In this study, participants had negative perceptions about the safety of local tap water (Tables 2 and 3, Fig. S1), believing it could result in both acute and chronic diseases (i.e., GI illness, lupus, and cancer) (Table 3), and perceived bottled and other sources of purchased water to be safer for consumption. In fact, 73% (n = 66) stated that they would drink their tap water if they knew it was not contaminated, even if they did not like the taste. The perception of bottled and other purchased water to be safer for consumption may be attributed to significantly lower water-related outbreaks in bottled water than in tap water sold in U.S.  and the fact that bottled water purveyors are more likely to promote their products in regions similar to the Nogales, Arizona area as a safer alternative to tap water .
Risk perceptions of drinking water by geographical location
Participants’ perceptions of tap water as being unsafe did not widely apply to all geographical locations (San Francisco, CA; Vancouver, British Columbia, Canada; Nogales, Sonora, México; Guadalajara, Jalisco, México). Participants perceived the risks of consuming tap water to be lower in other places in the U.S. (San Francisco, CA) and in Vancouver, British Columbia, Canada, but much higher in Nogales, Mexico and Guadalajara, Jalisco, Mexico (Table 4).
In comparison to drinking Nogales, Arizona tap water, participants considered drinking tap water in Nogales, Mexico (with a history of experiencing recurring water quality issues) to be as risky (Table 4). Mexican immigrants comprise a large proportion of the population living in Nogales, Arizona, and previous studies have demonstrated decreased tap water use among immigrants due to fear of subsequent illness . It should be noted in this study that there was no statistically significant difference by immigration status. However, the consistency in risk perceptions for tap water in Nogales, Arizona and Nogales, Mexico provides evidence of cross-border perceptions of municipal water quality and safety in this region . The perception of tap water to be unsafe extends beyond Nogales, Arizona and has been reflected in surveys of other U.S. communities, where greater proportions of Hispanic (16.39%, 876/5,048) and Black participants (8.48%, 434/5,132) viewed tap water as unsafe than non-Hispanic White participants (5.07%, 1,338/26,407) . However, it should be noted that the proportion of Hispanic participants (16.39%) who perceived tap water to be unsafe in the larger U.S. study conducted by Javidi & Pierece (2018) is notably smaller than the proportion of participants in this study who stated that their primary reason for not drinking local tap water was fear of chemical or microbial contamination that may result in illness (79%, n = 71). This reiterates that drinking water perceptions are not homogeneous across communities or ethnic and racial groups, demonstrating the value in studying the risk perceptions of specific low-income, marginalized communities with historic water quality challenges.
The fear of tap water in Nogales, Arizona seemed to be shared by the community at large, where many participants reported being told by friends and family not to drink their tap water (Fig. S1, Table 2). Nogales, Arizona has had drinking-water wells closures due to chemical contamination  and there are concerns that increases in number of maquiladoras across the Border in Sonora may lead to contaminated groundwater through improper disposal of solvents used by these factories . In addition, several small water purveyors in the area had reported prior drinking-water violations for noncompliance . As a result, many bottled water purveyors in Nogales, Arizona have promoted their product to be a better and safer alternative to local tap water. Many participants reported drinking tap water when they were younger and later changing to bottled water, possibly due to these contamination events personal experiences, new beliefs, or via the influence of advertising. Individuals tend to adopt the attitudes or behaviors of others in the same social networks or communities [18, 52, 53].
Perceptions of negative health outcomes from drinking tap water
Most participants feared that drinking their tap water could result in adverse health effects, like GI illnesses, cancer, and lupus, where lupus was the most frequently listed potential health outcome and with one of the highest average dread scores (Table 3). While there are several studies that report associations between contaminated drinking water and GI illnesses [16, 54] and some types of cancers (liver, lung, bladder and kidney) , there is limited evidence showing or describing the association between contamination of drinking water and lupus. Drinking water was identified as a statistically significant risk factor for systemic lupus erythematosus (SLE) in a study in the Anhui Province, China, where those who drank pond or well water had 2.04 (1.18–3.51) greater odds of SLE, relative to those who drank running water . However, a mechanistic hypothesis was not offered.
An animal model has been used to demonstrate the influence of drinking water pH on gut microbiota, with subsequent effects on progression of lupus in mice . Other potential risk factors for SLE development include exposure to solvents, trichloroethylene (TCE), and pesticides, but with less evidence than other risk factors (i.e., smoking and crystalline silica exposure) . Nogales, Arizona has a TCE plume , and TCE has been detected in the breast milk of mothers in Nogales, AZ and in household water . There is also evidence of transgenerational effects of environmental exposures , where epigenetic changes resulting from exposures can pose increased lupus risk for multiple generations. While the causal relationship between chemical contamination or characteristics of local tap water and the prevalence of lupus has yet to be elucidated, the Nogales area experiences rates of lupus that are 4 to 7 times above the national average . Further investigation is needed to explore whether water sources contribute to this health burden.
Risk perceptions of Nogales, AZ tap water consumption compared to other activities
In comparison to other activities, participants perceived drinking local tap water to be as risky as activities with risk of injury or death. For example, participants viewed local tap-water consumption to be as risky as drinking and driving, a high-risk activity . Participants also perceived drinking local tap water to be more risky than using Raid™ and smoking, both of which pose chronic adverse health outcomes [61, 62]. Interestingly, these two activities perceived as less risky than drinking tap water are risk factors for lupus development , a top health concern in this community within the context of water consumption.
The lack of statistically significant differences in risk perception of tap water by demographic characteristics could be due in part to a relatively small sample size (n = 90), and even smaller subsets of participants for comparing across demographics. For example, most of the households were of families with both parents (68%, 61/90), where the men were more likely to be at work and unavailable to participate or opted not to take part in the study. This made it challenging to compare risk perceptions between male and female participants. The low participation of males in population surveys, especially from ethnic or racial minorities, has been observed in other studies [3, 28]. While analyses were stratified by sex due to evidence that women may tend to experience higher risk levels than perceived men [23, 46], the low number of male participants may have contributed to a lack of any statistically significant finding.
The small sample size in this case also challenged the use of other statistical approaches, such as the use of linear regression models, where we would have been limited in the number of explanatory variables and many of them are highly correlated. Future studies with larger sample sizes should consider the use of other methods for comparing the magnitude and direction of relationships between demographic variables and risk perceptions for informing public health outreach efforts. However, it should be noted that while the sample size is small, the participants of this study were from a low-income community in a city on the U.S.-Mexico Border, a community that is difficult to access without the assistance of and collaboration with trusted community members (i.e., promotoras). Considering the challenges in forming these community connections and the limited data available on low-income Border communities, these data hold important public health value.
It should also be noted that our study population is not intended to represent the city of Nogales; rather, the objective was to capture risk perceptions of low-income community members who primarily drank bottled water in order to develop future interventions. It was therefore challenging to evaluate whether our specific study participants were representative of this specific community within Nogales. In comparison to the city, our recruited population did indeed have lower income than the city: more than half (53%) of the participants had a household income of < $15,000, lower than the median household income reported in 2020 ($29,043). This indicates that our participants may experience a greater economic tradeoff, relative to the rest of the city, of accepting the larger cost of drinking bottled water relative to tap water in response to perceived risks from drinking tap water.
In addition to small sample size, another possible explanation for a lack of statistically significant risk perception differences by demographic characteristics is that perceived risks are homogeneous in the study population due to the inclusion criteria. This hypothesis is supported by an argument made by Greenberg and Schneider showing that communities “stressed” by environmental risks tend to have relatively homogenous risk perceptions . Additionally, the participants in this study were of low-income and reported primarily drinking bottled water. If the risk perceptions among the participants are truly homogeneous, it does not mean risk perceptions are homogeneous in other communities or among those in this community that do drink the tap water. The purpose of the limited inclusion criteria was to better understand why low-income families in a historically marginalized community use their limited resources to purchase bottled water and what information would need to be provided to increase their trust in municipal tap water. More data are needed to investigate how risk perceptions among the Nogales, Arizona Latino community may differ from other communities who primarily consume bottled water to inform community-specific interventions or educational programs that may be more effective. It should also be noted that the survey utilized in English and Spanish was not formally evaluated for bias or differences in interpretation between the two versions. Future work is needed to evaluate and validate survey instruments for reliably capturing risk perceptions in communities where multiple languages are spoken.