Assessment of the Hazard and Ecotoxicity of the Residues of Paiche Leather Dyed with Natural and Synthetic Colourants: A Focus on Environmental Sustainability

Abstract

The aim of this research was to assess the hazardousness and ecotoxicity of paiche leather (Arapaima gigas) dyed with natural colourants (turmeric and purple corn) versus synthetic colourants (anilines). To determine hazardousness, the methodology included the assessment of flammability, corrosivity, reactivity to H2S and HCN, toxicity from metals, and organic compounds of dyed leather. Additionally, its ecotoxicity was determined using the California red worm (Eisenia fetida) as a bioindicator through a bioassay, with treatments at 0.02, 0.04, 0.08, 0.16, and 0.20 g of leather/g of substrate, including undyed leather and a negative control in the investigation. The hazardousness analysis results indicated that leather samples dyed with both natural and synthetic colourants are not hazardous. However, the concentrations of chromium, nickel, cadmium, and lead exceed the permitted values for their use in footwear according to the European Union. Regarding ecotoxicity, the results demonstrate that acute toxicity to E. fetida is lower for natural colourants compared to synthetic colourants, where 100% mortality occurs at concentrations between 0.04 and 0.08 g of leather/g of the substrate. Concerning chronic toxicity, after 12 weeks of exposure, the tolerance concentration for undyed paiche leather is 0.035 g of leather/g of the substrate, and for leather dyed with purple corn and turmeric, it is 0.2 g of leather/g of the substrate. It is shown that the active compounds of natural colourants have a positive effect on worm survival, and it is concluded that paiche leather dyed with these colourants presents environmental advantages over leather dyed with synthetic colourants.