Pharmaceutical products, as well as insecticides and antimicrobials, have been extensively studied, but knowledge of their effects—especially those caused by their mixtures with microplastics—on aquatic organisms remains limited. However, it should be borne in mind that the state of knowledge on acute and chronic effects in aquatic organisms for pharmaceuticals and pesticides is not similar. In response, this investigation analyzed the presence of microplastics (polyvinyl chloride) and their impacts on the toxicity of chlorpyrifos (an insecticide) and triclosan (an antibacterial) when they coincide in the environment, alongside the two most consumed drugs of their type (hypolipemic and anticonvulsant, respectively), namely simvastatin and carbamazepine, in Artemia salina. LC₅₀ and cholinesterase enzyme activity were calculated to determine the possible neurotoxicity associated with emergent contaminants in the treatments. The LC₅₀ values obtained were 0.006 mg/dm³ for chlorpyrifos, 0.012 mg/dm³ for chlorpyrifos associated with microplastics, 4.979 mg/dm³ for triclosan, 4.957 mg/dm³ for triclosan associated with microplastics, 9.35 mg/dm³ for simvastatin, 10.29 mg/dm³ for simvastatin associated with microplastics, 43.25 mg/dm³ for carbamazepine and 46.50 mg/dm³ for carbamazepine associated with microplastics in acute exposure. These results indicate that the presence of microplastics in the medium reduces toxicity, considering the LC₅₀ values. However, exposure to chlorpyrifos and carbamazepine, both alone and associated with microplastics, showed a decline in cholinesterase activity, confirming their neurotoxic effect. Nevertheless, no significant differences were observed with the biomarker cholinesterase between the toxicant and the toxicant with microplastics.

Respirometry, as used in wastewater treatment, is the measurement and interpretation of the respiration rate of microorganisms in activated sludge. The respiration rate is the amount of the oxygen per unit of volume and time that is consumed by the microorganisms. For a long time respirometry has been recognized as a valuable basis for controlling the activated sludge process. The reason for this is that respiration rate is directly linked to two important biochemical processes that must be controlled in a wastewater treatment plant: biomass growth and substrate consumption. This paper shows different experiments to quantify toxic or inhibitory effects as determined by the toxicity protocol for respirometry. The protocol used was based on the utilization of the respiration of activated sludge to measure and quantify toxic effects of compounds. Our purpose was for both the protection and treatment ability determination of wastewater plants, depending on the problems (e.g. pollution), needs of customers and possibilities for biodegradation of the tested products.