426 This pattern indicates that mining-related environmental events are not always priced instantaneously. In several cases, the market seems to incorporate the implications of the event progressively, as legal, regulatory, and reputational consequences become clearer over time. 4. DISCUSSION The results suggest that environmental disasters in mining have heterogeneous financial effects. Strong and statistically significant market penalties are concentrated in the most severe events, particularly catastrophic tailings failures. At the same time, several events show economically meaningful negative CAR without statistical significance, which highlights the importance of considering both magnitude and precision. For peer firms, the evidence points to moderate spillover effects rather than strong synchronized market reactions. Although peers rarely show individual significance, negative average CAR and high fractions of negative peer responses in events such as Samarco, MinasRio, and Mount Polley indicate that investors may partially reassess sector-wide environmental risk following major incidents. Taken together, the results support the view that environmental failures in mining can affect not only the responsible firm, but also related firms through partial contagion. However, this effect is not uniform across events and appears to depend on the severity, visibility, and broader relevance of each incident. An additional insight is that environmental risk in mining may behave as a shared reputational component, rather than being purely firm-specific. In Samarco, peers exhibit an average CAR of around -33%, with 100% negative responses, suggesting a sector-wide reassessment of risk. However, the absence of similar spillovers in events such as Brumadinho indicates that this effect is conditional on event severity and representativeness. A second aspect relates to the information and uncertainty channel. Several events show large negative CAR without statistical significance, and in many cases the most adverse CAR appears in longer windows, indicating gradual market adjustment. This suggests that short-window analyses may underestimate total impact, while external factors complicate causal attribution. 5. CONCLUSIONS This paper examined the financial impact of ten major mining-related environmental events on both responsible firms and their sectoral peers using an event-study framework based on the Fama–French three-factor model. The results reveal several robust and quantitatively significant insights.
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