Development of a test method for protective gloves against nanoparticles in conditions simulating occupational use

Nanoparticle manufacture and use are in full expansion. The associated risks of occupational exposure raise large concerns due to their potential toxicity. Even if they stand as a last resort in the traditional occupational Health & Safety (H&S) risk management strategy, personal protective equipment (PPE) against nanoparticles are an absolute need in the context of precautionary principle advocated by H&S organizations worldwide. However no standard test method is currently available for evaluating the efficiency of PPE against nanoparticles, in particular in the case of gloves. A project is thus underway to develop a test method for measuring nanoparticle penetration through protective gloves in conditions simulating glovenanoparticle occupational interaction. The test setup includes an exposure and a sampling chamber separated by a circular glove sample. A system of cylinders is used to deform the sample while it is exposed to nanoparticles. The whole system is enclosed in a glove box to ensure the operator safety during assembly, dismounting and clean-up operations as well as during the tests. Appropriate nanoparticle detection techniques were also identified. Results are reported here for commercial 15nm TiO2 nanoparticles powder and colloidal solutions in 1,2-propanediol, ethylene glycol and water and four types of protective gloves: disposable nitrile and latex as well as unsupported neoprene and butyl rubber gloves. They show that mechanical deformations and contact with colloidal solution liquid carriers may affect glove materials. Preliminary results obtained with TiO2 powder indicate a possible penetration of nanoparticles through gloves following mechanical deformations. With the growing expansion of nanotechnologies worldwide, increasing risks of exposure to nanoparticles are expected. This is especially worrying in the case of occupational settings, where the level of toxicological risk has been evaluated as significant [1]. In the context of precautionary principle advocated by numerous H&S organizations around the world [2], large efforts are directed towards the development of standards [3], guides [4,5] and risk assessment and control methodologies [6] specific for nanomaterials. Indeed, it has been estimated that the number of workers involved in nano-related activities would reach 2 millions by 2015 [7]. As a result and even if they stand as a last resort in the traditional occupational H&S risk management strategy, PPE against nanoparticles are Nanosafe2010: International Conference on Safe Production and Use of Nanomaterials IOP Publishing Journal of Physics: Conference Series 304 (2011) 012066 doi:10.1088/1742-6596/304/1/012066 Published under licence by IOP Publishing Ltd 1 needed right away [8]. Yet, knowledge, data and test methods in this area are scarce whereas questions have been raised about the efficiency of existing PPE products against nanoparticles [9]. If some progress has been accomplished regarding respiratory PPE against nanoparticles, the question of dermal protection is still largely unexplored [9]. However, studies are increasingly showing that skin is a possible uptake route for nanoparticles, either when injured by abrasion [10], after repeated flexions [11] or even intact [12]. Pores, hair follicles and sweat may also increase the likelihood of nanoparticles percutaneous transportation [13]. A limited number of groups have reported research carried out on protective clothing and gloves against nanoparticles. Most of it involves aerosols. In the case of air-permeable fabrics, tests have been performed with oleic acid, KCl, NaCl, graphite, TiO2 and Pt nano-aerosols as small as 10nm in diameter [14-20]. According to some authors, the variation of the nanoparticle penetration ratio through fabrics as a function of the particle diameter and air flow rate is in agreement with the filtration theory [15,16,21]. Others have reported diverging results, for example a plateau in the penetration of graphite nanoparticles larger than 50 nm through woven cotton with a 0.6 cm/s face velocity [18], and a higher penetration of 30nm graphite nanoparticles through a paper fabric than 80nm ones [9]. A much higher efficiency against nanoparticle penetration was observed for a thin high-density polyethylene non-woven membrane than with other, thicker fabrics, with and without air flow [17-20]. In the case of protective gloves, the results seem conflicting. Diffusion of 30 and 80nm graphite nanoparticles through nitrile, vinyl, latex and neoprene commercial glove samples has been reported [17] while no penetration was later measured for the same gloves with 40nm graphite and 10nm TiO2 and Pt particles [18,19]. These data involving nano-aerosols were obtained without air flow. Exposure to nanoparticles in occupational settings may also involve powder and colloidal solutions. This situation is especially relevant to protective gloves. Scanning electron microscopy (SEM) observations of latex and nitrile rubber gloves after static and dynamic contact with clay and alumina powders have shown that nanoparticles tend to accumulate inside micrometer-size pores on the surface of the gloves [22]. In the case of nanoparticles in colloidal solutions, some concerns have been raised about increased risks related to the liquid carrier [23]. In addition, the mechanical deformations suffered by gloves in service as well as the presence of a microclimate inside the gloves may also affect the penetration of the nanoparticles. It is thus important that test methods take into account conditions experienced by PPE while in use [21]. This paper reports on the development of a test method for measuring nanoparticle penetration through protective gloves in conditions simulating glove occupational use. It describes the setup designed for the test as well as the nanoparticle detection techniques investigated. Finally, it provides preliminary results obtained with commercial 15nm TiO2 powder and colloidal solutions, and four types of protective gloves: disposable nitrile and latex as well as unsupported neoprene and butyl rubber.