Bioaccessibility studies of ferro‐chromium alloy particles for a simulated inhalation scenario: A comparative study with the pure metals and stainless steel

Abstract

The European product safety legislation, REACH, requires that companies that manufacture, import, or use chemicals demonstrate safe use and high level of protection of their products placed on the market from a human health and environmental perspective. This process involves detailed assessment of potential hazards for various toxicity endpoints induced by the use of chemicals with a minimum use of animal testing. Such an assessment requires thorough understanding of relevant exposure scenarios including material characteristics and intrinsic properties and how, for instance, physical and chemical properties change from the manufacturing phase, throughout use, to final disposal. Temporary or permanent adverse health effects induced by particles depend either on their shape or physical characteristics, and/or on chemical interactions with the particle surface upon human exposure. Potential adverse effects caused by the exposure of metal particles through the gastrointestinal system, the pulmonary system, or the skin, and their subsequent potential for particle dissolution and metal release in contact with biological media, show significant gaps of knowledge. In vitro bioaccessibility testing at conditions of relevance for different exposure scenarios, combined with the generation of a detailed understanding of intrinsic material properties and surface characteristics, are in this context a useful approach to address aspects of relevance for accurate risk and hazard assessment of chemicals, including metals and alloys and to avoid the use of in vivo testing. Alloys are essential engineering materials in all kinds of applications in society, but their potential adverse effects on human health and the environment are very seldom assessed. Alloys are treated in REACH as mixtures of their constituent elements, an approach highly inappropriate because intrinsic properties of alloys generally are totally different compared with their pure metal components. A large research effort was therefore conducted to generate quantitative bioaccessibility data for particles of ferro-chromium alloys compared with particles of the pure metals and stainless steel exposed at in vitro conditions in synthetic biological media of relevance for particle inhalation and ingestion. All results are presented combining bioaccessibility data with aspects of particle characteristics, surface composition, and barrier properties of surface oxides. Iron and chromium were the main elements released from ferro-chromium alloys upon exposure in synthetic biological media. Both elements revealed time-dependent release processes. One week exposures resulted in very small released particle fractions being less than 0.3% of the particle mass at acidic conditions and less than 0.001% in near pH-neutral media. The extent of Fe released from ferro-chromium alloy particles was significantly lower compared with particles of pure Fe, whereas Cr was released to a very low and similar extent as from particles of pure Cr and stainless steel. Low release rates are a...

Influence of Citric Acid on the Metal Release of Stainless Steels

“…1, Fe was predominantly released from both grades followed by the release of Ni, Cr, and Mn. This is in agreement with previous investigations of metal release from these grades in citric acid and other aqueous acidic or neutral solutions [11][12][13][14][15][16][17][18][19] . The release pattern is related to the passive mixed surface oxide of Cr 2 O 3 and Fe 2 O 3 with metallic nickel present in the alloy surface layer beneath the surface oxide 11,20) .…”

Particles, sweat, and tears: A comparative study on bioaccessibility of ferrochromium alloy and stainless steel particles, the pure metals and their metal oxides, in simulated skin and eye contact

“…Detailed compositional analysis of the surface oxide has been presented elsewhere (Leygraf et al 1979;Castle and Qiu 1990;Midander et al 2007aMidander et al , 2009bHerting et al 2008b). The relative proportions of Cr and Fe (Cr/[Cr þ Fe]) in the surface oxide of FeCr and 316L particles are presented in Figure 3 compared with their corresponding relationship in each bulk alloy.…”

Chemical Stability of Chromium Carbide and Chromium Nitride Powders Compared with Chromium Metal in Synthetic Biological Solutions

“…The release of chromium from the different powders was quantified for time periods up to one week at standard conditions in artificial biological fluids of varying pH and composition of relevance for human contact. Since the release of dissolved metal species, an extent not possible to predict from bulk compositional data [2,37], is believed to induce acute effects on human health, measurement of released metal species into artificial body fluids can indicate whether in vivo toxicity, at least acute is likely to occur.…”

“…Elaborate studies have been performed generating data on release, dissolution, and solubility aspects of chromium and chromium-containing alloys such as stainless steels and ferrochromium alloys [1][2][3][4][5][6][7][8][9], data that has been utilised within the framework of the European chemicals legislation (REACH) implemented in 2007. Bioaccessibility and environmental impact aspects of chromium have been discussed by, for example, [9][10][11].…”