Developing Predictive Models to Quantify Future POU Needs and Benefits
By Kelly A. Reynolds, MSPH, PhD and Marc Verhougstraete, PhD
At press time, the rainfall from hurricane Florence ceased in North Carolina but the storm’s impact on the nearby residents remains far from complete. At least 35 people are reportedly dead due to storm related hazards.1 In addition, millions of livestock have perished and multiple rivers are at peak capacity. In the wake of the storm, homes have been destroyed, tens of thousands of people are residing in remote shelters and hundreds of thousands are without electricity. Storm waters continue to rage, as relief efforts are underway to deliver food, water and other supplies to those in need. Drinking and recreational waters are undoubtedly contaminated with a broad range of industrial, agricultural and human wastes. The challenge, however, is to determine when water supplies will again test below the minimum allowable concentration levels for known hazards and how POU devices can aid in avoidance of harmful exposures.
Post-disaster waterborne disease risks
Eventually communities affected by hurricane Florence will return home, clean up and rebuild. Eventually the current supply of canned and bottled emergency water will cease and residents will utilize their plumbed-in tap water as their primary drinking water source. Nevertheless, is the water safe? How can residents be sure? Unfortunately, following natural disasters, the source-water quality, stability of the drinking water distribution system and the safety of the delivered supply may be impaired temporarily or even long-term. In the absence of a current site-assessment, the risks of contaminants in the drinking water supply are simply unknown.
Severe flooding and strong hurricanes can disrupt the safe distribution of drinking water to regional populations. Waterborne diseases have been recorded after major flooding across the world, including in the US, and extreme precipitation events have been linked to increased gastrointestinal illness cases.2-4 Many climate models predict an increase in frequency and severity of extreme weather events that are likely to result in additional waterborne disease outbreaks.
Everyday need for POU security
Even under the best of conditions, an estimated 20 million cases of waterborne illnesses occur each year from exposure to drinking water contaminated with microorganisms.5 Despite progressive advancement of water treatment technologies, exposure to contaminated water is expected to increase, given current infrastructure failure rates coupled with historically slow replacement rates.
This year, the US and Canada will experience on average 14.0 failures/100 miles of water-main lines, an increase of 27 percent from 2012.6 On average, the replacement rate of infrastructure is just 0.8 percent (equivalent to a 125-year replacement schedule), far exceeding the expected infrastructure material useful life. Population increases in many areas place added burdens on water supply infrastructure, and extreme climatic events further exacerbate infrastructure stress.
Failure to plan is planning to fail
Few are immune to the destruction of Mother Nature. Approximately 80 percent of Americans reside in areas that have experienced a natural disaster over the last decade. Sixty-one percent of the population, however, does not have a preparedness plan in place to access safe water or to treat contaminated water following a disaster.7 Therefore, an estimated 198,688,699 Americans are at risk of exposure to unsafe water should a natural disaster happens.
POU devices can be used to alleviate waterborne disease cases and mortality when facing increased disasters and the uncertainty of reliable and safe drinking water. POU and certain POE water treatment technologies are capable of reducing concentrations of bacterial pathogens up to nine logs and protozoa greater than five logs, and have been shown to reduce diarrheal diseases by up to 63 percent in urban environments and developing countries.8,9 Treatment at the tap can improve health outcomes when water quality is compromised, suggesting POU devices should be included in disaster preparedness and community response plans when drinking water infrastructure disturbances are anticipated.
Predicting POU needs and benefits
Anticipating when the quality of drinking water is compromised (and for what duration of time) is the primary condition consumers and water providers would like to accurately characterize. Tools in predictive risk-assessment modeling can be useful to determine likely probabilities of adverse effects given a set of known conditions. Development of these predictive mathematical models use available or published data sets to inform estimates that can be used to forecast future outcomes. Similar to predictive models for weather reports, in the water sector, predictive models are commonly used to determine effects of system design changes and processes, as well as to target optimal treatment options and technologies for maximum effect.10
The benefit of predictive modeling is that scenarios can be artificially explored to determine which variables have the greatest impact on risk mitigation. For example, we can evaluate which POU technologies are most effective in advance of an incident, given estimated baseline contamination levels and hazard types. Model-scenario testing can aid in decision-making, allowing for more rapid evaluation compared to direct environmental or traditional experimental approaches. A range of technologies can be explored and scenarios can even incorporate cost-benefit analyses.
POU water treatment systems have been shown to reduce diarrheal illness incidence in communities impacted by poor water quality due to flooding events.11 Even during typical, endemic exposure scenarios, in-home water treatment was found to reduce infection, disease sequelae and mortality rates from major waterborne pathogens.12 This same study performed a cost-benefit analysis and found a national intervention using POU devices would be cost-beneficial when considering the totality of waterborne diseases and their known economical burden.
Little quantitative information is published describing the magnitude of post-disaster waterborne disease burdens. In the absence of real-world data, the development of plausible predictive models are particularly beneficial and provide evidence needed to inform communities of the need for water treatment interventions. More research is needed to make sure the models are good at predicting optimal POU-use scenarios and the related health and cost benefits.
- Hurricane Florence aftermath: Flooding crisis in North and South Carolina–live updates as rescues continue–CBS News. https://www.cbsnews.com/live-news/hurricane-florence-aftermath-weather-flooding-power-outage-death-toll-fema-latest-forecast-live/. Accessed September 18, 2018.
- Sun R, An D, Lu W, et al. Impacts of a flash flood on drinking water quality: case study of areas most affected by the 2012 Beijing flood. Heliyon. 2016;22:e00071. doi:10.1016/j.heliyon.2016.e00071.
- Curriero FC, Patz JA, Rose JB, Lele S. The association between extreme precipitation and waterborne disease outbreaks in the United States, 1948-1994. Am J Public Health. 2001;918:1194-1199.
- Bush KF, O’Neill MS, Li S, et al. Associations between extreme precipitation and gastrointestinal-related hospital admissions in Chennai, India. Environ Health Perspect. 2014;1223:249-254. doi:10.1289/ehp.1306807.
- Reynolds KA, Mena KD, Gerba CP. Risk of waterborne illness via drinking water in the United States. Rev Environ Contam Toxicol. 2008;192:117-158. www.ncbi.nlm.nih.gov/pubmed/18020305. Accessed June 19, 2018.
- Folkman S. Water Main Break Rates In the USA and Canada: A Comprehensive Study. Logan, UT; 2018.
- Sixty Percent of Americans Not Practicing for Disaster: FEMA urges everyone to prepare by participating in National PrepareAthon! Day on April 30. US Department of Homeland Security Federal Emergency Management Agency. 2018.
- Sobsey MD, Stauber CE, Casanova LM, Brown JM, Elliott MA. Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World. Environ Sci Technol. 2008;42(12):4261-4267. doi:10.1021/es702746n.
- Lothrop N, Wilkinson S, Verhougstraete MP, et al. Home Water Treatment Habits and Effectiveness in a Rural Arizona Community. Water. 2015;7(3):1217-1231. doi:10.3390/w7031217.
- Weir MH, Pepe Razzolini MT, Rose JB, Masago Y. Water reclamation redesign for reducing Cryptosporidium risks at a recreational spray park using stochastic models. Water Res. 2011;45(19):6505-6514. doi:10.1016/j.watres.2011.09.047.
- Colindres RE, Jain S, Bowen A, Mintz E, Domond P. After the flood: an evaluation of in-home drinking water treatment with combined flocculent-disinfectant following Tropical Storm Jeanne — Gonaives, Haiti, 2004. J Water Health. 2007;5(3):367. doi:10.2166/wh.2007.032.
- Verhougstraete M, Reynolds K, Tamimi A, Gerba C. Cost Benefits of Point-of-Use Devices in Reduction of Health Risks from Drinking Water. 2017. www.wqrf.org/uploads/8/3/5/5/83551838/2017_costbenefit_execsummary.pdf. Accessed September 18, 2018.
About the authors
Dr. Kelly A. Reynolds is a University of Arizona Professor at the College of Public Health; Chair of Community, Environment and Policy; Program Director of Environmental Health Sciences and prior, Director of Environment, Exposure Science and Risk Assessment Center (ESRAC). She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at email@example.com
Dr. Marc Verhougstraete is an Assistant Professor at the University of Arizona College of Public Health. He holds a doctorate degree in Environmental Microbiology from Michigan State University. Verhougstrate is also co-Director of the Environment, Exposure Science and Risk Assessment Center, specializing in understanding the sources, occurrence and transport of waterborne organisms. He can be reached via email at firstname.lastname@example.org