Troubled Waters

The town of Rigolet, Canada, is barely a speck on the map. It hasn’t changed much in decades—other than its 310 residents, its main attractions are a dock, a few houses, and the Grub Box, a tiny restaurant with a single table.

Rigolet lies on the far eastern end of Lake Melville, a saltwater estuary that stretches more than 100 miles inland from the coast, forming a basin roughly the size of Long Island Sound. It’s a beautiful spot, flanked by lush pine forests and rolling mountains that crest occasionally into bald, rocky peaks. There are no major roads for miles.

This remote and pristine region, and the nearby Atlantic coast, is becoming a bellwether for some of the unexpected impacts that climate change may have on human health. As global temperature rises, the fish and wildlife that local Inuit hunt for food are absorbing growing amounts of mercury, a potent neurotoxin.

For the past century, that mercury has been generated at lower latitudes, as a by-product of burning fossil fuels. Once airborne, it drifts northward before falling as rain and snow in the Arctic. Normally, mercury is locked away in ice and permafrost. As the global climate warms, however, that ice is starting to disappear, releasing decades’ worth of contaminants.

Winter | 2018
by David Levin

“As the landscape literally melts, you’re seeing it introduce pollutants back into the environment. It’s negatively impacting an important food supply for local Inuit,” says Elsie Sunderland, associate professor of environmental science and engineering at the Harvard T.H. Chan School of Public Health and the John A. Paulson School of Engineering and Applied Sciences. “They don’t have a lot of other options—they can’t just run out to the grocery store. It has a direct impact on their health.”

Sunderland studies mercury contamination and other effects of pollutants in the far north. She has found that, once freed from the ice, mercury compounds build up in the flesh of fish and other animals—and eventually, in the humans who eat them. In adults, she notes, even relatively low levels of exposure to these contaminants can impair brain development, as well as cardiovascular and immune function. According to ongoing studies by Philippe Grandjean, adjunct professor of environmental health at the Harvard Chan School, the effects are most pronounced in children and infants, and can range from stunted fetal growth to impaired cognition.

This isn’t just a problem for the 310 residents of Rigolet. Arctic fish species like halibut and pollock, which are commercially caught in the region, are shipped all over the world. That means Arctic mercury could wind up on a dinner plate in Las Vegas or Warsaw or Hong Kong.

Warming climate is also changing the direction and strength of massive ocean currents, Sunderland says, dragging more pollutants from lower latitudes northward. Fieldwork she conducted recently in Massachusetts suggests that dangerous chemicals like perfluorinated compounds—which are found in everything from firefighting foam to dental floss—are finding their way into local water supplies and, eventually, to the world’s oceans, where they work their way up the food chain, with dramatic health effects on humans.

“Perfluorinated chemicals are incredibly stable compounds, and most do not appreciably degrade in the environment. They’ve been linked to diabetes and have been associated with a few different types of cancer. They’re also some of the most toxic chemicals we’ve ever seen for the immune system,” says Sunderland. “In my mind, they’re a disaster as a class of compounds.”

Across the Harvard Chan campus, researchers are exploring these and other direct and indirect effects of climate change on water-related diseases. The scientists’ work ranges from studies of vectorborne infections in the Amazon to food security in central Africa. The aim is to uncover how global warming and other trends are generating new public health emergencies and exacerbating old ones.

According to the National Snow and Ice Data Center, based in Boulder, Colorado, the most direct effects of climate change and water are felt on global coastlines. Melting polar ice has boosted sea level by more than three inches since the early 1990s, causing major flooding in low-lying areas of the world, such as Bangladesh, South Florida, and parts of coastal China. Increased temperature also fuels unusually intense hurricanes and cyclones, creating a one-two punch that may destroy infrastructure, overwhelm aging sewage systems, and expose residents to fecal pathogens.

Meanwhile, standing water from heavy rainfall is expanding ideal mosquito-breeding locations and a subsequent spread in insectborne diseases like Zika, dengue, and chikungunya. In a 2017 study published in PLOS Neglected Tropical Diseases, researchers found that, in many parts of the world, when temperatures rise, mosquitoes that transmit those infections not only thrive but increase their biting rate.

While the most salient aspect of climate change on the east coast of North America may be swamped coastlines, the rise in atmospheric temperature is responsible for intense drought in other regions. From southern California to South Sudan, shifting weather patterns are exacerbating already-dry conditions, evaporating surface water, and forcing residents to rely heavily on finite aquifers. As those sources drain from overuse, salt water can seep into them from the ocean, making much of their remaining water dangerous to drink. High heat can also bake moisture out of the topsoil, rendering entire farms infertile. In nations where subsistence farming is the norm, this catastrophic chain of events leads to malnutrition, starvation, population displacement, and regional conflict over dwindling resources.

“In areas like northeast Syria, drought-induced migration is sparking serious conflict. It’s part of what started the war there,” says Jennifer Leaning, François-Xavier Bagnoud Professor of the Practice of Health and Human Rights at the Harvard Chan School, and director of the Harvard FXB Center for Health and Human Rights. “This ripple effect of climate change is beginning to percolate within the larger consciousness of public health and development circles. There’s high urgency right now in figuring out, ‘What is Ghana going to do about food security? How is Nigeria going to deal with its drought-stricken northeast provinces? How is Chad going to make it as more and more of its countryside becomes desert?’”

WHO predicts that rising temperatures will cause approximately 250,000 additional deaths around the world between 2030 and 2050. While almost 95,000 of those deaths will be linked to childhood undernutrition due to disappearing cropland, 50,000 may stem from diarrheal diseases caused by sewage-contaminated water.

In the United States, waterborne pathogens like norovirus, the giardia parasite, and the salmonella bacterium already strike between 12 million and 19 million people annually—and increased rainfall is partly to blame. In the last century, annual precipitation jumped by 20 percent in U.S. Midwest. Much of that has come in the form of powerful storms that dump massive amounts of rain, overwhelming aging drainage systems and causing overflows of raw sewage.

In May 2000, a downpour in Walkerton, Ontario, Canada, tainted the city’s drinking water with E. coli bacteria from untreated human waste, infecting 2,300 people and killing seven. Other urban Great Lakes cities like Buffalo, Chicago, and Duluth, Minnesota, face similar scenarios that expose residents to infection—and if storms continue to intensify, these hazards will worsen. In a 2008 study at the University of Wisconsin, researchers predicted that the Great Lakes could experience a 50 percent to 120 percent increase in overflow events by the year 2100.

After a downpour in 2000, the water supply in Walkerton, Ontario was contaminated with E. coli bacteria from untreated human waste, killing seven residents and infecting 2,300. More frequent and intense storms, coupled with aging infrastructure, could leave other cities similarly at risk. Andrew Wallace / Reuters

“If we don’t dramatically reshape the urban landscape and make it much more impervious to heavy rainfall—by doing things like increasing urban vegetation or making paved surfaces more porous—then the runoff into these sewer systems is going to continue to promote overflow events and expose more people to harmful bacteria,” says Aaron Bernstein, associate director of the Center for Health and the Global Environment at the Harvard Chan School and instructor in pediatrics at Harvard Medical School.

Heavy rainfall can also lead to an uptick in insectborne diseases. WHO predicts that in the next three decades, 40,000 additional deaths worldwide may be caused by malaria, which is spread by mosquitoes in areas of standing water. Although the disease isn’t a problem in the U.S., other mosquitoborne ailments are. In 2012, the federal Centers for Disease Control and Prevention reported more than 5,600 cases of West Nile virus—an all-time record—leading to 286 deaths across the country.

Surprisingly, new research shows that lack of water can also foster the spread of certain insectborne infections. The worldwide Zika outbreak in 2015, for example, started in the midst of a historic drought in Brazil, brought on by an unusually powerful El Niño event that cut off normal rainfall in the region. Other ailments also spiked during that time, says Marcia Castro, associate professor of demography at the Harvard Chan School. “In São Paulo state, the drought got so bad that officials almost thought about rationing water. Yet that year, the region had the worst outbreak of dengue in history,” she says.

Castro notes that changing climate may promote these vectorborne infections. The mosquito that carries Zika, dengue, and chikungunya—Aedes aegypti—needs only a tiny amount of water to breed, and in urban areas it has no trouble finding that, even during dry periods. Small pools that exist perennially within trash piles, scrap yards, and makeshift water tanks are hot spots for the species.

“If you don’t have municipal water available during a drought, people will store water at home in different kinds of containers, many of which may be open to the air or not well sealed. Mosquitoes get into these quite easily,” says Castro. As temperatures rise, it boosts the rate at which those mosquitoes breed and feed, making them even more dangerous for residents, she adds.

Western Brazil, however, faces a different threat. Instead of Aedes, these regions are overrun by Anopheles mosquitoes, which carry the malaria parasite. This species likes to breed in areas of open water—and in the Amazon, some towns have unwittingly given them the equivalent of four-star hotels.

“Years ago, the Brazilian government promoted the opening of fish ponds in the deep Amazon to promote the livelihood of populations in that area. And it did—but fish ponds are lovely breeding grounds for Anopheles mosquitoes, so transmission of malaria went up,” says Castro. As the climate warms and the mosquitoes become more active, she adds, that transmission will continue to rise.

Simple solutions, like bed nets, work well for some species of the insect—but in the Amazon, Anopheles  mosquitoes usually feed outdoors at dawn and dusk, when residents are outside the home. That means spraying walls or hanging nets won’t help much. Instead, Castro says, the solution will require going straight to the source.

Marcia Castro, associate professor of demography at the Harvard Chan School, sprays biological larvicides on fish ponds near the Brazilian city of Mâncio Lima. The ponds are breeding grounds for malaria-carrying Anopheles mosquitoes, and as the climate warms and mosquitoes become more active, disease transmission is expected to rise. Photo courtesy of Marcia Castro.

Near the city of Mâncio Lima, a tiny municipality in the western Amazon, Castro is testing the efficacy of biological larvicides, chemical pellets that kill off young mosquito larvae. In photographs of her fieldwork, she looks like she’s reenacting a scene from Ghostbusters. Her right hand holds a long, gun-like nozzle, connected by a thick hose to a yellow plastic larvicide hopper on her back. With a pull of the trigger, she sends a burst of the tiny pellets into the water.

As strange as this looks, Castro says it could be an inexpensive way to to cut down on malaria transmission in the region. “We’re testing to see if this is a viable solution,” she says. “We’re planning to do a pilot program to decide the best product to use, and then we’re going to measure the impact on larval density, adult mosquito density, and transmission to humans.” That data, she notes, may prove a valuable tool for public health interventions in the region, helping to slow the impacts of changing climate on the spread of insectborne disease.

As more and more people move into the Amazon, however—some for mining jobs, others to try their hand at farming—Castro notes that an increasing proportion of forest will be cleared, creating new breeding grounds for Anopheles mosquitoes. In the process the new residents will  dump massive amounts of greenhouse gases into the atmosphere, further fueling the climate change cycle.

Changing the way farmers operate could help reduce the overall carbon footprint of Brazil and other nations. In fact, altering how humans produce food in general may be one of the most viable ways to avert warming temperatures, says Walter Willett, professor of epidemiology and nutrition at the Harvard Chan School.

“To really make a dent in climate change, we need to look at everything we consume, whether it be lettuce or fish, and figure out how to produce it in a way that’s sustainable,” he says. “Our current global food production system creates about 25 percent to 30 percent of total greenhouse gas emissions every year. So it’s a two-way street: Our food production affects water availability by contributing to climate change, and climate change in turn affects our ability to produce food.”

By tipping the scales away from livestock—which are water- and carbon-intensive and produce great amounts of methane—to a more plant-based diet, Willett says, it may be possible to nudge the global thermometer back in the other direction, especially if producers cultivate crops locally instead of transporting them across the globe. It’s not unfeasible: a 2008 study at Michigan State University showed that unheated greenhouses in areas with harsh winters were capable of  producing greens year-round. In the process, they could eliminate the need for fossil-fuel-intensive shipping.

To help reach this goal, Willett is partnering with the Culinary Institute of America to create menus that are both environmentally sustainable and attractive to consumers. “If done right, a plant-based diet has the potential to be more varied and enjoyable than our traditional diet, which is heavily animal-oriented,” Willett says. “Addressing climate change may be partly a matter of modifying our diets, and partly using new technologies like efficient drip irrigation to change food production.”

Improving public health in the face of a warming climate may also require humans to re-examine their basic relationship to water, says Aaron Bernstein. “Most people in developed nations treat water like air: you just turn on a tap and there it is. That’s an amazing state of affairs. I think we need to recognize that water is a completely irreplaceable resource—if we don’t have it, everything falls apart,” he says.

Developing nations already recognize the problem. India, which is on track to house nearly 20 percent of the world’s population by 2050, is already a water-scarce region. Populations living there will face not only the pressures of climate change, but also a lack of reliable infrastructure and water management plans, says S.V. “Subu” Subramanian, professor of population health and geography at the Harvard Chan School. As it is, he says, a majority of people in the nation don’t have regular access to clean water, which leads to a growing social inequity. “It is more or less guaranteed that the poor, particularly in low-income countries, will bear the most adverse health consequences of that inequity,” he notes.

Subramanian believes that solving these issues in the long term will require not only better governance of water use, but also shifting the focus toward local solutions. Without a vast network of pipelines, sending water over long distances can consume huge amounts of fossil fuels. By providing local governments with their own control over available water sources, it may be possible to reverse existing water inequities.

“My experiences in India have shown me that we can move forward by thinking on the scale of small towns or clusters of villages. We need decentralized units that are able to produce a sustainable system of harvesting local water resources,” he says. “If you think about electricity, it’s the same idea. Most rural villages are not on the grid at all—in fact, electrification has horribly low penetration in the country. But solar power has leapfrogged the need to lay down cables from production source to consumer, eliminating all the inefficiencies associated with it. We need to do the same thing with water.”

In other words, any viable solution to climate-change-induced water problems will require a return to some of the original goals of the public health profession, when the field sought to transform living conditions in major Western cities such as London and New York in the late 19th and early 20th centuries.

“Public health is environmental health,” Subramanian says. “We’ve been distracted by behavioral change for the last 30 years—don’t smoke, don’t drink. But if you think about the 19th and early 20th centuries, it was all about water and hygiene. That’s mostly a resolved issue in developed economies for now. In developing nations, though, we need to put water—and its vulnerability to climate change—near the top of the public health agenda.”

David Levin is a science writer based in Boston.