Characterisation of Engineered Nanomaterials in Nano-Enabled Products Exhibiting Priority Environmental Exposure

Abstract

Analytical limitations have constrained the determination of nanopollution character from real-world sources such as nano-enabled products (NEPs), thus hindering the development of environmental safety guidelines for engineered nanomaterials (ENMs). This study examined the properties of ENMs in 18 commercial products: sunscreens, personal care products, clothing, and paints—products exhibiting medium to a high potential for environmental nanopollution. It was found that 17 of the products contained ENMs; 9, 3, 3, and 2 were incorporated with nTiO2, nAg, binaries of nZnO + nTiO2, and nTiO2 + nAg, respectively. Commonly, the nTiO2 were elongated or angular, whereas nAg and nZnO were near-spherical and angular in morphology, respectively. The size ranges (width × length) were 7–48 × 14–200, 34–35 × 37–38, and 18–28 nm for nTiO2, nZnO, and nAg respectively. All ENMs were negatively charged. The total concentration of Ti, Zn, and Ag in the NEPs were 2.3 × 10−4–4.3%, 3.4–4.3%, and 1.0 × 10−4–11.3 × 10−3%, respectively. The study determined some key ENM characteristics required for environmental risk assessment; however, challenges persist regarding the accurate determination of the concentration in NEPs. Overall, the study confirmed NEPs as actual sources of nanopollution; hence, scenario-specific efforts are recommended to quantify their loads into water resources.

Assessment of Nanopollution from Commercial Products in Water Environments

“…The SUN2-released ENMs sizes were 27-30 × 33-37 nm, while SUN3released ENMs were 21-22 × 25-28 nm. The average size of SUN2-released ENMs was in agreement with previously reported sizes [41]. The distribution of the SUN1-released nZnO particles (W × L) in Milli-Q water and freshwater were comparable, and the distribution densities were similar to the ENMs incorporated in SUN1.…”

“…SUN1-released nTiO 2 were elongated, while nZnO was angular in shape. SUN2-3-released nTiO 2 were angular in shape, shapes that were previously reported [41]. Product-released ENMs were still predominantly associated with aluminium (Al) and silicon (Si) (Figures S1 and S3), indicative of remnants of coating agents [49][50][51], either intact on the surface of product-released ENMs or in the release media.…”

“…The particles were negatively charged, and the nTiO 2 phase was rutile or anatase. The total amounts of ENMs differed between NEPs [41].…”

“…Six NEPs, namely three sunscreens, SUN1 (nTiO 2 + nZnO), SUN2-3 (nTiO 2 ); body cream CA1 (nTiO 2 + nAg); sanitiser; SAN1 (nAg); and socks SK1 (nTiO 2 + nAg) were purchased from South African retailers. The physicochemical properties of the ENMs incorporated in the six NEPs varied and were previously reported [41]. Briefly, SUN1 contained elongated nTiO 2, and angular nZnO particles sized 14 × 62 nm and 35 × 38 nm, respectively.…”

“…The release of ENMs from SK1 was undertaken by adapting previously developed methods [44,45]. Briefly, areas (spots/regions) of the sock material marketed and experimentally confirmed to be incorporated with nAg and nTiO 2 [41] were cut from SK1 samples and transferred into 1 L glass bottles, washed with 200 mL of the release media (Milli-Q water, tap water, and sodium dodecyl sulfate as a detergent). The detergent media was prepared in two ways: (i) sodium dodecyl sulfate 1, which was prepared in Milli-Q water, while (ii) sodium dodecyl sulfate 2 was prepared in tap water.…”