While extractive industries contribute to the Canadian economy, energy and mineral developments pose many risks and benefits to affected communities. Hundreds of active mines, and thousands of potential sites, are located in rural and remote regions; notably near Indigenous communities facing population health equity challenges. Impact assessment (IA) is the key regulatory review process for identifying and mitigating risks to socio-ecological determinants of health, involving regulators, proponents, public health stakeholders, other government stakeholders, civil society, affected communities, and rights-holders (with constitutionally protected interests). Critical public health perspectives are needed for a system-level framework to advance socio-ecological determinants of health during impact assessments, with direct application to highly contested Canadian contexts.

Realist interviews were conducted with thirty-five government officials, researchers, knowledge brokers, and consultants working in Canada, and internationally. Polycentric regulatory analysis provided a middle-range theory to structure the presentation of research findings across three themes and six subthemes: mechanisms for establishing and maintaining the legitimacy of IA regimes (with subthemes of affirming the socio-ecological determinants of health, and integrating sustainability and population health equity); mechanisms for collaborative accountability in IA processes (with subthemes of mandated and adaptive responsibilities and surveillance and engagement techniques); and mechanisms for communicating legitimacy and accountability in IA practice settings (with subthemes of free, prior, and informed consent and social learning and field building). These themes provide a system-level framework to orient the advancement of socio-ecological outcomes in pluralistic IA processes, supporting more sustainable population health equity improving activities and initiatives in the regulation of extractive industries.