The US-Mexico border region has experienced rapid population growth during the past 30 years. Conservative estimates suggest that the population of this region will increase by 34% between 2000 and 2030; more liberal estimates indicate a 97% increase (1). This population growth has been influenced in part by increased industrialization and trade, resulting from government policies in Mexico and the United States. An example of this increased trade is the more than 13,000 commercial freight crossings per day on the US-Mexico border, a 66% increase from 1999 (2).