DRI scientists investigate effectiveness of heat warnings along US-Mexico border

DRI scientists investigate effectiveness of heat warnings along US-Mexico border

DRI scientists investigate effectiveness of heat warnings along US-Mexico border

AUG 25, 2020

Population Heath

Above: Aerial view of California’s Imperial Valley, where daytime temperatures during summer months can reach as high as 120 degrees. Credit: Thomas Barrat/Shutterstock.com

Featured research by DRI’s Kristin VanderMolen, Ben Hatchett, Erick Bandala, and Tamara Wall


In July and August, daytime temperatures along parts of the US-Mexico border can reach as high as 120 degrees – more than 20 degrees above normal human body temperature. For agricultural workers and others who live and work in the region, exposure to these extreme high temperatures can result in serious health impacts including heat cramps, heat exhaustion, heat stroke, and heat-related death.

Although the National Weather Service and public health organizations issue heat warnings to communicate risk during extreme heat events, heat-related illness and death are still common among vulnerable populations. Now, a group of DRI scientists led by Kristin VanderMolen, Ph.D., Assistant Research Professor with DRI’s Division of Atmospheric Sciences, is trying to figure out why.

“With the continued increase in episodes of extreme heat and heat waves, there has been an increase in warning messaging programs, yet there continue to be high numbers of heat-related illness and death in communities along the US-Mexico border,” VanderMolen said. “So, there’s this question – if agencies are doing all of this messaging, and people are still getting sick and even dying, then what’s going on?”

An agricultural field in California’s Imperial Valley

An agricultural field in California’s Imperial Valley, where DRI researchers are exploring questions about heat messaging and vulnerability in populations of agricultural workers and others who are vulnerable to heat-related illness and death. 

Credit: Winthrop Brookhouse/Shutterstock.com

Assessing heat messaging: An interdisciplinary approach


In 2018, VanderMolen and colleagues Ben Hatchett, Ph.D., Erick Bandala, Ph.D., and Tamara Wall, Ph.D. received funding from NOAA’s International Research and Applications Project (IRAP) to explore questions about heat messaging and vulnerability in two pairs of US-Mexico border cities, San Diego-Tijuana and Calexico-Mexicali. Collectively these areas form the boundaries of the Cali-Baja Bi-national Megaregion. This unique transboundary location integrates the economies of the United States and Mexico, exporting approximately $24.3 billion worth of goods and services each year.

With expertise in the areas of anthropology, meteorology, climatology, and population health, this interdisciplinary team of researchers is now working on this problem from several angles. They are using climate data to characterize and assess past heat extremes as well as using long-range weather forecasts and climate projections to help improve the ability to put out advance messaging about future heat waves. They are working to identify and map populations that are particularly vulnerable to extreme heat and are collaborating with local agencies to understand why people may or may not take protective action during heat waves.

From initial conversations with local civic organizations and public health agencies, the team has learned that the reasons people may not be following heat warnings are complex. Recommended actions such as “stay indoors and seek air-conditioned buildings,” or “take longer and more frequent breaks,” may not be realistic for agricultural workers or others who don’t have access to air-conditioned spaces. There can even be negative consequences for those who choose to seek medical help.

“A big piece of the story that we’ve heard from some of the independent groups that work with agricultural workers in the region is that if someone gets sick and doesn’t show up for work, they can lose their job,” Hatchett explained. “If they go to the hospital and somebody sees them or hears about it, they can lose their job. There are some really big issues related to people not feeling okay with trying to get the help they need.”

“There is evidence to suggest that cases of heat-related illness and death are underreported, probably severely underreported,” VanderMolen added. “The demographics of the individuals for documented cases don’t reflect the population demographics overall. We know that there are a lot of inequalities in that area that may get in the way of people reporting illness.”

A map of summer maximum near-surface temperatures in Imperial Valley, CA

A map of summer maximum near-surface temperatures over the 30-year period from 1981–2010 shows that Imperial Valley (at the border between Mexico and the southeastern corner of California) is the hottest place in in North America, with an average maximum temperature from June to August of 40° Celsius (104° Fahrenheit). Data is from the North American Regional Reanalysis.

Credit: Ben Hatchett/DRI

COVID-19 complications and next steps


Originally, VanderMolen was planning to travel to the US-Mexico border this summer to do one-on-one interviews with members of vulnerable populations, but the COVID-19 pandemic has resulted in unforeseen complications.

Imperial County has been hit very hard by COVID-19, compounding the effects of extreme heat for the vulnerable populations that VanderMolen and her team hope to work with. The pandemic has also made it unfeasible to travel to the region to do face-to-face interviews, and has created challenges in coordinating with local agencies that are now overwhelmed in their efforts to address COVID-19.

“It’s a really interesting place and time to do this work because there are questions about what it means to be on stay-at-home orders and limited travel orders when it’s 114 degrees outside and you don’t have reliable air conditioning or its cost is prohibitive,” VanderMolen said. “At the same time, because they’re so overwhelmed right now with caseload, most folks in the area can’t really afford to address issues beyond COVID-19.”

As the research team works to navigate a path forward that is safe for both the interviewers and interviewees, they remain committed to developing information that will help vulnerable populations along the border.

“I hope that the information we provide is something decision-makers can use to make the right decision or create legislation that can help protect workers in the field, or at least call attention to the kind of inequalities and risk that the people there are being exposed to,” Bandala said. “Or, if we can produce information to change the mindset of the people to start thinking of themselves as a population at risk, and put more attention on the heat warnings, that will suffice for me to feel satisfied with the results of our research.”

The US-Mexico border is just one of many places around the globe where heat-related illness is a problem, added Hatchett – and many of those places happen to be where a lot of our food is grown or where important industries are located.

“I think this is a somewhat ubiquitous problem around the planet. We have these really important places that are susceptible to environmental extremes and these people that we rely on to have these regions be productive in terms of agriculture or industry. Unfortunately, those people are often the most susceptible and underserved populations to these compound environmental hazards,” Hatchett said. “It’s so easy to forget them, but one of the goals of this project is really to bring to light the importance of aiming much-needed resources at trying to help those populations and those places.”

Additional information

For more information on the members of this DRI research team, please visit: 

This research was supported by NOAA’s International Research and Applications Project (IRAP).

Engineered Processes for the Separation and Degradation of Microplastics in Freshwater

Engineered Processes for the Separation and Degradation of Microplastics in Freshwater

Photo: The sand band used to prepare hydrochar from microplastics. Credit: Erick Bandala/DRI.


By Nicole Damon, Nevada Water Resources Research Institute

Microplastics, plastic fragments that are smaller than 5 mm in any dimension, have been found in ecosystems worldwide. These emerging contaminants are even in environments that are supposed to be free from human contact, such as Antarctica and the deep ocean floor, and their toxic properties make them a significant environmental hazard.

“After the first acknowledgement of microplastics in the early 2000s, their presence in the environment has raised ever-increasing concerns because of their effects on organisms and ecosystems, and because approximately 1.5 million tons of microplastics are estimated to be released into aquatic environments every year,” explains Dr. Erick Bandala, the principal investigator of this project, which also includes Dr. Menake Piyasena from New Mexico Tech, graduate research assistants Adam Clurman and Ahdee Zeidman, and summer intern Yajahira Dircio. “Unfortunately, very little is known about the capability of engineered separation and/or degradation technologies to remove this highly ubiquitous contaminant.”

Commercial products that are manufactured to contain microplastics—such as personal care and pharmaceutical products, industrial abrasives, drilling fluids, and 3D printing products—are the primary sources of microplastics. However, the degradation of plastic debris can also generate microplastics.

“Wastewater treatment plant effluents are the main pathway for microplastics to be released into aquatic environments,” Bandala says. “Although the microplastic removal rate of a conventional wastewater treatment plant is reported to be in the range of 73 to 79 percent, the treated effluent can carry as much as 220,000 to 1.5 million microplastic particles per day.”

Yajahira Dircio, a student at Rancho High School and summer intern on the project, is preparing hydrochar from MPs using a sand band

Yajahira Dircio, a student at Rancho High School and summer intern on the project, is
preparing hydrochar from MPs using a sand band. Credit: Erick Bandala/DRI

In recent years, the effects microplastics have been found to have on aquatic species and their unknown effects on human health have increased concerns about their presence in water sources.

“Because conventional water treatment processes are unable to effectively eliminate microplastics in water, developing new technologies that can separate them from effluents and prevent their release into the environment is a high priority to protect water quality and water security,” Bandala says.

For this project, the researchers will use acoustic focusing and electrocoagulation to separate microplastics in freshwater effluents and determine the removal process mechanisms.

“Acoustic standing waves are a fast, noncontact, gentle particlemanipulation technique for microfluidic conditions that have emerged as a promising new technology for the purification, separation, and concentration of beads and biological cell samples,” Bandala explains.

The researchers will also assess the efficacy of using electrocoagulation to remove MPs from wastewater.

“Electrocoagulation has several significant advantages to conventional chemical coagulation, such as it increases treatment efficiency, generates less sludge, requires less space, and prevents chemical storage,” Bandala adds. “It has been proven to be highly efficient in removing contaminants. Our research group has used it for water defluoridation and to pretreat effluents that were heavily contaminated with petrochemicals.”

Because microplastics in freshwater are increasingly detected, it is even more important to find effective water treatment process that remove them.

“Although ultrafiltration, or microfiltration, have microplastic removal efficiencies as high as 99.4 percent, they also have high operational and maintenance costs and require skilled operators,” Bandala explains. “Finding efficient, costeffective methods to separate microplastics from freshwater effluents is critical to preventing population exposure.”

Adam Clurman, an undergraduate student at Nevada State College, is conducting the electrocoagulation experiments for the project.

Adam Clurman, an undergraduate student at Nevada State College, is conducting the
electrocoagulation experiments for the project. Credit: Erick Bandala

Another challenge that microplastics in freshwater present is how to dispose of them once they are removed from water. For this project, the researchers will use advanced oxidation processes (AOPs) as complementary processes to degrade the plastic waste after it has been separated from the wastewater. Advanced oxidation processes are an eco-friendly way to degrade organic compounds. In previous projects, the research group has tested the capability of these processes to degrade a wide variety of dissolved organic contaminants in water.

“Advanced oxidation processes have been used to degrade organics and have shown high cost-efficiency and short detention time compared with conventional water treatment processes,” Bandala explains. “Using AOPs to degrade microplastics will not only be an interesting challenge because of the complexity of their polymeric chains, but also because these contaminants are suspended in water and treating contaminants in a different phase in water using AOPs has not yet been reported.”

Maintaining the quality of water sources is an increasing issue, particularly in arid and semiarid regions with rapidly growing populations, such as Nevada.

“Desert Research Institute has reported the presence of MPs in places such as the Sierra Nevada and Lake Tahoe, which are the origin of several drinking water supply systems in Nevada,” Bandala explains. “We live in a region with a moderate-high water stress and as Nevadans, we need to protect our water sources from contamination to ensure the sustainable development of our communities.”

This story was originally written for the Nevada Water Resources Research Institute (NWRRI) Summer 2020 Newsletter. Success and the dedication to quality research have established DRI’s Division of Hydrologic Sciences (DHS) as the Nevada Water Resources Research Institute (NWRRI) under the Water Resources Research Act of 1984 (as amended). The work conducted through the NWRRI program is supported by the U.S. Geological Survey under Grant/Cooperative Agreement No. G16AP00069.

For more information on the NWRRI, please visit: https://www.dri.edu/nwrri/ 


Researchers identify connection between more frequent, intense heat events and deaths in Las Vegas

Researchers identify connection between more frequent, intense heat events and deaths in Las Vegas

Photo: Hotter temperatures and longer, more frequent heat waves are linked to a rising number of deaths in the Las Vegas Valley over the last 10 years.


Las Vegas, Nev. (June 4, 2019) – Over the last several decades, extreme heat events around the world—particularly in the North American Southwest—have gotten hotter, occurred more frequently, and lasted longer. These trends pose significant health risks to the growing number of people making cities like Las Vegas home.

A new study by faculty and undergraduate students at the Desert Research Institute (DRI), Nevada State College, and Universidad de Las Americas Puebla traces the relationship between extreme heat and mortality rates, identifying a clear correlation between heat wave episodes and heat-related deaths in Las Vegas over the last ten years.

“Current climate change projections show an increased likelihood of extreme temperature events in the Las Vegas area over the next several years,” explained Erick Bandala, Ph.D., assistant research professor at DRI and lead author on the study. “Understanding recent extreme heat trends and their relationship to health hazards is essential to protecting vulnerable populations from risk in the future.”

Researchers analyze data on computer.

Erick Bandala, PhD (left), shows a graduate student the data he and his team analyzed for this study.

Urban areas of the Southwest are of particular concern because several factors compound the health-related risks of extreme heat events. The heat-absorbing properties of common materials like asphalt exacerbate already high temperatures in cities (called the urban heat island effect), particularly at night. What’s more, populations in cities like Las Vegas are growing rapidly, especially among those 55 and older, which means that more and more people are exposed to risk.

In this study, the research team analyzed two measures of extreme heat—heat index and excess heat factor—for the Las Vegas metropolitan area in the June, July, and August months from 2007 to 2016. Heat index (HI) accounts for how the human body reacts to surface temperature and relative humidity. Excess heat factor measures (EHF) heat wave intensity in relation to historic temperature trends to account for how acclimated the public is to a given temperature threshold. Because both HI and EHF incorporate the human body’s response to extreme heat, they are ideal metrics for assessing public health impacts, and both were shown to rise over the study period.

The annual average of severe heat events per year in Las Vegas also showed significant increases in this study, from an average of 3.3 events per year from 2007-2009 to 4.7 per year in the 2010-2016 period. These findings match historic trends, which show a steady increase in severity and frequency of excess heat in Las Vegas since 1980.

Strikingly, the number of heat-related deaths in Las Vegas map onto these trends: as heat wave intensity increases, the number of heat-related deaths does, too.

Graphs of heat index and excess heat factor.

Heat Index (HI) and Excess Heat Factor (EHF) are metrics that go beyond just temperature to also account for the human body’s response to heat. This study found that rising trends in these measures tracked closely with the number of heat-related deaths in Las Vegas.

“From 2007 to 2016, there have been 437 heat-related deaths in Las Vegas, with the greatest number of those deaths occurring in 2016,” explained Bandala. “Interestingly, 2016 also shows one of the highest heat index measures over the last 35 years. This shows a clear relationship between increasingly intense heat events in our area and public health effects.”

Bandala’s team found that the subpopulation particularly at risk of heat-related deaths is adults over 50 years old—76% of the heat-related deaths in the study period were individuals in this subpopulation. Of the deaths in this group, almost all individuals also showed evidence of pre-existing heart disease. Researchers note that these findings are highly significant given that the population of adults over 50 in Las Vegas is increasing, with more retirees choosing Clark County as a retirement destination.

Only 23% of heat related deaths occurred in the subpopulation of adults aged 20 to 50 years; interestingly, the most common pre-existing condition for this group was drug and alcohol use. More research is needed to understand how heat is impacting this segment of the population, Bandala noted, because though the number of deaths in this group is comparatively smaller, it is still nearly one quarter of heat-related deaths in the Las Vegas Valley. Additionally, this subpopulation includes economically active adults.

With more intense, more frequent, and longer lasting heat events projected in the coming years, the research team hopes that the trends identified in this study can assist local decision-makers in taking steps to protect the most vulnerable groups in Las Vegas.

“This research helps us better understand the connection between the climate changes we’ve experienced in Las Vegas and their impact to public health over the last 35 years,” Bandala said. “Ideally, this data analysis will help our community adapt to the changes yet to come.”

The full study, titled “Extreme heat and mortality rates in Las Vegas, Nevada: inter-annual variations and thresholds”, is published in the International Journal of Environmental Science and Technology. The study abstract and references are available here: https://link.springer.com/article/10.1007%2Fs13762-019-02357-9 

This study is based on work supported in part by the National Science Foundation, NASA, and the Desert Research Institute. Other members of the project team include Kebret Kebede, Nikole Jonsson, Rebecca Murray, and Destiny Green, all of Nevada State College; John Mejia of DRI; and Polioptro Martinez Austria of the Universidad de Las Americas Puebla. 

Meet Erick Bandala, Ph.D.

Meet Erick Bandala, Ph.D.

Erick Bandala, Ph.D., is an assistant research professor of environmental science with the Division of Hydrologic Sciences at the Desert Research Institute in Las Vegas. Erick specializes in research related to water quality and water treatment, including the use of nanomaterials in developing new water treatment technologies. He is originally from Mexico, and holds a bachelor’s degree in chemical engineering from Veracruz State University, a master’s degree in organic chemistry from Morelos State University, and a Ph.D. in Engineering from the National Autonomous University of Mexico. Erick has been a member of the DRI community since 2016, when he moved to Las Vegas to begin his current job. In his free time, Erick says that he enjoys doing nothing – a passion that is not shared by his wife of nearly 30 years, who enjoys doing many things.

DRI: What do you do here at DRI?

EB: My work here is to develop advanced technologies for water treatment, such as processes that can deal with the pollutants in the water that are not removed by conventional water treatment methods.

DRI: We understand that a lot of your work involves nanomaterials. What are nanomaterials, and how do you use them in your research?

EB: Nanomaterials are materials that are so small that if you compare the size of one of these materials with a basketball, it’s like comparing the size of the basketball with the size of the earth. These nano-sized materials have applications in many different fields.

In my case, what I’m doing with the nanomaterials is using them to promote reactions in the water that can produce chemical species capable of destroying contaminants. Not only to remove the contaminants, but to destroy them from the water.

Erick Bandala, Ph.D. at work in DRI's Environmental Engineering Lab. Credit: Dave Becker, Nevada Momentum.

Erick Bandala, Ph.D. at work in DRI’s Environmental Engineering Lab. Credit: Dave Becker, Nevada Momentum.


DRI: What type of contaminants do you hope to remove? Can you tell us about one of your projects? 

EB: Right now, we are trying to get nanoparticles made of something called zerovalent iron, which is iron with no charge on it. We are planning to use this to remove antibiotics from water. As you know, we all use antibiotics every now and then. And when you use them, the antibiotics get into your body and you will probably only use about 15 percent of the total amount that is present. Whatever remains is discarded with your feces or urine into the wastewater.

Once the wastewater arrives at the water treatment plant, the conventional water treatment processes will probably not be able to remove the antibiotic. So, the antibiotic passes through the wastewater treatment system and keeps going with the treated effluent. In the case of Las Vegas for example, it goes back to Lake Mead. This is a problem, because we are learning now that bacteria can become resistant to antibiotics just by exposure – and when bacteria in the environment become resistant to the antibiotics, there is no way for people to treat infections.

So, in our work, we hope to use nanoparticles to destroy the contaminants in the wastewater. At the moment we are just running some trials in the lab, but we eventually hope to run the experiment at pilot level to see if we can treat wastewater coming back from plants to the lake, and ensure that we will not have these contaminants going back to our environment.

Another part of my research is on how to use solar energy to remove contaminants from water. This way you can save some money by using an energy source that is common in Nevada, widely available. We have a lot of sunshine here.

Information about nanomaterials from DRI's Environmental Engineering Lab. Credit: Dave Becker, Nevada Momentum.

Information about nanomaterials from DRI’s Environmental Engineering Lab. Credit: Dave Becker, Nevada Momentum.


DRI: How did you become interested in working on water treatment and water quality?

EB: My very first job was working in a research institute in Mexico that was devoted entirely to water. The group that I arrived to work with was dealing with water quality and treatment in wastewater and drinking water. So, I started down this path just because it was available and I needed the job – but my plan was to spent two years working on this and now it has been more than 25 years. I feel very passionate about this field of work. I feel like this is the way that I have to try to help people, and I love it.

DRI: You are originally from Mexico. What brought you to DRI?

EB: When the position at DRI opened three years ago, I started learning about the water related issues that Nevada and particularly Las Vegas was facing, and was fascinated. The city gets its water supply from Lake Mead then sends treated wastewater back to the lake — so having almost 100 percent recycling of the water is something that caught my attention immediately. Not only because it’s wonderful, but that it may also result in other problems like the recycling of some pollutants that you probably don’t want in your drinking water. That idea really captured me. So I decided to apply for the job, and have had three years of great fun trying to deal all of those problems and promote some solutions that may help to deal with the reality we’re facing in Las Vegas. Reno is not that different – we all need water when we’re living in places where water resources are so scarce. I was really intrigued by how to deal with all of these problems and how I might help.

Erick Bandala (second from left) and his colleagues from DRI's Environmental Engineering Lab. 

Erick Bandala (second from left) and his colleagues from DRI’s Environmental Engineering Lab.


For more information about Erick and his research, please visit https://www.dri.edu/directory/erick-bandala.