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Description
Synthetic food dyes are widely used in Ghana, yet their ecological effects on freshwater ecosystems remain understudied. This study investigated the acute toxicity of five commonly used synthetic food dyes (Tartrazine, Allura Red, Sunset Yellow, Carmoisine, and Green S) on two standard aquatic test organisms, Daphnia magna and Lemna minor. The tests on Daphnia magna and Lemna minor were conducted following OECD 202 and OECD 221 protocols respectively. The results for the physicochemical properties suggest that synthetic dyes, even in dilute form, can alter water chemistry significantly. Whiles the EC, salinity and TDS values for Sunset Yellow were relatively low (8.12 mS/cm, 7.50 psu, and 2.98 g/L respectively), Tartrazine, Carmoisine, and Green S recorded high levels of EC, TDS, and salinity. Levels of Cd and Hg in all the dyes were below detection limit (<0.001 mg/L). Carmoisine, however, recorded 0.003 mg/L for Cd. Levels of Cr, Pb, Fe, and Mn were above the limits in food dyes (≤ 0.002, ≤ 0.043, and ≤ 0.006). Allura Red is the most toxic among the dyes with Tartrazine being the dye with the least toxicity. All the dyes showed potential toxicity and when released into the environment without treatment will have adverse effect on the aquatic environment. Bioaccumulation potential revealed that Pb, Mn, As, and Hg were bioaccumulated by daphnia, whiles Cr, Cd, and Fe were not due to their low solubility, ionic competition, and strict cleansing mechanisms by daphnia. These findings highlight the potential ecological risks of unregulated dye pollution in Ghanaian waters and underscore the need for improved environmental regulations and monitoring. It also highlights the importance of region-specific ecotoxicological data in informing environmental policy and wastewater management practices.
Keywords: Synthetic dyes, Ecological effects, Freshwater, Heavy metals, Bioaccumulation, Acute toxicity