The predictive model results can help members of the public, water suppliers and regulators understand the potential for PFAS contamination, guide future studies and inform strategic planning for water resources.

USGS scientists are the first to report national estimates of PFAS occurrence in untreated groundwater that supplies water to public and private wells. This research also provides the first estimate of the number of people across the country who are potentially affected by PFAS-contaminated groundwater.

Along with a scientific report, the USGS published an interactive, online map so users can see probability estimates of PFAS occurrence. Note that predictive results are intended to be evaluated at state, regional and national scales rather than at individual household levels. Probability estimates are for the presence of PFAS in groundwater and do not account for any subsequent actions taken by states, municipalities or individuals to treat drinking water. The model does not include estimates of PFAS concentrations; testing is the only way to confirm the presence of contaminants.

Exposure to certain PFAS may lead to adverse health risks in people, according to the U.S. Environmental Protection Agency. PFAS are a group of synthetic chemicals used in a wide variety of common applications, from the linings of fast-food boxes and non-stick cookware to fire-fighting foams and other purposes. PFAS are commonly called “forever chemicals” because many of them do not easily break down and can build up over time, making them a concern for drinking water quality.

“This study’s findings indicate widespread PFAS contamination in groundwater that is used for public and private drinking water supplies in the U.S.,” said Andrea Tokranov, USGS research hydrologist and lead author of this study. “This new predictive model can help prioritize areas for future sampling to help ensure people aren’t unknowingly drinking contaminated water. This is especially important for private well users, who may not have information on water quality in their region and may not have the same access to testing and treatment that public water suppliers do.”

The EPA has established legally enforceable levels, called maximum contaminant levels, for six types of PFAS in drinking water. The EPA regulates public water supplies, and some states have additional regulations for drinking water. Some homes use private water supplies, where residents are responsible for the maintenance, testing and treatment of their drinking water. Those interested in treatment processes and testing options can read EPA’s guidance or contact their state officials or water supplier.

The states with the largest populations relying on public water supplies with potentially contaminated groundwater sources are Florida and California. Regarding private wells, Michigan, Florida, North Carolina, Pennsylvania, New York and Ohio have the largest populations relying on potentially contaminated groundwater.

The study also presents data according to population percentage. In Massachusetts, for example, the source water for 86 to 98% of people who rely on groundwater from public water supplies could be contaminated with PFAS. In Connecticut, the source water for 67 to 87% of the people who rely on groundwater from private wells could be affected. Details by state can be seen in the report’s tables S6 through S8.

“To derive these estimates, the team analyzed 1,238 groundwater samples collected by USGS scientists and determined how factors such as urban development and well depth can impact PFAS occurrence,” continued Tokranov. “With that information, a detailed machine learning model was developed and used to identify which geographic areas have a higher likelihood for contamination. That information was combined with existing USGS research on the number of people in a given area who rely on groundwater for drinking water to establish population estimates.”

Scientists present separate estimates for public and private wells because they typically receive water from different groundwater depths. Public wells using groundwater as the primary water source are usually deeper than private wells.

There are more than 12,000 types of PFAS, not all of which can be detected with current tests; the USGS study tested for the presence of 24 common types. The USGS estimates consider the presence of at least one of those 24 types of PFAS. The most frequently detected compounds were perfluorobutane sulfonate known as PFBS, perfluorooctane sulfonate known as PFOS and perfluorooctanoate known as PFOA.

This research provides a broad outlook for the Lower 48 states and presents state-level estimates. Scientists did not look in detail at specific cities or provide estimates for the types of PFAS present or PFAS concentrations.

Just published in the journal Science, the University of Otago study provides arguably the world’s most clear-cut case of animal evolution in response to change made by humans.

Co-author Professor Jon Waters, of the Department of Zoology, says the stonefly has become a different colour due to recent deforestation.

“In natural forested regions, a native species has evolved ‘warning’ colours that mimic those of a poisonous forest species, to trick predators into thinking they are poisonous too.

“But the removal of forests since humans arrived has removed the poisonous species. As a result, in deforested regions the mimicking species has abandoned this strategy — as there is nothing to mimic — instead evolving into a different colour.”

Scientists have long wondered whether humans are causing evolutionary changes in natural populations.

The most well-known example of evolution caused by humans was the peppered moth population in the United Kingdom, which changed colour in response to industrial pollution in the 1800s.

But Professor Waters says even that case has been considered controversial.

This new study shows how humans have changed the way native species interact.

Co-author Dr Graham McCulloch says humans have disrupted ecological interactions between species that evolved over millions of years, but some of our native species are resilient enough to overcome this.

“This study is important because it shows that, at least for some of our native species, there is the possibility of adapting to the environmental changes caused by humans, even when the change is rapid,” Dr McCulloch says.

“It also shows that independent populations have undergone similar changes in response to deforestation — there have been similar shifts independently in different parts of the species’ range — showing that evolution can be a predictable process.”

The study was a collaboration between scientists at Northwestern Medicine and a Nigerian team of scientists from the University of Lagos and Lagos University Teaching Hospital (LUTH) in Lagos, Nigeria. Of the 2,319 participants, 106 (4.6%) had long COVID with neurologic symptoms, and some were still experiencing symptoms up to two years after their initial episode of COVID-19. Researchers also found patients who were hospitalized for COVID-19 pneumonia reported a higher frequency of long COVID symptoms than those who were not hospitalized and had mild initial COVID-19 (11.5% vs 3.9%, respectively).

The findings were published today, October 24, in the Journal of NeuroVirology.

The findings highlight the need for improved screening, diagnosis and treatment of neuro-long COVID in Nigeria.

“Based on this data, there is hopefully going to be some intervention to alleviate their suffering,” said Dr. Igor Koralnik, chief of neuro-infectious disease and global neurology at Northwestern University Feinberg School of Medicine. “We’ve determined that even in a resource-limited setting where people have many other problems to worry about, we can still perform these studies, find those patients, and diagnose them.”

Scientists from the Nigerian team include neurologist Dr. Njideka U. Okubadejo and infectious disease physician Dr. Iorhen E. Akase, both of the University of Lagos and LUTH.

Koralnik and his team launched the Northwestern Medicine Neuro-COVID-19 Clinic in May 2020 and were soon evaluating a large number of patients who were exhibiting post-COVID neurologic symptoms. They then began researching the disease. In Nigeria, the opposite has happened. People in Nigeria are not aware that long COVID is a disease for which symptomatic treatments are available, and there was a scarcity of post-COVID clinics even during the height of the pandemic.

“This is why we have to start by doing the research to demonstrate the need for diagnosis and clinical care of these patients and advocate for specialized outpatient clinics,” Koralnik said. “If you don’t know that something exists, you can’t treat it.”

Breakdown of neurologic symptoms

The predominant neurologic symptoms among study participants at any time during the disease course included:

• Difficulty remembering/brain fog (59.4%)
• Fatigue (55.7%)
• Sleep problems (32%)
• Headache (31%)
• Paresthesia, or numbness and pins and needles (11.3%)
• Myalgia, or muscle pain (9.4%).

Of the 66 participants with neuro-long COVID who underwent an in-person neurological evaluation and cognitive screening, 16.9% completed the Montreal Cognitive Assessment, a widely used screening assessment for detecting cognitive impairment, and had results consistent with mild cognitive impairment.

Next steps

In a future study, the scientists plan to treat brain fog and cognitive dysfunction in neuro-long COVID patients in Nigeria by applying the same techniques he and his team are currently using in Chicago, Koralnik said.

COVID-19 continues to occur despite vaccination and boosters, and according to an ongoing household pulse study carried out by the National Center for Health Statistics, approximately 14 million adults in the U.S. are currently experiencing long COVID. Long COVID principally affects adults in their prime, affecting their quality of life and ability to work, contributing to profound public health and socio-economic impacts.

Millenia Jimenez who works in the Koralnik laboratory at Northwestern is a co-author on the study.