Micro- and nanoplastics (MNPs) are known to detrimentally impact a wide range of aquatic species, inducing mortality, decreased growth, a reduction in offspring production and increase in reactive oxygen species in their tissues. However, the genotoxic impact of MNPs in freshwater organisms remains understudied. In the present study we investigate the genotoxic impact of acute exposure to polystyrene nanoparticles (PSNPs) in Daphnia pulex using the comet assay, alongside immobilisation rate and hopping frequency. Daphnids were exposed to 100 nm PSNPs for 24 and 48 h at concentrations between 10 and 200 mg/L. Immobilisation increased with PSNPs concentration and exposure time, while hopping frequency among surviving daphnids decreased at concentrations above 100 mg/L after 24 h, and above 50 mg/L after 48 h. Comet assay results showed increasing DNA damage with concentration and exposure time, with significant DNA damage after 24 h of exposure to 200 mg/L PSNPs, and after 48 h of exposure to 100 and 200 mg/L. These results suggest that exposure to MNPs increases daphnid mortality, impacts behaviour, and induces genotoxicity. The incorporation of the comet assay into freshwater monitoring methods alongside existing techniques could further understanding of the full impact of MNP pollution upon ecosystem health.
Artisanal and small-scale gold mining (ASGM) is common in many developing countries; while it contributes to their socio-economic development, it also causes environmental pollution. This study examined the impact of ASGM activities on the quality of drinking water sources in the Asankrangwa District in Ghana, in terms of water quality index, heavy metal pollution index models, and human health risks. The results of physicochemical parameters indicate that 40.0% of all water sources are unsuitable for consumption. Heavy metal pollution indices indicated that 45.0% of the water sources were extremely polluted, and 25.0% were moderately polluted. For instance, cadmium (Cd) concentrations across all water sources reached levels up to 23 times the WHO limit (3.0 × 10-3 mg/L). Additionally, mercury (Hg) concentrations in 75.0% of the water sources (2.0 × 10-3-7.2 × 10-1 mg/L) exceed the maximum contaminant limit (2.0 × 10-3 mg/L) by approximately 361 times. Streams, in particular, exhibit higher Hg levels than groundwaters. Analysis revealed that 90% of the water sources pose a significant carcinogenic health risk upon consumption, with lifetime cancer risk values exceeding 1.0 × 10-4. The findings revealed that the pollution level is reduced and water quality improved 5 km from the ASGM sites; however, the water sources require treatment to render them suitable for consumption.
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