Tens of millions of people worldwide remain at risk of chronic arsenic exposure, including populations in Bangladesh, India, Pakistan, Taiwan, Vietnam, Mexico, China, Argentina, Chile, and the United States. Drinking contaminated well water remains the most important route of exposure in many settings, although diet can become a dominant source once water is controlled. Rice and rice-based products contribute measurable inorganic arsenic intake, and the European Union, Taiwan, and the United States have established regulatory limits for inorganic arsenic in rice, with stricter thresholds for infant foods. Brown rice generally contains higher arsenic concentrations than polished white rice, because arsenic accumulates in the outer husk layers.

Interpreting arsenic biomarkers is complicated by seafood, which contains mostly organic arsenic species such as arsenobetaine that are considered of low toxicity and rapidly excreted. Nevertheless, seafood consumption can elevate urinary arsenobetaine and dimethylarsinate, muddying the use of total urinary arsenic as a proxy for inorganic exposure in seafood-consuming populations. Urinary arsenic speciation, which separates inorganic arsenic and its methylated metabolites monomethylarsonic acid and dimethylarsinic acid, offers a more informative metric. In a long follow-up cohort from an arsenicosis-endemic area, low-to-moderate exposure was associated with urothelial tract cancers, with susceptibility signals concentrated among individuals with lower primary methylation index or higher secondary methylation index, indicating that the body’s capacity to methylate arsenic shapes disease risk.

A striking translational advance is an artificial intelligence-based, noninvasive tool that estimates arsenic exposure from standardized photographs of the hands and feet. The algorithm leverages cutaneous stigmata such as hyperkeratosis patterns to classify exposure categories, potentially enabling scalable screening where laboratory testing is limited. This matters because arsenic leaves visible fingerprints on the skin: palmoplantar hyperkeratosis and variegated pigmentation are clinical hallmarks of chronic poisoning, and arsenic-associated skin cancers are distinguished from classical UV-related skin cancers by their multiplicity and their predilection for sun-spared skin.

The skin serves as a sentinel organ for both exposure and immune disruption. Arsenic is classified by the International Agency for Research on Cancer as a Group 1 carcinogen, yet it is often considered a weak mutagen, acting predominantly at the promotion rather than initiation stage of chemical carcinogenesis. After decades of exposure, skin cancers and keratosis may precede internal cancers of the bladder, lung, and liver, making cutaneous lesions an early surrogate indicator of systemic risk. The observation that only a subset of exposed individuals develop cancers or vascular disease suggests that host factors, including immune responses, modulate susceptibility. In patients with arsenic-associated cancers, the in vivo delayed-type hypersensitivity response, which depends on antigen-presenting cells and T cells, is impaired, and in blackfoot disease, anti-endothelial cell IgG antibodies drive endothelial proliferation and VEGF-dependent angiogenesis.

Experimental evidence reveals how arsenic differentially affects immune cell types. Arsenic selectively induces Fas-dependent apoptosis of Th2 lymphocytes, mobilizes epidermal Langerhans cells, the professional antigen-presenting cells of the epidermis, and polarizes Th1 responses in arsenical cancers. Macrophages from exposed individuals show reduced adhesion capacity and impaired phagocytosis, while monocytes from exposed children produce less superoxide anion and nitric oxide. Cytokine signatures are context-dependent: in a mouse epicutaneous sensitization model, arsenic elevated IFN-γ and IL-12 secretion, supporting Th1 polarization, but in humans with arsenic-induced skin lesions, stimulated T-cell proliferation is dose-dependently impaired with reduced IFN-γ, TNF-α, and IL-2 output. Population studies in Bangladesh reported elevated circulating type 2 cytokines, eotaxin, and IgE in exposed individuals with skin lesions, while ex vivo stimulation assays showed broader cytokine suppression, indicating that steady-state serum signatures and stimulated T-cell capacity can diverge by disease stage.

Innate inflammatory pathways emerge as a consistent theme. Subchronic arsenic exposure activates the AIM2 inflammasome in human keratinocytes and mouse skin, leading to caspase-1 activation and increased IL-1β and IL-18 production. Analyses of human skin samples in arsenic-related pathology have reported increased IL-6 and IL-17 levels with progressive increases across worsening skin-damage severity, while functional T-cell assays from exposed individuals have reported decreased IL-10 secretion. Dose-response relationships appear non-linear: within low-to-moderate exposure ranges, several studies support dose-related shifts toward innate immune activation and systemic inflammation, with West Bengal women exposed to 11–50 μg/L arsenic in groundwater showing increased monocyte CD14 expression, NF-κB signaling, and elevated circulating TNF-α, IL-6, IL-8, and IL-12 alongside reduced IL-10. At higher cumulative exposures or in patients with established arsenic-associated cancers, evidence points toward adaptive immune suppression, particularly impaired T-cell responsiveness.

Perinatal exposure represents a critical window for immune programming. In a Taiwanese birth cohort with 15-year follow-up, prenatal heavy metal exposure including arsenic was associated with cord blood IgE levels and distinct IgE trajectory patterns in relation to atopic diseases. Prenatal inorganic arsenic exposure was also linked to higher risk of atopic dermatitis in young children, and a U.S. cord-blood study showed that maternal arsenic levels were inversely associated with cord-blood T helper memory cells. Prenatal co-exposure to other metals may further modify risk; a study from China reported that prenatal co-exposure to higher levels of arsenic and thallium contributed substantially to the combined risk of allergic rhinitis. These findings highlight developmental immunotoxicology as a frontier for integrating arsenic exposure, cutaneous immunology, and allergic disease risk across the life course.

Genetic and epigenetic susceptibility further shape individual risk. TIMP3 promoter polymorphisms were associated with increased susceptibility to arsenic-induced skin cancer in an exposed cohort, with in silico analyses suggesting allele-specific transcription factor binding effects that influence matrix metalloproteinase activity and tissue architecture. Arsenic methylation capacity, repeatedly implicated in differential disease risk, is itself coupled to inherited variation: AS3MT haplotype status has been associated with DNA methylation and expression of multiple genes near AS3MT, illustrating how germline variation can shape the epigenetic context for exposure response. The review’s authors propose that integrating genotype, methylation indices, immune phenotyping, and clinical outcomes could operationalize risk stratification, while water mitigation, which has been associated with a reduced burden of arsenic-related cancers in Taiwan with substantial age-cohort effects, remains the cornerstone of primary prevention. Because cancer risk persists for years to decades after exposure reduction, targeted long-term surveillance of previously exposed communities, combined with scalable phenotyping tools and precision prevention strategies, offers the most promising path forward for the tens of millions still living with arsenic’s invisible immune legacy.

Subject of Research: Immune dysregulation as a mechanism linking chronic arsenic exposure to cancers and allergic disease

Article Title: Immune perturbation in arsenic-induced adverse health effects and cancers

Article References: Hong, C.-H., Yu, S., Wang, S.-L., Yu, H.-S., & Lee, C.-H. (2026). Immune perturbation in arsenic-induced adverse health effects and cancers. Journal of Cutaneous Immunology and Allergy, 9, Article 16386. https://doi.org/10.3389/jcia.2026.16386

Image Credits: AI Generated

DOI: 10.3389/jcia.2026.16386

Keywords: arsenic, immune dysregulation, skin cancer, environmental toxicology, allergic disease, biomonitoring, perinatal exposure, genetic susceptibility, Immune, perturbation, arsenic-induced, adverse