PROVIDENCE – Walking along the Providence River today, it is replete with wildlife: ducks and geese paddle lazily through the slow-flowing water, and fish dart through the shallows as people stroll along the banks. Yet despite this liveliness, danger lurks below the surface: people are advised against swimming and fishing in the Providence River. 

Alongside bacteria and other pollutants, heavy metals such as lead and arsenic swirl in its currents and lie dormant in the sediment at the bottom – a legacy of Providence’s industrial past that may be exacerbated as the earth warms. In the face of this threat, the Ibarra Lab at Brown University has launched a project to better understand the impact of climate change on metal pollution in the Providence watershed.

Gavin Piccione sits at his desk in sturdy boots and canvas work pants, looking ready to rush out and collect samples from the river at a moment’s notice. On the wall, a huge map of Narragansett Bay hangs side-by-side with a Star Wars poster. As a postdoc in the Ibarra Lab, Piccione is one of the chief investigators spearheading the climate change and metal pollution project. 

“We started off thinking about this as sort of a lead exposure project. And then we realized that, based on our skills … we can use our understanding to have predictive power,” Piccione said. 

The team continued studying lead exposure but expanded the scope of the project to include a variety of heavy metals including lead, arsenic, cadmium, zinc, and copper. Over the past year, they have periodically measured the concentrations of these metals in select locations along the river system, forming a picture of where metal is concentrated in the rivers and how its levels change with time and various environmental factors. 

Some of the results, Piccione says, are encouraging. The concentration of metals in water samples exhibits relatively small fluctuations between sites, even at sites with significant legacy pollution like the Centredale Manor Superfund site. This means that the polluted sites are no longer actively releasing pollutants, and that remediation efforts are working. 

This finding is big news for Providence: legacy pollution, or pollution that persists in the environment long after it is initially produced, is deeply entwined with the city’s history. From the late 18th to the mid-20th centuries, Providence boasted a thriving manufacturing community that produced textiles, jewelry, and other goods. However, these factories often polluted the land and water around them; many factories directly dumped their waste into the river until it was paved over in the 1930s. 

Environmental regulations such as the Clean Water and Clean Air Acts, starting in the 1970s, followed by more recent river restoration initiatives and the decline of manufacturing in Providence, have reduced the river’s toxicity. The Ibarra Lab’s study has provided a concrete affirmation of the efficacy of remediation efforts.

While the river water shows relatively low metal levels, the riverbed sediment is a different story. The Ibarra Lab has identified elevated concentrations of metal in the sediment near known legacy pollution sites, suggesting that at least some of the pollution has remained over the decades since it was first deposited. 

Although most of these metals have mineralized, meaning they have converted into relatively stable forms, Piccione explains that chemical and physical disturbances can cause them to remobilize and dissolve into the water, making them more likely to come into contact with plants, animals, and humans.

While the effects of heavy metals on the ecosystem are not fully known, past studies have found that they can accrue in plants and animals, working their way up the food chain and growing more concentrated. This effect has also been observed with pollutants like mercury and is why people are often advised to avoid eating predatory fish higher in the food chain.

The Ibarra Lab is currently transitioning to the next phase of its project: identifying modern sources that are contributing metals to the river water. Piccione acknowledges that establishing cause-and-effect relationships will be much more difficult than simply measuring metal levels in the river. However, doing so will be an important milestone in the project’s broader goal of studying how heavy metal moves through the ecosystem and could inform future policy aimed at reducing heavy metal pollution. 

While the data are still preliminary, Piccione says that one of the most significant predictors of metal concentration in the water is precipitation. About once a month, the team stakes out the river in a tent to measure metal levels in 15-minute increments before, during, and after a rainstorm. They consistently observe a spike in metal concentrations as soon as runoff from the city reaches the river. 

While they have yet to conclusively identify the source, Piccione says the most likely culprits are modern infrastructure such as roads and other impervious surfaces – rainwater carries metals from these sources into the river. This mechanism is one of the clearest impacts of global warming on metal pollution: as the earth warms, Providence will experience more rain more frequently. Annual rainfall in Rhode Island has increased by about 5 inches per year since 1900 – significantly increasing the amount of metal being washed into waterways. To better understand these sources of pollution, research has taken Piccione further inland, examining potential metal sources throughout the Providence watershed. 

Collaborating with Scott Frickel, a sociologist at Brown who has compiled a detailed history of the timing and locations of legacy pollution in Rhode Island, the Ibarra Lab has taken samples from the soil of suspected pollution sites throughout the area. They found that many known legacy pollution sites still had traces of heavy metals. More strikingly, newer sources of pollution, such as small laundromats, are often overlooked for cleanup of the site before it is repurposed, despite soil testing revealing elevated metal concentrations. 

For now, the Ibarra lab is focusing surveying efforts on the places where people spend the most time in contact with soil: personal and community gardens. With the owners’ consent, lab members take soil samples from the gardens to test for concentrations of different metals and inform the owners if elevated metal levels are detected. 

They are also currently consulting with experts in Brown’s Department of Epidemiology and at the Warren Alpert Medical School to design robust assessment methods for the health effects of living at these sites. Piccione says it won’t be easy, but that the outcomes are still important. 

“People have done a lot of analysis on acute exposures,” Piccione said. “It’s easy to link someone whose job exposes them to lead … but environmental hazards play out over decades.” 

Metal pollution remains a pressing concern for many in Rhode Island. Recently, concerns about pollution have overshadowed the Army Corps of Engineers’ plan for dredging of the Providence River. The hulking 694-page outline, released by the Corps in May 2025, describes a plan to move approximately 4.8 million cubic yards of dredged sediment into a covered underwater pit called a contained aquatic disposal (CAD) cell in Edgewood Shoals, just off the eastern coast of Cranston. 

Several objections and suggestions to the plan were raised by Save The Bay, a nonprofit organization dedicated to protecting and improving Narragansett Bay, including a relocation of the CAD cells to an alternative location where fewer polluted sediments already in the seabed would be disturbed.

Weston de Lomba, a Cranston native, spends a great deal of time fishing on the east coast of Cranston, just downstream from Edgewood Shoals, and said that he often swims in the water to retrieve his lures. He stated that he had not been informed about the plan and was opposed to it. 

“I know you shouldn’t swim there anyway, but that’s all because of Providence, right? ‘Cause they’re always dumping stuff in the rivers … they should bring it somewhere else,” de Lomba said. His concerns were shared by the Edgewood Yacht Club, the members of which often sail in the proposed disposal area, and the Rhode Island Shellfisherman’s Association, which recommends relocation of the estimated 8 million quahogs living in the area where CAD construction is planned. 

The dredging project is just one of the many ways in which Rhode Islanders must continue to grapple with metal pollution. Despite the pollution’s prevalence, Piccione says he remains optimistic. 

“There’s a lot of evidence that we’ve been moving in the right direction, and I think that by doing work like this and working with community partners, we can inform residents…and eventually bring knowledge to policymakers.”

He said he hopes that the Ibarra Lab’s project will help guide future policy changes regarding remediation of polluted sites. 

This story was published as part of a collaboration between ecoRI News and students in Brown University’s Science Journalism class. The stories examine the science, history, and human experiences connected to the Ocean State’s rivers — from water quality and wildlife restoration to flooding, pollution, social justice, and the communities working to protect them. To read more of these stories, click here.