Duke University Medical Center
Department of Community & Family Medicine
Division of Occupational & Environmental Medicine
Box 3834, Durham, NC 27710
August 11, 2003
Fax: 919-286-5647
Tel: 919-286-5744
Determination of the Magnitude of Clay to Skin and Skin to Mouth
Transfer of Phthalates Associated with the Use of Polymer Clays
Woodhall Stopford, MD, MSPH; John Turner, PhD
a
; Danielle Cappellini, BSc, MHA
a
;
Background
Polymer clays are modeling materials made up of polyvinyl chloride, plasticizers, fillers and
pigments. Use of these clays requires hand contact and then oven curing and exposures can occur
both during the handling and curing process. Curing at oven temperatures is associated with release
of small amounts of phthalate plasticizers. When over heating occurs, the artwork is destroyed and
hydrogen chloride gas is released.
In addition to exposure to thermal decomposition products, exposure can occur from incidental
hand-to-mouth activities or from contamination of food. Our risk assessment assumes that such
activities will transfer 100 mg of clay to the mouth each day. This presumption is similar to that
assumed by EPA for ingestion of dirt and dust by children under the age of 6 (EPA,1997). Hand-
to-mouth transfer is usually assessed in one of two ways: by measuring the uptake of a tracer or
by objective measurements of hand-to-mouth transfer in association with quantitative
measurements of hand contamination. Tracer studies of dirt intake (using measurements of
naturally present minerals both in dirt and stool) have been the primary source of estimates of
dirt ingestion. Hawley (1985) estimated that an individual might ingest Ā½ the dirt present on the
fingers by hand-to-mouth or hand-to-food contact (25% of the amount on the hands for children,
14% for adults). Actual measurement of hand-to-mouth transfer of soil found a similar transfer:
26% of dirt on a hand can be transferred to the mouth with licking of the thumbs and fingertips
of both hands (Kissel, et al., 1998).
In order to determine whether or not the assumption of ingestion of 100 mg of polymer clay a day
is conservative, we investigated the rate of hand contamination, both under laboratory conditions
and when professional artists work with polymer clays, and investigated hand-to-mouth and
hand-to-food transfer of plasticizers under heavy use situations.
a
Angeline Kirby Memorial Health Center, Wilkes-Barre PA
Methods
Preliminary transfer to hand studies were done under controlled conditions. Three polymer clays
sold in the US were tested. Each polymer clay was vigorously kneaded and rolled for 30 to 45
minutes. Weight change of the polymer clay was determined with a Mettler balance sensitive to
0.1 mg. Hands were washed twice for 1 minute with an hypoallergenic liquid hand soap followed
by rinsing with deionized water (DI water) prior to each session. Timers and scales were
calibrated against NBS or NIST-traceable standards. Results were standardized to measured
contact area (Kissel, et al., 1998) to allow he results to be compared between laboratory and in-
field studies.
Plasticizers were removed from the hands using a double washing technique with liquid hand soap
(Kimberly-Clark) as described by Brouwer et al. (2000). This technique has a mean removal
efficiency of up to 96% for pesticides. The efficiency of this technique for recovering plasticizers
from 3 types of clay was determined in duplicate under heavy use laboratory loading conditions
prior to field trials using the same technique as used in the preliminary manipulation studies. Overall
recovery efficiencies for the washing and analysis stages were determined by placing butyl benzyl
phthalate(BBP) on hands and then using the Brouwer et al (2000) method to compare added to
recovered BBP. Blank hand washing solution was spiked with the phthalates analyzed in this study
and recovery efficiencies were determined. Wash water and mouth wash samples were collected in
glass sample bottles with Teflon-lined caps for transfer to the USEPA-certified analytical laboratory.
Hand contact areas were determined by outlining each hand on pre-weighted (to 0.1 mg) and
measured parchment, cutting out and weighing the outlined areas. The contact surface area was
then determined by multiplying the weight ratio times the surface area of the uncut parchment
sheet.
Samples of each clay and any clay particles from recovery experiments were analyzed and transfer
and recovery determinations were expressed in terms of the amount of phthalates in manipulated or
chewed clay samples. The clay samples were ultrasonically extracted using EPA SW-846 Method
#3550. (The ultrasonic process ensures intimate contact of the clay with the extraction solvent.)
A 1.0g sample of clay or settled particles were serially extracted three times with 60ml of
cyclohexane. The extract was filtered through a Whatman 41 filter and dried over sodium
sulfate in a 250ml Erlenmeyer flask. The extract was concentrated on a water bath to a volume
of 1ml. The concentrated extract was then analyzed by Gas Chromatography/Mass Spectrometry
(GC/MS) using EPA SW-846 Method #8270.
A Separatory Funnel Liquid-Liquid Extraction Method (EPA SW-846 Method #3510) was used
to prepare the wash water and mouth wash samples for analysis. This method was used to isolate
organic compounds from aqueous samples. A measured volume of sample (the actual sample or
1000 mL) was serially extracted three times with 60 mL of cyclohexane at a neutral pH (5-7).
The extracts were dried over anhydrous sodium sulfate and then concentrated in a Kunderna-
Danish Concentator to a final volume of 1 mL. The concentrates were then analyzed for
phthalate esters by gas chromatography/mass spectrometry using EPA Method SW-846 Method
2
#8270.
Results were adjusted to take into account the laboratory extraction method percent recovery of
each phthalate ester and hand wash recovery efficiency of butyl benzyl phthalate.
The efficiency of various materials to remove polymer clays from the mouth was assessed by
coating a 5 cm aluminum weighing pan with 13-24 mg of polymer clay, ārinsingā the pan for 15
seconds while agitating with a sable brush and then rinsing the pan three times with de-ionized
water. The removal efficiency for various rinse solutions was as follows:
Solution Removal
Efficiency
DI
Water
18%
1%
tooth
paste
50%
1%
detergent
48%
Listerine
Mouthwash
91%
Based upon the above results, Listerine Mouthwash was chosen for recovery of clays after
transfer to mouth studies.
Hand-to-food transfer of phthalate esters was determined by manipulating two clay samples, as
above, for 45 minutes followed by vigorously rubbing lettuce leaves between the fingers and thumbs
of both hands, after the model of Bidawid, et al. (2000) to assess food contamination by professional
food handlers, but extending the manipulation time to 5 minutes and the compression force to 40-72
gm/cm
2
. This technique results in visible hand-to-food transfer of polymer clay.
Hand-to-mouth transfer of phthalate esters was determined by manipulating two clay samples, as
above, for 45 minutes followed by placing the distal phalange of each digit of each hand in the
mouth. The mouth was then rinsed with Listerine for 60 seconds followed by 3 rinses with DI
water. To determine recovery efficiencies for hand-to-mouth transfer studies, samples of the two
types of clay were placed in the mouth and mouthed for 2 minutes, followed by the rinsing
procedure above.
Three clays were chosen to determine rates of transfer of phthalates to hands. The methodology
used for the preliminary studies based on weight transfer was used to assess phthalate transfer
rates under controlled manipulation conditions. Two of these clays were then used in the field by
professional polymer clay artists to produce works of art over a 3 hour period. Hands were
washed twice with liquid soap followed by DI water rinses (as with the controlled, in laboratory
studies) prior to beginning each session. At the end of each session, hands were washed again
using the Brouwer et al. (2000) methodology. Wash water samples were collected in glass sample
bottles with Teflon-lined caps for transfer to the analytical laboratory. For one session (Clay A)
there were 4 artists. For the second session (Clay B), there were 5 artists.
3
Results
Laboratory mass transfer to hand experiments
Transfer rate for various weights
Clay A was tested for the effect of the amount of clay manipulated on transfer rates by adding
another 22 gm block to the manipulated mass each 15 minutes with the following results:
1
st
15 min
2
nd
15 min
3
rd
15 min
Clay B
73.3 mg
32.0 mg
8.8 mg
Transfer rate changes with time
Weight changes with clays were evaluated every 5 minutes for one clay for 15 minutes and every
15 minutes for all 3 clays. The transfer rate was constant for the first 15 minutes. As with Clay
A, the transfer rate for Clay B and C dropped in subsequent intervals as well as seen in the
following table:
1
st
15 min
2
nd
15 min
3
rd
15 min
Clay A
119.3 mg
70.4 mg
44.5 mg
Clay C
37.9 mg
38.9 mg
17.0 mg
Transfer rates standardized for surface area
The overall transfer rates were as follows, when standardized for either measured contact area
(327 cm
2
) or calculated hand surface area based on height and weight (1010 cm
2
). The latter
calculation includes total hand surface area.
Contact transfer (mg/cm
2
)
per 45 min
Hand transfer (mg/cm
2
) for
total hand area per 45 min
Clay A
0.72
0.23
Clay B
0.35
0.11
Clay C
0.29
0.09
Measurement of hand transfer during one 60 minute sculpting session with clay A found a
transfer to hand rate of 0.49 mg/cm2 of contact surface (0.15 mg/cm
2
of hand surface).
Phthalate recovery efficiencies
Recovery efficiencies from blank wash water
I. Kimberly Clark Hand Soap/DI Water Rinse Blank/Detection Limits
Test
Results (ug/l)
4
Butyl Benzyl Phthalate
< 200
Di-n-hexyl Phthalate
< 200
Di-n-octyl Phthalate
< 200
Di-n-decyl Phthalate
< 200
Di(2-ethyl hexyl)Terephthalate (DOTP)
< 200
II. Kimerbly Clark Hand Soap/DI Water Rinse Blank Spiked With Phthalates
Test Phthalate
Spike Value (ug/l) Value Obtained (ug/l)
% Recovery
Butyl Benzyl Phthalate
1,514
1,270
84.0
Di-n-hexyl Phthalate
1,919
1,620
84.4
Di-n-octyl Phthalate
1,708
1,230
72.0
Di-n-decyl Phthalate
1,834
1,410
76.7
Di(2-ethyl hexyl)Terephthalate (DOTP)
2,199
2,440
113.8
Overall:
86.2%
Recovery Efficiencies from hands spiked with butyl benzyl phthalate
Spike Value (ug/l) Value Obtained (ug/l)
% Recovery
Trial 1:
110700
90070
81.4
Trial 2:
110700
78260
70.7
Trial 2 (duplicate)
77070
69.6
Average:
75.8%
Clay and Plasticizer Analyses
(average of analyses of duplicate assays)
Āµ
g/gm#
Clay A
Butyl Benzyl Phthalate
1,730
Di-n-hexyl Phthalate
460
Di-n-octyl Phthalate
14,050
Di-n-decyl
Phthalate
9,930
Di(2-ethyl hexyl)Terephthalate (DOTP)
14,680
Total phthalates
40,850
Clay B
Di-n-hexyl Phthalate
13,470
Di-n-octyl Phthalate
97,480
Di-n-decyl Phthalate
111,340
Total phthalates
222,290
Clay C
Butyl Benzyl Phthalate
39,820
Di-n-hexyl
Phthalate
<
100
Di-n-octyl
Phthalate
<
100
Di-n-decyl
Phthalate
<
200
Di(2-ethyl hexyl)Terephthalate (DOTP)
129,850
Total phthalates
170,070
#corrected for analysis recovery efficiencies
5
Di-n-alkyl plasticizer used in polymer clays
Di-n-hexyl Phthalate
220,000
Di-n-octyl Phthalate
440,000
Di-n-decyl Phthalate
340,000
Phthalate recovery efficiencies from clay in mouth
(average of duplicate runs)
Detection limits/blank values for rinse
Āµ
g
Butyl Benzyl Phthalate
< 20
Di-n-hexyl Phthalate
< 20
Di-n-octyl Phthalate
< 40
Di-n-decyl Phthalate
< 20
Di(2-ethyl hexyl)Terephthalate (DOTP)
< 20
Recovery of phthalates from clay mouthed for 2 minutes
Āµ
g/gm recovered#
% to mouth
Clay A (380.1 and 87.4 mg)
Butyl Benzyl Phthalate
3,680
213
Di-n-hexyl Phthalate
740
161
Di-n-octyl
Phthalate
30,050
214
Di-n-decyl
Phthalate
17,860
177
Di(2-ethyl hexyl)Terephthalate (DOTP)
34,900
238
Overall: 87,230
214%
Clay B (285 and 88.3 mg)
Di-n-hexyl Phthalate
5,920
44
Di-n-octyl Phthalate
55,940
57
Di-n-decyl
Phthalate
65,670
59
Overall:
127,530
57%
#corrected for analysis recovery efficiencies
Laboratory phthalate transfer to hand experiments
Āµ
g transferred* %
recovery
I. Clay B Trial #1 (71.3mg Transferred to Hands)
Di-n-hexyl Phthalate
560
58
Di-n-octyl Phthalate
4,610
66
Di-n-decyl Phthalate
5,220
66
Overall:
10,390 63%
II. Clay C Trial #1 (101.6mg Transferred to Hands, duplicate analyses)
Butyl Benzyl Phthalate
6,160
152
6
Di(2-ethyl hexyl)Terephthalate (DOTP)
5,680
43
Overall:
11,840
69%
Āµ
g transferred* %
recovery
Clay C Trial #2 (98mg Transferred to Hands)
Butyl Benzyl Phthalate
8,420
216
Di(2-ethyl hexyl)Terephthalate (DOTP)
9,580
75
Overall:
18,000 108%
Combined clay C:
Butyl
Benzyl
Phthalate
184
Di(2-ethyl hexyl)Terephthalate (DOTP):
59
Overall:
88%
*corrected for recovery efficiencies (analysis and transfer)
Laboratory phthalate transfer to food experiments
I. Blank lettuce leaf (detection limits/blank values)
Test
phthalate
(ug/leaf)
Di-n-hexyl
Phthalate
<
4
Di-n-octyl
Phthalate
<
4
Di-n-decyl
Phthalate
<
10
Butyl
Benzyl
Phthalate <
10
Di(2-ethyl hexyl)Terephthalate (DOTP)
< 10
Āµ
g transferred* %
transferred
II. Clay B, Trial #1 (37.0 mg Transferred to Hands)
Di-n-hexyl
Pht
halate
<
4.0
nd
(<0.60)
Di-n-octyl
Phthalate
22.1
0.45
Di-n-decyl
Phthalate
<
10
nd
(<0.15)
Clay B, Trial #2 (66.3 mg Transferred to Hands)
Di-n-hexyl
Phthalate
<
4.0
nd
(<0.36)
Di-n-octyl
Phthalate
<4.0
nd
(<0.12)
Di-n-decyl
Phthalate
<
10
nd
(<0.11)
Average transfer for clay B
Di-n-hexyl
Phthalate
<4
<0.57%
Di-n-octyl
Phthalate:
<13
<0.26%
Di-n-decyl
Phthalate:
<10
<0.13%
Total
for
clay
B:
<27
<0.23%
III. Clay C, Trial #1 (103.8mg Transferred to Hands)
7
ug/transferred* %
transferred
Butyl Benzyl Phthalate
6.4
0.11
Di(2-ethyl hexyl)Terephthalate (DOTP)
186
1.04
ug/transferred* %
transferred
Clay C, Trial #2 (72.0 mg Transferred to Hands)
Butyl Benzyl Phthalate
4.8
0.13
Di(2-ethyl hexyl)Terephthalate (DOTP)
161
1.30
Average transfer for clay C
Butyl Benzyl Phthalate:
5.6
0.16
Di(2-ethyl hexyl)Terephthalate (DOTP):
173
1.52
Total for clay C:
179
1.20%
*corrected for recovery efficiencies (analysis and transfer)
Laboratory phthalate transfer from hands to mouth experiments
ug/sample* % to transferred mouth
I. Clay B, Trial #1 (58.7 mg Transferred to Hands)
Di-n-hexyl Phthalate
<40
nd (<4.4)
Di-n-octyl
Phthalate
<40
nd
(<0.53)
Di-n-decyl
Phthalate
<20
nd
(<0.23)
Clay B, Trial #2 (75.3 mg Transferred to Hands)
Di-n-hexyl
Phthalate
<40
nd
(<3.0)
Di-n-octyl
Phthalate
<40
nd
(<0.41)
Di-n-decyl
Phthalate
<20
nd
(<0.18)
Average transfer for clay B
Di-n-hexyl
Phthalate:
<40
nd
(<4.4%)
Di-n-octyl Phthalate:
<40
nd (<0.61%)
Di-n-decyl
Phthalate:
<20
nd
(<0.20%)
Total
for
clay
B:
<100
nd
(<0.67%)
II. Clay C, Trial #1 (80.1 mg Transferred to hands)
Butyl
Benzyl
Phthalate
22.9
0.38
Di(2-ethyl hexyl)Terephthalate (DOTP)
<40
nd (<0.29)
Clay C, Trial #2 (85.9 mg Transferred to Hands)
Butyl Benzyl Phthalate
<40
nd (<0.91)
Di(2-ethyl hexyl)Terephthalate (DOTP)
<40
nd (<0.27)
Average transfer for clay C
Butyl Benzyl Phthalate
<31
<0.93
8
Di(2-ethyl hexyl)Terephthalate (DOTP)
<40
<0.37
Total
for
clay
C:
<71
<0.50%
*corrected for recovery efficiencies (analysis and transfer)
Transfer to Hand: Comparison with In-Field Studies
(expressed as
Āµ
g transfer/cm
2
of contact surface)
Laboratory
Studies* In-Field
Studies*
(
Āµ
g/cm
2
)
(
Āµ
g/cm
2
Ā±
sd)
Clay A
Butyl
Benzyl
Phthalate
1.7
Ā±
0.5
Di-n-Hexyl Phthalate
<0.47
Di-n-Octyl
Phthalate
6.0
Ā±
3.0
Di-n-Decyl Phthalate
<0.52
Di(2-ethyl hexyl)Terephthalate (DOTP)
3.9
Ā±
1.9
Totals
for
clay
A:
12.6
Clay B
Di-n-hexyl Phthalate
1.7
1.1
Ā±
0.3
Di-n-octyl phthalate
14.1
8.0
Ā±
3.3
Di-n-decyl Phthalate
16.0
12.9
Ā±
4.5
Totals for clay B:
31.8
22.0
Ā±
8.1
Clay C
Butyl
Benzyl
Phthalate
22.3
Di(2-ethyl hexyl)Terephthalate (DOTP)
21.3
Total for clay C:
43.6
*corrected for recovery efficiencies (analysis and transfer)
Summary of toxicology, metabolism and pharmacokinetics of phthalate esters found in
polymer clays
Di(2-ethylhexyl) Terephthalate (DOTP)
DOTP is not acutely toxic with LD50s greater than 20 g/kg both orally in rodents and by skin
application in guinea pigs. It is not a skin or eye irritant or skin sensitizer in humans. Repeat skin
application in guinea pigs results in moderate skin irritation. It is slowly hydrolyzed in the gut to
2-ethylhexyl phthalate (2EH) and terephthalic acid (TPA). With a single dosing experiment,
36.6% remains in the gut in rats as unchanged DOTP (Barber, et al, 1994). Long chain
phthalates are poorly absorbed though the skin. Using the isomer Di(2-ethylhexyl) phthalate as a
surrogate, DOTP is likely to have a skin absorption rate of <0.5% per 24 hours of skin contact
(Barber, et al, 1992; Elsisi et al, 1989).
9
DOTP does not have the antiandrogenic or estrogenic effects seen with some phthalate esters
when rats were dosed from gd 14 through post natal day 3 at 750 mg/kg/d (Gray et al, 2000). A 2
generation study in rats at doses up to 1% in the feed (equivalent to 500-700 mg/kg/d) found no
evidence of reproductive toxicity (Eastman Chemical). The NOEL for developmental toxicity
was 0.3% (150-300 mg/kg/d) based on reduced pup weight and offspring weight gain at 0.6 and
1.0% dosing levels. Parental toxicity occurred in the high dose group with reduced weight gain
and maternal deaths. When dosing was restricted to gestational days 0-20, there was no evidence
of developmental toxicity at doses of DOTP up to 747 mg/kg/d (Eastman Chemical). No
testicular toxicity occurs with dosing rats with DOTP at daily doses of up to 561 mg/kg/d for 90
days (Eastman Chemical).
Chronic dosing of DOTP at doses up to 561 mg/kg/d for 90 days in rats resulted in no evidence
of organ-specific toxicity. Dosing of DOTPās metabolite, TPA, in rats at doses of 3837 mg/kg/d
resulted in bladder stones with no stone formation or bladder effects seen at 1220 mg/kg/d
(Amoco). This would be equivalent to an absorbed dose of 2859 mg DOTP/kg/d. Based on
saturation kinetics of TPA in human urine, 5624 mg of DOTP/kg/d would have to be absorbed
prior to seeing a risk of stone formation. No peroxisomal proliferation was found at chronic
dosing of DOTP in rats up to 617 mg/kg/d (Barber & Topping, 1995).
DOTP is not clastogenic or mutagenic (Barber, 1994; DiVincenzo et al, 1985). Lifetime dosing
experiments have been done with both its metabolites. With TPA lifetime feeding was associated
with bladder stone formation and bladder tumors in rats in two studies. In one study effects were
seen at 1000 mg/kg/d in female rats with a NOEL of 142 mg/kg/d (EPA/OTS). In the second
study bladder effects were seen at 2500 mg/kg/d with no effects seen at 500 or 1000 mg/kg/d
(Eastman Chemical). No bladder or other carcinogenic effects have been seen in mice dosed
with TPA at 750 mg/kg/d for 12 months (NCI, 1979). Lifetime studies have also been done with
2EH. No carcinogenic effects have been seen in rats at doses up to 750 mg/kg/d. There was a
positive trend for hepatocellular carcinoma in mice with a significant increase in female mice at
the highest dose level, 750 mg/kg/d. Because of the high death rate in this group, the
interpretation of the results is considered limited with 2EH being, at best, a weak or equivocal
carcinogen (Astill, et al, 1996).
Diisononyl Phthalate (DINP)
DINP is not acutely toxic by the oral or dermal routes with LD50 values of >50 g/kg orally in
rats and >3 g/kg dermally in rabbits. Little is absorbed via the skin with a transdermal absorption
rate of 0.3-0.6% per 24 hours in mice (NTP-CERHR, 2000). At high oral doses DINP causes
reduced testicular weight in mice but not rats. In feeding studies in mice decreased testicular
weight without histological changes occurred at 470 mg/kg/d for 4 weeks. No testicular toxic
effects were seen in rats in a 1 and 2 generation feeding studies to 960 mg/kg/d (EPA). DINP is
not a reproductive toxin with no effects seen in 1 and 2 generation studies in rats to 1 g/kg/d
(Waterman et al, 2000). DINP is not teratogenic when administered to rats to 1 g/kg/d, gd 6-15
(Waterman et al, 1999). Skeletal and visceral variations were seen in rats at maternally toxic
doses (1000 mg/kg/d) but not at non-maternally toxic doses (500 mg/kg/d) (101). DINP is
fetotoxic at 1100 mg/kg/d with reduced pup survival in rats but no effects were seen at 760
mg/kg/d (Waterman et al, 2000). DINP appears to have a slight antiandrogenic effect at 750
10
mg/kg/d in rats dosed from gd 14 to post natal day 3, with permanent nipples and testicular
changes in 7.7% of offspring.
In a 2 year ingestion study in rats at exposures up to 375 mg/kg/d, liver and kidney enlargement
was seen. The kidney enlargement was associated with a dose-dependent accumulation of alpha
2u globulin in male rats. No organ enlargement or excessive accumulation of alpha 2u globulin
was seen at a DINP dose of 17 mg/kg/d. No peroxisomal proliferation was seen in this study
(Waterman, et al, 2000).
DINP is not mutagenic or clastogenic with negative Ames, mouse lymphoma assay, rat
hepatocyte DNA repair assay, rat bone marrow clastogenicity (to 5 mg/kg/d x 5 d) and mouse
cell transformation assays. Chronic exposure was associated with excesses in mononuclear
leukemia in one study, a common tumor in aging rats and felt to be of no relevance to man
(Lington et al, 1997).
Butyl Benzyl Phthalate (BBP)
BBP is not toxic by the oral or dermal routes and is not an irritant or skin sensitizer. Skin
absorption studies have not been done but the dermal absorption of other phthalates of similar
molecular weight is slow (<1.2% per 24 hours in rodents). BBP is a testicular toxin. In a 26
week study in rats, testicular atrophy was seen at 2.5% BBP in the diet but not at 0.83% (470
mg/kg/d; IRIS). It has antiandrogenic effects on male offspring when fed in the diet at 750 mg/kg/d
from gd 14 to postnatal day 3 (Gray et al, 2000). BBP is not fetotoxic at maternally toxic doses (500
mg/kg/d; Ema et al, 1992). When administered during pregnancy to rats by gavage there is evidence
of fetotoxic and testicular effects with no effects at 350 mg/kg/d (Piersma et al, 2000) In a 2
generation study in rats there was no evidence of reproductive toxicity or male or female
reproductive organ effects at 500 mg/kg/d though there was a depression in testosterone levels at this
dose (NOEL 100 mg/kg/d; Nagao, 2001).
With chronic dosing BBP causes both liver and pancreatic inflammation. The latter appears to be
a more sensitive endpoint occurring at 381 mg/kg/d in rats but not at 151 mg/kg/d. BBP elevates
enzyme markers of peroxisomal proliferation in rats at doses of 300 mg/kg/d and higher with no
effect seen at 240 mg/kg/d for 1 year (NTP, 1997).
BBP is not a mutagen (Omori, 1976). BBP is not carcinogenic in mice. Chronic dosing in rats is
associated with mononuclear cell leukemia in females, a common neoplasm in rats (Kluwe et al,
1982). IARC (1999) has evaluated this data and felt that the results were equivocal and that no
evaluation can be made for the carcinogenic risk of BBP to man.
Di-n-alkyl phthalates: di-n-hexyl phthalate (DNHP), di-n-octyl phthalate (DNOP) and di-n-
decyl phthalate (DNDP)
A mixture if di-n-akyl phthalates (DNHP, DNOP and DNDP) is used as a plasticizer in polymer
clays. These phthalate esters either individually are as a mxiture are not toxic with oral and
dermal LD50s >20 g/kg in rodents. The mixture is not irritating to eyes or skin. Phthalates of in
this moleculare weight range are poorly absorbed through the skin: 1.2% of DNHP, 0.3% for di-
n-heptyl phthalate and 0.05% of diisodecylnonyl phthalate in 24
o
(Elsisi et al, 1989). Alkyl
11
phthalates are hydrolyzed in the gut to a mono alkyl phthalate and alcohol (Gangolli, 1982).
DNHP is a reproductive toxin in rodents causing decreased fertility in a 2 generation mouse
study at 0.43 mg/kg/d (Morrissey et al, 1989). At 1.87 g/kg/d in mice there was no fetotoxicity or
changes in ovarian histology but evidence of testicular pathologic effects (Morrissey et al, 1989).
Similarly evidence of testicular toxicity in rats at 1.4 g/kg/d. DNOP is not a testicular toxin
with chronic exposure to 5% in the diet in rats or mice 7.5 g/kg/d in mice (Heindel et al, 1989:
Morrissey et al, 1989). DNOP is not fetotoxic in a 2 generation mouse study to 7.5 g/kg/d
(Morrissey et al, 1989). No adeverse effects have been seen in rats dosed with 500 mg/kg/d
DNOP for 10 weeks (DeAngelo et al, 1986). DNOP is not a peroxisomal proliferator at dosing
of 2 g/kg/d in rats for 21 days (Hinton et al, 1986). Di6,8,10 phthalate was given to rats at
0,.0.3,1.2,2.5% in their diets for 21 days. No morphologic changes occurred at any dose and
there was no evidence of peroxisomal proliferation using cyanide insensitive palmitoyl-CoA
oxidation to develop a peroxisomal index (Lin, 1987). DNDP has not been studied for
reproductive or chronic toxicity. Its isomer, di-n-isodecyl phthalate, is not fetotoxic in mice at
9.65 g/kg/d (Hardin et al, 1987).
DNHP is hepatotoxic in rats when administered as 2% of their diets but without evidence of
peroxisomal proliferation (Mann et al, 1985). However rats exposed at 2.5% in the diet to
mixture of di-n-alkyl phthalates did no have any morphological changes of their livers nor
evidence of peroxisomal proliferation (Lin, 1987). This mixture contains 22% of DNHP, 44% of
DNOP and 34% of DNDP by analysis. Thus the NOEL for DNHP hepatotoxicity is 0.55% in the
diet or 275 mg/kg/d, for DNOP 1.1% of the diet or 550 mg/kg/d and for DNDP 1.4% of the diet
or 700 mg/kg/d. DNOP causes changes in rat thyroids when administered at 5000 ppm in the diet
but not at 500 ppm (25 mg/kg/d).
DNHP and DNOP are not mutagenic (Omori, 1976).
Acceptable Daily Intake (ADI) for phthalate esters used in polymer clays
Di(2-ethylhexyl) Terephthalate
DOTP is not acutely or chronically toxic at doses that do not result in reduced food intake and
reduced weight gain. There is a theoretical risk of bladder stone formation from absorption of
one of its metabolites, TPA. Bladder stone formation is associated with bladder inflammation,
epithelial hypertrophy and tumor formation. This appears to be a non-genotoxic effect secondary
to bladder mucosal inflammation. Neither DOTP or TPA are mutagenic or clastogenic. It is
reasonable to address bladder cancer risk in terms of prevention of bladder stone formation. The
calculated no effect level for stone formation is 2859 mg of absorbed DOTP per kg/d. Because of
limited hydrolysis of DOTP, this would be equivalent to ingesting 4509 mg of DOTP/kg/d.
Using an uncertainty factor of 10 for intraspecies differences in the metabolism of DOTP and an
uncertainty factor of 10 for variations in urine saturation of TPA in humans, the ADI for DOTP
to prevent bladder stones would be 45 mg/kg/d. This assessment is conservative. Heck and Tyl
(1985) used only a range of 2 in addressing the range of TPA saturation in human urine: an
uncertainty factor of 10 for variability in human metabolism of DOTP and TPA could be
considered excessive.
12
DOTP is fetotoxic at maternally toxic doses. In a 2 generation study there was reduced fetal
weight at daily doses of 500-600 mg/kg/d with an NOEL of 250-300 mg/kg/d. Using an
uncertainty factor of 10 for interspecies differences in the metabolism of DOTP and an
uncertainty factor of 10 for variations in human susceptibility, the ADI for DOTP to prevent
fetotoxic effects would be 2.5 mg/kg/d. This assessment appears to be conservative. When
dosing is limited to pregnancy, there were no fetal effects associated with DOTP exposures at
levels up to 747 mg/kg/d. Further DOTP does not have antiandrogenic, estrogenic or testicular
toxic effects that may be overlooked in a traditional reproductive toxicity assay. In this same
study DOTP was found to be developmentally toxic when exposure occurred during the pre-
weaning and pos-weaning period with reduced pup weight at daily doses of 500-600 mg/kg/d
with an NOEL of 250-300 mg/kg/d. Using an uncertainty factor of 10 for interspecies differences
in the metabolism of DOTP and an uncertainty factor of 10 for variations in human
susceptibility, the ADI for DOTP to prevent reduced weight gain would be 2.5 mg/kg/d.
Diisononyl Phthalate
DINP is a fetotoxin causing reduced fetal growth an visceral and skeletal anomalies. The NTP-
CERHR Expert Panel on DINP found the NOEL level for visceral effects to be 200 mg/kg/d. For
skeletal anomalies they used a benchmark approach and found the 5% effect level to be 193
mg/kg/d. Using an uncertainty factor of 10 for interspecies differences in the metabolism of
DINP and an uncertainty factor of 10 for variations in human susceptibility, the ADI for DINP to
decrease risk of fetotoxic effects would be 1.9 mg/kg/d.
Although chronic dosing with DINP is associated with tumors in rats, the tumors are either
common in rats (mononuclear cell leukemia) and not felt to be of relevance to man or renal
tumors associated with excessive accumulation of alpha 2u globulin in male rats, a tumor also
felt to be of no relevance to man. Chronic dosing is also associated with liver and kidney
enlargement. These endpoints have been chosen both by CPSC and their CHAP on DINP
toxicity for determining the most sensitive ADI for DINP. Using a benchmark approach and a
5% effect level, the CHAP determined an ADI for DINP of 120 mcg/kg/d.
Butyl benzyl phthalate
Piersma et al. (2000) used a benchmark approach to determine critical effect doses for various
developmental toxic endpoints. They found that the most sensitive endpoint was abnormal testes
location. Using a critical effect size of 1%, they found the critical effect dose for abnormal testes
location was 95 mg/kg/d at the 5% lower confidence limit. This assessment is similar to that of
Nagao who found no testicular effects at 100 mg/kg/d (Nagao, 2001) Using an uncertainty factor
of 10 for interspecies differences in the metabolism of BBP and an uncertainty factor of 10 for
variations in human susceptibility, the ADI for BBP to decrease risk of developmental toxic
effects would be 1 mg/kg/d.
With chronic dosing BBP causes peroxisomal proliferation and inflammation of the liver and
pancreas. The NOEL for pancreatic inflammation is 151 mg/kg/d. Using an uncertainty factor of
10 for interspecies differences in the metabolism of BBP and an uncertainty factor of 10 for
13
variations in human susceptibility, the ADI for BBP to decrease risk of liver or pancreatic toxic
effects would be 1.5 mg/kg/d.
DNHP, DNOP and DNDP mixture
The NTP-CERHR Expert Panel determined the LOEL for reproductive toxicity of DNHP in
mice was 380 mg/kg/d. Using an uncertainty factor of 10 for interspecies differences in the
metabolism, an uncertainty factor of 10 for variations in human susceptibility, and an uncertainty
factor of 10 for converting from LOEL to NOEL, the ADI for DNHP to decrease risk of
reproductive toxicity is 380 mcg/kg/d. DNHP is also hepatotoxic with an NOEL of 275
mg/kg/d. Using an uncertainty factor of 10 for interspecies differences in the metabolism and an
uncertainty factor of 10 for variations in human susceptibility, the ADI for DNHP to decrease
risk of liver effects would be 2.75 mg/kg/d.
For DNOP
the NTP-CERHR Expert Panel found that excessive exposure was associated with
thyroid effects and that the dietary NOEL is 36 mg/kg/d (M) and 40 mg/kg/d (F) for these effects.
Using an uncertainty factor of 10 for interspecies differences in the metabolism and an
uncertainty factor of 10 for variations in human susceptibility, the ADI for DNOP to decrease
risk of thyroid effects would be 360-400 mcg/kg/d. This compares to the ADI developed by
ATSDR of 400 mcg/kg/d for intermediate duration oral exposures based on liver enzyme and
thyroid changes (ATSDR, 1997).
The acceptable daily intakes for phthalate esters used in polymer clays are summarized in Table 1.
For chronic effectswepresume that the weight of the user is that of a 5 year old child. For fetotoxic
effects,weuse the weight of an adult female (USEPA, 1997).
Table 1: Acceptable Daily Intake for Phthalates used in Polymer Clays
Phthalate
Effect
ADI (mg/kg/d)
ADI (mg/d)
DOTP Bladder
stones
45
900
Reduced
weight
gain
2.5 50
Fetotoxicity
2.5
163
DINP Fetotoxicity
1.9 124
Liver & Kidney
changes
0.12 2.4
BBP Fetotoxicity
1.0 65
Pancreatic
inflammation
1.5 30
DNHP Fetotoxicity
0.38 25
Liver
toxicity
2.75
55
DNOP Thyroid
effects
0.36 7.2
DNHP-DNOP-DNDP Fetotoxicity
1.7
111
14
mixture
Thyroid
effects
0.82
16
Comparison of Phthalate ADIs to polymer clay transfer to mouth rates
USEPA has found that the average intake of dirt by a child is 110 mg by either hand to mouth or
hand to food transfer and that 50% of the amount of dirt on the fingers (25% of the amount on
the hands) will be transferred by these routes. There would have to be 440 mg of dirt on the
hands to account for this transfer rate. Our experiments with polymer clay found that both the
amount of clay that contaminated hands (37-234 mg during vigorous clay manipulation) as well
as the transfer rate to mouth and food (<0.9-1.7%, using phthalate esters as tracers) was less than
for dirt. Further the transfer to hand rates under laboratory conditions were greater than in the
field when polymer clay was used by professional artists in their work. It appears that our
measurements of phthalate transfer to mouth and food after vigorous manipulation of polymer
clays is conservative. Combined transfer rates of phthalates to mouth and food after polymer clay
work are compared to the ADIs for these phthalates in the following table:
Table 2. ADIs vs. transfer rates
Phthalate
Effect
ADI (mg/d)
Total Phthalate
Transfer to
mouth and food
(mg)
Transfer as a
percentage of
ADI (%)
DOTP Bladder
stones
900 <0.25 <0.03
Reduced
weight
gain
50 <0.25
<0.50
Fetotoxicity
163
<0.25
<0.15
DINP Fetotoxicity
124 <0.05
<0.004
(Using DNOP as
surrogate)
Liver & Kidney
changes
2.4 <0.05
<2.1
BBP Fetotoxicity
65 <0.04
<0.06
Pancreatic
inflammation
30 <0.04
<0.13
DNHP Fetotoxicity
25 <0.05 <0.20
Liver
toxicity
55
<0.05
<0.09
DNOP Thyroid
effects
7.2 <0.05 <0.69
DNHP-DNOP-
DNDP mixture
Fetotoxicity 111
<0.12
<0.11
Thyroid
effects
16
<0.12
<0.75
Discussion
Initial studies of polymer clay transfer to hands during heavy use conditions (continuous
kneading and rolling of the clay) found that clay transfer was constant for 15-30 minutes then
15
dropped rapidly and that transfer appeared to be a function of surface contact and not related to
the amount of clay being used and that transfer rates over 45 minutes of use ranged from 0.29-
0.72 mg/cm
2
of hand contact area. These values are within the rang of hand loading of dirt to
contact surfaces associated with outdoor activities of 0.51-3.75 mg/cm
2
assumed by Hawley
(1985) and 0.5-1.0 mg/cm
2
assumed by Sheppard (1995).
We found that the transfer of phthalate esters to mouth and food after placing fingers and thumbs in
the mouth or rubbing lettuce leaves vigorously after vigorously manipulating polymer clay for 45
minutes ranged from <0.9-1.7% of the amount of phthalates deposited on the hands as estimated by
clay weight transfer to hands. This range is 8 fold or less that estimated by Hawley (1985) for
ingestion of dirt from contaminated hands in adults and 15 fold less than that estimated for ingestion
of dirt from contaminated hands in young children. It would appear that the potential for hand-to-
mouth and hand-to-food transfer of polymer clays is considerably less than that for dirt, our default
exposure presumption.
We found that the proportional relationship of phthalate esters found in wash water after hand
manipulation or in mouth wash after mouthing of polymer clays was similar to that found in the
clays themselves. It is therefore reasonable to use the measured phthalate esters as ātracersā to
estimate the amount of polymer clay that could be ingested from incidental transfer activities to
mouth or food. We estimate that this amount ranges from <0.33-4 mg/day when we use the range of
clay-to-hand transfer after vigorous clay manipulation in a laboratory as a base. This estimate is
likely conservative. Hand contact area is likely to relate to the amount of clay transferred to hands
with clay manipulation activities. We compared hand contamination after correcting for surface area
in actually use situations by professional polymer clay artists to transfer rates measured after
vigorous clay manipulation in the laboratory. We found that transfer rates measured in the laboratory
from 44 to 225% higher than under actual use situations.
For the most part the amount of phthalate esters transferred with hand-to-mouth or hand-to-food
activities was below the detection limit for each measured phthalate ester. Assuming that these esters
were present either at the measured level or detection limit of not detected, then total phthalate
ingestion range from 127-250
Āµ
g/day depending on the clay being used. We compared the measured
or detection limit for each phthalate for combined hand-to-mouth and hand-to-food transfer to our
acceptable daily intakes (ADIs) for phthalate esters that are used in polymer clays. For this analysis
we assumed that an adult female would be using the clay for fetal effects and that a 20 kg 5 year old
child would be using the clay for other chronic effects. For determining ADIs we either accepted
published risk assessments for the phthalate esters or, if effect-specific ADIs were not available,
used uncertainty factors of either 100 for an effect NOEL or 1000 for an effect LOEL. When we
compared these ADIs to estimates of daily phthalate ester ingestion from manipulating polymer
clays, we found that the most conservative ADI for any phthalate ester was a factor of 50-750 fold
less than our estimate of daily phthalate ingestion.
We limited our assessment of polymer clay hand contamination to 3 hours of activity by professional
polymer clay artists. We found that the amount of clay transferred per unit time decreased with
continued clay manipulation: additional manipulation time would not proportionally increase clay
transfer. To further address whether or not a 3 hour testing interval was adequate to determine the
range of phthalate hand contamination by polymer clay users, we compared this interval to that
16
determined for sculptors in a national survey.
NFO Research maintains a representative
population of 20000 households. In their 1991 survey, 9.0% of households responding
to a screening questionnaire had one or more occupants who were artists. Of the 2165
artists identified by the screening questionnaire, 385 received a detailed questionnaire
on art material usage. This sample was chosen to be representative of the larger group
of artists with respect to geography, market size, size of household, age of household
head, total household income and type(s) of art done by each artist. The surveyors
strictly adhered to generally accepted research principles and sample selection methods
in order to be able to use the data to make accurate projections to artists across the
country. Responses were received from 69.9% of the artists. The results are considered
representative of the population of the United States at a precision of Ā±5.9% at a 95%
confidence interval. Sculptors in this survey spent an average of 2.0 hours a day in their
art work.
Polymer clays are also used by children. To determine whether or not a 3 hour use interval was
sufficient to estimate exposures during use by children, we compared this interval with a national
survey of teachers and parents. Princeton Research and Consulting Center analyzed questionnaires
sent to 40,000 households who were chosen to reflect US population household demographics. Of
25,128 completed questionnaires, 138 individuals were identified who taught art at an elementary
level. 59 of these teachers and a representative sample of 134 parents of elementary school children
who responded to this survey were further questioned concerning art use by children under their
care. Children worked with clays an average of 0.19 hours/month in school and an average of 0.20
hours/month in the home with clays for a total of 0.39 hours per month or 0.01 hours/day. It would
appear that a 3 hour use evaluation interval gives a conservative estimate of daily exposure for
childrenās use of polymer clays as well.
17
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