Abstract
Zerovalent iron nanotechnologies are widely used for groundwater remediation and increasingly considered for advance oxidation treatment in drinking water applications. Iron nanoparticles have been detected in drinking water systems and considered for food fortification; therefore, the potential for human exposure through ingestion can be a concern. This study aimed to assess whether ingestion of iron nanoparticles from drinking water could be detected through flavor perception using In Vitro salivary lipid oxidation as an indicator for metallic flavor perception. Ten female subjects, aged 29–59 years, donated saliva samples for use in the In Vitro experiments. Test samples consisted of 1:1 mixture of saliva and bottled drinking water (control) and three treatment solutions, spiked with ferrous sulfate, stabilized zerovalent iron nanoparticles (nZVI), and an aggregated/microsized suspension of mixed zerovalent iron and microsized suspension of iron and iron oxide metal powder, (mZVI). Upon mixing, samples were subjected to 15 min incubation at 37 °C to resemble oral conditions. Salivary lipid oxidation (SLO) was measured in all samples as micromoles of thiobarbituric acid reactive substances (TBARS)/mg Fe. Exposure to iron in all three forms induced significant amount of SLO in all treatment samples as compared to the control (p < 0.0001). The mean SLO levels were the highest in the ferrous treatment, followed by nZVI and mZVI treatments; the differences in the mean SLO levels were significant (p < 0.05). The findings indicate that oral exposure to stabilized ZVI nanoparticles may induce sensory properties different from that of ferrous salt, likely predictive of diminished detection of metallic flavor by humans.
Highlights
Metallic iron in its zerovalent form has been widely used in the treatment of contaminated groundwater since the early 1990s, when it was first discovered that chlorinated hydrocarbons, such as trichlorethene (TCE), could be dehalogenated in the presence of iron metal [1,2]
Microrather than nanoparticles, with the the average size estimated at STAR, behaved as micro—rather than nanoparticles, with the average size estimated at 635 nm and the zeta potential measured at −19 mV
The findings from this study indicate that ferrous iron salt, being the most soluble compared to the two nanoiron products, induced the highest level of oxidative stress response in human salivary in human lung cells when compared to microsized particles
Summary
Metallic iron in its zerovalent form has been widely used in the treatment of contaminated groundwater since the early 1990s, when it was first discovered that chlorinated hydrocarbons, such as trichlorethene (TCE), could be dehalogenated in the presence of iron metal [1,2]. The use of metallic iron as applied in the form of permeable reactive barriers (PRBs) has been widely reported in groundwater remediation sites [3]. Scientific explorations in the field of nanoscience have opened many more intriguing possibilities with reported uses of stabilized zerovalent iron nanoparticles (nZVI) for the removal of toxic contaminants, such as nitrate, perchlorates, arsenic, hexavalent chromium, uranium, and antibiotics, from soil and water matrices and the use of magnetic iron oxides for targeted drug delivery and food fortification [4,5,6,7,8,9,10,11]. Public Health 2020, 17, 3622; doi:10.3390/ijerph17103622 www.mdpi.com/journal/ijerph
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