Study Area
Nogales abuts the international border and its sister-city, Nogales, Arizona (Fig. 1). Newer colonias marginales have developed and continue to develop in the hills and mountains that comprise the watershed boundary around the historic, central district of the city (Norman et al. 2006; Lara-Valencia et al. 2008; Wilder et al. 2011). Our experimental design involved collecting data from homes in a neighborhood with piped water and a neighborhood receiving water via pipas. Using determinations of socio-environmental vulnerability determined by Lara-Valencia et al. (2008), we chose Colonia Luis Donaldo Colosio (Colosio) to represent high vulnerability and Colonia Lomas de Fatima (Fatima) to represent low vulnerability, based on their accessibility, safety, personal contacts, and information on access to piped water (Fig. 1). We began our research by meeting with people associated with binational environmental health in Ambos Nogales (see Acknowledgments), to discuss design, implementation, cultural competency, relevancy, shared interests, and desired outcomes. This canvassing period culminated in a kick-off presentation at a binational health meeting called Consejo Binacional de Salud (COBINAS) on April 8, 2010, in Nogales, Arizona. The study design, neighborhood locations, and associated survey were presented and reviewed following our presentation and via e-mail correspondence by members of this group, including local physicians and promotoras, as well as city and state employees. Promotoras are community leaders who live in the colonias that have been trained to educate neighbors about government, education, and medical and social services that otherwise might be out of reach (Ramos et al. 2001; Hunter et al. 2004). Additionally, the survey describing water consumption, frequency of diarrhea, and perception of water quality was approved for the protection of human subjects (Caldeira et al. 2011).
A total of 21 households were sampled from both neighborhoods: 14 from the highly socio-environmentally vulnerable colonia (Colosio; Fig. 4a) and 7 from a more affluent and less socio-environmentally vulnerable colonia (Fatima; Fig. 4b). Unforeseen weather conditions, resources, and timing forced us to reduce our optimal 20-house sample size per colonia that was intended for the study. During the field investigations, households were chosen based on proximity to the street, with a representative from the City of Nogales, Mr. Alejandro Araiza, acting as the main liaison with residents. Interviewers asked to speak with the head of the household who was 18 years or older and then asked if the person would be willing to participate in our study.
Water samples were collected from each of the 21 households, three times in the summer during monsoon season (August 21, August 28, and September 4, 2010) and once during the winter (January 15, 2011), to test for seasonal variability. Water samples were collected from each participating household to test for microbes, and 67 inorganic chemicals. A survey was administered during the first visit in the summer (August 21, 2010) and followed up again in the winter (January 15, 2011).
Survey
Using concepts of perceived risks and effects on behavior from Sadalla et al. (2000) and the investigation of ways to improve life adapted from Collins et al. (2010a), we examined the current quality of life in Nogales, where presence or absence of diarrhea was the outcome variable (Caldeira et al. 2011). Questions about how water is obtained, stored, and purified as well as rate of consumption were asked based on Sadalla et al.’s (2000) research. Quality of life questions were asked to mimic work done by Collins et al. (2010b), in terms of personal satisfaction with government resources, public infrastructure, living conditions, and the environment, on a scale from 1 to 5, in order to investigate trends in ratings of quality of life among different income levels, as well as to illustrate perceptions of resource priority. Questions pertaining to the prevalence of diarrhea in the household, sources of water, and open-ended questions related to community involvement were created by Caldeira et al. (2011). This suite of questions was created to develop a relationship between gastrointestinal illness and water, specifically asking the respondent to answer yes or no to the following questions: did/do you or anyone in the household (i) have an episode of diarrhea in the past four weeks, (ii) get hospitalized due to diarrhea, (iii) miss work or school because of it, (iv) believe water was the cause of your sickness, and (v) think water can make you sick?
After the survey was drafted, it was revised based on feedback from stakeholder meetings. The Spanish version of the survey was translated by the authors then sent to the City of Nogales for a formal Spanish revision and cultural competency. After the final draft was completed, the survey and accompanying consent materials was sent for approval to the University of Arizona’s Office for the Responsible Conduct of Research or Internal Review Board (IRB) and approval was received on July 14, 2010.
In order to recruit multiple households and administer surveys concurrently at multiple locations, student volunteers from the University of Arizona’s Mel and Enid Zuckerman College of Public Health and the College of Science, and the City of Nogales were recruited and trained on the study’s protocols, based on their Spanish proficiency, Human Subjects Training Certification, and willingness to help.
The respondents from Nogales reported conditions for all members of the household. The surveys were conducted on Saturday, August 20, 2010. The average amount of time taken to complete the 30 question survey was about 35–40 minutes. In all, 21 households were represented; 14 from Colosio and 7 from Fatima. A short, five-question, follow up survey was also approved by the IRB and administered at the same participating households during the winter of 2011 (January 15, 2011) in order to test for any seasonal variability on the prevalence of diarrhea (Caldeira et al. 2011).
Water Sampling
Compliance monitoring frequently occurs at the wellhead and measures contaminant content of the water from the aquifer. Human health is most susceptible to the quality of water at the point of use (POU). Water quality at the POU reflects water quality from the well and the influence of infrastructure on water quality. In Nogales, microbiological contamination can be introduced or exacerbated by broken pipes, shallow wells within the watershed impacted by sanitary sewer overflows, insufficient chlorination, storage of water in unclean containers (aljibe, tinacos, tambos), or contamination during transport by truck.
The EPA has established National Primary Drinking Water Regulations, called maximum contaminant levels (MCLs), that set mandatory water-quality standards to protect the public against consumption of drinking water contaminants that present a risk to human health (U.S. Environmental Protection Agency 2012b).
Microorganisms
Gastrointestinal (GI) illness is caused by a variety of different microbes and germs, such as parasites, viruses, or bacteria. Testing for total coliforms is a relatively easy and inexpensive way to test for the presence of microbial pathogens. Total coliform are bacteria naturally found in the environment. Fecal coliforms are types of total coliform that mostly exist in human and animal fecal waste and E. coli is a sub-group these. Disease-causing microbes (pathogens) in feces can cause diarrhea, cramps, nausea, headaches, and more. Infants and children with their less fully develop immune systems, as well as people with severely compromised immune systems tend to be more susceptible. According to EPA MCLs, finding total coliforms (including fecal coliform and E. coli) exceeding zero indicate that potentially harmful bacteria (pathogens) may be present (U.S. Environmental Protection Agency 2012b).
Water samples for microbial analysis were collected from study participants’ POU (i.e. kitchen faucet, tinaco, tambo, etc.) in 100 mL autoclaved containers to which sodium thiosulfate was added to ensure dechlorination (removal of hypochlorite anion). The samples were stored on ice until delivery for analysis at the OOMAPAS-NS water-quality laboratory. All samples were delivered to the laboratory within the 6-hour hold time. Samples were analyzed for total coliform bacteria and E. coli. Using membrane filtration, samples were incubated for 24 hours at 35 °C with m-Coliblue24®broth (Hach Company, Loveland, CO) followed by differentiation and enumeration. We collected additional, or “repeat,” water samples for testing to help with quality assurance.
Inorganic Chemicals
Inorganic chemicals occur naturally in the environment, but industrial use and improper waste disposal can create conditions exceeding MCLs and threaten public health. Antimony (Sb) exceeding 0.006 mg/L can cause an increase in blood cholesterol and/or a decrease in blood sugar. Arsenic (As) exceeding 0.010 mg/L can cause skin damage, problems with circulation, and elevate cancer risk. Cadmium (Cd) exceeding 0.005 mg/L can cause kidney damage. Copper (Cu) exceeding 1.3 mg/L can create gastrointestinal distress and/or liver or kidney damage. Lead (Pb) exceeding 0.015 mg/L can cause delays in physical or mental development in children, and in adults, kidney problems and/or high blood pressure. Selenium (Se) exceeding 0.05 mg/L can cause hair or fingernail loss, numbness in fingers or toes, and/or other circulatory problems (U.S. Environmental Protection Agency 2012b). In addition, EPA has established National Secondary Drinking Water Regulations that set non-mandatory secondary maximum contaminant levels (SMCLs). Examples include sulfate (SO4), which when exceeding 250 mg/L can cause diarrhea and chloride (Cl), which when exceeding 250 mg/L, can make the water taste different and in some cases can cause dehydration (U.S. Environmental Protection Agency 2012b).
Samples to be analyzed for metal and major ion concentrations were collected from the sites using a 250 ml polypropylene bottle. The samples were filtered on-site at 0.45 μm using disposable filters and 60 cc syringes. Samples for cation analysis were collected in acid rinsed polypropylene bottles and acidified with ultra-pure HNO3. Unfiltered, unacidified subsamples for anion analysis were refrigerated until analyzed. Clean procedures were used throughout, following the protocols outlined in Ficklin and Mosier (1999). Raw samples were tested for tested Alkalinity, pH, Conductivity, Total Dissolved Solids (TDS), and submitted for ion content analysis, including fluoride (F), chloride (Cl), nitrate-nitrogen (NO2, as N, and NO3, as N), bromide (Br), phosphorus (PO4, as P), and sulfate (SO4).
Filtered and acidified samples were submitted for trace metal analysis. Water samples were analyzed by Activation Laboratories Ltd, Canada by inductively coupled plasma (ICP) atomic emission spectroscopy (AES cations), ICP mass spectrometry (MS, cations), and ion chromatography (anions). Quality assurance/quality control (QA/QC) concerns were addressed through the use of site duplicates, analytical duplicates, blanks and standards. Further descriptions of sample preparation, sample digestion, analytical methods and QA/QC protocol are found in Arbogast (1996).