How to Quantitatively Assess Dermal Exposure to Volatile Organic Compounds

How to Quantitatively Assess Dermal Exposure to Volatile Organic Compounds Creta et al. (2017) present a method to assess dermal exposure to volatile organic compounds (VOCs) using activated charcoal cloth (ACC Perma-TecTM pads). They clearly demonstrate that in a controlled environmental chamber charcoal cloth patches adsorb vapour in the same way as organic vapour monitors (3MTM 3500). There was a high degree of linearity between the response of the two measurement systems when tested against 181 different VOCs. However, the authors did not undertake any field tests of their system and, surprisingly for a sampler designed to measure dermal exposure, they did not test it using a liquid challenge. They also do not report the mass of VOC required to saturate the adsorbent—a key issue for effective quantification of dermal exposure. Finally, they did not consider how their measurements might relate to dermal uptake, which presumably is the purpose of the sampling system. We have previously described problems in measuring dermal exposure to VOCs using ACC (Lindsay et al., 2006). A major difficulty encountered was the relative oversampling of vapour compared to liquid in the context of uptake via the skin, with workplace trials showing that about 23% of the mass of VOC sampled on the ACC came from vapour whereas we expected uptake to skin from vapour would have contributed little to body burden (Brooke et al., 1998). ACC samplers were also prone to saturating with liquid challenge after short periods of handling even small volumes. However, a more important limitation is that ACC measures deposition onto the sampler surface where the VOC is effectively adsorbed, whereas VOC deposited on skin can be lost by evaporation. For these reasons, we considered ACC is a poor surrogate for dermal uptake as it will considerably oversample the mass of VOC that would be taken up through the skin in most environments. The Perma-Tec monitors, while appropriate for their intended purpose of detecting breakthrough with chemical protective gloves, are wholly unsuitable for monitoring dermal exposure to VOCs. A more suitable way of assessing the risk from skin exposure to VOCs would be to use a simple model of dermal exposure loading, such as RISKOFDERM (Warren et al., 2006), coupled with a model to estimate intake while accounting for evaporation, such as IH-SkinPerm (Tibaldi et al., 2013). In Lindsay et al. (2006), we used ACC in the scenario where a worker was employed to spread rubber compound onto a cloth backing before it was pressed by rollers on a spreading machine. The rubber compound contained around 10% toluene. In this circumstance, RISKOFDERM predicts the median dermal loading (of toluene) on the hands to be around 750 mg and the 90th percentile of the estimate to be 16000 mg. [This is based on modelling exposure for someone dispersing product with a handheld tool; assuming a short handle device was used in a downward orientation, with 0.1 l/min of toluene handled in a viscous product; over a 4-h period]. We measured around 1300 mg on the hands of workers undertaking this task, assuming around 1000 cm2 of skin was exposed (Lindsay et al., 2006). Using IH-SkinPerm showed that over a 4-h exposure period for the above scenario around 93% of the deposited toluene would have evaporated and only around 50 mg would have been absorbed in to the skin. This was around 8% of the likely inhaled intake of 592 mg over the same period, (i.e. 98 mg/m3 [measured toluene air concentration] × 240 min [duration] × 0.025 m3/min [inhalation volume per minute] = 592 mg of toluene). In this situation, using measurement made with ACC samplers would have provided a completely erroneous view of the likely toluene dermal intake, i.e. more than twice the inhaled intake coming from skin contact rather than around 8%. Declaration There was no financial support for the preparation of this letter and no conflicts of interest. References Creta M, Poels K, Thoelen Let al.   ( 2017) A method to quantitatively assess dermal exposure to volatile organic compounds. Ann Work Expo Health ; 61: 975– 85. Google Scholar CrossRef Search ADS PubMed  Brooke I, Cocker J, Delic JIet al.  ( 1998) Dermal uptake of solvents from the vapour phase: an experimental study in humans. Ann Occup Hyg ; 42: 531– 40. Google Scholar CrossRef Search ADS PubMed  Lindsay FE, Semple S, Robertson Aet al.  ( 2006) Development of a biologically relevant dermal sampler. Ann Occup Hyg ; 50: 85– 94. Google Scholar PubMed  Tibaldi, R, ten Berge W, and Drolet D. ( 2013) Dermal absorption of chemicals: estimation by IH SkinPerm. J Occup Environ Hyg ; 11: 19– 31. Google Scholar CrossRef Search ADS   Warren ND, Marquart H, Christopher Yet al.  ( 2006) Task-based dermal exposure models for regulatory risk assessment. Ann Occup Hyg ; 50: 491– 503. Google Scholar PubMed  © The Author(s) 2017. Published by Oxford University Press on behalf of the British Occupational Hygiene Society. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Annals of Work Exposures and Health (formerly Annals Of Occupational Hygiene) Oxford University Press

How to Quantitatively Assess Dermal Exposure to Volatile Organic Compounds

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Publisher
British Occupational Hygiene Society
Copyright
© The Author(s) 2017. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
ISSN
2398-7308
eISSN
2398-7316
D.O.I.
10.1093/annweh/wxx098
Publisher site
See Article on Publisher Site

Abstract

Creta et al. (2017) present a method to assess dermal exposure to volatile organic compounds (VOCs) using activated charcoal cloth (ACC Perma-TecTM pads). They clearly demonstrate that in a controlled environmental chamber charcoal cloth patches adsorb vapour in the same way as organic vapour monitors (3MTM 3500). There was a high degree of linearity between the response of the two measurement systems when tested against 181 different VOCs. However, the authors did not undertake any field tests of their system and, surprisingly for a sampler designed to measure dermal exposure, they did not test it using a liquid challenge. They also do not report the mass of VOC required to saturate the adsorbent—a key issue for effective quantification of dermal exposure. Finally, they did not consider how their measurements might relate to dermal uptake, which presumably is the purpose of the sampling system. We have previously described problems in measuring dermal exposure to VOCs using ACC (Lindsay et al., 2006). A major difficulty encountered was the relative oversampling of vapour compared to liquid in the context of uptake via the skin, with workplace trials showing that about 23% of the mass of VOC sampled on the ACC came from vapour whereas we expected uptake to skin from vapour would have contributed little to body burden (Brooke et al., 1998). ACC samplers were also prone to saturating with liquid challenge after short periods of handling even small volumes. However, a more important limitation is that ACC measures deposition onto the sampler surface where the VOC is effectively adsorbed, whereas VOC deposited on skin can be lost by evaporation. For these reasons, we considered ACC is a poor surrogate for dermal uptake as it will considerably oversample the mass of VOC that would be taken up through the skin in most environments. The Perma-Tec monitors, while appropriate for their intended purpose of detecting breakthrough with chemical protective gloves, are wholly unsuitable for monitoring dermal exposure to VOCs. A more suitable way of assessing the risk from skin exposure to VOCs would be to use a simple model of dermal exposure loading, such as RISKOFDERM (Warren et al., 2006), coupled with a model to estimate intake while accounting for evaporation, such as IH-SkinPerm (Tibaldi et al., 2013). In Lindsay et al. (2006), we used ACC in the scenario where a worker was employed to spread rubber compound onto a cloth backing before it was pressed by rollers on a spreading machine. The rubber compound contained around 10% toluene. In this circumstance, RISKOFDERM predicts the median dermal loading (of toluene) on the hands to be around 750 mg and the 90th percentile of the estimate to be 16000 mg. [This is based on modelling exposure for someone dispersing product with a handheld tool; assuming a short handle device was used in a downward orientation, with 0.1 l/min of toluene handled in a viscous product; over a 4-h period]. We measured around 1300 mg on the hands of workers undertaking this task, assuming around 1000 cm2 of skin was exposed (Lindsay et al., 2006). Using IH-SkinPerm showed that over a 4-h exposure period for the above scenario around 93% of the deposited toluene would have evaporated and only around 50 mg would have been absorbed in to the skin. This was around 8% of the likely inhaled intake of 592 mg over the same period, (i.e. 98 mg/m3 [measured toluene air concentration] × 240 min [duration] × 0.025 m3/min [inhalation volume per minute] = 592 mg of toluene). In this situation, using measurement made with ACC samplers would have provided a completely erroneous view of the likely toluene dermal intake, i.e. more than twice the inhaled intake coming from skin contact rather than around 8%. Declaration There was no financial support for the preparation of this letter and no conflicts of interest. References Creta M, Poels K, Thoelen Let al.   ( 2017) A method to quantitatively assess dermal exposure to volatile organic compounds. Ann Work Expo Health ; 61: 975– 85. Google Scholar CrossRef Search ADS PubMed  Brooke I, Cocker J, Delic JIet al.  ( 1998) Dermal uptake of solvents from the vapour phase: an experimental study in humans. Ann Occup Hyg ; 42: 531– 40. Google Scholar CrossRef Search ADS PubMed  Lindsay FE, Semple S, Robertson Aet al.  ( 2006) Development of a biologically relevant dermal sampler. Ann Occup Hyg ; 50: 85– 94. Google Scholar PubMed  Tibaldi, R, ten Berge W, and Drolet D. ( 2013) Dermal absorption of chemicals: estimation by IH SkinPerm. J Occup Environ Hyg ; 11: 19– 31. Google Scholar CrossRef Search ADS   Warren ND, Marquart H, Christopher Yet al.  ( 2006) Task-based dermal exposure models for regulatory risk assessment. Ann Occup Hyg ; 50: 491– 503. Google Scholar PubMed  © The Author(s) 2017. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Journal

Annals of Work Exposures and Health (formerly Annals Of Occupational Hygiene)Oxford University Press

Published: Mar 1, 2018

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