The U.S-Mexico border is a dynamic region 2000 miles long and 125 miles wide that provides a very unique window onto the effects of globalization at the interface of two very different countries (1). One such example can be seen in the Tijuana-San Diego city-region, where the disparity in wealth is dramatic. San Diego and Tijuana are inextricably bound together in a sprawling transfrontier metropolis. Home to more than 4 million people (2.8 million in the larger San Diego metropolitan area and 1.3 million in Tijuana), the San Diego-Tijuana city-region is the most populated and busiest city-region of all 14 twin cities along the U.S. Mexican border. Tijuana’s annual growth rate is 4.9%, nearly double that of San Diego’s. Together the two cities have a total gross regional product of $125 billion ($120B San Diego; $5B Tijuana). The city-region’s population is expected to swell to 8 million by 2030 (2). Although the city of San Diego has a population approximately the same size as the city of Tijuana, Tijuana’s municipal budget is one-fourteenth of San Diego’s—about $100 million versus approximately $1.4 billion (3). This has made it difficult to develop region-serving infrastructure in the San Diego-Tijuana area. Transboundary flows (north-to-south, as well as south-to-north) of water, air, people, capital, goods and wastes are part of daily-life in our region and are at the heart of what gives rise to many unique health and environmental concerns along the border (4,5). Group page: RESEARCH TEAM: New Regionalism and Global Environmental Health: Challenges posed by transboundary flows of material, energy and knowledge (mentor: Hiram Sarabia, Carlos Graizbord)