Socio-Environmental Health Analysis in Nogales, Sonora, Mexico

People become more susceptible to health problems when exposed to contaminated water, including infectious intestinal diseases. The impacts and risk perceptions of environmental health are not well understood in the developing world where waterborne disease is a major problem (Morua et al. 2011). Deficiencies in water management and inequities in water consumption in Mexico make the low-income groups particularly susceptible to disparities in water access (Brans 1997). The US–Mexico border zone stretches about 3,000 km from the Pacific Ocean to the Gulf of Mexico and 100 km north and south of the line as defined by the 1983 La Paz Agreement (US Environmental Protection Agency 1983), which includes land in four American states and six Mexican states. People living in colonias, unincorporated communities that are lacking in water or wastewater infrastructure along the US–Mexico border, often face a disproportionately high level of environmental problems that are magnified by poverty, lack of education, and migratory status (Good Neighbor Environmental Board 2004; Lara-Valencia et al. 2008; Norman 2008, 2010; Norman et al. 2008, 2009, 2010a, 2012; Ramos et al. 2001). Infrastructure (i.e., potable water, sewer, pavement and availability of electricity) is poorly developed among neighborhoods (colonias marginales) distant from the established core of Nogales, Sonora, Mexico (Fig. 1; Lara-Valencia et al. 2008; Norman et al. 2006, 2012; Sadalla et al. 2000; Sanchez 1995). Colonias marginales are communities established in Mexico when migrant squatters settle on unoccupied land (Norman et al. 2006; Sanchez 1995; Tolan 1990). Homes are constructed using available materials, without permits, inspections, nor official recognition by the city. Public health is negatively affected by exposure of children and others to water contaminated by sewage, garbage, and occasionally industrial discharges (Ingram et al. 1994; Lara-Valencia et al. 2010; Norman 2008).

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Over the past 20 years, a unique dynamic of commerce and trade has affected the region, in part due to the ratification of the North American Free Trade Agreement (NAFTA) and associated relocation of assembly plants from the United States to Mexican border towns where maquiladoras are established. The maquiladora industry contributes to environmental degradation in the Borderlands. Indirectly, the promise of employment and opportunity lure migrants from central and southern Mexico to border cities, like Nogales, Sonora, Mexico (hereafter referred to as ‘Nogales’), and increased population challenges local governments to provide supporting infrastructure. Directly, maquiladoras dispose of their waste material in an unmonitored fashion (Williams 1995). Williams and Homedes (2001) identified maquiladoras as being responsible for environmental contamination and also suggest that they may contribute to changes in family cohesiveness.

Ingram et al. (1994) identified inequalities in quality, cost, and access to water—as well as inequalities of risk to human health in Ambos Nogales (both Nogales, Arizona, United States, and Nogales, Sonora, Mexico). Water-quality tests implemented by Sanchez (1995) showed the wells being used to supply water to colonias marginales in Nogales to be polluted and more expensive than better-quality water being piped to more affluent colonias. Varady and Mack (1995) conclude that poor water quality is a root cause of prevalent gastrointestinal (GI) disease in Nogales. In 2000, Sadalla et al. recognized that residents of colonias marginales in Nogales are at an increased health risk associated with poor access to clean water and inadequate water sanitation and storage practices which health authorities in the city associated with GI disease.

Prolonged dry periods threaten groundwater resources in the US–Mexico border, leading to the depletion of shallow aquifers (Varady and Morehouse 2004). Water scarcity compromises the ability of people living in colonias marginales to practice good sanitation (Fewtrell et al. 2007; Good Neighbor Environmental Board 2004; Norman et al. 2010b). According to Seager et al. (2007), climate models predict a drier borderlands region transitioning to an even more arid climate within a time frame of years to decades. The health implications of climate change for vulnerable populations living in colonias marginales are not good (Patz et al. 2005).

In 1990, the Council on Scientific Affairs of the American Medical Association declared that “the border area is a virtual cesspool and breeding ground for infectious diseases” (Williams 1995). Since then, a lot of attention has been placed on the impacts of maquiladoras on water quality, quality of life, and health. Binational initiatives in the areas of environmental health and water quality have successfully implemented change in the Ambos Nogales Watershed.

In order to answer these questions, a study was developed to evaluate water quality for metals, chloride, sulfates, and bacteria at point of use (POU) in two neighborhoods with radically different infrastructure, to determine how water quality differs with water-delivery system and season. We identified a vulnerable colonia marginal and a prominent colonia, in Nogales to compare differences in socio-economic classes. We developed a survey and concurrent sampling regime to determine water quality, quality of life, prevalence of diarrhea, and/or perceptions of problems and performed our investigations in the summer monsoon season and the dry winter season, to consider seasonal implications.

The Nogales Wash is a major tributary of the Santa Cruz River that flows directly through Ambos Nogales, draining both cities, before converging with the river near the Nogales International Wastewater Treatment Plant (NIWTP), located in Rio Rico, Arizona, 6 miles north of the border. Wastewater produced by Nogales is gravity-fed to a conveyance pipe called the International Outfall Interceptor (IOI), which delivers wastewater to the NIWTP (http://www.azdeq.gov/obep/download/wateren.pdf). The Nogales Wash flows above ground in a northerly direction in Nogales into a concrete tunnel though Nogales, Arizona, United States (hereafter referred to as ‘Nogales, Arizona’) that emerges into an open concrete channel and returns to a natural sediment bed channel.

During summer “monsoon” season, torrential rains commonly trigger overland flow and runoff, resulting in flash flood inundation in downtown Nogales; this sometimes causes near-surface sewerlines to break and erupt into sanitary sewer overflows, or fugas in Spanish (Huth and Tinney 2008; ADEQ 2009). Many residents in the outlying colonias marginales of Nogales use latrines or open pits for the disposal of human waste, which also regularly overflow during periods of heavy rainfall and discharge raw sewage (Austin and Trujillo 2010). Any fugitive wastewater (not captured by the sewer system) represents a threat to the public health of citizens of Ambos Nogales (Sprouse 2005). During these extreme flood events, health hazards increase from exposure to raw sewage and likely propagation and spreading of infectious disease agents (Norman et al. 2010a).

In 1990, fugas led to levels of fecal coliform and volatile organic compounds (VOCs) in the Nogales Wash inciting Santa Cruz County government to declare a health emergency (Frisvold and Osgood 2011). In the early 1990s, the Citizens’ Environmental Laboratory (formerly the National Toxics Campaign) sampled waterways in several cities at the US–Mexico border, including Nogales and detected petroleum, naphthalene, total xylene, chromium, copper, and other materials (Williams 1995). In 1991, cyanide and mercury were detected at levels that exceed Environmental Protection Agency (EPA) limits (Ingram and White 1993). Varady and Mack (1995) report detections of Giardia, Cryptosporidium, parasites, petroleum, and heavy metals in the Nogales Wash. In 2000, Sadalla identified bacteriological pollution associated with deficiencies in the municipal sewerage system in Nogales—he also reported that surface-water samples in the Nogales Wash contained high levels of coliform. The International Boundary and Water Commission (IBWC) reported that portions of the Nogales Wash aquifer in Sonora were contaminated with a suspected carcinogen, tetrachloroethylene (PCE), which was also detected in border monitoring wells in Arizona (IBWC 2001; Sprouse 2005). In the Nogales Wash, at Nogales, Arizona, just downstream from Nogales, King et al. (1999) reported high levels of chromium and sediment in the water and PCBs in the fish. In 2009, ADEQ found pollutant loadings of Escherichia coli (E. coli), ammonia, chlorine, and dissolved copper to exceed surface water-quality standards in Nogales, Arizona. Chlorine is added directly to the Nogales Wash in an effort to reduce pathogens from untreated sewage entering into Arizona from Mexico, but the chlorine in the wash now exceeds Aquatic and Wildlife warm water (A&Ww) quality standards (ADEQ 2009). In 2010, researchers from the U.S. Geological Survey’s Border Environmental Health Initiative sampled surface water at five points along the upper Santa Cruz River that incorporate the same sites that King et al. (1999) had sampled, including the Nogales Wash (Norman et al. 2010b; Paretti et al. 2010). Preliminary results indicate that organic and inorganic compound concentrations increase when water is routed through Ambos Nogales, yet inorganic metals concentrations are below primary and secondary water-quality standard requirements (Paretti et al. 2010).

The surface-water/groundwater interactions in this area are largely undocumented, but contaminants have been detected in the local potable water supplies, which some people relate to leaks in sewer and water-delivery pipes (Frisvold and Osgood 2011). Researchers in the late 1980s and early 1990s found bacterial contamination, measurable amounts of the carcinogens trichloroethylene (TCE) and tetrachloroethylene (PCE), and other volatile organic compounds (VOCs) in excess of the Arizona Based Guidance Levels (ABGL) as well as maximum contaminant levels (MCL) in wells of Nogales (IBWC 2001; Varady and Mack 1995; Sanchez 1995; Tolan 1990; Williams 1987). Specific metal concentrations were not reported, but results of the 1987 ADHS analysis indicated that chromium, iron, lead, manganese, and mercury were present at several sites in unfiltered samples (Sanchez 1995).

The major aquifers have been identified as recent stream alluvium and basin fill and the groundwater flows north towards the Santa Cruz River (Arizona Department of Water Resources 2010). People living in Nogales pump water from three local well-fields: (1) from the aquifer located east of the Ambos Nogales watershed, under the Santa Cruz River; (2) from the Nogales Wash Aquifer, located underneath the city; and (3) from the Los Alisos aquifer, located 11 miles south of the city in the Rio Magdalena watershed (Sprouse 2005).

Piped water delivery in Nogales is available to established colonias from the municipal system at certain times each day, varying by location (Varady and Mack 1995). Wilder et al. (2011) identified 85 % of the city as connected to a staggered water service (tandeo) across the municipality, ranging from 3 to 24 hours. The other 15 percent, who live on the edges of the city purchase water from trucks (pipas; Ingram et al. 1994; Varady and Mack 1995).

Most residents use storage systems to ensure access to potable water at any time of day. In colonias with piped water, most homes have an aljibe. An aljibe is a cement storage tank at each home, typically located underground, which provides water to the house at a relatively constant rate (Fig. 2a). When water is available from the city system, it is delivered directly to the aljibe. During daily household use, water is pumped from the aljibe to the house and subsequently replaced by the city’s intermittent water delivery. Because the aljibe is underground, the lid is at ground level and the system is subject to potential contamination from precipitation that infiltrates the tank during surface runoff events (Fig. 2b).

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In colonias marginales residents purchase water from tank trucks or pipas, and usually store their purchases in plastic containers called tinacos or metal containers called tambos. Pipas are operated by the municipal water company, el Organismo Operador Municipal de Agua Potable Alcantarillado y Saneamiento—Nogales, Sonora (OOMAPAS-NS), and also by private owners. Publically owned pipas get water from wells that adhere to water-quality standards; while private pipa operators do not.

Tinacos (plastic water storage tanks) are purchased from home improvement stores and mounted on rooftops in colonias with wealthy residents (Ingram et al. 1994). A hose attached to the tinaco delivers water to the house by gravity (Fig. 3). Tambos (metal water storage tanks) are most often found in the less affluent colonias marginales and are usually scavenged from local industries and placed at ground level (Ingram et al. 1994). Little, if any, information about the tambo’s prior contents is known by the user.

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Since the majority of these studies have been published, the population explosion has subsided (somewhat) and people have taken action. In 1993, the Border Environment Cooperation Commission (BECC) and the North American Development Bank (NADB) were created for the purpose of enhancing the environmental conditions of the US–Mexico border region and advancing the well-being of residents in both nations (Border Environment Cooperation Commission 2012). In 2000, the United States–Mexico Border Health Commission (BHC) was created to provide international leadership to optimize health and quality of life along the US–Mexico border (US–Mexico Border Health Commission 2003). In 2002, the ‘Border 2012’ program was established to protect the environment and public health in the US–Mexico border region, consistent with the principles of sustainable development and in 2012, this is being updated to ‘Border 2020’ (U.S. Environmental Protection Agency 2012a). In 2004, the USGS launched the US–Mexico Border Environmental Health Initiative (BEHI) to provide science data in support of environmental health studies and to examine and analyze linkages between human and environmental health (US Geological Survey 2012).

In border cities like Ambos Nogales, the two federal governments are working together binationally with state and local governments to improve the environmental quality and quality of life for residents. Citizen environmentalists and public servants from both sides of the border are stepping up to improve their environmental health by volunteering to sample and monitor water quality (Brown 2003), measuring rainwater and flood detention features (Norman et al. 2010b), and embracing new methods for managing waste materials (Austin and Trujillo 2010).

Current infrastructure projects are meant to reduce flooding, reduce leaks in pipes, and improve water quality, while increasing piped water delivery to colonias marginales. The NIWTP is operated and maintained by the United States Section of the IBWC, originally designed to treat 12 million gallons per day (MGD), was expanded to accommodate up to 17.2 MGD in the 1990s (King et al. 1999). In 2000, BECC certified a plan to upgrade the NIWTP to accommodate 22 MGD and build a new wastewater treatment plant in the Los Alisos basin to accommodate flows above the allotted Mexican portion of sewage (9.9 MDG) at the NITWP. The plan also called for wastewater collection systems in Ambos Nogales to be upgraded and for a conveyance system to transport the wastewater to the Los Alisos basin (Sprouse 2005). The Los Alisos Wastewater Treatment Plant and Conveyance System Construction was completed at the beginning of 2012 and expected to come online this year. With support from Border 2012, OOMAPAS-NS opened the first certified water-quality laboratory located along the Arizona-Sonora border for preliminary analysis of wastewater in 2006 (Border 2012 U.S.–Mexico Environmental Program 2008). An expansion of the water-distribution system in the city of Nogales to the colonias marginales has been approved by the BECC. This project, called the Colonia Luis Donaldo Colosio Drinking Water Distribution Expansion, would cover almost all the residents living in Colonia Flores Magon, Los Torres, Las Primaveras, Jardines de la Montana, El Rastro and Colosio, in which currently only 52 percent are serviced by the water-distribution system (U.S. Environmental Protection Agency 1999).

As Collins et al. (2010a) stated, there is a common misconception by outsiders that quality of life in Mexico is low, yet people living in Nogales report being generally happy and satisfied. We discovered that the two colonias varied not only by economic status and water-delivery system, but by perceived health risk associated with water quality and personal behavior.

Microbial contamination is high, particularly in the marginalized colonia, Colosio, which lacks access to piped water. Observations are similar to those found by earlier researchers (Varady and Mack 1995; Sanchez 1995; Williams 1987) who sampled wells. However for this project water was obtained from the household’s reported point of use (i.e. kitchen faucets running from tinacos and or aljibes or standalone tinacos and tambos). Sanchez (1995) stated that no microbial contamination was observed in water sampled from the municipal water system, but there is no mention of which locations in the municipal water system were sampled (i.e. point of use, pipas, distribution site, treatment plant, city pipes, etc.). Since we found microbial contamination in excess of the US EPA’s recommended MCL of 0 mg/L for majority of the households in Colosio, water is contaminated at levels that are unsafe at the point at which it reaches the user. Intermediate points of contamination could be aljibes, tambos or tinacos because water from the municipal system reaches these containers prior to entering the home. Most residents indicated that the only disinfection practice they use is chlorine treatment, without mention of sanitizing their storage containers when empty. Research volunteers also observed numerous water containers without lids which could lead to environmental exposure. Despite the fact that Fatima receives municipally treated piped water, we detected coliform bacteria in these homes, possibly indicating that there is an intermediate route of contamination that impacts the municipal water supply as it is delivered to the home. Alternatively, homes could have leaking pipes or lack back flow valves that might be sources of contamination.

There was marked seasonality of E. coli and total coliform concentrations in Nogales (Fig. 5). The average E. coli count in Colosio dropped from 26.7 (summer) to 3.7 colonies per 100 mL (winter). Total coliform bacteria were similarly reduced from 79.4 in the summer to 65.8 average colonies/100 mL during winter in the Colosio neighborhood. Mann-Whitney U tests indicate that E. coli and total coliform concentrations, between neighborhoods, differed significantly in both summer and winter seasons (p=0.05). The decline in reported diarrhea from summer to winter was far greater in the Fatima neighborhood than in the Colosio but neither neighborhood reported diarrhea in the winter.

The rate of diarrhea is high during the summer as reported through interviews with individual residents of households, yet diarrhea occurrence appears independent of water quality. Our hypothesis was that Fatima residents would not report elevated GI illness during the summer because homes in Fatima receive piped water, but this was not the case. Although they differ in magnitude, diarrhea rates in both colonias are high and compromise health. This suggests that the occurrence of diarrhea or perceived occurrence may be independent of water quality alone and therefore other confounding factors, independent of the water system, may play a role in the subject’s overall health profile during the summer months. In Colosio, residents use latrines with limited containment of human waste, and runoff from heavy rainfall can transport waste and excrement throughout the city. Fecal-laden runoff can contaminate improperly sealed aljibes. As conditions dry the resulting dust can contaminate tinacos and tambos via wind transport. These pathways of contaminant transport are potential causes of the elevated levels of microbes found during the summer season in Nogales. Elevations in temperature and humidity, found in Nogales during the summer, increase the survival rate of bacteria (Maier et al. 2009). The cooler temperatures of winter may limit survival of bacteria on surfaces. It is also possible that summer exposures to unrefrigerated food, dust containing feces, and hand to mouth contact from contaminated surfaces are potential hazards that might not be as great during winter conditions when indoor environments may be cooler and drier. The increase in microbial contamination during the rainy summer season may likely be caused by heavy runoff (Curriero et al. 2001). Curriero et al. (2001) discovered that there was a statistically significant association between rainfall and waterborne disease outbreaks between 1948 and 1994 due to surface-water contamination from extreme precipitation. This information has serious public health implications since the region has experienced an increase in extreme weather recently (including both drought and rainfall-flooding events) attributable to climate change (Lara-Valencia et al. 2010; Morehouse et al. 2000; Norman et al. 2010a). Seasonal differences in these exposures, in addition to water exposures, may account for elevated diarrhea rates during the summer and the non-occurrence of diarrhea during the winter months in Nogales.

Chloride in water may be an indicator of naturally present salt in the environment or may indicate exposure to anthropogenic sources such as inorganic fertilizers, landfill leachates, septic tank effluents, animal feeds, industrial effluents, irrigation drainage and chlorine treatment (World Health Organization 2003). Because residents in Colosio have their water storage containers exposed to the environment and report treating with chlorine (Caldeira et al. 2011), elevated levels of chloride are expected (World Health Organization 1979).

In addition to climate, factors such as insufficient chlorination, food preparation and contamination, medication, prior illnesses, and hygiene may contribute to GI problems. Numerous reports illustrate the impact that social equity has on accessing clean piped water and the increased risk of illness and mortality to less privileged individuals (Aldous 2003; Colford et al. 2006; Chiller et al. 2006; Esrey et al. 1990; Ezzati et al. 2005; US–Mexico Border Health Commission 2003). According to our results, people living in more affluent areas of Nogales have less E. coli and less total coliform in their water than the more vulnerable populations, yet percent-wise, report more cases of diarrhea. It is important to point out that calculation for this research is dependent on a low sample size, and in Fatima are based on only 7 households, so a difference of only one household could drastically change percentages.

Metal concentrations were well below the US EPA’s MCL, unlike research in the past (Varady and Mack 1995; Sanchez 1995; Williams 1987). Sanchez (1995) stated that contaminants found in well water within the watershed were traced to industries in the area. The recent attention to environmental health and waste disposal may have indirectly and directly played a part in the improved quality of the water.

This study investigates health as it pertains to gastrointestinal disease by using qualitative and quantitative methods in two neighborhoods in Nogales, by implementing a survey that inquires about quality of life, water delivery, rate of diarrhea, and disinfection practices, as well as chemically analyzing water from POU. Previous work in Nogales did not investigate the direct effect of water quality on health and water-quality samples were obtained from wells rather than from POU. A successful collaboration of people from both sides of the border, including researchers, local epidemiologists, directors of public health agencies, health care professionals, directors of zoning and planning, local water technicians, and government officials, worked together to develop and shape the study, to make it useful for stakeholders.

To improve future surveys, we hope to increase sample size and representation of additional colonias. Collection of samples during four seasons over multiple years would provide a more complete picture of seasonal variability. It would be advantageous to collect water samples from every point within the distribution system (i.e. well, treatment facility, pipa, city pipe line, tinaco/tambo/aljibe) to better identify sources of contamination. A comparison of the neighborhoods in Nogales, Arizona, would complement this research greatly. Due to time constraints, weather, and limited resources, sample size was reduced from the original study design. Although limited in scope, we strongly believe the results provide researchers and stakeholders with a status report regarding potential concerns and issues and add to the literature on environmentally related risk perceptions in the Borderlands.

It has been documented that people living along the US–Mexico border are subject to environmental injustice because of the mixed cultures, administrative authorities, clashing priorities, and distance from each country’s capital. Policies that have been developed to allow international trade foster economic incentive that has little regard for impacts on the health and quality of life for borderland residents. However, the people who live in the borderland region have been working together to change the way they live. Recent collaboration in binational environmental and watershed management has brought about changes in lifestyle and infrastructure in Nogales, Sonora, Mexico, and its sister-city, Nogales, Arizona, United States, that is improving environmental health and quality of life for the people.