Microparticles in Table Salt: Levels and Chemical Composition of the Smallest Dimensional Fraction

Abstract

This study evaluates the chemical composition of microplastic materials (MPs) and non-synthetic particles in different table salts of marine origin by the µFT-IR technique. This research focuses on the microparticles fraction within 10–150 µm of size. Eleven commercial trademarks coming from Italy (IT = 6) and Croatia (CRO = 5) were grouped in two different cost ranges, cheap (n = 5) and expensive (n = 6) and were analysed in replicates (n = 3). Levels and chemical composition of microparticles measured in commercial products were correlated on a statistical basis to some factors of variability of potential scientific interest (geographical origin of marine salt, cost of commercial products, etc.). Results of analyses performed on the tested size fraction of microparticles (10–150 µm) evidence that: (i) levels of MPs are within 0.17–0.32 items/g (IT) and 0.07–0.20 items/g (CRO); (ii) non-synthetic particles detected are mostly made by fibres made of cellulose acetate; (iii) Nations show a different chemical composition of MPs recovered in analysed trademarks (PET and PVC from Italy; PA, PP, and nylon from Croatia); (iv) the annual amount ingested by humans from marine salt consumption ranges between 131.4–372.3 items/y (CRO) and 306.6–580.35 items/y (IT) considering a dose of 5 g of salt per day; (v) statistics performed on factors of interest evidenced that the geographical origin of marine salt do not affect neither levels nor chemical composition of MPs in tested trademarks; while slight correlations are recorded with non-synthetic particles. Further studies are needed to better explore on statistical basis if both levels and chemical composition of MPs in table salts of marine origin can be used or not as good indicators of marine pollution.

Microplastics in Food: A Review on Analytical Methods and Challenges

“…Table 1 summarizes the range of microplastics per kilogram of salt along with the analytical methods used. As shown in the table, the concentration of microplastics varied widely from not detected (n.d.) to 5400 particles per kilogram [ 14 , 15 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Hydrogen peroxide (H 2 O 2 ) was often used to digest organic matter in the solution after dissolving sea salts [ 14 , 15 , 29 , 30 ].…”

“…In all foods, PE, PP, PS, and PET (including polyesters) account for more than 50% of microplastics. Cellophane was found to be dominant in table salt [ 35 ], fish [ 40 ], and clams [ 90 , 91 ]. However, cellophane is a thin regenerated form of cellulose and is difficult to discern from naturally occurring plant-derived polymers through spectroscopic identification of smaller-sized particles.…”

Microplastic contamination of salt intended for human consumption: a systematic review and meta-analysis

“…When the searches were rerun, 3 more studies were included after the first and second level screening ( Fig. 1), resulting in 10 studies [64][65][66][67][68][69][70][71][72][73] finally included in this systematic review. All 10 studies were included in the SR and 4 in the meta-analysis.…”

“…However, the lower mean content for the Italian salts is eight times higher than the closest reported mean content. This study was one of five [65,66,[68][69][70] that did not use digestion in the particle-extraction procedure and the one of the three [68][69][70] that did not use a densityseparation technique to separate MPs from non-polymeric particles. Their analysis protocol fails to report important information: the number of replicates they used, the results of their procedural blank samples to account for after-sampling contamination and whether the results of the procedural blanks were subtracted from the final results.…”

“…In the light of these reporting omissions, the results and conclusions should be interpreted with caution. In their later work [70], they identified extremely lower content of 70-320 MPs/kg of salt (in the size fraction of 10-150 μm) and recognize that systematic composition analysis is necessary to avoid overestimations. Kim et al [67] also report high ranges compared to the other studies.…”