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Impact of Household UV Drinking Water Treatment System in Mexico

Development Challenge

Approximately 800 million people around the world lack access to safe drinking water.[1] Microbial contamination of drinking water is a significant development challenge, which contributes to the high burden of waterborne illnesses globally; diarrhea is the second leading cause of death in children under 5 years.[2] Lack of access to clean water also imposes significant economics costs and undermines the potential development of affected communities around the world. The sustainability and effectiveness of current point of use water treatment options is largely unknown. This study investigates the impact of a novel household water treatment technology in Baja California Sur (BCS) in Mexico on household water quality and individual health.


Rural communities in BCS, Mexico, have limited access to basic infrastructure like piped water, paved roads, and electricity.  Most households rely on wells and springs to collect water for domestic use; drinking water is commonly stored in open containers that are prone to contamination within the household. In response, Fundacion Cantaro Azul (FCA), a Mexican non-profit, developed a novel UV household water treatment system, Mesita Azul, in collaboration with UC Berkeley researchers. FCA further developed and piloted a safe water program to promote safe water habits and distribute the Mesita Azul to rural communities in BCS. 

Evaluation Strategy

Researchers investigated the effects of the safe drinking water program, which offered the Mesita Azul system to rural communities, on household water quality and individual level health outcomes (diarrhea). The intervention leveraged the phased roll out of Mesita Azul safe water program by randomizing the sequence in which FCA introduced the program to new communities (a “stepped wedge design”). The study included 24 eligible communities (444 households), which received the program in six distinct “steps”; every two months, four new communities were phased-in to the treatment group.  Household surveys and water quality testing were used to collect data on several key indicators including adoption and use of the system and safe water habits, levels of Escherichia coli (E. Coli) in drinking water, and the prevalence of diarrhea among participants (7-day period prevalence). Using this data, the team estimated the impact of the intervention on study outcomes.   

Results and Policy Implications

The Mesita Azul safe water program on average increased access to (23% to 62%) and exclusive use of treated and safely stored water (19% to 50%) over the course of the study. The intervention, likely mediated by increased use of safe water habits, improved household water quality (risk difference:-19% [95%CI: -27%,-14%]). While there was evidence that the intervention reduced diarrhea by 20% on the relative scale, chance could not be ruled out as an explanation of this finding (Relative Risk: 0.80 [95%CI: 0.51,1.27]).

The results from this evaluation suggest that while the evidence regarding the health impact of the Mesita Azul safe water program was inconclusive, continued expansion of the program is justified based on the substantial, measured improvements in household water quality. A possible explanation for no findings of a health impact could be explained by a lower than expected prevalence of diarrhea in the control arm, which left little room for improvement. Additional evaluations of a safe water program that promotes and distributes the Mesita Azul would be valuable in contexts with a higher burden of diarrheal illness that what was measured in BCS, Mexico. 

[1] UNDP. “Goal 7: Ensure Environmental Sustainability.” UNDP Millennium Development Goals. 2013.

[2] WHO. “Diarrheal Disease: Fact Sheet N. 330.” World Health Organization.  April 2013.

Photo Credit from Partner Fundacion Cantaro Azul.