Final  Report

Assessment of Exposures and Risks from the Use
      of Pulp-Containing Medical Devices

          EPA Contract  No.  68-D9-0166
                  Task No.  2
                 Prepared for

     U.S.  Environmental  Protection Agency
          Office of Toxic Substances
         Exposure Evaluation Division
          Exposure Assessment Branch
               401 M Street, SW
             Washington, DC 20460
                 Prepared  by

                 Versar  Inc.
              6850  Versar Center
         Springfield, Virginia  22151
               October 30, 1989
              (Updated July  1990)

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                                 DISCLAIMER
    This document has been reviewed and approved for publication by the
Office of Toxic Substances, Office of Pesticides and Toxic Substances,
U.S. Environmental Protection Agency.  The use of trade names or
commercial products does not constitute Agency endorsement or
recommendation for use.
                                     11

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                             TABLE OF CONTENTS
                                                                Page No,
1.  INTRODUCTION 	     1
2.  ESTIMATES OF EXPOSURES AND RISKS FROM DERMAL CONTACT WITH
    PULP-CONTAINING MEDICAL DEVICES 	     3
    2.1   Exposure Parameters 	     3
          2.1.1   Specific Medical Devices 	     8
          2.1.2   Exposure Duration 	     9
          2.1.3   Absorption Rate 	     9
    2.2   Exposure/Risk Assessment for Medical Devices 	    10
3.  UNCERTAINTY ANALYSIS 	    15
4.  CONCLUSIONS 	    17
5.  REFERENCES 	    18
                                    111

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Table 1-1.


Table 2-1.

Table 2-2.



Table 2-3.



Table 2-4.
                              LIST OF TABLES
Medical Devices for Which Exposure and Risks
Were Estimated and Their Corresponding Uses 	

Exposure/Risk Parameters for Medical Devices 	

Average Concentrations of 2,3,7,8-TCDD and
2,3,7,8-TCDF in Pulp Calculated Based on Results
from the 104-Mi 11 Data Base	
Page No.


   2

   4
Average Concentrations of 2,3,7,8-TCDD and
2,3,7,8-TCDF in Pulp at Pulp Mills that Produce
Dissolving Cellulose 	
Estimates of Risks to Individuals from the Use
of Pulp-Containing Medical Devices 	
   6


  11
                                     IV

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1.        INTRODUCTION
    Under the terms of the July 1988 Consent Decree between EPA,  EOF,  and
NWF, EPA must assess risks associated with the use of medical  devices
since these devices are known to contain bleached wood pulp or
derivatives of bleached wood pulp.  This report provides the estimated
exposures and risks associated with the use of medical devices containing
bleached wood pulp.  The scope of this assessment is limited to "patients"
(nonoccupational); occupational exposures and risks were not estimated.

    This assessment has been developed in cooperation with the Food and
Drug Administration (FDA) Center for Devices and Radiological  Health
(CRDH).  The Center has provided a list of medical devices that contain
bleached wood pulp, numerous parameters/assumptions concerning product
use and wood pulp content, and general guidance on how each product is
used.

    Table 1-1 provides a list of those medical devices believed to
contain bleached wood pulp.  Note, however, that FDA  is not certain
whether other medical devices may contain bleached wood pulp because
manufacturers are not required to provide FDA information regarding the
ultimate source of the raw materials.  Therefore, the products listed  in
this table are FDA's best estimate on what products contain bleached wood
pulp.  These devices are used at medical facilities,  and several may be
purchased over the counter for home use.

    This report 1s organized into three parts.  Section 2 contains all
the exposure and risk estimates, along with input parameters used to
derive these estimates.  A discussion on uncertainties is presented in
Section 3, and Section 4 presents conclusions.
6914H

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          9215H
                                      Table 1-1.  Medical Devices for Witch Exposures and Risks Were Estimated and Their Corresponding Uses
          Medical device
                                                                                                          Use
rv>
Unscented Menstrual pad
Scented menstrual pad
Unscented Menstruat tampon
Scented •enstrual tampon
Alcohol pads
Skin preparation for dressing wounds
Mnarbable hemostatlc agents
Vbund dressings containing carboxymethyl
  cellulose
Surgical apparel
Mult diapers
Medical disposal bedding
Medical absorbent fiber
Absorbent tipped applicator
Examination own
Ophthalmic sponges
Hydroxpropymethyl cellulose
Cottonoid paddie
Electraconductive Media
Cutaneous electrode
Anesthetic conduction filter
 Breathing circuit  bacteria filter

 Heat and Moisture condensers
 Isolation gowns
To absorb Menstrual  discharge
To absorb Menstrual  discharge
To absorb Menstrual  discharge
To absorb Menstrual  discharge
To apply alcohol or  other disinfectants to the  surface of  the skin
To clean cuts or wounds before applying a permanent  bandage
A small sponge used during surgery
To cover cuts or wounds

Morn by surgeons, nurses, and patients during surgery (e.g.. hoods, caps. Masks, gowns, foot coverings, drapes)
To absorb urine or feces uncontrollably released by adults
To cover Mattresses
Cotton-like pads used to apply Medication or to absorb small amounts  of  fluid fro* a patient's body surface
lo apply Medications or remove specimens from a patient
Mom by patients during examinations
Small sponges used to absorb fluids during eye surgery
lo replace fluids in the eye  lost during surgery
lo absorb body  fluids (i.e.. a cotton ball)
Conductive creams or gels used to reduce the impedance to the electrode  from the surface of the skin
An electrode applied directly to the skin to either record physiological signals or apply stimulation
A microporous filler used to  remove particulars from anesthesia or olher gases
lo filter Microbiological and partlculate matter from a breathing circuit (which administers medical gases to a
patient)
lo preserve  the purity  and physical state of gases used in a respirator  or  as an anesthesia
Worn  to  isolate patients at a hospital

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2.       ESTIMATES OF EXPOSURES AND RISKS FROM DERMAL CONTACT WITH PULP-
         CONTAINING MEDICAL DEVICES
2.1   Exposure Parameters
    The exposure parameters used to estimate exposure and risks from
dermal contact with pulp-containing medical devices are listed in
Table 2-1.  Unless otherwise noted, the data in this table were obtained
directly from FDA (letter from Mel Stratmeyer, Food and Drug
Administration, to Greg Schweer, U.S. Environmental Protection Agency,
dated June 5, 1989).

    In addition to the exposure parameters listed in Table 2-1, the
industry average concentrations of 2,3,7,8-TCDD and 2,3,7-8-TCDF found in
pulp in the 104 Mill Study were used to estimate exposures and risks for
all medical devices, except those made from rayon.  This was necessary
because, in most cases, concentrations of 2,3,7,8-TCDD and 2,3,7,8-TCDF
in pulp at individual mills could not be traced to specific medical
devices.  In calculating the average values, one-half the detection limit
was substituted for nondetected values (see Table 2-2).  However, the
average concentrations were similar to average concentrations calculated
without nondetected values.

    For those medical devices made from rayon, the identities of those
mills that produce dissolving cellulose pulp used to make rayon were
identified by the American Paper Institute.  The locations of the sites
and the concentrations of 2,3,7,8-TCDD and 2,3,7,8-TCDF in pulp from
those sites as found in the 104 Mill Study are presented in Table 2-3.

    Of the devices listed in Table 2-1, the following subset belongs  in
the category of rayon-containing devices:

    Unscented Menstrual Tampon
    Scented Menstrual Tampon
8914H

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 921SH
                                                   Table 2-1.  Exposure/Risk Parameters for Medical Devices


Device
Pulp in
Pulp
•ass in
•ass* product* product*
Device name*
Unscented Menstrual Pad
Scented Menstrua) Pad
unscented Menstrual Tampon
Scented Mentrual Tampon
Alcohol Pads
Skin Prep. Mipe for
Dressing Wounds
Absorbable Hemostatic Agents
(e.g.. SurgicelR. Oxycel)
Wound Dressings Containing
Carboxyaethyl Cellulose
Surgical Apparel: Hood. Cap.
Masks. GOMU. Foot Cov.. Drapes
Adult Diapers
Medical Disposable Bedding
Medical Absorbent Fiber
Absorbent Tipped Applicator
Examination Gown
Ophthalmic Sponges
Hydroxypropyaethyl Cellulose
Cottonoid Paddie
Electro Conductive Media
Cutaneous Electrode
Anesthetic Conduction Filter
Breathing Circuit Bacteria Filter
Heat 1 Moisture Condensers
Isolation GOMIS
Contact type*
Skin
Skin
Intact Nat. Channel
Intact Rat. Channel
Skin
External. Short Tem

Internal. Short Term

Compromised Tissue

External

Skin
Skin
Skin
Skin
Skin
Surgical Aids
Intraocular Surtj Aid
Compromised Tissue
Skin Surface! Intact)
Skin Surface! Intact)
No Direct Contact
No Direct Contact
No Direct Contact
External
(g-)
10
10
3-5
3-5
0.5-1
2

3-5

4

150 (GVNS)
7-10 (MSKS)
113.5
113.5
<0.5
0.25
113.5
0.5

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9315H

 Table 2-2.  Average Concentrations of 2.3.7.8-TCOO and 2.3,7.8-TCOF in
             Pulp Calculated Based on Results fro* the 104-Mill Data Base
                    Highest
                     cone.
                    (pg/g)
                     Average
                   cone, without
                     nondet.
                     (pg/g)
                    Average
                   cone, with
                     nondet.
                     (pg/g)
2.3.7.8-TCOO
2.3.7.8-TCOf
  116
2.620
8.4
84.4
 8.5
84.4

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9215H
    Table 2-3.
Concentrations of 2.3.7.8-TCDO and 2,3.7.8-TCDF  in
Pulp at Pulp Mills that Produce Dissolving  Cellulose



Conpany
Alaska Pulp Corp.
International Paper Co.

ITT Rayonier. Inc.





Ketch ikan Pulp ft Paper
Proctor ft 6art>le Co.
Weyerhaeuser Co.






Nill location
Sitka. AK
v Natchez. MS

Fernandina Beach. FL
Jesup, GA



Port Angeles. UA.
Ketch ikan. AK
Mehoopany. PA
CosBOpolls. UA



2.3.7.8-
TCOO
cone.
(P9/9)
0.7 (NO)
3.6
2.2
0.2 (NO)
0.6 (NO)
0.3 (NO)
0.7 (NO)
0.7 (NO)
0.6 (NO)
0.3 (NO)
2.0
1.0 (NO)
NQ
0.3 (NO)
0.3 (NO)
2.3.7.8-
TCDF
cone.
(P9/9)
1.4
15.0
3.0
0.5 (NO)
0.8 (NO)
0.8
0.6
0.9
2.1
0.3 (NO)
1.1
6.3
6.4
2.9
3.1
AVERAGE CONCENTRATION9
                                   0.8
3.0
NO « Non-Oetect.
NQ • Not Quantified.

a In calculating the average concentrations. NO values were assumed to
  be one-half the detection limit.

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9215H
a There •ill be no direct contact for these products.  The only poten-
  tial exposure route is through inhalation of dioxin that leaves the fil-
  ter or condenser and enters the indoor air.  The exposure through this
  pathway  is expected to be negligible because only a very snail amount of
  dioxin will  leave these products and enter the air, and of the amount
  that does enter the indoor air. very little will actually enter the
  lungs and be absorbed.
  HDDs were calculated as follows: 8
  (Concentration (j£) x. Pulp Mass ( q 1 x Exposure Duration (Days) x Volume of Liquid on Skin/Total  Volume
                  9                day
         x letting Factor (unitlessl x I/Partition Coefficient [unit less) < Absorption Rate [X))
                          Body Weight (Kg) x Lifetime (70 years) x 365 days/year.

  There «ere two exceptions, however.  The first exception mas the net hod
  to estimate LADD for surgical apparel. Medical disposable bedding.
  examination gowns, and isolation gowns and this was explained in foot-
  note h in Table 8-2.  The other exception MS for products where FDA
  already estimated the total mass of the product available for exposure
  (skin prep, wipe for dressing wounds, absorbable heaostatic agents, and
  wound dressings containing carboxyaethyl cellulose).  In this case, LADO
  was estimated as follows:8
      (Concentration x Total Mass Exposed x Volume of Liquid on Skin/Total Volune
             x Wetting Factor x I/Partition Coefficient x Absorption Rate 1
                         Body Weight x 70 years x 365 days/year
c The slope factors are as follows for TCDO:  EPA 1.56 x 1(T ("g/kg
  day)'1; FOA • 1.75 x 10* (ag/kg day)'1; CPSC - 6.7 x ID4 (•g/kg/day)'1 .
d The slope factors are as follows for TCDF:  EPA 1.56 x 104 (ng/kg
day}'1;  FOA = 1.7S x 103 l«g/ks day)'1; CPSC = D.
e For EPA and FOA cancer slope factors, risk was estimated as follows:
  Risk • potency factor (ag/kg-day)'1 x 10~9 •g/pq x LAM (pq/kg-day)/O.S5.
  However,  for the CPSC cancer slope factor, risk was estimated as
  follows:   Risk - potency factor (ig/kg-day)'1 x 10"9 ag/pg x LADO
  (pg/kg-day) / 0.75.  The divisor is changed to 0.75 (from 0.55) because
  a different bloassay was used.   The total risk 1s the SUM of the risks
  fro* TCOO and TCOF.

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    Would Dressings Containing Carboxymethyl  Cellulose
    Medical Absorbent Fiber
    Hydroxpropymethyl Cellulose

    The exposure parameters in Table 2-1  that require further explanation
are detailed below.

2.1,1    Exposure Duration

    Depending on the specific situation,  alcohol  pads  are used  rarely  to
daily.  As a worst use assumption it is assumed that each application  of
alcohol pads lasted 30 seconds and will be administered 365 days  per year
for 50 years.

    Surgical apparel and isolation gowns are used only during surgery.
It is assumed that surgery lasts 2 hours or 0.083 day and occurs  twice
over a 70-year lifetime.   In addition, exposure to medical dispos-
able bedding will occur for hours on a rare basis.  It is assumed that
exposure to medical disposable bedding would last 12 hours per visit and
would occur twice over a 70-year lifetime.  The examination gowns used by
patients are worn occasionally for hours.  It  is assumed that the gowns
are worn for } hour every  5 years over a 70-year lifetime.

    Exposures to medical absorbent fiber and absorbent tipped applicators
occur for  seconds on an occasional to  daily  basis.  As a worst-case
assumption, it is assumed  that these devices are used for 60 seconds at a
rate of 365 days per year  over 70 years.

    Both ophthalmic  sponges and  hydroxypropymethyl  cellulose are  used dur-
ing eye surgery.   Eye  surgery  lasts  less than  1 hour and occurs once  or
twice per  lifetime.  Therefore,  it  is  assumed  that  eye  surgery will last
1 hour and that  it  occurs  twice  over a 70-year lifetime.
                                      8
S914H

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    Cottonoid paddies are used  several  minutes  to hours on a negligible
basis; therefore, it is assumed  that  the  paddies  are used once for 12
hours over a 70-year lifetime.   Electro conductive media and cutaneous
electrodes are used on a negligible basis for minutes to days.  It is
assumed that the exposure duration  for  these devices occur once for 2
days over a 70-year lifetime.

2.1.2    Absorption Rate

    The rate of 2,3,7,8-TCDD  transferred  to the skin over a 24-hour
period from surgical apparel, medical disposable  bedding, and examination
and isolation gowns is calculated  as  0.012 (0.0005/hr x 24 hr) (Babich
1989).  In addition, it was assumed that  25 percent of this amount will
be absorbed.  There is no partition coefficient since this is based on
dry skin transfer.  Therefore,  the  amount transferred and absorbed over a
24 hour period is 0.012 x 0.25  - 0.003  or 0.3%.  Since there  is no
partition coefficient, the LADD was calculated differently than for the
other products:

Concentration (pg/g) x Pulp Mass (a/day) Exposure Duration (days) x Transfer Rate 1%) x Absorption Rate (*'.)
                  Body Weight (kg) x  Lifetime (70 years) x 365 days/year
    For those products in contact  for long periods of time with internal
body fluids or in contact with  compromised tissue in a wetted state,  100
percent absorption was assumed.

2.1.3    Partition Coefficient

    The partition coefficients  used are those reported  for paper  pulp
using ethanol, synthetic urine,  or saline solution  in Babich  et al.
(1989).  The partition coefficient used for alcohol pads  is based on  the
ethanol results.  Ethanol closely  approximates the  rubbing alcohol
solution actually used.  The  transfer medium for the use  of absorbent
tipped applicators, cottonoid paddies,  electro conductive media,  and
8914H

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cutaneous electrode is assumed to be analogous to the transfer  medium
assumed by Babich (1989) for make-up removal  using facial  tissues
(ethanol).  This assumption provides a worst-case scenario for  the
partition coefficient.

    For all other medical devices, with the exception of diapers,  saline
solution was assumed to be the most representative partitioning/transfer
medium.  For adult diapers, the results from the urine partitioning
experiment were used.

    The final general point about Table 2-1 is that when no actual data
were available, reasonable or reasonable worst-case assumptions were used.
For example, for the "volume of liquid on skin/total volume" and the
"wetting factor," reasonable worst-case assumptions were used.   For parti-
tion coefficients, the most reasonable case was selected; however, if no
clear choice could be made, the worst-case option was used.  The estima-
tion of the exposure duration was also based on the most "reasonable"
assumptions.  However, if accurate data were not available, reasonable
worst-case assumptions were used.

2.2    Exposure/Risk Assessment for Medical Devices

    Table 2-4 lists the exposure/risks associated with the use of the
medical devices listed in Table 1-1.  A few general  points should be noted
when reviewing this table.  First, lifetime average  daily dose (LADD) was
estimated using three slightly different methods, depending on the way the
product is used and the type of data available.   The most common  method
was as follows:
          	fCUPMKEDUVUWFHl/PCHARl	
          Body Weight (kg) x Lifetime  (70 years)  x  365 Days/Year
                                     10
8914H

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                          Table 2-4.  Estimates of  Risks  to the General Population fro» the Use of Pulp-Containing Medical Devices
Lifetime average
dally dose
(LADO)b
(DQ/ko/dav)
2.
2.3.7.8-
Devlce MK
Unscented Menstrual Pad
Scented Menstrual Pad
Unscented Menstrual Ta^ion
Scented Menstrual Tampon
Alcohol Pad
Skin Prep. Wipe for Dressing
Wounds
Absorbable Hanstattc Agent
(e.g.. SurglceTR. Oxycel)
Mound Dressing Containing
Carboxyaethyl Cellulose
Surgical Apparel: Hood. Cap.
Mask. Gowi. Foot cov.. Drape
Adult Diaper
Medical Disposable Bedding
Medical Absorbent Fiber
Absorbent-Tipped Applicator
Examination Gown
Ophtha talc Sponge
Hydroxypropyaethyl Cellulose

Cottonoid Paddle
Electro-Conductive Media
Cutaneous Electrode

4
4
t
t
2
2

1

7

3
TCOO
.49E-08
.49E-08
.70E-07
.701-07
.67E-09
.081-10

.66E-08

.82E-12

.64E-07
TEQ
1.6SE-07
1.6SE-07
S.43E-07
S.43E-07
5.32E-09
7.64E-10

6.11E-08

1.57E-1I

7.2SE-07
EPA
4.68E-11
4.68E-1I
1.S4E-10
1.54E-10
1.51E-12
2.17E-13

1.73E-1I

4.46C-15

2.06E-10
3.7.8-
TCOO
(X)
27
27
50
50
50
27

27

50

50
c.d
Lifetime individual cancer risk
2.3.7.8-

FDA
5.25E-12
5.25E-12
I.73E-11
1.73E-11
1.70E-13
2.43E-14

1.95E-12

5.01E-16

2.31E-1I
TCOO
(X)
27
27
50
50
50
27

27

50

50

CPSC
4.01E-12
4.01E-12
2.41E-1I
2.41E-11
2.39E-13
1.86C-I4

1.48E-12

6.99E-16

3.25E-1I
,e
2.3.7.8-
1COO
(X)
100
100
100
100
100
100

100

100

100


Potentially
exposed
population
3.96E«07
3.71E«07
2.B3E+07
5.20E+06
l.OE+06 - 1
Millions

Millions

Hundreds of





OE+07




Thousands

Millions (patients)
Thousands (health care)
1
1
3
1
9
1
2

2
3
3
.05E-10
.62C-06
.46E-11
.26E-09
.7 IE -07
.5BE-11
.501-12

.38E-12
.S6E-12
.56E-12
3.43E-10
3.23E-06
6.96E-I1
2.51E-09
1.94E-07
5.15E-1I
5.03E-12

4.74E-12
7.10E-12
7.10E-12
9.73E-14
9.1SE-10
I.97E-14
7.13E-13
5.49C-IO
1.46E-14
1.43E-1S

1.34E-15
2.01E-I5
2.01E-15
31
50
50
50
50
31
50

50
50
50
I.09E-14
1.03E-10
2.22E-15
8.00E-14
6.16E-11
I.ME 15
I.60E-16

1.5IE-16
2.26C-16
2.26E-16
31
50
50
50
50
31
50

50
50
50
9.4IE-15
I.45E-IO
3.09E-I5
1.13E-13
8 6/E-ll
1.42E-15
2.24E-16

2.12E-16
3.18E-I6
3.18E-16
100
100
100
100
100
100
100

too
100
100
.OC+06 -
.OE+06 -
.OE+06 -
.OE*06 -
.OC«06 -

1.5 Million
Oper./Tear
Millions
Millions
Millions
OE»07
OCH17
OE*07
OE*07
OE+07

Cataract




Anesthetic Conduction Filter'
Breathing Circuit Bacteria Fltr.a
Heat ft Moisture Condensers*
Isolation Gowi
3.64E-07    7.25E-07
                            2.06C-10
                                         50
                                                2.31E-11
                                                             SO
                                                                     3.25E-1I
                                                                                  100
Millions
Millions
Millions
Millions (patients)
Thousands (health care)

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921SH
                                                                  Table 2-4.  (continued)
                           the
                                                              -ttr i
                                                                           .ir.
                                                                                     llttb .1.1
                                                                                                               the
b LAOOs «ere calculated as follows:
    (Concentrate g1) . Pulp H.,,
                                         « E-posun, Our.t.on (Days)  . Vol« of Houid on Skin/Total Vol« x -etting Factor  (unitless)
                                          1/Partition Coefficient (unUless) « Absorption Rate (%}}
                                          Body yeight (Kg) » Ufette (70 years) K 365 days/year

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where:

    C  = Concentration  (pg/g) of 2,3,7,8-TCDD or TCDF
    PH = Pulp mass (g/day)
    EO = Exposure duration (days/lifetime)
    V  = Volume of liquid on skin/total volume
    WF = Wetting factor  (unitless)
    PC = Partition coefficient (unitless)
    AR = Absorption rate  (%)

    This method estimates the amount of 2,3,7,8-TCDD/TCDF available on
the skin surface, the transfer rate of dioxin from the medical device to

the surface of the skin  (partition coefficient), and the absorption rate

through the skin.  For several products (skin preparation for dressing

wounds, absorbable hemostatic agents, and wound dressing containing

carboxymethyl cellulose), FDA provided the total mass of product an

individual may reasonably be exposed to over a lifetime.  Therefore, this

altered the way that the amount of 2,3,7,8-TCDD/TCDF available on the

skin surface was estimated.  For these products, LADD was estimated as

follows:

          	fCHTMHVHHFHl/POfAR)	
          Body Weight (kg) x Lifetime (70 years) x 365 days/year

where:
    C
    TM
    ED
    V
    WF
    PC
    AR
Concentration (pg/g)
Total mass exposed
Exposure duration (days/lifetime)
Volume of liquid on skin/total volume
Wetting factor (unitless)
Partition coefficient (unitless)
Absorption rate (%)
    For three other devices (surgical apparel, medical disposable bedding,
and examination gowns), the rate of 2,3,7,8-TCDD/TCDF transferred to the
skin and the absorption rate were combined.  This transfer and absorption
rate was used by Babich (1989), and 1t applies to products that will

undergo dry contact with the skin surface.  In these situations, LADD was

estimated as follows:
                                     13
8914H

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                            (CUPHUEDHTRHAR)
          Body Weight (kg) x Lifetime (70 years) x 365 days/year
where:
    C  = Concentration (pg/g)
    PM = Pulp mass (g/day)
    ED = Exposure duration (days)
    TR = Transfer rate (unitless)
    AR » Absorption rate (%)
    As shown in Table 2-4, LADDs for 2,3,7,8-TCDD were found to range from
2.38 x 10"12 pg/kg/day for cottonoid paddies to 1.62 x 10"6 pg/kg/day
for medical disposable bedding.  LADDs for 2,3,7,8-TCDF were found to
range from 2.36 x 10"11 pg/kg/day for cottonoid patties to 1.61 x
10~5 pg/kg/day for medical disposable bedding.  The other categories
with the highest exposure levels are isolation gowns, examination gowns,
surgical apparel, and tampons.  Exposures for all these categories were
estimated using the transfer and absorption rate of 0.3 percent because
they involve dry skin contact.  This method may be yielding unrealistic-
ally high estimates since it is expected that,  in reality, dry skin
contact would yield a lower dose.

    Estimated risks were found to vary from 2.22 x  10"16 to 9.15 x  10"
using EPA slope factors.  They were found to vary from 2.49 x  10"    to
1.03 x 10"10 using FDA slope factors and 5.07 x  10"17 to 1.45  x  10"10
using the CPSC factor (CPSC does not place the  same emphasis on  risks
calculated by the TEQ method as  it does for 2,3,7,8-TCDD itself  when
estimating carcinogenic potency.  Therefore, Table  2-4 presents  CPSC risk
estimates based on 2,3,7,8-TCDD  alone).
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3.       UNCERTAIHTY ANALYSIS
    The goal of an analysis of uncertainties is to provide decision  makers
with the complete spectrum of information concerning the quality of  an
assessment, including the variability in the estimated exposures and
risks, the inherent variability in the input parameters, data gaps,  and
the effect these gaps have on the accuracy or reasonableness of the  expo-
sure and risk estimates developed.  The general causes of uncertainty in
an exposure/risk assessment are as follows:

       Measurement error;
       Use of indirect empirical or generic data;
       Variability;
       Use of models to estimate exposure/risk; and
       Use of professional judgment/disagreement.
    For this assessment, uncertainties will occur from all of the above
areas.  All areas are important, with the possible exception of measure-
ment errors.  Measurement errors will occur (e.g., in determining the
product mass),  but compared to other errors, they will usually be
insignificant.   The remainder of this section discusses how the specifics
of this assessment apply to the major areas of uncertainty.

    Indirect or empirial data create uncertainties when the surrogate data
used do not directly apply.  The most important example is the partition
coefficient because most partition coefficients were usually not estimated
using the transfer medium in which the exposure will take place.  It is
anticipated that the partition coefficient can affect the results by over
an order of magnitude, and this may be the single most  important area of
uncertainty.

    Use of models to approximate the process of transfer and absorption
of dioxin thru human skin introduces uncertainty into the assessment.
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Uncertainty may be  further compounded by the selection of the input
parameters because  errors associated with these parameters may be
propagated by the use of these models.

    Variability and professional judgment are most important in terms of
the input parameters used in the exposure and risk models.  All parameters
are affected to some degree by these two areas of uncertainty, with
exposure duration likely to have the largest effect on the results.  For
some categories (e.g., menstrual products), exposure duration is known
within reasonable limits.  In most other categories, however, a wide
range of possible exposure durations is expected, and thus a high level of
uncertainty will occur.  Professional judgment is also particularly
important for "volume of liquid on skin/total volume" and "wetting
factor," since in most cases, measured data were not available.
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4.       CONCLUSIONS

    Based on the analysis presented in this report, risks from individual
medical devices are very small.  The most significant risk, medical
disposable bedding, was found to be 9.15 x 10   .   It is possible that
risks to health care workers could be greater than other subpopulations
because this population will have significantly higher exposure durations
and may be exposed to multiple medical devices.  Unfortunately, this sub-
population could not be characterized with the existing data.  If
additional work is done on risks from dipxins and furans in medical
devices, additional data should be gathered, and risks to health care
workers should be characterized.
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 5.        REFERENCES

 Babich MA,  Adams M, Cinalli  C,  Galloway D,  Hoang K,  Huang  S,  Rogers  P.
 1989.   Common assumptions for the assessment of human  dermal  exposure  to
 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)  and 2,3,7,8-tetratetrachloro-
 dibenzofuran (TCDF).  Interagency Dioxin-in-Paper Workgroup,  Dermal
 Bioavailability Workgroup,  December 12, 1989.

 Babich MA.   1989.   CPSC staff assessment of the risk to  human health from
 exposure  to chlorinated dioxins and dibcnzofurans in paper products.
 Memorandum  from Dr. Michael  A.  Babich (U.S.  Consumer Product  Safety
 Commission) to Lois Dicker  (U.S.  Environmental  Protection  Agency,  Office
 of  Toxic  Substances).   January  25,  1990.

 Stratmeyer  ME.   1989.   Letter from Dr.  Mel  E.  Stratmeyer (U.S.  Food  and
 Drug Administration, Center  for Devices and Radiological Health)  to  Greg
 Schweer (U.S.  Environmental  Protection  Agency,  Office  of Toxic
 Substances).   June  5,  1989.
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