Cumulative low-dose ionizing radiation exposure in frequent emergency department encounters and implications of carcinogenic risk.

e23157 Background: Repeated low-dose ionizing radiation (IR) over short intervals can accumulate causing DNA damage and increased long-term carcinogenic risk. Frequent emergency department (ED) users may represent an underrecognized population at risk for clinically significant cumulative radiation exposure. We quantified cumulative IR exposure among frequent ED users and identified demographic and clinical factors associated with elevated exposure relevant to malignancy risk. Methods: 714 patient records were abstracted from 404,000 ED encounters (June 2021–June 2023). Encounters per patient over 2 years were stratified by frequency. 20 patients per stratum were randomly sampled for 1–25 visits and all patients with > 25 visits were included (n = 214) Radiologic imaging type and anatomic region were recorded, cumulative IR exposure was calculated using a standardized dosage table (mSv). Demographics and comorbidities were abstracted. Patients were categorized by cumulative exposure ≥100 mSv vs < 100 mSv, 50 mSv was considered a clinically significant annual threshold. Linear regression modeled encounters required to reach high-risk thresholds. Results: Mean age 48 ± 19 years, 60.6% female, 63.6% White, Medicaid predominated. Mean ED encounters: 22 ± 21, mean CT scans: 11 ± 12 per patient. Mean cumulative IR: 114 ± 129 mSv. Regression modeling demonstrated that approximately 17 ED encounters over 2 years sufficient to reach 100 mSv. Age weakly correlated with IR (r = 0.185, p < 0.001), females had higher exposure (p = 0.04), race differences were not observed. Total imaging strongly correlated with cumulative IR (r = 0.842, p < 0.001). Psychiatric/behavioral health diagnoses including mood disorders, anxiety, chronic pain, substance use and nonadherence were significantly associated with exposure ≥100 mSv (all p < 0.05). Conclusions: Among very frequent ED users, particularly socioeconomically disadvantaged females with psychiatric comorbidities, cumulative IR exposure was substantial with approximately half of patients exhibiting exposure ≥100 mSv a dose range linked to higher risk of solid and hematologic malignancies. Although 95.3% of encounters and 99.6% of patients were not at concern a small but clinically meaningful subset accrued high exposure. Emerging data suggest that cumulative exposures near 50 mSv may also confer deleterious risk. Findings identify an underrecognized at-risk population and support targeted imaging stewardship to mitigate long-term oncologic risk.