Toxic pollution is a form of violence. This article explores the gradual brutalities that communities surrounded by petrochemical infrastructure endure over time. Contributing to political geographies of violence and environmental justice, this paper puts the concept of 'slow violence' into critical comparison with work on 'structural violence'. In doing so, the paper makes two key contributions: First, it emphasizes the intimate connections between structural and slow forms of harm, arguing that structural inequality can mutate into noxious instances of slow violence. Second, the paper pushes back against framings of toxic landscapes as entirely invisible to the people they impact. Instead of accepting the standard definition of slow violence as 'out of sight', we have to instead ask the question: 'out of sight to whom?' In asking this question, and taking seriously the knowledge claims of communities who inhabit toxic spaces, we can begin to unravel the political structures that sustain the uneven geographies of pollution. Based on long-term ethnographic research in a postcolonial region of Louisiana, nicknamed 'Cancer Alley', this paper reveals how people gradually 'witness' the impacts of slow violence in their everyday lives. Finally, drawing on the notion of 'epistemic violence', the paper suggests that slow violence does not persist due to a lack of arresting stories about pollution, but because these stories do not count, thus rendering certain populations and geographies vulnerable to sacrifice.