Metal-free, low-cost, organic photocatalytic graphitic carbon nitride (g-C₃N₄) has become a promising and impressive material in numerous scientific fields due to its unique physical and chemical properties. As a semiconductor with a suitable band gap of ~2.7 eV, g-C₃N₄ is an active photocatalytic material even after irradiation with visible light. However, information regarding the toxicity of g-C₃N₄ is not extensively documented and there is not a comprehensive understanding of its potential adverse effects on human health or the environment. In this context, the term “toxicity” can be perceived in both a positive and a negative light, depending on whether it serves as a benefit or poses a potential risk. This review shows the applications of g-C₃N₄ in sensorics, electrochemistry, photocatalysis, and biomedical approaches while pointing out the potential risks of its toxicity, especially in human and environmental health. Finally, the future perspective of g-C₃N₄ research is addressed, highlighting the need for a comprehensive understanding of the toxicity of this material to provide safe and effective applications in various fields.

This study investigates the potential contamination of cash register employees in the Slovak Republic with 148 selected pharmaceuticals, illicit drugs, and their metabolites. Of these, 42 substances were detected, and it was found that the target group—cashiers—regularly handle large volumes of banknotes, increasing their exposure to contaminants compared to the general population. This study revealed that commonly prescribed and over-the-counter medications significantly contribute to the contamination of cash registers. This study found that cashiers exhibited notably higher detection rates of antibiotics, including penicillin-V (2×), azithromycin (23×), and erythromycin (up to 64×), than the general population. Additionally, there was an alarming increase in illegal substances, with methamphetamine levels rising fivefold and cocaine up to fifteenfold. This study highlights a broader environmental concern, suggesting that routine handling of contaminated banknotes may lead to the transfer of micropollutants. Furthermore, personal hygiene practices, particularly handwashing, could play a role in introducing pharmaceuticals and narcotics into wastewater, potentially contributing several milligrams of contaminants daily.

The rapid, field-ready detection of methamphetamine (MET) directly in sewage under flow remains a bottleneck for public health and law enforcement surveillance. We engineered a low-cost, 3D-printed flow-through electrochemical cell that houses a commercial screen-printed carbon electrode and operates in both non-flow and flow regimes. The platform was validated using the [Ru(NH₃)₆]^3+/2+ couple, confirming negligible kinetic hindrance and suitability for voltammetric sensing under convective transport. Using square wave voltammetry and chronoamperometry, MET was quantified in filtered wastewater, with limits of detection of 15.9 µg L⁻¹ in non-flow and 211.2 µg L⁻¹ in flow conditions. Specificity tests yielded well-separated faradaic responses for the pre precursor α-phenylacetoacetonitrile (APAAN) and for MET, while amphetamine produced only a weak signal, enabling side-by-side discrimination in a single run. To our knowledge, this is the first demonstration of direct electrochemical sensing of MET in flowing wastewater using a 3D-printed flow-through platform. The simple, disposable design provides an actionable foundation for portable, near-real-time sewer surveillance and motivates antifouling/auto-cleaning strategies for long-term deployment.

This study investigated 11 psychoactive contaminants in wastewater influents at a municipal wastewater treatment plant in Slovakia between 2015 and 2018, based on 44 samples collected under regular conditions and an additional five samples collected during two music festivals in 2018. In addition, 17 progestagens were analyzed only in 2018 during festival days and their corresponding background days. Seasonal variation in normalized mass loads was generally minor, whereas interannual differences were more pronounced, particularly for psychoactive pharmaceuticals, which showed an overall decrease in 2018. Short-term but substantial increases in contaminant loads were observed during the festivals. During the multi-genre music festival, the normalized mass load of 3,4-methylenedioxymethamphetamine increased by more than 110-fold on the second festival day compared to the pre-festival average, while benzoylecgonine increased approximately 17-fold and dienogest by 1.3-fold. During the country/folk music festival, tramadol loads increased approximately twofold. Principal component analysis explained 70.75% of the total variance using the first two components and revealed a clear separation between festival and background samples. Overall, the results demonstrate that music festivals represent episodic pollution events capable of markedly altering wastewater influent composition over short time periods.