Marine microplastic pollution and cancer incidence from 2013 to 2021 in US coastal counties: an ecological analysis.

BACKGROUND

Microplastics (MPs) are pervasive environmental contaminants detected in human tissue samples, including the lungs, liver, placenta, gastrointestinal tract, and tumors. Previous studies suggest carcinogenic mechanisms, including oxidative stress, DNA damage, metabolic disruption, and chronic inflammation. However, population-level evidence linking environmental MP contamination to cancer incidence remains limited.

OBJECTIVE

Evaluate ecological associations between environmental MP contamination and site-specific cancer incidence across U.S. coastal counties.

METHODS

Ecological analysis of U.S. coastal counties was conducted using 2013-2021 Surveillance, Epidemiology, and End Results (SEER) Program data. Applying 20 km buffers, National Oceanic and Atmospheric Administration (NOAA) MP data was spatially linked with counties to generate exposure scores (ranges 1-5). Annual county-level cancer incidence was merged with sociodemographic, behavioral, and environmental covariates. Association estimates using Poisson regression models applied fixed year effects, population offsets, and county-clustered robust standard errors. Incidence rate ratios (IRRs) were reported per 1-unit MP score increase, with false discovery rate controlled at 5%.

RESULTS

MP data was linked to 89 coastal counties comprising a mean annual population of ∼54 million residents. 1-unit MP score increases were associated with moderate increases in overall cancer incidence (IRR = 1.01; 95% CI: 1.01-1.02; q = 0.004). Each cancer site was modeled separately. After false discovery rate correction, positive associations were observed for digestive, endocrine, oral cavity and pharynx, respiratory, and male genital cancers (site-specific IRRs 1.02-1.05). Subsite analyses showed heterogeneity, with associations for several digestive cancers, thyroid, prostate, lung and bronchus cancer, and acute myeloid leukemia. Sensitivity analyses found all findings consistent.