Low Dose, Long Career:
A Slowly Accumulating Risk

Healthcare professionals working with ionising radiation — radiologists, radiographers, interventional cardiologists, nuclear medicine technologists, radiotherapy staff — represent the largest single occupational group with chronic, low-level radiation exposure. Unlike high-dose, acute exposure scenarios, the health implications of years or decades of low-dose occupational exposure remain a subject of active scientific scrutiny.

The dominant regulatory framework, built around dose limits recommended by the International Commission on Radiological Protection, is designed on the assumption that risks scale linearly with dose and that compliance with limits ensures acceptable risk. What this 2025 systematic review — published in the Journal of Radiological Protection — asks is a more pointed question: even within those limits, what is the biological evidence of harm?

How the Review
Was Constructed

The review followed PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), the internationally recognised standard for systematic review methodology. Articles were sourced from three major databases — Scopus, PubMed, and Web of Science — and restricted to publications in English from January 2019 to December 2023, ensuring the evidence base reflects the most current five-year period of research.

Inclusion required that studies specifically addressed adverse biological effects in healthcare professionals in medical applications — excluding general population, patient, or industrial radiation exposure studies. The professions covered spanned interventional cardiology, radiology (diagnostic and interventional), radiotherapy, and nuclear medicine.

Four Categories
of Biological Impact

The review identified four primary areas where the evidence of biological effect from occupational radiation exposure is consistent and substantiated. These are not theoretical risks extrapolated from high-dose studies — they are biological markers measured directly in exposed healthcare workers.

Speciality Matters:
Interventional Staff Lead Exposure

The review's breakdown of included studies by clinical speciality reveals where the evidence of biological impact is most concentrated. Of the 32 studies meeting inclusion criteria, five focused specifically on interventional cardiologists — a cohort particularly well-represented in the genotoxicity and lens opacity literature. Nineteen studies included radiology and radiotherapy department staff, reflecting the breadth of occupational exposure across imaging specialities.

Interventional cardiology emerges as a speciality of particular concern, owing to the combination of high fluoroscopy time per procedure, close operator proximity to the radiation source, and the cumulative nature of exposure over a long career of high-volume procedural work. The biological evidence documented in the review is, for this group, extensive and specific.

Dose Limits Are a Floor,
Not a Guarantee

Perhaps the most important conceptual contribution of this review is the implicit challenge it poses to complacency about dose limit compliance. Current regulatory limits — 20 mSv per year averaged over five years for whole-body dose, with a 50 mSv ceiling in any single year — are designed as the upper boundary of acceptable occupational exposure, not a safe threshold below which no biological effect occurs.

The evidence reviewed by Lopes, Teles and Santos documents measurable biological effects — chromosomal aberrations, elevated micronuclei frequency, lens changes, genotoxic markers — in workers whose recorded doses fall within those limits. This is not a contradiction of the regulatory framework; it is a reflection of the linear no-threshold model on which that framework is built. The implication is that minimising dose, rather than simply staying within limits, remains the appropriate professional and institutional standard.

The ALARA principle (as low as reasonably achievable) has been the cornerstone of radiation protection practice for decades. This review's findings are a reminder of the biological rationale behind it — and of the importance of protective equipment, dose monitoring, technique optimisation, and departmental culture in keeping occupational exposure genuinely minimal.

What This Means
for Radiation Protection Practice

The systematic review does not prescribe clinical solutions — its purpose is to characterise the evidence base, not to evaluate interventions. But the findings have clear implications for how departments, employers, and individual practitioners should approach occupational radiation protection.