Based on the
 economic analyses, an economies of scale
 was  developed  (i.e., the economics for
 different amounts of  slide  production) to
 illustrate the net savings and payback pe-
 riods for each of the three options. Scale
 Level A  represents  laboratories  with
 monthly slide sample throughput of 8,000
 or more slides; Scale Level B throughput
 of 1,000 to 8,000 slides; Scale Level C
 throughput of less than  1,000 slides.
   In  Table  1  the cost  analysis data for
 ECH  (i.e.,  pollution  prevention  cost  as-
 sessment factors determining technical
 feasibility) are summarized: the total capi-
 tal investment, the net operating cost sav-
 ings,  and the payback period (total capital
 investment/net operating cost savings per
 month) for each  option,  and each level of
 throughputs. Payback evaluatbn worksheets
 for the solvent recovery option are presented
 in the final report. The payback evaluation
 was based on solvent waste recovery for
 xylene and  ethanol  only  because these
 two solvents can economically be recov-
 ered  with the use of the  same solvent
 waste recovery unit. Recovering methanol
 would require a separate unit or the imple-
 mentation of a solvent waste segregation
 program. Worksheets for solvent substitu-
 tion and  solvent reduction  were not pre-
 pared. No savings are  realized from the
 use of solvent (material) substitutes. The
 data  reporting savings  from volume  re-
 duction from the use of  automated equip-
 ment  are presented only as a  case study
 since ECH already  uses an  automated
 system, and no additional improvement is
 possible.

 Conclusions and
 Recommendations
  The technical  and economic results of
the feasibility analysis phase are summa-
 rized  in the next  column.
   Solvent recovery: This option is clearly
the most beneficial to ECH, provided that
the  relatively high payback (97  mo)  is
attractive to their operations. It can be an
effective pollution prevention method for
xylene, ethanol, methanol, and other his-
tology solvents;  however, solvent waste
segregation is important to make this op-
tion feasible.
   Substitution: Although this option may
provide the use of  less toxic substances,
the relatively high cost of the substitutes
and  their less  effective performance for
tissue cleaning  (compared with xylene)
make their benefit  as  a waste minimiza-
tion option less significant.
   Volume reduction: ECH, like most
laboratories,  is currently using automated
equipment. This option may provide labo-
ratories using manual tissue processors
and  slide  stainers  a significant  savings
because solvent purchased as  well as
disposal costs are reduced.
   In conclusion, the economy  of scale
analysis indicates  that solvent  recovery
can be  a cost-effective and attractive pol-
lution prevention option to  implement  in
large throughput histology  laboratories
(8,000 slides/mo or larger) as indicated by
the low payback period (11  mo). It is a
less  attractive option for the smaller scale
laboratories having  slide  throughputs of
less  than 8,000/mo (payback period 97
mo). The purchase of a solvent  recovery
unit  to  allow the recovery of  methanol
along with xylene and ethanol  would in-
crease the economic feasibility of solvent
recovery.  Material substitution offers the
benefits of less  toxic material; however,
its higher  cost  (compared with current
practice) may not be justified unless con-
sidered primarily  on  environmental
grounds. Volume reduction from the use
of automated equipment can offer signifi-
cant  savings in  laboratories still using
manual processors. This  option  has al-
ready been implemented  in most histol-
ogy laboratories, including ECH.
  The  full report was submitted in fulfill-
ment of EPA Contract No. 68-C8-0061 by
Science Applications International Corpo-
ration, Cincinnati, OH, under the sponsor-
ship of the  U.S. Environmental Protection
Agency.
                                                                                     'U.S. Government Printing Office: 1992 — 648-060/60132

-------
Table 1.  Summary of Cost Analysis Data for Pollution Prevention Options
  Option Description
        Capital Investment
1.   Solvent Recovery
      Scale Level A
      Scale Level B
      Scale Level C

2.   Material Substitution
      Scale Level A
      Scale Level B
      Scale Level C
     Volume Reduction
      Scale Level A
      Scale Level B
      Scale Level C
                                   12,800-18,900
                                   8,500-10,900
                                    7,900-8,500
No capital investment required


No capital investment required


No capital investment required
      25,500-32,750
      22,200-25,500
      18,300-22,200
                                                           Cost Savings/Month *
                                                                   Payback Period (Months)
                                    Up to $1,780
                                    Up to $120
                                    Up to $68
 None, will increase operating cost
 by about $384-$2,137/mo.

 None, will increase operating cost
 by about $72-$401/mo.

 None, will increase operating cost
 by about $21-$117/mo.
Up to $1,190
Up to $793
Up to $477
                                           11
                                          97
                                         124
                                                                                               Costs cannot be recovered
                                                                                               Costs cannot be recovered
                                                                                               Costs cannot be recovered
                                                                                                       21-28
                                                                                                       28-32
                                                                                                       38-47
 * These savings were calculated utilizing solvent cost as follows: xylene, $7.50/gal; ethanol, $7.60/gal;andmethanol, $2.00/gal.

 * Data for solvent volume reductions were provided by a major equipment vendor. The data compare total solvent cost requirements for manual tissue
 processors and the same requirements for an automatic processor provided with solvent evaporation and fume control. Total savings of$274/wk was
 reported for the Level A operation (based on Hacker Instruments estimation). Savings on Levels B and C operations were proportioned based on total slide
 throughput capacity.
  George Wahl and Deana Stamm are with Science Applications International
    Corporation, Cincinnati, OH 45203; Jeffery Driver and Joe Bob Cravens are
    with Versar, Inc., Springfield, VA 22151.
  Kenneth R. Stone is the EPA Project Officer (see below).
  The complete report, entitled "Pollution Prevention Opportunity Assessment:
      Histology Laboratory Xylene Use, Fort Carson, Colorado," (Order No.
      PB92-228 436/AS; Cost: $19.00, subject to change) will be available only
      from:
          National Technical Information Service
          5285 Port Royal Road
          Springfield,  VA 22161
          Telephone: 703-487-4650
  The EPA Project Officer can be contacted at:
          Risk Reduction Engineering Laboratory
          U. S. Environmental Protection Agency
          Cincinnati, OH 45268
 United States
 Environmental Protection Agency
 Center for Environmental Research Information
 Cincinnati, OH 45268

 Official Business
 Penalty for Private Use
 $300
                                                                              BULK RATE
                                                                        POSTAGE & FEES PAID
                                                                                  EPA
                                                                           PERMIT No. G-35
 EPA/600/SR-92/187

-------