Abstract 2377: Heavy-metal exposure and cancer incidence in Puerto Rico

Abstract Background: Puerto Rico (PR) exhibits geographic variation in overall cancer incidence, with rising early-onset cases suggesting region-specific factors that shape cancer risk. Persistent toxic exposure to heavy metals associated with industrial activity and legacy pollutants may underlie these regional differences. Heavy metals are pervasive environmental contaminants; accumulating exposures have been linked to disruptions in DNA methylation and other epigenetic mechanisms that regulate the cell cycle, DNA repair, and immune function, providing a plausible biological basis for increased cancer susceptibility. Evidence from diverse populations links metal exposure to cancer risk, suggesting regional metal profiles may affect local cancer burden. To date, there have been only a limited number of studies testing the association between regional metal exposures and cancer incidence across PR. Objective: This study tests the hypothesis that population-wide exposure to heavy metal toxic releases aligns with cancer incidence patterns across PR when analyzed at the municipal level. Leveraging existing data, we integrated industrial-emission data from federal databases and cancer incidence records from the Puerto Rico Central Cancer Registry (PRCCR) spanning 2018-2022. Methods: Age-adjusted incidence rates for overall and early-onset cases of the most prevalent cancer types in PR were obtained from the PRCCR for the period 2018-2022. Metal emission data were sourced from the U.S. EPA Toxics Release Inventory for 2008-2018 and aggregated at the municipality level. Out of 78 municipalities, 23 were identified with positive emissions values and were included in the analysis. Spearman correlations with p-values were used to quantify relationships between heavy metal emissions and cancer rates. Bivariate choropleth maps using Jenks Natural Breaks and proportional symbols were used to visualize geographic patterns. Statistical analyses were conducted in R 4.3.2 using RStudio, and spatial mapping was done in QGIS 3.40. Results: Mercury and lead exposure showed the strongest associations with overall cancer incidence, with r = 0.70 (p < 0.001) and r = 0.68 (p < 0.001), respectively. Lead and mercury also correlated with prostate cancer (r = 0.53, p < 0.01; r = 0.65, p < 0.001). Mercury and nickel were associated with leukemia (r = 0.40, p < 0.05; r = 0.41, p < 0.05). Cobalt and zinc were associated with thyroid cancer (r = 0.467, p < 0.05; r = 0.69, p < 0.001). Additionally, these metals correlated with early-onset thyroid cancer (r = 0.42, p < 0.05; r = 0.45, p < 0.05). Manganese showed associations with both overall and early-onset uterus cancer (r = 0.40, p < 0.05; r = 0.38, p < 0.05). Conclusion: Collectively, these patterns suggest that specific metal exposure may contribute to cancer risk. Future work should incorporate other exposure routes and pursue hypothesis-driven studies to identify targeted prevention strategies for high-exposure regions. Citation Format: Ingrid M. Montes-Rodríguez, Yoel A. Velázquez-Oliver, Hilmaris Centeno-Girona, Camille Zenon, Elba V. Caraballo. Heavy-metal exposure and cancer incidence in Puerto Rico [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2377.