Intervention Points: Governing Diffuse Contamination from Source to Sink

Abstract

Diffuse contamination presents governance challenges that differ fundamentally from those posed by point-source pollution. Unlike industrial discharges that can be permitted, monitored, and enforced at identifiable locations, diffuse contaminants arise from countless dispersed sources, travel through complex environmental pathways, and manifest their effects far from their origins. This article develops an intervention-point framework for understanding and governing diffuse contamination, arguing that effective responses require strategic action across multiple stages of the contaminant pathway rather than concentration on any single control measure. Drawing on recent research on tire-derived contaminants, nanomaterial remediation, and photocatalytic treatment, the analysis identifies four intervention points—source control, transport interception, treatment at concentration, and end-of-pipe removal—each with distinct technical possibilities, governance requirements, and equity implications. The framework is applied to the case of 6PPD-quinone, a tire transformation product that has emerged as a paradigmatic diffuse contaminant, to illustrate how intervention-point thinking can inform strategy. The analysis reveals that current approaches tend to over-rely on end-of-pipe treatment while neglecting upstream opportunities for source reduction and transport interruption. Rebalancing intervention portfolios requires policy frameworks capable of coordinating action across scales, sectors, and jurisdictions, as well as technologies appropriate to each intervention point. The article concludes by proposing a research agenda for intervention-point governance and discussing implications for regulatory design.