USGS Fact Sheet 2004–3140

December 2004

U.S. Department of the Interior

U.S. Geological Survey

Internet Map Service for Environmental Health in the 

U.S.-Mexico Border Region

Background: The border region of the 

United States and Mexico encompasses 

a vast and diverse array of physical 

settings and habitats that include wetlands, deserts, rangeland, mountains, and 

forests, which are unique in terms of the 

diversity of their water, mineral, and 

biological resources. The region is interconnected economically, politically, and 

socially owing to its binational heritage. In 

1995, nearly 11 million people lived 

immediately adjacent to the border. By 

one account, that population could more 

than double by 2020. 

This rapid population growth and consequent economic development and landuse changes are pushing the limits 

of environmental sustainability and quality. 

Infrastructure development has lagged 

behind the rapid growth of the region, 

resulting in a shortage of water for 

municipal, agricultural, and industrial uses. 

These stressors threaten the quality of life 

in the region and raise concerns about the 

interdependence of environmental quality 

and human health. 

To allow for continued economic growth 

while protecting the area’s natural 

resources and fostering a high quality of 

life, the United States and Mexico 

need an improved understanding of 

the threats posed by these anthropogenic changes. 

Issues of particular concern include 

(1) contaminants in ground water, 

surface water, and biota from 

agricultural, municipal, and 

industrial activities; (2) airborne 

pollutants from fossil-fuel combustion and other activities; 

(3) contaminants from past 

and present mining activities 

and mineral deposits; and 

(4) pathogens, pharmaceuticals, hormones, and other contaminants released in treated and 

untreated human and animal 

wastewaters. 

Science Objective: The objective of 

this project is to provide an earth and 

biological resources database within a 

geographic framework using an Internet 

Map Service (IMS) to further our 

understanding of the linkages between 

the condition of the physical environment 

and public health issues. The IMS is 

now available on the Internet at 

borderhealth.cr.usgs.gov 

Geographic Extent: The project is 

planned to ultimately encompass the 

entire U.S.-Mexico border region. 

However, initial efforts have focused on 

watersheds and aquifers along the Rio 

Grande/Rio Bravo below Falcon Reservoir 

to the lower part of the Laguna Madre of 

Texas and the nearshore parts of the Gulf 

of Mexico. The region encompasses 

10,240 square miles—6,155 in Mexico 

and 4,085 in the United States. In Texas, 

the primary population centers are 

McAllen, Harlingen, and Brownsville; in 

Tamaulipas, they are Reynosa and 

Matamoros. Among the unique habitats of 

this segment of the international border 

region are the resacas (oxbow lakes) of 

the lower Rio Grande Valley. As in other 

border areas, the water resources and 

associated plants, fish, and wildlife of the 

lower Rio Grande Valley are increasingly 

subject to the effects of human activities.

Data Assimilation and Integration: 

Through partnerships with local, State, 

and Federal agencies in both the United 

States and Mexico, the U.S. Geological 

Survey identified biologic, geologic, 

hydrologic, environmental, public health, 

and demographic datasets for 

incorporation into the binational IMS. 

Scientific Utility of Data: To facilitate 

binational analysis of environmental 

issues concerning human health, major 

efforts have been made to seamlessly 

integrate U.S. and Mexico geospatial 

datasets along common themes. The 

procedures are documented in Federal 

Geographic Data Committee-compliant 

metadata files and can be applied to other 

areas along the U.S.-Mexico border. 

Base cartographic data representing 

anthropogenic themes provide a locationbased foundation for analyzing the human 

interaction with the environment. Mapping 

the distribution of human modifications to 

the environment, such as transportation 

networks and manmade structural features, spatially narrows the hypothetical 

relations between potential urban contaminants and the environment. 

Demographic census data, health 

statistics, and various boundary 

datasets, such as county, census, 

and zip code boundaries, provide 

the information needed to study 

the statistical relations between 

reportable health incidences and 

population trends. 

Landsat 7 Enhanced Thematic 

Mapper Plus (ETM+) medium 

resolution satellite data provide the 

ability to monitor regional landscape 

trends. To identify and map data at 

the local scale, 1-meter resolution 

digital orthophotos provide additional 

photo interpretation opportunities. 

Best-available elevation data, varying 

from 3.3- to 30-meter resolution, 

Figure 1. U.S.-Mexico Border Environmental Health 

Project study area. 
Version 1.0

provide a topographic base to evaluate 

flood inundations and to model air and 

water transport mechanisms such as 

slope relations, surface-water runoff, and 

water accumulations that might transport 

contaminants. 

Geologic maps, soil maps, geochemical 

data from soil analyses, and geophysical 

data from aeromagnetic/radiometric 

surveys provide information on environmental contamination from naturally 

occurring toxic materials in soil and 

underlying rocks. These databases are 

important in defining the distribution and 

source of geologic materials. Distribution 

and source information are useful for 

establishing natural baseline occurrence 

and assessing environmental and healthrelated risks associated with selected 

geologic materials. 

Binational hydrography data, such as 

where streams are located on the 

landscape in the United States and 

Mexico and where the streams are 

monitored for quality and quantity, provide 

information to facilitate our understanding 

of linkages between the physical environment and human disease. Ready 

access to these datasets will assist public health researchers in determining 

contaminants in ground and surface 

water and identifying pathogens, pesticides, pharmaceuticals, and hormones 

associated with human and animal 

waste. Development-related stressors, 

such as raw and under-treated sewage, 

pesticide exposure, toxic metals in 

sediment, and increasing salinities, are 

potential linkages in the U.S.-Mexico 

border area. 

Geographic display of hydrologic data 

for the United States and Mexico allows 

resource managers to readily identify 

gaps in monitoring networks and provides 

visual information for future opportunities 

to begin more collaborative hydrologic 

monitoring. The geographic information 

system framework of these products 

improves the binational understanding 

of the occurrence and distribution of 

disease-causing agents in the environment and their exposure pathways in 

water, air, biota, and soil. 

Data on the presence of environmental 

contaminants in water, aquatic sediments, 

and biota provide an indication of the 

nature and extent of anthropogenic 

pollution in the study area. The presence 

of toxic chemicals in the environment 

serves as a sentinel of environmental 

health and frequently has implications for 

public health. 

Opportunities for Collaborative 

Science: An anticipated outcome of this 

project will be increased opportunities for 

collaboration and communication among 

scientific researchers in the public health, 

natural resources, and environmental 

protection fields. Such collaborations 

could ultimately provide greater insight 

into the interdependence of environmental 

quality and human health and will assist in 

achieving the goal of a healthy border 

environment. 

For more information, contact 

Denny Buckler, (573) 876–1803 

dbuckler@usgs.gov or 

Jim Stefanov, (512) 927–3543 

jestefan@usgs.gov

Figure 2. U.S.-Mexico Border Environmental Health Project IMS Web site with a view of potential sources of contamination 

(PSOCs) overlaid onto a binational geologic map of the McAllen and Reynosa urban areas.