International attention is focusing increasingly on environmental concerns, from global warming and extreme weather to persistent chemical pollutants that affect our food supplies, health and well-being. These environmental exposures disproportionately affect the poor and those residing in developing countries, and may partly explain the persistent social gradients in health that exist within and between nations. We support recent calls for environmental epidemiologists to play a more active role in furthering the global agenda for sustainability, environmental health and equity. We further suggest that the discipline of environmental epidemiology, as well as relevant funding agencies, broaden their focus to include rigorous research on the upstream, larger-scale societal factors that contribute to inequitable patterns of exposure and health outcomes. By widening the scope of our vision and increasing the strength and breadth of the evidence base about how poverty and environment together affect health, we can better participate in efforts to promote social justice and responsible use and protection of the environment, and thus reduce health inequities. That is both a primary mode and rationale for achieving sustainability.