Nano-enabled products in South Africa and the assessment of environmental exposure potential for engineered nanomaterials

Abstract

In order to address risks associated with nanotechnology, there needs to be improved understanding of potential sources of engineered nanomaterials (ENMs) into the environment. Nano-enabled products (NEPs) are amongst such sources, and the current study identified NEPs sold in South Africa as a means of examining their potential to emit ENMs into the environment. Two hundred and sixty-four products were identified, mainly from the health and fitness category (66.7%), followed by electronics and computers (15.2%), home and garden (10.6%), appliances (3.8%), automotive (2.7%) and food and beverage category (1.1%). The chemical identity of ENMs was reported in 62.8% of those products with the top five most common being ENMs (in the descending order) Ti, C, Ag, Si and bisoctrizole. Determining the NEPs environmental exposure potential indicated that 63.6% exhibited high exposure potential comprising predominantly health and fitness, personal care, cosmetics and clothing products. The priority NEPs in terms of environmental exposure were sunscreens, hair relaxers, moisturising lotions, eye creams, cosmetic sera and socks. Assessed through analytical examination, NEPs were found to contain ENMs with length and width ranges of 15-350 and 8-185 nm, respectively. Our study suggests that most NEPs sold in South Africa pose a high potential for nanopollution, with water resources as the highest risk. Mandatory labelling of NEPs is recommended in order to better estimate the extent of nanopollution arising from usage of the NEPs.

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

“…The incorporation of rutile [ 4 , 13 , 19 ], anatase [ 4 , 19 , 20 ], brookite [ 21 ], or a mixture of rutile and anatase [ 21 ] in products has been reported previously. Rutile nTiO 2 is preferred because of its high UV absorption gap (wavelength of 407 vs. 387 nm for anatase) [ 22 ] and because of the low photo-reactivity compared to highly reactive anatase that can produce hydroxyl radicals under ultraviolet treatment [ 23 ].…”

“…This possibility was further supported by TEM-EDX analysis ( Figure 8 C), whereby the ENMs (especially nAg) were seen to be deposited in a straight line inside the textile fibre. The location of ENMs in NEPs plays a significant role in the release potential of ENMs; for example, ENMs that are surface coated exhibit high release potential as compared to ENMs suspended in solid/matrix [ 19 ]. Similar to other personal care products (excluding CM1), the sample mass obtained after SK1 ashing was not sufficient to perform XRD analysis.…”

“…Nonetheless, advances have been made in this niche of research despite the persisting analytical challenges, resulting in better knowledge and understanding of the characteristics of ENMs in NEPs [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Overall, the literature indicates that the ENMs type, quantities, and characteristics in NEPs tend to vary widely even for closely related product types.…”

“…Overall, the literature indicates that the ENMs type, quantities, and characteristics in NEPs tend to vary widely even for closely related product types. For example, the commonly incorporated nTiO 2 in sunscreens vary in morphology (elongated, angular, irregular), size (18 to 90 nm), surface area (9.1 to 60.8 m 2 /g), and phase (rutile, anatase, or both) properties [ 17 , 18 , 19 , 28 , 29 , 30 ]. Hence, it is not simple to make solid assumptions and estimations based on a few studies, but rich datasets need to be developed in order to strengthen modeling exercises used to predict the environmental fate and effects of ENMs released from NEPs.…”

“…These NEPs are in the product categories of health and fitness (e.g., personal care products, sunscreens, cosmetics) as well as home and garden (cleaning products, paints, laundry cleaning products) [ 5 , 7 , 18 ]. From the different NEPs categories, sunscreens are the most widely studied [ 17 , 18 , 19 , 20 , 21 , 23 , 24 , 25 , 26 ], despite the evidence of high ENMs’ environmental exposure potential in NEPs such as paints [ 33 , 34 , 35 , 36 , 37 ] and other personal care products/cosmetics (e.g., toothpaste, shampoos, and face creams) [ 38 , 39 ]. While nTiO 2 can be expected to be emitted at relatively higher volumes due to their wide application in a spectrum of NEPs, the incorporation of other ENM types such as nAg, nSiO 2 , and nZnO have been reported in other market active NEPs within the health and fitness, as well as home and garden categories [ 7 , 18 , 32 ].…”