Journal of Hazardous Materials 283 (2015) 53–59
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Health risk assessments of DEHP released from chemical protective gloves Keh-Ping Chao ∗ , Chan-Sheng Huang, Chung-Ying Wei Department of Occupational Safety & Health, China Medical University, Taiwan, ROC
h i g h l i g h t s • • • •
BTEX solvents permeated through the chemical protective gloves and dissolved DEHP from the gloves. The larger amount of DEHP leaching from the gloves, the higher the permeation resistance of gloves. An exposure model was developed to evaluate the dermal absorption of DEHP released from test gloves. Leaching of DEHP from test gloves may pose a potential health risk to workers who handle with BTEX.
a r t i c l e
i n f o
Article history: Received 6 February 2014 Received in revised form 4 September 2014 Accepted 5 September 2014 Available online 16 September 2014 Keywords: Di-2-ethylhexyl phthalate Plasticizer Permeation Dermal exposure Chemical resistance
a b s t r a c t The substance di-2-ethylhexyl phthalate (DEHP) is widely used as a plasticizer in chemical protective gloves to improve their flexibility and workability. However, it is possible that workers using protective gloves to handle various solvents may be exposed to DEHP leached by the solvents. Using an ASTM F739 permeation cell, it was found that BTEX solvents permeating through the glove samples dissolved DEHP from the gloves. Even without continuously contacting the permeant, DEHP was released from the contaminated glove samples during the desorption experiments. The DEHP leaching amounts were found to be inversely correlated to the permeability coefficients of BTEX in the glove samples. This result implied that the larger the amount of DEHP released from the glove samples, the higher the permeation resistance of gloves. Although chemical protective gloves provide adequate skin exposure protection to workers, the dermal exposure model developed herein indicates that leaching of DEHP from the glove samples may pose a potential health risk to the workers who handle BTEX. This study suggests that the selection of protective gloves should not only be concerned with the chemical resistance of the gloves but also the health risk associated with leaching of chemicals, such as DEHP, used in the manufacturing of the gloves. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Di-2-ethylhexyl phthalate (DEHP) is primarily used in the polymeric materials as a plasticizer for a wide variety of industrial, domestic and medical products. Plasticizers embed themselves between the chains of polymers, resulting in separation of the chains and a reduction of the friction between the polymer molecules. Because plasticizers are not permanently bound to the polymer molecules, they can be released from polymeric materials [1–3]. DEHP can be dermally absorbed as well as cause skin irritation and burning sensations. The guinea pig studies have indicated a LD50 of 10 g/kg for dermal exposure [4], and the permeability coefficient of DEHP through human skin is 1.05 ± 0.21 × 10−7 cm/h [5]. Animal studies have indicated that DEHP has
∗ Corresponding author at: Department of Occupational Safety & Health, China Medical University, 91 Hsueh-Shih Rd., Taichung 40402, Taiwan, ROC. Tel.: +886 4 22053366x6205; fax: +886 4 22070500. E-mail address: [email protected] (K.-P. Chao). http://dx.doi.org/10.1016/j.jhazmat.2014.09.010 0304-3894/© 2014 Elsevier B.V. All rights reserved.
reproductive hazards, and the primary target organs are the liver and kidneys [6,7]. DEHP is known to induce the proliferation of peroxisomes, which has been associated with carcinogenesis [8]. The USEPA classifies DEHP as a group B2 carcinogen, i.e. probable human carcinogen, based on sufficient evidence in animals and inadequate evidence in humans, and considers it inappropriate to quantify the carcinogenic risk [9]. DEHP is an endocrine-disrupting compound and has been included on the list of Substances of Very High Concern (SVHC) and on the Annex XVII list of the EU REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) legislation. Therefore, the producers and users should submit authorization requests to the European Chemicals Agency to use DEHP. For example, the potential risks to children from dermal exposure to DEHP by skin contact the air mattress [10] and synthetic shoes [11] have been assessed. In the EU Risk Assessment Report [12], three occupational exposure scenarios were considered concerning exposure during production of DEHP, industrial use of DEHP and industrial end-use of products containing DEHP. Based on the calculation of the EASE (Estimation and Assessment of Substance Exposure) model, the dermal exposure dose was mainly via end-use of semi-manufactured products and end-products containing DEHP, such as adhesives/sealings lacquers/paints
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Flow meter
Permeation cell
Pump
Sampling port
Teflon bottle Incubator @ 25 ± 1oC
Fig. 1. Sketch of closed-loop permeation system.
rubber, inks for textiles and ceramics for electronic purpose. However, the available information on industrial end-use of DEHP is insufficient to directly estimate the dermal exposure of DEHP in workers. The polymeric materials of chemical protective gloves, such as PVC and nitrile, have added DEHP [13,14]. Tsumura et al. [2] investigated the DEHP contamination of foods sold in retail packed lunches and set lunches for restaurants in Japan. They found that the disposable PVC gloves used in the preparation of foods contained 22–41% (w/w) of DEHP. The alcohol solution sprayed onto the PVC gloves, for a disinfection purpose, increased the releasing and migration of DEHP from gloves into the food samples. Swedish Chemicals Agency [15] has estimated that a health care worker wearing the medical PVC gloves for 2 h/day could receive a DEHP dermal dose on the order of 7 g/kg/day. For practical purposes, there is a need to characterize the amount of DEHP that would be released from the chemical protective gloves and subsequently taken up by the body via dermal absorption. In this study, the permeation of organic solvents, such as benzene, toluene, ethyl benzene, and xylene (BTEX), through PVC and nitrile gloves was conducted using the ASTM F739 cell. The potential leaching of DEHP from the glove samples was determined during the permeation and desorption experiments. Moreover, a dermal exposure model was proposed to estimate the health risk to the leaching of DEHP for a practical scenario of using the protective gloves. The present work will provide an understanding on the potential leaching and risk of DEHP for a worker wearing the gloves to protect against hazardous chemicals.
2. Materials and methods 2.1. Glove samples and chemicals Test specimens were cut from the palm portion of nitrile (Best 727-11, USA) and PVC gloves (Best BO710, Japan), rinsed with deionized water, and air-dried for 24 h at a temperature of 25 ± 1 ◦ C and relative humidity of 50 ± 5%. The thicknesses of glove samples were measured at five random locations to the nearest 0.01 mm using a dial thickness gauge (Teclock Co., Okaya, Japan). The average thickness of the glove samples were 0.46 ± 0.01 and 0.27 ± 0.01 mm for nitrile and PVC, respectively. Organic solvents used for the permeation experiments were benzene, toluene, ethyl benzene, and xylene which were chosen because of their wide use in industry. These four solvents were of purity greater than 98%, and their physical–chemical properties are given in Table 1. DEHP, with purity >99%, was purchased from Sigma–Aldrich. 2.2. Permeation of organic solvents through gloves Permeation experiments were conducted using the ASTM F739 test method [16] with a closed-loop system. The schematic flow diagram of the experimental apparatus is shown in Fig. 1. The stainless steel permeation cell (Pesce Lab Sales, Kennett Square, PA) with a diameter of 25-mm was separated by the glove sample into the collection and challenge chambers. De-ionized water has been widely used as the collection medium for permeation experiments. However, DEHP is practically insoluble in water. Several
studies have indicated that methanol has no effect on the glove materials, such as degradation and back permeation [17,18]. In this study, methanol (GC grade, Macron), with a total volume of 170 mL, was circulated through the collection chamber using a MasterFlex® PTFE-Tubing pump system (Cole-Parmer, Vernon Hills, IL) at a flow rate of 50 mL/min. As shown in Fig. 1, a spherical stirrer was used to mix the collection medium in the Teflon bottle. All equipment constituting the closed-loop system was connected with Teflon tubing and placed in an incubator at a temperature of 25 ± 1 ◦ C. The permeation test was conducted until a constant rate of permeation occurred, which indicated the permeation of organic solvents through glove sample had reached a steady state. After the test solvent was added to the challenge chamber, 0.5-L aliquots of the collection medium were collected from the downstream sampling point every 15 min intervals using a micro-syringe. The samples were immediately injected into the gas chromatograph (GC) equipped with mass spectrometer (Turbomass Mass Spectrometer, Perkin Elmer, Norwalk, Conn.) for analysis the concentrations of permeants and DEHP. The temperature of the GC capillary column (EquityTM -5, Supelco, Bellefonte, PA) was kept at 80 ◦ C for 2 min, and then ramped to 290 ◦ C at a rate of 30 ◦ C/min with a final hold of 5 min. The temperatures of the injection port and detector were maintained at 250 ◦ C and 300 ◦ C, respectively. The flow rate of the carrier gas helium (purity of 99.999%) was 1 mL/min. Mass range was scanned at 0.5 s/scan, where ions were produced through selected ion recording (SIR) mode. The limit of detection (LoD) for BTEX is shown in Table 1. At the end of permeation experiments, it was observed that the thickness of nitrile glove samples increased by 3.2–6.8%, while the thickness of PVC gloves remained approximately constant. Therefore, the effect of swelling of glove samples for the permeation test can be assumed to be negligible. 2.3. Desorption of organic solvents from gloves As the permeation test was terminated, the permeation cell was immediately disassembled. The contaminated glove sample was blotted dry to remove excess liquid chemicals using filter papers, and then placed in a second permeation cell. The closedloop system of the second cell was reassembled. Fresh methanol was circulated through the collection chamber, and the elapsed time for the desorption experiment was clocked. The challenge chamber of the reassembled cell was emptied of the test chemical. This effort was to simulate the scenario where a worker wears the used gloves but without contact with the chemical. Reassembling of the second cell was completed within 10 min, and the apparatuses of the closed-loop system were subsequently placed back in an incubator at 25 ± 1 ◦ C. The sampling and analysis procedures were the same as the permeation tests. For each test solvent, the permeation and desorption experiments were repeated at least three times. 2.4. Blank test for collection medium In this study, the blank tests for the collection medium were conducted using a similar experimental procedure for the desorption experiment. The closed-loop system of the permeation cell was assembled using the nitrile and PVC gloves, while the challenge chamber was emptied of chemicals. Methanol was circulated through the collection chamber and analyzed for DEHP every 15 min intervals. The blank experiments were repeated three times for both nitrile and PVC gloves. During a test period of 240 min, the amount of DEHP leached from PVC gloves was 0.032 ± 0.006 mg/g. The concentrations of DEHP in the collection medium were lower than its detection limit, i.e. 0.011 mg/L, for the blank experiments of nitrile gloves. Therefore, the effect of methanol on the leaching
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Table 1 Physical and chemical properties of permeation solvents. Chemical
Grade
Mw (g/mol)
WS (mg/L)
Log Kow
LoD (mg/L)
Benzene (Sigma–Aldrich) Toluene (Mallinckrodt) Ethyl benzene (Merck) p-Xylene (Merck)
ACS ACS GC ACS
78.1 92.1 106.2 106.2
1780 515 187 198
2.12 2.73 3.15 3.15
0.005 0.051 0.183 0.068
Properties are at 25 ◦ C and abbreviations are as follows: Mw: molecular weight; WS: water solubility; log Kow : octanol–water partition coefficient; LoD: limit of detection.
of DEHP from glove samples can be neglected as compared to the results of permeation and desorption experiments. 3. Results and discussion
P = Js L = ˛
3.1. Permeation of organic solvents Fig. 2 shows the permeation results of test solvents through the glove samples. Once breakthrough was occurred, the concentrations of permeants in the collection medium increased linearly. In 6,000
(a) Nitrile glove
Benzene Toluene
5,000
Ethyl benzene Xylene
Concen. (mg/L)
4,000
slope α
3,000
2,000
1,000
0 0
50
100
150
200
250
Time (min) 4,000
(b) PVC glove
3,500 3,000
slope α
2,500
Concen. (mg/L)
a closed-loop system, the permeability coefficient, P (M L−1 T−1 ), of organic solvents in the glove sample was determined as follows [19]:
2,000 1,500 1,000
V L A
(1)
where Js is the steady state permeation rate of organic solvents in the glove (M L−2 T−1 ); L is the thickness of glove sample (L); ˛ is the slope of linear portion of the permeant concentrations in the collection medium (M L−3 T−1 ), i.e. steady state permeation show in Fig. 2; V is the total volume of the collection medium in the closedloop system (L3 ), i.e. 170 mL; A is the area of glove sample exposed to the permeant, i.e. 5.06 cm2 . Table 2 presents the permeability coefficients of test solvents in the glove samples. The average permeability coefficients of BTEX were 48.34–5.19 and 13.84–3.28 g/cm/min for nitrile and PVC gloves, respectively. The results of permeability coefficients indicate that BTEX were less permeable through the PVC gloves than nitrile samples. According to the principle of “like dissolves like”, a polar chemical is more easily dissolved in a polar solvent. In general, the lower the octanol-water partition coefficient of a chemical, the higher the polarity. Because the nitrile and PVC gloves are polar materials, the chemical with lower Kow will have a stronger attraction to the nitrile and PVC gloves, resulting in a higher permeation through the gloves. Fig. 3 shows that the permeability coefficients of BTEX were inversely proportional to their octanol-water partition coefficients (log Kow ) for the nitrile (r = 0.983) and PVC gloves (r = 0.964). During the permeation experiment, DEHP was analyzed in the collection medium. As shown in Fig. 4, the leaching amounts of DEHP from the glove samples were increased with the permeation time. This result implied that the weak bonds between DEHP and the polymer molecules were broken due to the diffusion of BTEX molecules. Therefore, leaching of DEHP from the gloves may pose a health threat to the worker. The content of DEHP in flexible polymer materials, such as PVC, varies but is often around 30% (w/w) [12]. Tsumura et al. [2] found that the content of DEHP in PVC gloves was as high as 22–41% (w/w). For the BTEX permeants, the amount of DEHP leached from PVC gloves was approximately one order of magnitude higher than that from nitrile gloves. A possible reason for this result may be that a larger amount of DEHP was added in the production process of PVC gloves compared with the nitrile samples. Fig. 5 indicates that the amounts of DEHP leached from the gloves were inversely correlated (r ≥ 0.766) to the permeability coefficients (mol/cm/min) of BTEX. It is plausible that the amounts of DEHP released from the glove Table 2 Permeability coefficients of BTEX for the glove samples.
500
Chemical
Permeability coefficienta (g/cm/min) Nitrile glove
0 0
50
100
150
200
250
Time (min) Fig. 2. Concentrations of BTEX in the collection medium for the permeation experiments.
Benzene Toluene Ethyl benzene p-Xylene a
Mean ± SD.
48.34 15.78 5.99 5.19
± ± ± ±
2.85 1.21 0.88 0.39
PVC glove 13.84 10.42 3.42 3.28
± ± ± ±
0.58 0.38 0.03 0.66
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60
0.20
Toluene
50
0.16
PVC (r=0.964)
Ethyl benzene Xylene
0.14
DEHP (mg/g)
40
P (μg/cm/min)
(a) Nitrile glove
Benzene
0.18
Nitrile (r=0.983)
30
20
0.12 0.10 0.08 0.06 0.04
10
0.02 0.00
0
0
0
1
2
3
4
50
100
5
Dermal exposure of DEHP may occur immediately once DEHP leaches from the glove. The dermal dose was calculated under an exposure scenario, i.e. leaching of DEHP from the glove sample at
(b) PVC glove
1.8 1.6
samples may be directly proportional to the permeation resistance of gloves of the solvent.
3.3. Potential health risks of DEHP
250
2.0
Fig. 3. Permeability coefficients of BTEX in glove samples inversely proportional to their octanol–water partition coefficients.
1.4
DEHP (mg/g)
Fig. 6 shows the concentrations of BTEX in the collection medium during the desorption experiments. Even without contacting BTEX, the residual BTEX was desorbed from the contaminated glove samples. As seen in Fig. 6(a), the BTEX concentrations were significantly increased in the collection medium and then remained approximately constant for the nitrile gloves. Fig. 6(b) indicates that the BTEX concentrations were increased in the collection methanol for the PVC gloves during a test period of 240 min. The residual BTEX desorbed from the nitrile gloves was significantly greater than that from the PVC gloves. This result is plausible because the initial concentration profiles of BTEX inside the contaminated glove for the desorption experiments were the same as that for the permeation experiments. As compared with Fig. 2, the order of permeability coefficients for BTEX from the highest to lowest was different from the order of the residual BTEX desorbed from the nitrile and PVC gloves. For example, the permeability coefficients for PVC gloves were benzene > toluene > ethyl benzene > xylene; while the desorbed levels were toluene > xylene > benzene > ethyl benzene for the desorption experiments. These findings suggest that the chemical with a greater permeability could be not easily desorbed from the contaminated glove. Fig. 7 shows that leaching of DEHP from the contaminated glove samples occurred during the desorption experiments. The leaching levels of DEHP from the PVC gloves were greater than that from the nitrile gloves for the same BTEX compound. For example, the leaching amounts of DEHP were 0.228 and 0.039 mg/g-glove for the contaminated PVC and nitrile gloves, respectively. However, the leaching levels of DEHP for the permeation experiments were approximately twice as compared to the desorption experiments.
200
Time (min)
log Kow
3.2. Concentration profile of residual BTEX and DEHP
150
1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
50
100
150
200
250
Time (min) Fig. 4. Amounts of DEHP leaching from the glove samples during the permeation experiments.
an average rate during BTEX permeation through the glove. If a worker wore the protective glove and was continuously contacted to BTEX, the level of DEHP body burden resulting from the dermal absorption of DEHP through one hand, i.e. dermal dose, might be estimated by Eq. (2) [17]. Dermal dose =
Jd × As × Et × Ef × Ed Bw × At
(2)
where Jd is the dermal permeation rate of DEHP through the human skin (M L−2 T−1 ); As is the exposed skin area of the whole hand, i.e. 840 cm2 [20]; Et is the daily exposure time, i.e. 8 h/day; Ef is the exposure frequency, i.e. 250 day/year; Ed is the exposure duration, i.e. working for 40 years; Bw is the body weight, i.e. 70 kg; and At is the averaging lifetime, i.e. 70 years or 25,550 day. Table 3 shows that the average leaching rates of DEHP were 0.027–0.073 and 0.079–0.091 g/cm2 /min for the nitrile and PVC gloves, respectively, for the permeation experiments. According to the results of the permeation experiments, the concentrations of DEHP exposed to the hand of a worker can increase while the
K.-P. Chao et al. / Journal of Hazardous Materials 283 (2015) 53–59
0.7
1,400 Benzene
Nitrile (r=0.766) 0.6
PVC (r=0.77)
(a) Nitrile glove
Toluene
1,200
Ethyl benzene Xylene
0.5
1,000
Concen. (mg/L)
P (mole/cm/min)
57
0.4 0.3
800
600
0.2
400 0.1
200 0 0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
Leaching DEHP (mg/g)
0
50
100
Carcinogenic risk = dermal dose × DerSF
200
250
300
Time (min)
Fig. 5. The leaching amounts of DEHP inversely correlated to the permeability coefficients of BTEX in glove samples.
250
(b) PVC glove 200
Concen. (mg/L)
worker wears the glove and handles BTEX. Therefore, the dermal permeation rate of DEHP was used in Eq. (2) to evaluate the dermal dose. Scott et al. [21] indicated that the in vitro permeation rate of DEHP through the human skin is 0.093 g/cm2 /min. If the average leaching rate of DEHP was lower than 0.093 g/cm2 /min, Jd calculated in Eq. (2) was assumed to be the average leaching rates of DEHP as indicated in Table 3. On the other hand, Jd was assumed to be 0.093 g/cm2 /min for the case if the average leaching rate of DEHP was greater than 0.093 g/cm2 /min. Based on the parameters assumed in this study, Table 3 indicates that the average daily dermal dose of DEHP was 1.1–3.8 g/kg/day for a 70 kg worker. To evaluate the potential health effects of DEHP, the carcinogenic risk from DEHP due to dermal contact by workers wearing the glove was obtained as follows [22]:
150
150
100
50
(3)
where DerSF is the dermal carcinogenic slope factor for DEHP. However, because of the unavailability of dermal SF for DEHP, oral to dermal SF was extrapolated using the gastrointestinal absorption factor (GIAF) as follows [3,11,23]: OralSF GIAF
0 0
50
100
150
200
250
300
Time (min)
(4)
Fig. 6. Concentrations of BTEX in the collection medium for the desorption experiments.
Table 3 Dermal doses and carcinogenic risks of DEHP for BTEX permeation through nitrile and PVC gloves.
where OralSF is the oral carcinogenic slope factor for DEHP, i.e. 1.4 × 10−2 kg-day/mg [3,24]. The recommendation of USEPA is to assume a 100% GIAF value for DEHP [23], indicating that DEHP is generally well absorbed (>50%) across the gastrointestinal tract. On the other hand, the Risk Assessment Information System of USDOE suggests a GIAF value of 0.19 for DEHP [3]. To account for the uncertainties in the extrapolation of OralSF, DerSF of 1.4 × 10−2 and 7.37 × 10−2 kg-day/mg was used respectively to estimate the carcinogenic risk from DEHP. At present the USEPA has defined acceptable risks for carcinogens as within the range of 10−4 –10−6 excess lifetime cancer risk. Table 3 indicates that the average carcinogenic risks from DEHP were 0.16–2.77 × 10−4 for a worker wearing the test gloves, falling in the “alert” range of acceptable risks. However, OSHA (Occupational Safety and Health Administration) accepts higher risk levels, in the range of 10−4 –10−3 , for occupational exposure [25]. In this study, it should be noted that the major uncertainties in calculating the carcinogenic risks can result from using the
DerSF =
Chemical
DEHP leaching ratea (g/cm2 /min)
Average dermal dose (g/kg/day)
Carcinogenic risk (10−4 ) DerSFb
DerSFc
Nitrile glove Benzene Toluene Ethyl benzene p-Xylene
0.027 0.062 0.067 0.073
± ± ± ±
0.012 0.011 0.023 0.016
1.1 2.5 2.3 2.7
0.16 0.35 0.32 0.38
0.81 1.84 1.70 1.99
PVC glove Benzene Toluene Ethyl benzene p-Xylene
0.079 0.083 0.096 0.091
± ± ± ±
0.022 0.017 0.018 0.026
3.2 3.4 3.8 3.7
0.44 0.47 0.53 0.52
2.36 2.51 2.77 2.73
a b c
Mean ± SD. DerSF of 1.4 × 10−2 kg-day/mg. DerSF of 7.32 × 10−2 kg-day/mg.
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K.-P. Chao et al. / Journal of Hazardous Materials 283 (2015) 53–59
0.06
(a) Nitrile glove
Benzene Toluene
0.05
Ethyl benzene Xylene
DEHP (mg/g)
0.04
0.03
0.02
0.01
4. Conclusions
0.00 0
50
100
150
200
250
300
Time (min) 1.0
(b) PVC glove
0.9 0.8 0.7
DEHP (mg/g)
can result in an increase in the leaching rates of DEHP from the gloves. For practical purposes, assessment of carcinogenic risk from the leaching DEHP should be conducted, if desired, using the results of permeation tests for a solvent mixture and under the temperature condition as found in the manufacturing work condition. Chao et al. [17] conducted the permeation tests of re-exposed gloves to simulate a practical scenario of glove reuse. They found that the permeability coefficients of re-exposed gloves were lower than those of the new glove samples. It was speculated that the additives, such as plasticizers, were dissolved from the re-exposed gloves during the permeation tests [18,26]. Therefore, reuse of gloves could result in a lower leaching of DEHP from the gloves, thus decreasing the carcinogenic risk from DEHP compared to use of new gloves.
0.6 0.5 0.4
For the permeation experiments, BTEX solvents permeated through the glove samples and dissolved DEHP from the gloves. The DEHP leaching amounts were found to be inversely correlated to the permeability coefficients of BTEX in the glove samples. It is speculated that the chemical resistance of protective gloves to permeation by BTEX was enhanced as DEHP dissolved from the gloves. On the other hand, our evaluation suggests that dermal absorption of DEHP released from the gloves may pose a potential health risk to the workers who come into contact with BTEX. The dermal exposure model developed herein can provide the quantitative information for technical control measures to reduce the health risks resulting from DEHP. It should be noted that the health effect of plasticizers on the chemical resistance of protective gloves should be determined using the chemical constituents in their actual composition as applied in industrial processes. Acknowledgments
0.3
The study was financially supported by the National Science Council, Taiwan, ROC (100-2221-E-039-007, 101-2221-E-039009).
0.2 0.1
References
0.0 0
50
100
150
200
250
300
Time (min) Fig. 7. Amounts of DEHP leached from the glove samples for the desorption experiments.
DEHP leaching rates determined by the permeation experiments. For a worst-case exposure scenario where the DEHP leaching rate was calculated as the 95th percentile upper confidence limit (i.e., mean + 2SD), the dermal dose of DEHP was estimated to be 3.2 g/kg/day for a worker wearing the nitrile glove and contacting ethyl benzene, with an increase in carcinogenic risk by 38.8%. Another possible source of uncertainty in calculating the carcinogenic risk is the in vitro permeation rate of DEHP through the human skin. The evaluation of permeation rate of DEHP through human skin should be a pre-requisite for the assessment of health risk associated with using protective gloves. However, there is currently no human in vivo study for the absorption of DEHP via the skin [10,24]. Based on the carcinogenic risks evaluated herein, it is suggested that the scenario of industrial end-use of products containing DEHP, such as chemical protective gloves, cannot be neglected. It should be noted that the co-solvent effect may enhance leaching of DEHP from the gloves if a worker is exposed to a mixture of solvents. Moreover, handling the solvents at a higher process temperature
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K.-P. Chao et al. / Journal of Hazardous Materials 283 (2015) 53–59 [13] J.L. Perkins, Solvent–polymer interactions, in: D.H. Anna (Ed.), Chemical Protective Clothing, The AIHA Press, Fairfax, VA, 2003. [14] K. Aalto-Korte, K. Alanko, M. Henriks-Eckerman, T. Estlander, R. Jolanki, Allergic contact dermatitis from bisphenol A in PVC gloves, Contact Dermat. 49 (2003) 202–205. [15] KEMI, Risk Assessment – Bis(2-ethylhexyl)phthalate, Swedish Chemicals Agency, Sundbyberg, Sweden, 2000. [16] ASTM F739-07, Resistance of Protective Clothing Materials to Permeation by Liquids or Gases under Conditions of Continuous Contact, Philadelphia, PA, 2007. [17] K.P. Chao, P. Wang, C.P. Chen, P.Y. Tang, Assessment of skin exposure to N,N-dimethylformamide and methyl ethylketone through chemical protective gloves and decontamination of gloves for reuse purposes, Sci. Total Environ. 409 (2011) 1024–1032. [18] K.P. Chao, C.P. Chen, J.S. Lai, P.Y. Tang, Effects of collection medium on permeation test for chemical protective gloves, Polym. Test. 29 (2010) 258–264. [19] K.P. Chao, J.S. Lai, H.C. Lin, Comparison of permeation resistance of protective gloves to organic solvents with ISO, ASTM and EN standard methods, Polym. Test. 26 (2007) 1090–1099.
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[20] M.F. Boeniger, T.D. Klingner, In-use testing and interpretation of chemicalresistant glove performance, Appl. Occup. Environ. Hyg. 17 (2002) 368–378. [21] R.C. Scott, P.H. Dugard, J.D. Ramsey, C. Rhodes, In vitro absorption of some ophthalate diesters through human and rat skin, Environ. Health Perspect. 74 (1987) 223–227. [22] United States Environmental Protection Agency (USEPA), Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment), Office of Superfund Remediation and Technology Innovation, Washington, DC, 2004. [23] United States Environmental Protection Agency (USEPA), Guidelines for Carcinogen Risk Assessment, 2005, EPA/630/P-03/001F. [24] Integrated Risk Information System, IRIS. http://www.epa.gov/iris/subst/ 0014.htm [25] S. DiNardi, The Occupational Environment: Its Evaluation, Control, and Management, 2nd ed., The AIHA Press, Fairfax, VA, 2003. [26] P. Gao, B. Tomasovic, Change in tensile properties of neoprene and nitrile gloves after repeated exposures to acetone and thermal decontamination, J. Occup. Environ. Hyg. 47 (2005) 543–552.
Contents lists available at ScienceDirect
Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat
Health risk assessments of DEHP released from chemical protective gloves Keh-Ping Chao ∗ , Chan-Sheng Huang, Chung-Ying Wei Department of Occupational Safety & Health, China Medical University, Taiwan, ROC
h i g h l i g h t s • • • •
BTEX solvents permeated through the chemical protective gloves and dissolved DEHP from the gloves. The larger amount of DEHP leaching from the gloves, the higher the permeation resistance of gloves. An exposure model was developed to evaluate the dermal absorption of DEHP released from test gloves. Leaching of DEHP from test gloves may pose a potential health risk to workers who handle with BTEX.
a r t i c l e
i n f o
Article history: Received 6 February 2014 Received in revised form 4 September 2014 Accepted 5 September 2014 Available online 16 September 2014 Keywords: Di-2-ethylhexyl phthalate Plasticizer Permeation Dermal exposure Chemical resistance
a b s t r a c t The substance di-2-ethylhexyl phthalate (DEHP) is widely used as a plasticizer in chemical protective gloves to improve their flexibility and workability. However, it is possible that workers using protective gloves to handle various solvents may be exposed to DEHP leached by the solvents. Using an ASTM F739 permeation cell, it was found that BTEX solvents permeating through the glove samples dissolved DEHP from the gloves. Even without continuously contacting the permeant, DEHP was released from the contaminated glove samples during the desorption experiments. The DEHP leaching amounts were found to be inversely correlated to the permeability coefficients of BTEX in the glove samples. This result implied that the larger the amount of DEHP released from the glove samples, the higher the permeation resistance of gloves. Although chemical protective gloves provide adequate skin exposure protection to workers, the dermal exposure model developed herein indicates that leaching of DEHP from the glove samples may pose a potential health risk to the workers who handle BTEX. This study suggests that the selection of protective gloves should not only be concerned with the chemical resistance of the gloves but also the health risk associated with leaching of chemicals, such as DEHP, used in the manufacturing of the gloves. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Di-2-ethylhexyl phthalate (DEHP) is primarily used in the polymeric materials as a plasticizer for a wide variety of industrial, domestic and medical products. Plasticizers embed themselves between the chains of polymers, resulting in separation of the chains and a reduction of the friction between the polymer molecules. Because plasticizers are not permanently bound to the polymer molecules, they can be released from polymeric materials [1–3]. DEHP can be dermally absorbed as well as cause skin irritation and burning sensations. The guinea pig studies have indicated a LD50 of 10 g/kg for dermal exposure [4], and the permeability coefficient of DEHP through human skin is 1.05 ± 0.21 × 10−7 cm/h [5]. Animal studies have indicated that DEHP has
∗ Corresponding author at: Department of Occupational Safety & Health, China Medical University, 91 Hsueh-Shih Rd., Taichung 40402, Taiwan, ROC. Tel.: +886 4 22053366x6205; fax: +886 4 22070500. E-mail address: [email protected] (K.-P. Chao). http://dx.doi.org/10.1016/j.jhazmat.2014.09.010 0304-3894/© 2014 Elsevier B.V. All rights reserved.
reproductive hazards, and the primary target organs are the liver and kidneys [6,7]. DEHP is known to induce the proliferation of peroxisomes, which has been associated with carcinogenesis [8]. The USEPA classifies DEHP as a group B2 carcinogen, i.e. probable human carcinogen, based on sufficient evidence in animals and inadequate evidence in humans, and considers it inappropriate to quantify the carcinogenic risk [9]. DEHP is an endocrine-disrupting compound and has been included on the list of Substances of Very High Concern (SVHC) and on the Annex XVII list of the EU REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) legislation. Therefore, the producers and users should submit authorization requests to the European Chemicals Agency to use DEHP. For example, the potential risks to children from dermal exposure to DEHP by skin contact the air mattress [10] and synthetic shoes [11] have been assessed. In the EU Risk Assessment Report [12], three occupational exposure scenarios were considered concerning exposure during production of DEHP, industrial use of DEHP and industrial end-use of products containing DEHP. Based on the calculation of the EASE (Estimation and Assessment of Substance Exposure) model, the dermal exposure dose was mainly via end-use of semi-manufactured products and end-products containing DEHP, such as adhesives/sealings lacquers/paints
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Flow meter
Permeation cell
Pump
Sampling port
Teflon bottle Incubator @ 25 ± 1oC
Fig. 1. Sketch of closed-loop permeation system.
rubber, inks for textiles and ceramics for electronic purpose. However, the available information on industrial end-use of DEHP is insufficient to directly estimate the dermal exposure of DEHP in workers. The polymeric materials of chemical protective gloves, such as PVC and nitrile, have added DEHP [13,14]. Tsumura et al. [2] investigated the DEHP contamination of foods sold in retail packed lunches and set lunches for restaurants in Japan. They found that the disposable PVC gloves used in the preparation of foods contained 22–41% (w/w) of DEHP. The alcohol solution sprayed onto the PVC gloves, for a disinfection purpose, increased the releasing and migration of DEHP from gloves into the food samples. Swedish Chemicals Agency [15] has estimated that a health care worker wearing the medical PVC gloves for 2 h/day could receive a DEHP dermal dose on the order of 7 g/kg/day. For practical purposes, there is a need to characterize the amount of DEHP that would be released from the chemical protective gloves and subsequently taken up by the body via dermal absorption. In this study, the permeation of organic solvents, such as benzene, toluene, ethyl benzene, and xylene (BTEX), through PVC and nitrile gloves was conducted using the ASTM F739 cell. The potential leaching of DEHP from the glove samples was determined during the permeation and desorption experiments. Moreover, a dermal exposure model was proposed to estimate the health risk to the leaching of DEHP for a practical scenario of using the protective gloves. The present work will provide an understanding on the potential leaching and risk of DEHP for a worker wearing the gloves to protect against hazardous chemicals.
2. Materials and methods 2.1. Glove samples and chemicals Test specimens were cut from the palm portion of nitrile (Best 727-11, USA) and PVC gloves (Best BO710, Japan), rinsed with deionized water, and air-dried for 24 h at a temperature of 25 ± 1 ◦ C and relative humidity of 50 ± 5%. The thicknesses of glove samples were measured at five random locations to the nearest 0.01 mm using a dial thickness gauge (Teclock Co., Okaya, Japan). The average thickness of the glove samples were 0.46 ± 0.01 and 0.27 ± 0.01 mm for nitrile and PVC, respectively. Organic solvents used for the permeation experiments were benzene, toluene, ethyl benzene, and xylene which were chosen because of their wide use in industry. These four solvents were of purity greater than 98%, and their physical–chemical properties are given in Table 1. DEHP, with purity >99%, was purchased from Sigma–Aldrich. 2.2. Permeation of organic solvents through gloves Permeation experiments were conducted using the ASTM F739 test method [16] with a closed-loop system. The schematic flow diagram of the experimental apparatus is shown in Fig. 1. The stainless steel permeation cell (Pesce Lab Sales, Kennett Square, PA) with a diameter of 25-mm was separated by the glove sample into the collection and challenge chambers. De-ionized water has been widely used as the collection medium for permeation experiments. However, DEHP is practically insoluble in water. Several
studies have indicated that methanol has no effect on the glove materials, such as degradation and back permeation [17,18]. In this study, methanol (GC grade, Macron), with a total volume of 170 mL, was circulated through the collection chamber using a MasterFlex® PTFE-Tubing pump system (Cole-Parmer, Vernon Hills, IL) at a flow rate of 50 mL/min. As shown in Fig. 1, a spherical stirrer was used to mix the collection medium in the Teflon bottle. All equipment constituting the closed-loop system was connected with Teflon tubing and placed in an incubator at a temperature of 25 ± 1 ◦ C. The permeation test was conducted until a constant rate of permeation occurred, which indicated the permeation of organic solvents through glove sample had reached a steady state. After the test solvent was added to the challenge chamber, 0.5-L aliquots of the collection medium were collected from the downstream sampling point every 15 min intervals using a micro-syringe. The samples were immediately injected into the gas chromatograph (GC) equipped with mass spectrometer (Turbomass Mass Spectrometer, Perkin Elmer, Norwalk, Conn.) for analysis the concentrations of permeants and DEHP. The temperature of the GC capillary column (EquityTM -5, Supelco, Bellefonte, PA) was kept at 80 ◦ C for 2 min, and then ramped to 290 ◦ C at a rate of 30 ◦ C/min with a final hold of 5 min. The temperatures of the injection port and detector were maintained at 250 ◦ C and 300 ◦ C, respectively. The flow rate of the carrier gas helium (purity of 99.999%) was 1 mL/min. Mass range was scanned at 0.5 s/scan, where ions were produced through selected ion recording (SIR) mode. The limit of detection (LoD) for BTEX is shown in Table 1. At the end of permeation experiments, it was observed that the thickness of nitrile glove samples increased by 3.2–6.8%, while the thickness of PVC gloves remained approximately constant. Therefore, the effect of swelling of glove samples for the permeation test can be assumed to be negligible. 2.3. Desorption of organic solvents from gloves As the permeation test was terminated, the permeation cell was immediately disassembled. The contaminated glove sample was blotted dry to remove excess liquid chemicals using filter papers, and then placed in a second permeation cell. The closedloop system of the second cell was reassembled. Fresh methanol was circulated through the collection chamber, and the elapsed time for the desorption experiment was clocked. The challenge chamber of the reassembled cell was emptied of the test chemical. This effort was to simulate the scenario where a worker wears the used gloves but without contact with the chemical. Reassembling of the second cell was completed within 10 min, and the apparatuses of the closed-loop system were subsequently placed back in an incubator at 25 ± 1 ◦ C. The sampling and analysis procedures were the same as the permeation tests. For each test solvent, the permeation and desorption experiments were repeated at least three times. 2.4. Blank test for collection medium In this study, the blank tests for the collection medium were conducted using a similar experimental procedure for the desorption experiment. The closed-loop system of the permeation cell was assembled using the nitrile and PVC gloves, while the challenge chamber was emptied of chemicals. Methanol was circulated through the collection chamber and analyzed for DEHP every 15 min intervals. The blank experiments were repeated three times for both nitrile and PVC gloves. During a test period of 240 min, the amount of DEHP leached from PVC gloves was 0.032 ± 0.006 mg/g. The concentrations of DEHP in the collection medium were lower than its detection limit, i.e. 0.011 mg/L, for the blank experiments of nitrile gloves. Therefore, the effect of methanol on the leaching
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55
Table 1 Physical and chemical properties of permeation solvents. Chemical
Grade
Mw (g/mol)
WS (mg/L)
Log Kow
LoD (mg/L)
Benzene (Sigma–Aldrich) Toluene (Mallinckrodt) Ethyl benzene (Merck) p-Xylene (Merck)
ACS ACS GC ACS
78.1 92.1 106.2 106.2
1780 515 187 198
2.12 2.73 3.15 3.15
0.005 0.051 0.183 0.068
Properties are at 25 ◦ C and abbreviations are as follows: Mw: molecular weight; WS: water solubility; log Kow : octanol–water partition coefficient; LoD: limit of detection.
of DEHP from glove samples can be neglected as compared to the results of permeation and desorption experiments. 3. Results and discussion
P = Js L = ˛
3.1. Permeation of organic solvents Fig. 2 shows the permeation results of test solvents through the glove samples. Once breakthrough was occurred, the concentrations of permeants in the collection medium increased linearly. In 6,000
(a) Nitrile glove
Benzene Toluene
5,000
Ethyl benzene Xylene
Concen. (mg/L)
4,000
slope α
3,000
2,000
1,000
0 0
50
100
150
200
250
Time (min) 4,000
(b) PVC glove
3,500 3,000
slope α
2,500
Concen. (mg/L)
a closed-loop system, the permeability coefficient, P (M L−1 T−1 ), of organic solvents in the glove sample was determined as follows [19]:
2,000 1,500 1,000
V L A
(1)
where Js is the steady state permeation rate of organic solvents in the glove (M L−2 T−1 ); L is the thickness of glove sample (L); ˛ is the slope of linear portion of the permeant concentrations in the collection medium (M L−3 T−1 ), i.e. steady state permeation show in Fig. 2; V is the total volume of the collection medium in the closedloop system (L3 ), i.e. 170 mL; A is the area of glove sample exposed to the permeant, i.e. 5.06 cm2 . Table 2 presents the permeability coefficients of test solvents in the glove samples. The average permeability coefficients of BTEX were 48.34–5.19 and 13.84–3.28 g/cm/min for nitrile and PVC gloves, respectively. The results of permeability coefficients indicate that BTEX were less permeable through the PVC gloves than nitrile samples. According to the principle of “like dissolves like”, a polar chemical is more easily dissolved in a polar solvent. In general, the lower the octanol-water partition coefficient of a chemical, the higher the polarity. Because the nitrile and PVC gloves are polar materials, the chemical with lower Kow will have a stronger attraction to the nitrile and PVC gloves, resulting in a higher permeation through the gloves. Fig. 3 shows that the permeability coefficients of BTEX were inversely proportional to their octanol-water partition coefficients (log Kow ) for the nitrile (r = 0.983) and PVC gloves (r = 0.964). During the permeation experiment, DEHP was analyzed in the collection medium. As shown in Fig. 4, the leaching amounts of DEHP from the glove samples were increased with the permeation time. This result implied that the weak bonds between DEHP and the polymer molecules were broken due to the diffusion of BTEX molecules. Therefore, leaching of DEHP from the gloves may pose a health threat to the worker. The content of DEHP in flexible polymer materials, such as PVC, varies but is often around 30% (w/w) [12]. Tsumura et al. [2] found that the content of DEHP in PVC gloves was as high as 22–41% (w/w). For the BTEX permeants, the amount of DEHP leached from PVC gloves was approximately one order of magnitude higher than that from nitrile gloves. A possible reason for this result may be that a larger amount of DEHP was added in the production process of PVC gloves compared with the nitrile samples. Fig. 5 indicates that the amounts of DEHP leached from the gloves were inversely correlated (r ≥ 0.766) to the permeability coefficients (mol/cm/min) of BTEX. It is plausible that the amounts of DEHP released from the glove Table 2 Permeability coefficients of BTEX for the glove samples.
500
Chemical
Permeability coefficienta (g/cm/min) Nitrile glove
0 0
50
100
150
200
250
Time (min) Fig. 2. Concentrations of BTEX in the collection medium for the permeation experiments.
Benzene Toluene Ethyl benzene p-Xylene a
Mean ± SD.
48.34 15.78 5.99 5.19
± ± ± ±
2.85 1.21 0.88 0.39
PVC glove 13.84 10.42 3.42 3.28
± ± ± ±
0.58 0.38 0.03 0.66
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60
0.20
Toluene
50
0.16
PVC (r=0.964)
Ethyl benzene Xylene
0.14
DEHP (mg/g)
40
P (μg/cm/min)
(a) Nitrile glove
Benzene
0.18
Nitrile (r=0.983)
30
20
0.12 0.10 0.08 0.06 0.04
10
0.02 0.00
0
0
0
1
2
3
4
50
100
5
Dermal exposure of DEHP may occur immediately once DEHP leaches from the glove. The dermal dose was calculated under an exposure scenario, i.e. leaching of DEHP from the glove sample at
(b) PVC glove
1.8 1.6
samples may be directly proportional to the permeation resistance of gloves of the solvent.
3.3. Potential health risks of DEHP
250
2.0
Fig. 3. Permeability coefficients of BTEX in glove samples inversely proportional to their octanol–water partition coefficients.
1.4
DEHP (mg/g)
Fig. 6 shows the concentrations of BTEX in the collection medium during the desorption experiments. Even without contacting BTEX, the residual BTEX was desorbed from the contaminated glove samples. As seen in Fig. 6(a), the BTEX concentrations were significantly increased in the collection medium and then remained approximately constant for the nitrile gloves. Fig. 6(b) indicates that the BTEX concentrations were increased in the collection methanol for the PVC gloves during a test period of 240 min. The residual BTEX desorbed from the nitrile gloves was significantly greater than that from the PVC gloves. This result is plausible because the initial concentration profiles of BTEX inside the contaminated glove for the desorption experiments were the same as that for the permeation experiments. As compared with Fig. 2, the order of permeability coefficients for BTEX from the highest to lowest was different from the order of the residual BTEX desorbed from the nitrile and PVC gloves. For example, the permeability coefficients for PVC gloves were benzene > toluene > ethyl benzene > xylene; while the desorbed levels were toluene > xylene > benzene > ethyl benzene for the desorption experiments. These findings suggest that the chemical with a greater permeability could be not easily desorbed from the contaminated glove. Fig. 7 shows that leaching of DEHP from the contaminated glove samples occurred during the desorption experiments. The leaching levels of DEHP from the PVC gloves were greater than that from the nitrile gloves for the same BTEX compound. For example, the leaching amounts of DEHP were 0.228 and 0.039 mg/g-glove for the contaminated PVC and nitrile gloves, respectively. However, the leaching levels of DEHP for the permeation experiments were approximately twice as compared to the desorption experiments.
200
Time (min)
log Kow
3.2. Concentration profile of residual BTEX and DEHP
150
1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
50
100
150
200
250
Time (min) Fig. 4. Amounts of DEHP leaching from the glove samples during the permeation experiments.
an average rate during BTEX permeation through the glove. If a worker wore the protective glove and was continuously contacted to BTEX, the level of DEHP body burden resulting from the dermal absorption of DEHP through one hand, i.e. dermal dose, might be estimated by Eq. (2) [17]. Dermal dose =
Jd × As × Et × Ef × Ed Bw × At
(2)
where Jd is the dermal permeation rate of DEHP through the human skin (M L−2 T−1 ); As is the exposed skin area of the whole hand, i.e. 840 cm2 [20]; Et is the daily exposure time, i.e. 8 h/day; Ef is the exposure frequency, i.e. 250 day/year; Ed is the exposure duration, i.e. working for 40 years; Bw is the body weight, i.e. 70 kg; and At is the averaging lifetime, i.e. 70 years or 25,550 day. Table 3 shows that the average leaching rates of DEHP were 0.027–0.073 and 0.079–0.091 g/cm2 /min for the nitrile and PVC gloves, respectively, for the permeation experiments. According to the results of the permeation experiments, the concentrations of DEHP exposed to the hand of a worker can increase while the
K.-P. Chao et al. / Journal of Hazardous Materials 283 (2015) 53–59
0.7
1,400 Benzene
Nitrile (r=0.766) 0.6
PVC (r=0.77)
(a) Nitrile glove
Toluene
1,200
Ethyl benzene Xylene
0.5
1,000
Concen. (mg/L)
P (mole/cm/min)
57
0.4 0.3
800
600
0.2
400 0.1
200 0 0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
Leaching DEHP (mg/g)
0
50
100
Carcinogenic risk = dermal dose × DerSF
200
250
300
Time (min)
Fig. 5. The leaching amounts of DEHP inversely correlated to the permeability coefficients of BTEX in glove samples.
250
(b) PVC glove 200
Concen. (mg/L)
worker wears the glove and handles BTEX. Therefore, the dermal permeation rate of DEHP was used in Eq. (2) to evaluate the dermal dose. Scott et al. [21] indicated that the in vitro permeation rate of DEHP through the human skin is 0.093 g/cm2 /min. If the average leaching rate of DEHP was lower than 0.093 g/cm2 /min, Jd calculated in Eq. (2) was assumed to be the average leaching rates of DEHP as indicated in Table 3. On the other hand, Jd was assumed to be 0.093 g/cm2 /min for the case if the average leaching rate of DEHP was greater than 0.093 g/cm2 /min. Based on the parameters assumed in this study, Table 3 indicates that the average daily dermal dose of DEHP was 1.1–3.8 g/kg/day for a 70 kg worker. To evaluate the potential health effects of DEHP, the carcinogenic risk from DEHP due to dermal contact by workers wearing the glove was obtained as follows [22]:
150
150
100
50
(3)
where DerSF is the dermal carcinogenic slope factor for DEHP. However, because of the unavailability of dermal SF for DEHP, oral to dermal SF was extrapolated using the gastrointestinal absorption factor (GIAF) as follows [3,11,23]: OralSF GIAF
0 0
50
100
150
200
250
300
Time (min)
(4)
Fig. 6. Concentrations of BTEX in the collection medium for the desorption experiments.
Table 3 Dermal doses and carcinogenic risks of DEHP for BTEX permeation through nitrile and PVC gloves.
where OralSF is the oral carcinogenic slope factor for DEHP, i.e. 1.4 × 10−2 kg-day/mg [3,24]. The recommendation of USEPA is to assume a 100% GIAF value for DEHP [23], indicating that DEHP is generally well absorbed (>50%) across the gastrointestinal tract. On the other hand, the Risk Assessment Information System of USDOE suggests a GIAF value of 0.19 for DEHP [3]. To account for the uncertainties in the extrapolation of OralSF, DerSF of 1.4 × 10−2 and 7.37 × 10−2 kg-day/mg was used respectively to estimate the carcinogenic risk from DEHP. At present the USEPA has defined acceptable risks for carcinogens as within the range of 10−4 –10−6 excess lifetime cancer risk. Table 3 indicates that the average carcinogenic risks from DEHP were 0.16–2.77 × 10−4 for a worker wearing the test gloves, falling in the “alert” range of acceptable risks. However, OSHA (Occupational Safety and Health Administration) accepts higher risk levels, in the range of 10−4 –10−3 , for occupational exposure [25]. In this study, it should be noted that the major uncertainties in calculating the carcinogenic risks can result from using the
DerSF =
Chemical
DEHP leaching ratea (g/cm2 /min)
Average dermal dose (g/kg/day)
Carcinogenic risk (10−4 ) DerSFb
DerSFc
Nitrile glove Benzene Toluene Ethyl benzene p-Xylene
0.027 0.062 0.067 0.073
± ± ± ±
0.012 0.011 0.023 0.016
1.1 2.5 2.3 2.7
0.16 0.35 0.32 0.38
0.81 1.84 1.70 1.99
PVC glove Benzene Toluene Ethyl benzene p-Xylene
0.079 0.083 0.096 0.091
± ± ± ±
0.022 0.017 0.018 0.026
3.2 3.4 3.8 3.7
0.44 0.47 0.53 0.52
2.36 2.51 2.77 2.73
a b c
Mean ± SD. DerSF of 1.4 × 10−2 kg-day/mg. DerSF of 7.32 × 10−2 kg-day/mg.
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K.-P. Chao et al. / Journal of Hazardous Materials 283 (2015) 53–59
0.06
(a) Nitrile glove
Benzene Toluene
0.05
Ethyl benzene Xylene
DEHP (mg/g)
0.04
0.03
0.02
0.01
4. Conclusions
0.00 0
50
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(b) PVC glove
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DEHP (mg/g)
can result in an increase in the leaching rates of DEHP from the gloves. For practical purposes, assessment of carcinogenic risk from the leaching DEHP should be conducted, if desired, using the results of permeation tests for a solvent mixture and under the temperature condition as found in the manufacturing work condition. Chao et al. [17] conducted the permeation tests of re-exposed gloves to simulate a practical scenario of glove reuse. They found that the permeability coefficients of re-exposed gloves were lower than those of the new glove samples. It was speculated that the additives, such as plasticizers, were dissolved from the re-exposed gloves during the permeation tests [18,26]. Therefore, reuse of gloves could result in a lower leaching of DEHP from the gloves, thus decreasing the carcinogenic risk from DEHP compared to use of new gloves.
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For the permeation experiments, BTEX solvents permeated through the glove samples and dissolved DEHP from the gloves. The DEHP leaching amounts were found to be inversely correlated to the permeability coefficients of BTEX in the glove samples. It is speculated that the chemical resistance of protective gloves to permeation by BTEX was enhanced as DEHP dissolved from the gloves. On the other hand, our evaluation suggests that dermal absorption of DEHP released from the gloves may pose a potential health risk to the workers who come into contact with BTEX. The dermal exposure model developed herein can provide the quantitative information for technical control measures to reduce the health risks resulting from DEHP. It should be noted that the health effect of plasticizers on the chemical resistance of protective gloves should be determined using the chemical constituents in their actual composition as applied in industrial processes. Acknowledgments
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The study was financially supported by the National Science Council, Taiwan, ROC (100-2221-E-039-007, 101-2221-E-039009).
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References
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Time (min) Fig. 7. Amounts of DEHP leached from the glove samples for the desorption experiments.
DEHP leaching rates determined by the permeation experiments. For a worst-case exposure scenario where the DEHP leaching rate was calculated as the 95th percentile upper confidence limit (i.e., mean + 2SD), the dermal dose of DEHP was estimated to be 3.2 g/kg/day for a worker wearing the nitrile glove and contacting ethyl benzene, with an increase in carcinogenic risk by 38.8%. Another possible source of uncertainty in calculating the carcinogenic risk is the in vitro permeation rate of DEHP through the human skin. The evaluation of permeation rate of DEHP through human skin should be a pre-requisite for the assessment of health risk associated with using protective gloves. However, there is currently no human in vivo study for the absorption of DEHP via the skin [10,24]. Based on the carcinogenic risks evaluated herein, it is suggested that the scenario of industrial end-use of products containing DEHP, such as chemical protective gloves, cannot be neglected. It should be noted that the co-solvent effect may enhance leaching of DEHP from the gloves if a worker is exposed to a mixture of solvents. Moreover, handling the solvents at a higher process temperature
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