The United States and Mexico share more than 2000 miles of common border. More than nine million people live in the border area, mostly in fifteen "sister city" pairs. The rapid increase in population and industrialization in the border cities has overwhelmed existing wastewater treatment, drinking water supply, and solid waste disposal facilities. Untreated and industrial sewage often flows north into the U.S. from Tijuana, Mexicali, and Nogales, and into the Rio Grande.

Some 300,000 people on the U.S. side of the border also lack safe drinking water, wastewater collection and treatment systems, or adequate solid waste disposal facilities. They live in unincorporated areas called "colonias." Over 1,200 colonias have been identified in Texas and New Mexico.

Human health threats from inadequate wastewater collection and treatment and the lack of safe drinking water make such diseases such as cholera, hepatitis A and giardiasis a continuing problem in the colonias. Diseases transmitted by mosquitos, flies, and rats are ever present due to poor garbage disposal practices. About 60% of colonias are located in the Lower Rio Grande Valley (Hidalgo, Cameron, Willacy, and Starr Counties) and 17% are in El Paso County.

The Texas border is one of the poorest areas in the nation. Laredo, a border city, is the poorest city in the U.S. Over 41% of residents on the border fall below the federal poverty line, compared to 18% statewide. Over half of all children under 18 live in poverty.Unemployment rates are often as much as much as twice the state average. The median household income is nearly $8,000 lower than the state average.

• Educational attainment is low. In some areas around the border as many as 50% of adults have not graduated from high school. On the border as a whole, 37% of residents over 25 have not attained a high school equivalency, compared to 28% statewide.

• Health conditions on the Texas-Mexico border are among the worst in the U.S. Cases of hepatitis A, tuberculosis, and dysentery occur at a rate at least twice the statewide average.

• Around 400,000 residents--nearly one in three border workers--earn less than what it takes to afford a house or apartment, compared to one in seven non-border workers. Although housing prices are about the same as the rest of the state, border wages trail the state average. A quickly growing population contributes to the problem, resulting in an acute lack of affordable housing.

• Because of the lack of affordable housing, around 1,400 colonias (subdivisions without adequate sewage or roads) have become home to an estimated 340,000 residents.

Public health is a major problem on the Mexican side of the border as well. Inadequate sewage facilities, pollution, and lack of medical services make this side of the border vulnerable to diseases like tuberculosis, hepatitis, and dysentery. Frequent traffic between the U.S. and Mexico allows any health problem to quickly spread from one side to the other.

El Cenizo is located fifteen miles south of the city of Laredo on the banks of the Rio Grande River. The colonia suffers from unpaved and poorly paved streets, a sewer system which is in very poor condition, lack of garbage collection and other basic city services.