American Scientist

Guatemala City, one of the largest and most populated cities in Central America, is considered a model for water purification infrastructure in the region, because of their virtual elimination of harmful microbes in their tap water. Still, no one knew what chemicals or heavy metals were in the tap water there until citizen scientists in Guatemala City joined a study to sample the water, led by Jennifer Hoponick Redmon of RTI International. Hoponick Redmon spoke at Science by the Slice on February 22 (see recorded talk below), a monthly lunch series cohosted by Sigma Xi and Science Communicators of North Carolina. Scroll to the end of this post to view live tweets by Imani Vincent, an intern at the Science Communicators of North Carolina.

Hoponick Redmon was motivated to study chemicals in the tap water in Guatemala City because, she says, “usually studies are limited to microbial risks in rural drinking water, an issue not faced by metropolitan regions such as Guatemala City.” However, chemical contaminants, such as heavy metals and PFAS, had never been studied in these drinking supplies. Heavy metals can enter the water system through various ways, with concerning health outcomes. Guatemala experiences volcanic activity, which can cause naturally occurring arsenic to enter the groundwater. Lead was historically used in water pipes and can leach into the tap water, as seen in the lead exposure in Flint, Michigan. Aluminum can enter the water system as a byproduct of water treatment to remove harmful microbes from drinking water.

PFAS, which stands for per-and polyfluoroalkyl substances, also known as “forever chemicals,” are a class of more than 9,000 human-made chemicals used to produce everyday items that are waterproof or greaseproof—think nonstick pans, dental floss, food wrappers, menstrual underwear, or waterproof jackets. As their nickname suggests, these chemicals do not readily degrade and have been found ubiquitously, including in 97 percent of Americans' blood. PFAS can cause health concerns ranging from cancer to thyroid disease. PFAS from industrial runoff plague the drinking water in all 50 of the United States, as seen on this interactive map, and disproportionately impacts the health of marginalized communities in the United States. Hoponick Redmon wanted to know if PFAS had made their way to water sources in Guatemala City, and if so, who was being exposed to them.

"We wanted to make sure that our enrollment demographics were geospatially and socioeconomically diverse,"  explained Hoponick Redmon. More than 100 people—representing students, faculty, and staff at the Universidad del Valle de Guatemala in Guatemala City—participated in the study. These community scientists came from widely ranging socioeconomic backgrounds, lived throughout the city and in surrounding rural areas, and relied on various water sources, including municipal water, private water companies, and well water. The recruited volunteer scientists were trained to gather samples of their household tap water and send them to Hoponick Redmon’s lab. At the lab, her team tested the water for heavy metals and PFAS. They found almost two-thirds of the households involved in the study had heavy metals in their tap water above the Guatemalan health standards. In particular, three metals exceeded the health standards:

1. Aluminum was found in about a quarter of samples. Hoponick Redmon and her team linked the aluminum to municipal water, which come from surface water such as lakes. It’s likely the aluminum came from treating the water and possibly from storing the water in concrete containers.

2. Lead was in just under 10 percent of the samples and was traced to individual household piping and plumbing.

3. Arsenic was found in a third of water samples and was most likely from naturally occurring arsenic in groundwater from municipal water.

The lab also detected six types of PFAS in the samples. Almost a fifth of samples had PFAS, and those that did were from households that used municipal water. However, the PFAS weren’t traced to the municipal water providers. Instead, Hoponick Redmond suspects that PFAS enter the water when it is held in outdoor plastic storage tanks used by some households. Hoponick Redmond and her team think that the natural hardening of the plastic water storage tanks as they sit in the sun can create PFAS as a byproduct, which can then leach from the plastic into the water. The presence of PFAS produced by this kind of process was unexpected, Hoponick Redmond said. The good news is that no PFAS were detected in water from private utilities, private wells, or cisterns filled by trucked water. Hoponick Redmon says this result indicates that “there has not been industrial manufacturing use or discharge of PFAS in this area.”

That's not the case in North Carolina, where many residents live either in an area with industrial manufacturing or in a region where discharge of PFAS is present. Even if these "forever chemicals" are completely phased out, they’ll be around for a while in residents' water, food, and blood. The best thing that vulnerable populations can do immediately is limit their exposure. Residents can consider installing an under-the-sink water filter, such as a reverse-osmosis filter. Water filters indicate whether they remove heavy metals, and many now specify whether they remove PFAS.

Unfortunately, these filters aren’t available for everyone. The community scientists in Guatemala City were concerned about the heavy metals in their water, but no one there was informed about PFAS prior to the study. After learning about the water study results, the participants wanted to learn how to improve the quality of their drinking water, which water treatment processes could address the problems, and who to contact to implement these changes. Frustratingly, there were few actions individuals in the study could do to improve their water quality. It’s difficult to get a water filter in Guatemala City, and most are only designed to remove odors and taste. Hoponick Redmon emphasizes that treating water to filter out toxic metals and chemicals with limited resources is a global issue: “These are concerns that most towns and cities are facing, and not just in Central America and the world, but also even within American towns and cities.”

Tweets highlighting the talk follow below.

This blog was produced in collaboration with Science Communicators of North Carolina.