Plastic pollution is a global environmental crisis, with conventional, biodegradable, and recycled plastics having the potential to release harmful chemical additives and transformation products into aquatic environments. This study evaluates the toxicological effects of leachates from conventional, biodegradable, and recycled plastics using in vitro and in vivo bioassays, alongside chemical analysis of metals. Leachates were tested pre- and post-artificial UV weathering to assess the impact of degradation on toxicity. Results revealed that biodegradable plastics exhibited the highest increase in toxicity (81%) post-UV weathering, with bBag and polylactic acid (PHA) showing significant toxicity indices. Recycled plastics, rPET and rBag, demonstrated high toxicity pre- and post-weathering, likely due to additional contaminants introduced during recycling. Conventional plastics were the least toxic, with minimal responses across bioassays. Post-weathering, metal concentrations, including zinc, aluminium, and copper, exceeded environmental guidelines in most plastic types. Lemna minor and Daphnia carinata bioassays were highly sensitive to leachate toxicity, particularly post-weathering. These findings highlight the potential environmental risks of biodegradable and recycled plastics, emphasising the need for further evaluation of their safety as alternatives to conventional plastics.