In the neighborhoods surrounding Puerto Rico's most contaminated sites, a silent threat is fueling a public health crisis.
Picture an island with sparkling beaches and lush rainforests, yet beneath this natural beauty lies a troubling reality: Puerto Rico has one of the highest densities of Superfund sites in the United States. These are the nation's most hazardous toxic waste locations, designated for federal cleanup. For decades, these sites have leaked dangerous chemicals into soil and groundwater, creating a lingering environmental threat.
Puerto Rico's age-adjusted thyroid cancer incidence rate is twice that of the mainland United States3 .
Meanwhile, Puerto Rico is experiencing a parallel health emergency. This alarming disparity has prompted scientists to ask a critical question: Could these two crises be connected? Emerging research is now uncovering disturbing patterns, revealing how contamination and cancer risk cluster together in specific Puerto Rican communities, with marginalized populations often bearing the heaviest burden.
The Superfund program, established by Congress in 1980, empowers the Environmental Protection Agency (EPA) to clean up the most severely contaminated sites across the United States. These locations are plagued by hazardous substances that pose serious risks to human health and the environment. Sites that make it onto the National Priorities List represent the "most serious sites identified for long-term clean up".
Puerto Rico hosts at least 18 active Superfund sites on the National Priorities List5 . This high concentration stems from a combination of factors:
The map of Puerto Rico's Superfund sites reveals contamination spread across the island, from the Cabo Rojo Ground Water Contamination site in the southwest to the Vieques weapons training area in the east5 .
Interactive map showing Superfund site locations across Puerto Rico
Linking specific environmental exposures to cancer patterns is scientifically complex. Cancer develops over years or decades, and people encounter numerous potential risk factors throughout their lives. However, scientists have established several biological mechanisms through which chemicals from Superfund sites can increase cancer risk:
Research has focused on heavy metals like cadmium, lead, and mercury—all identified at elevated levels in Puerto Rican soil3 . These metals are known endocrine disruptors that can interfere with hormonal systems. The thyroid gland, which regulates metabolism, is particularly vulnerable to these disruptions. Cadmium is additionally classified as a known carcinogen with the potential to directly trigger cancerous changes in cells3 .
Puerto Rico's geological history as a once-active volcanic island adds another layer to this story3 . Volcanic regions naturally have higher concentrations of heavy metals in their soil. Studies of populations near Mount Etna in Sicily found that those living closest to the volcano had double the risk of papillary thyroid cancer compared to those further away3 . This same phenomenon may be contributing to Puerto Rico's elevated thyroid cancer rates.
The distribution of Superfund sites isn't random. Analysis reveals that over half of pharmaceutical facilities with recent environmental violations are located within three miles of predominantly low-income communities of color. One investigation found that "geographic areas with Superfund sites tend to have elevated cancer risk, and also elevated proportions of minority populations"8 . This pattern represents a form of environmental racism where marginalized communities disproportionately bear the health burdens of industrial pollution.
| Heavy Metal | Health Effects | Status in Puerto Rico |
|---|---|---|
| Cadmium | Known carcinogen; endocrine disruptor | Elevated concentrations in soil; potential link to thyroid cancer3 |
| Lead | Endocrine disruptor; neurotoxic | Elevated concentrations in soil; detected at multiple Superfund sites3 |
| Mercury | Endocrine disruptor; neurotoxic | Elevated concentrations in soil; significant negative association with thyroglobulin antibody3 |
Scientists use sophisticated statistical methods called cluster analysis to identify patterns in complex health and environmental data. This approach "makes it possible to group EU members states into distinct country clusters" based on cancer risk factors7 , and the same methodology can be applied at the local level to map connections between Superfund sites and cancer incidence across Puerto Rican municipalities.
Recent research has revealed striking geographical patterns:
| Site Name | Municipality | Key Contaminants | Status |
|---|---|---|---|
| Barceloneta Landfill | Florida | Heavy metals, VOCs | Deleted from NPL (2011)2 |
| Fibers Public Supply Wells | Guayama | Asbestos, VOCs | Ongoing cleanup2 |
| Cabo Rojo Ground Water | Cabo Rojo | Volatile organic compounds | Plan implemented (2019)2 |
| Upjohn Facility | Barceloneta | Carbon tetrachloride | On NPL |
| GE Wiring Devices | Juana Díaz | Mercury | Deleted from NPL (2000)2 |
Interactive visualization showing cluster analysis of cancer rates and Superfund site locations
The municipality of Barceloneta represents a microcosm of Puerto Rico's broader challenges. This area hosts multiple Superfund sites linked to pharmaceutical manufacturing, including facilities associated with AbbVie, Merck, Pfizer, and Upjohn.
The story began decades ago when manufacturing operations led to groundwater contamination with toxic chemicals including carbon tetrachloride—a highly toxic liquid used for insecticides, cleaning fluids, and refrigerants.
At the Upjohn facility, an underground storage tank leaked, resulting in "the loss of an important groundwater supply" for the local community.
Despite cleanup efforts, the environmental legacy persists. The EPA continues to oversee remediation at the Upjohn facility, which remains on the National Priorities List due to "extremely high concentration of toxic waste".
The burden falls disproportionately on nearby residents, who face potential exposure to contaminated groundwater and air pollutants. The situation in Barceloneta illustrates how historical contamination and ongoing violations create cumulative health risks that demand more comprehensive regulatory response.
Pfizer's Barceloneta facility has been continuously violating the Lead and Copper Rule for drinking water since 2020.
Current Status: Ongoing remediation at multiple sites; continued environmental violations by pharmaceutical companies.
Epidemiologists use specific methods and tools to investigate potential links between environmental hazards and cancer risk:
This approach compares geographical patterns of contamination with disease incidence across different regions. Researchers might analyze metal concentrations in soil samples from various municipalities alongside cancer registry data to identify overlapping hotspots3 .
Scientists use biological indicators to measure exposure and potential health effects. In studying thyroid cancer, researchers might examine thyroglobulin antibodies (TgAb), which are "found to be more than twice as high in patients with differentiated thyroid cancers than in the general population"3 .
Advanced statistical methods like the spatial scan statistic help identify locations where cancer rates are significantly higher than expected8 . These tools can detect disease clusters and determine whether they correlate geographically with environmental hazards.
Mapping technology allows researchers to visualize the overlap between contaminated sites, demographic data, and health outcomes, revealing patterns that might be missed in traditional analyses.
| Method | Application | Example |
|---|---|---|
| NHANES Analysis | Assess association between metal exposure and thyroid antibodies | Analysis found significant negative association between mercury and thyroglobulin antibody3 |
| Spatial Scan Statistics | Identify geographic clusters of disease | Used to detect "locations and relative risks of spatial clusters in cancer rates"8 |
| Environmental Sampling | Measure contaminant levels in soil/water | Testing for volatile organic compounds in groundwater near Superfund sites2 |
| Cancer Registry Analysis | Track incidence patterns over time | Revealed Puerto Rico's thyroid cancer rate is double the U.S. average3 |
The clustering of Superfund sites and cancer risk in Puerto Rican municipalities represents both an urgent public health challenge and a stark environmental justice issue. Research continues to reveal the complex connections between the island's industrial legacy and the health of its people.
While cleanup efforts at some Superfund sites have been completed—with several locations deleted from the National Priorities List after remediation2 —many contaminated areas continue to threaten community health and groundwater resources.
As scientific understanding advances, the hope is that targeted interventions can reduce cancer risks and address the legacy of environmental contamination. The story of Puerto Rico's Superfund sites serves as both a cautionary tale and a call to action for communities everywhere facing similar challenges at the intersection of industry, environment, and public health.
Several locations have been deleted from the NPL after remediation2 .
Research continues to reveal connections between contaminants and health effects.
Environmental justice movements are bringing attention to these issues.