Abstract: Environmental threats have emerged as one of the most pressing global challenges of our time. While extensive research has examined the economic, social, and health-related consequences of environmental degradation, its impact on moral psychology remains underexplored. Existing studies have primarily focused on whether environmental threats elicit unethical behaviors, yet little is known about how such threats may influence individuals’ moral evaluations—specifically, their tolerance toward unethical behaviors. This paper proposes that perceived environmental threats not only influence individuals’ engagement in unethical behavior, but also shift moral standards themselves. We refer to this pattern as the “moral smog effect”.
Across five primary studies and two supplementary studies (N_total = 4, 733), we employed a multi-method approach that combined secondary data analyses with experimental methods to examine the relationship between perceived environmental threat and moral judgment. Studies 1a and 1b analyzed two large-scale datasets—the 2021 Chinese General Social Survey and the fifth wave of the World Values Survey (Chinese subsample)—using correlational methods to examine the association between perceived environmental threat and the acceptability of unethical behaviors. Supplementary Study S1 drew on the same sample as Study 1a and incorporated psychological stress as an additional variable, providing initial evidence that stress partially accounts for this association. Study 2 adopted a single-factor between-participants experimental design, manipulating environmental threat via scenario priming (high vs. low threat), followed by participants’ moral evaluations of a series of unethical behaviors. Study 3 utilized a 2 (perceived environmental threat: high vs. low) × 2 (psychological stress: induced vs. neutral) between-participants design, enabling a test of the mediating role of stress through a “manipulation-of-mediation-as-a-moderator” design. Study 4 and the supplementary study employed two 2 (perceived environmental threat: high vs. low) × 2 (moral agent: self vs. other) between-participants designs to test whether the moral agent (self vs. other) moderated the main effect of environmental threat on moral judgment.
The findings across these studies converge on the conclusion that perceived environmental threats consistently increased individuals’ acceptance of unethical behaviors. This relationship was robust across diverse measurement tools, data sources, and research designs. Experimental results further demonstrated that the experience of environmental threat elevates stress levels, which in turn reduces individuals’ cognitive capacity to uphold abstract moral norms, leading to greater moral leniency. Importantly, Study 4 and its supplementary analysis found no evidence of moral hypocrisy under threat: participants became equally tolerant of unethical behavior regardless of whether it was enacted by themselves or by others, and this pattern remained robust after controlling for social desirability. This finding suggests that environmental stress may impair individuals’ ability to differentiate between moral agents, potentially due to reduced cognitive resources under heightened stress.
This research advances theoretical understanding in both environmental psychology and moral cognition by demonstrating that environmental threats can systematically reshape individuals’ moral standards, rather than merely influencing their behavioral tendencies. The concept of the “moral smog effect” contributes to a broader recognition that the psychological consequences of environmental degradation extend beyond emotions and health to include value systems and social norms. Practically, these findings carry significant implications for public policy and moral education. In an era of escalating environmental risk, fostering psychologically safe and low-stress environments may help safeguard not only public well-being but also the moral fabric of society. Recognizing the moral costs of environmental threat thus adds a critical dimension to the discourse on sustainable development and ethical governance.

Key words: perceived environmental threat, unethical behavior, stress, moral hypocrisy