This study aimed to investigate whether global air pollution harms human morals beyond physiological and psychological health. To accomplish this, we conducted an original survey involving over 80,000 individuals across 30 countries, inquiring about their recent perceived unethical behaviors. Through regression analyses, we identified global evidence of a positive correlation between local monthly average concentrations of nitrogen dioxide (NO2) and perceptions of unethical behavior. This finding suggests that air pollution may potentially elicit unethical behavior through a complex response mechanism. It is noteworthy that the impact of air pollution on the inclination to perceive unethical behavior is heterogeneous across categories of unethical behavior and countries. For example, the effects of increasing air pollution concentrations vary even within the same European country: an increase in NO2 concentration in Greece and the Netherlands augments the inclination to perceive fatal unethical behaviors such as murder, terrorism, and suicide, while in Germany, NO2 concentration diminishes the inclination to perceive the same types of unethical behaviors. Overall, the societal costs of air pollution may be even more far-reaching than previously acknowledged, and further research is necessary to unveil the intricate response mechanisms underlying this issue.