Deadly fungi, toxic tides, and wildfire smoke

Researchers race to identify and mitigate the health hazards of climate change

Since fungus-riddled zombies unleashed the apocalypse, Justin Remais has been in high demand.

The calls started coming in January 2023, as much of the U.S. became obsessed with the HBO hit series The Last of Us, the story of a terrifying fungus that takes over the brains of its human hosts and turns them into killing machines. In the show, Cordyceps, a parasitic fungus that in reality is limited to insects, adapts to a warming planet and becomes comfortable in humans, with terrifying and tragic results for our species.

“Could this really happen?” reporters asked Dr. Remais, a Berkeley Public Health professor and world expert on the impact of climate change on infectious diseases.

“No. Not likely,” he would say.

But the troubling bit of truth that Remais knows is this: Certain fungal pathogens are indeed climate sensitive. And with the growth of antifungal drug resistance, along with a warming world, their public health significance has increased.

“In the show, climate change has led to the emergence of a new fungal pathogen that sweeps the globe,” said Remais. “In the real world, fungal pathogens are indeed becoming increasingly common and resistant to treatment, and we are only beginning to understand how climate change is contributing to these changes.”

As chair of BPH’s Division of Environmental Health Sciences—newly ranked #6 in the nation by US News & World Report—Remais leads a faculty tackling the health impacts of climate change on many fronts: the spread of harmful fungi; the susceptibility of vulnerable populations to wildfire smoke; the impact of heat on air pollution; and the consequences of extreme heat on farmworkers who are exposed to pesticides.

In a nearby building, Rachel Morello-Frosch, professor of Environmental Health Sciences and Community Health Sciences, runs the Sustainability/Health Equity (SHE) Lab. Since 2019, the SHE Lab has co-led the Toxic Tides project, a multi-institutional collaboration whose goal is to spatially analyze and communicate the health risks of coastal and inland flooding of contaminated sites in disadvantaged communities, to inform land use, and disaster planning efforts.

“The component of environmental equity is often missing in the discussions around sea-level rise, but should be central to climate action planning at every level,” said Dr. Morello-Frosch.

Berkeley Public Health’s climate change work features a strong environmental justice component with a drive to identify the health risks that climate change will bring, help communities develop resilience, and provide policymakers with solutions to mitigate harm.

Valley fever and the growing risk of fungal infections

“Studying pathogenic fungi in California was not part of my research plans,” said Remais, who has spent many years working on globally neglected pathogens and the diseases they cause amongst the world’s poorest and most vulnerable populations. “But we became increasingly aware that there were neglected environmental pathogens right in our own backyard. We were seeing them move outside of their historic ranges, and we saw signs of a rapidly growing threat to public health.”

Every year, fungal infections affect more than 1 billion people and kill an estimated 1.6 million around the world. In the U.S., millions of people are infected by pathogenic fungi, leading to an estimated $7.2 billion in economic losses each year.

Researchers know that fungal diseases respond to shifts in weather and climate. Some fungal pathogens infect people during natural disasters such as floods and hurricanes, often entering through open wounds. Others—such as Histoplasma and Aspergillus—live in the environment and infect people when they inhale fungal spores or come into contact with fungal filaments called hyphae. Climate influences where and how fast these pathogens grow and disperse.

Valley fever—or coccidioidomycosis—is a case in point. The illness is contracted by inhaling spores of Coccidioides, a pathogenic fungus that grows in soil. When the weather is hot and dry, the fungus develops spores that can become airborne. People who work closely with soil—such as agricultural and construction workers—tend to have the highest exposures, and if infected they can experience cough, fever, shortness of breath, headache, night sweats, and joint pain, among other symptoms. Although most cases clear up on their own within a few weeks to months, roughly 5% to 10% of people who get it will develop serious or long-term disease, especially when the pathogen spreads from the lungs to other parts of the body such as the brain.

Until recently, Valley fever was limited to the arid deserts in the southwestern United States. But the warming climate has enabled the Coccidioides fungus to survive across a wider area, especially in California, where it is moving north and towards the coast.

“California has seen a dramatic increase—over 800% in Valley fever from 2014 until now,” said Jennifer Head—a former assistant researcher in the division of Environmental Health Sciences. Head, who was recently appointed as assistant professor of epidemiology at the University of Michigan, studies the spread of the disease. In a study published in 2022, Dr. Head found that cycles of multi-year drought, followed by a wet winter, amplified transmission of the Coccidioides fungus. In wetter, coastal counties the disease was highly sensitive to temperature fluctuations, and recent warmer summers have allowed the disease to take hold in areas from San Luis Obispo to Monterey.

Head also found some significant increases in Valley fever in highly endemic areas that had experienced particularly large wildfires. Dr. Head hypothesized that fires can deplete vegetation, making the soil more susceptible to wind erosion.

The team, working with the California Department of Public Health, also found that the fungal spores are more likely to be found in borrows where rodents were actively present, compared to surface soils or burrows where rodents were absent. “Coccidioides is known to infect small mammals,” Dr. Head said. “It is possible that the fungus uses the carcasses of its animal hosts, or materials shed by them like hair or skin, as nutrients to support its growth.”

“The more we learn about where and how this pathogen lives in the soil, the better we will be at preventing the disease it can cause in otherwise healthy people,” she added. Dr. Head is now developing statistical models that use surveillance data to project the disease as climate change takes hold in the state.

“It will be warming in California,” she said. “How much Valley fever will we have?” Dr. Head is also concerned about Valley fever increasing outside of California, including in states that have not historically reported many cases, such as Utah, Texas, and New Mexico, where there is early evidence that the disease may be spreading faster.

Remais, who was the principal investigator on Head’s projects, said the research goal is to determine how environmental changes are driving shifts in fungal diseases so that state officials can make preparations necessary to lessen the impact.

“Fungal disease risks are rising, and climate change may be playing a role, but we need improved data and new analytical approaches to predict how climate change will affect these diseases in the years to come,” said Remais.

“Then we need to respond to these future risks by increasing doctor and patient awareness, and ensuring protective measures are made available to those most vulnerable to the impacts of climate change.”

To that end, Remais will lead a new $3.9 million, NIH-funded project to conduct the nation’s first big data study investigating how climate change is contributing to the emergence of Valley fever, histoplasmosis, aspergillosis, cryptococcosis, and other fungal diseases. The project will harness a massive, anonymized dataset of electronic health records—comprising more than 96 million patients—to study where fungal diseases are emerging and identify factors leading to disparities in fungal disease incidence and severity across vulnerable populations. The researchers hope to understand why, exactly, socially and economically disadvantaged populations face greater risk. By identifying the underlying factors driving these disparities, they plan to develop community investment measures that could support adaptation to climate extremes.

“Analyzing this remarkable, vast health dataset and integrating it with socioeconomic and climate information will help us understand how and why the risk of fungal diseases has been changing, identify areas at particularly high risk for emergence or intensification of fungal diseases, and help health practitioners to better predict, detect, and prevent future infections,” Remais said.

(Clockwise from top left) Rachel Morello-Frosch, Ajay Pillarisetti, Carly Hyland, Jennifer Head, Justin Remais, and David J.X. Gonzalez.

Toxic Tides

Unless more is done to slow climate change, Californians can expect more than three feet of sea level rise by 2100. This coastal flooding could overwhelm the state’s hazardous waste storage sites, oil refineries, sewage treatment plants, and other industrial facilities—unleashing torrents of toxic water.

Dr. Morello-Frosch has long studied the serious threat that toxic chemicals such as pesticides, plastics, and metals pose to public health—especially their impact on the developing brain. As co-leader of the Toxic Tides project, her work is focused on the unequal burden of chemical pollution that sea level rise is likely to pose to low income neighborhoods and communities of color.

In May, the Toxic Tides team released a preliminary set of data identifying 425 California hazardous materials sites that are vulnerable to coastal floods. The researchers also created an online mapping tool that visually depicts the endangered facilities, and lets users overly indicators of nearby residents’ social vulnerability, including the rates of poverty, unemployment, and other social stressors.

The majority of these at-risk facilities are in five counties: Alameda, Contra Costa, Los Angeles, Orange, and San Mateo. Within these counties, the facilities that are vulnerable to floods are much more likely to be located in disadvantaged neighborhoods than non-disadvantaged neighborhoods, as designed by the California Environmental Protection Agency.

Already, the researchers have pinpointed a total of 68,000 people living within .3 meter elevation of the local mean high tide, and more than 125,000 people living within .9 meter elevation of the mean high tide.

“Climate change is here,” said Rachel Morello-Frosch. “We have wildfires, tornados, floods. Sea-level rise is a much slower-moving storm. If we can ensure that climate mitigation and adaptation strategies protect the most vulnerable, then we have the best ability to protect environmental health.”

The Toxic Tides Project is a collaboration with UCLA’s Fielding School of Public Health and Climate Central, a research and communications group, along with five community groups. The SHE Lab is also working on a Climate Justice Initiative, which assesses the equity implications and potential benefits of California’s diverse climate change laws, particularly regarding efforts to curb greenhouse gas.

The U.S. Environmental Protection Agency recently funded Toxic Tides to expand its work throughout the country. Its interactive website will be updated to reflect the toxic vulnerabilities in 50 states.

With floods that cause releases of toxic substances are becoming more frequent;  researchers have a new word for natural disasters which spawn chemical contamination: Natech, short for natural hazards triggering technological disasters.

Across the country, households living near hazardous waste and industrial facilities are disproportionately low-income people of color who face additional challenges such as poor housing conditions, food insecurity, or pre-existing health conditions that exacerbate the health effects of pollutants.

The researchers are running a retrospective environmental justice analysis, examining the toxic releases associated with Hurricane Harvey, the August 2017 coastal storm that inundated parts of Texas and Louisiana. The storm devastated many communities, including parts of Houston, and killed more than 100 people.

“We’re looking into toxic releases into air, land, or water related to the storm,” Morello-Frosch said.

Wildfire smoke, pollution, and public health

California’s growing heat, and increasing frequency and severity of wildfires, has spurred researchers at Berkeley Public Health to assess the health risks and seek solutions. Faculty members—including Carly Hyland, Ajay Pillarisetti, and David J.X. Gonzalez—are working to address the serious public health challenges posed by smoke, pollution and heat in the state and beyond.

Agricultural workers often labor in extreme heat, with little shade, few water breaks, and minimal protection against pesticides, wildfire smoke and other health hazards. As workers face an increasing number of dangerously hot days, Carly Hyland is looking at strategies to protect them.

Dr. Hyland, an assistant professor of cooperative extension in environmental health, is conducting community-based research to minimize the impacts of climate change among agricultural and food systems workers. Her research focuses on preventing short-term hazards, such as dehydration or heat stroke, while also examining longer-term health risks from breathing in wildfire smoke, or being exposed to agricultural chemicals.

“It’s easy for academics to sit in their own silos and think of interventions that they believe would work,” Hyland said. “But the reality is that the farmworkers and food systems workers will understand better what the challenges are, so it’s absolutely critical to engage those stakeholders.”

Before arriving at UC Berkeley in 2023, Hyland conducted research at Boise State University, where she says farmworkers made clear that they are concerned about extreme heat and wildfire smoke. At the same time, however, she heard from farmworkers that it was often too hot to wear protective equipment such as a mask.

“But they had to keep working, or they wouldn’t get paid,” Hyland said.

Hyland is interested in using personal monitors to measure a worker’s heat temperature, and implementing procedures in which workers can take a break, get some cool water, and return to work when their body is back to a safe temperature.

“They go home and often don’t have access to air conditioning,” she said. “My goal is to work with farm owners, to help them see these interventions as important.”

“I would love to make the argument from a purely human health perspective, but a lot of the strategy will be talking to farmers about how these problems are already impacting farm productivity. Engagement from farm owners, and ultimately at a policy level, is my goal.”

Ajay Pillarisetti, an assistant professor of Environmental Health Sciences, is concerned with the link between climate change and air pollution. Since last year, he has been working with PSE Healthy Energy, a nonprofit research institution based in Oakland, to study how air pollution and heat are affecting birth outcomes and to develop targeted solutions to protect some of the Bay Area’s most vulnerable populations. Dr. Pillarisetti will also work to assess areas and communities that are at the greatest risk from wildfire smoke, other air pollution, and increased heat and humidity. Researchers will use low-cost air monitors in Contra Costa County, to study local variations in exposures—and birth outcomes—in different neighborhoods over three years.

In the final phase of the project, researchers will work with communities to develop interventions to mitigate exposures, ranging from retrofitting houses to planting trees.

David J. X. González, an assistant professor of Environmental Health Sciences who also joined the faculty in 2023, studies how energy production and climate-driven disasters such as wildfires affect maternal and infant health, and may exacerbate health disparities.

Already, Dr. González and others have shown that there are consistent health risks associated with living near oil and gas wells, such as preterm birth. Now he is building on that work, studying whether living near these wells poses a higher risk of  birth defects and other negative pregnancy outcomes. He is also looking into whether living near inactive wells could lead to health risks. In a recent study, Dr. González and colleagues found that one in five Californians live within 1 km (0.62 miles) of inactive wells, indicating how widespread exposure is in the state.

Dr. González, who did his postdoctoral fellowship in Morello-Frosch’s SHE Lab, is also looking into the intersection of climate and existing oil and gas infrastructure. In ongoing work, he and his colleagues are investigating to what extent wildfire threatens existing oil and gas infrastructure, which could lead to environmental health risks as climate change continues.

He is also researching whether exposure to wildfire smoke increases risks for the health of pregnant people, and whether previously reported health disparities worsen with exposure to smoke. “We expect that the risks are going to increase,” he said. “We know that wildfire smoke is worsening air pollution,” Dr. González said. “That’s bad because people who are exposed to chronic air pollution may be more susceptible to wildfire smoke.”

On the policy front, González is investigating the factors, such as redlining, that lead to the location of oil and gas wells in Black, Latino, and low-income communities.

These UC Berkeley researchers are involved in multiple interorganizational studies that all have the same thing at heart: social justice.

“UC Berkeley School of Public Health faculty are leading the charge for policies that reduce climate change-related threats to public and planetary health,” Remais said, “and at the same time, our faculty are among the most effective advocates for making environmental justice and social equity central to the solutions that we invest in.”

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