Low-dose Exposure Group Research Articles

Quantitative evaluation of light scattering intensities of the crystalline lens for radiation related minimal change in interventional radiologists: a cross-sectional pilot study

To evaluate low-dose X-ray radiation effects on the eye by measuring the amount of light scattering in specific regions of the lens, we compared exposed subjects (interventional radiologists) with unexposed subjects (employees of medical service companies), as a pilot study. According to numerous exclusionary rules, subjects with confounding variables contributing to cataract formation were excluded. Left eye examinations were performed on 68 exposed subjects and 171 unexposed subjects. The eye examinations consisted of an initial screening examination, followed by Scheimpflug imaging of the lens using an anterior eye segment analysis system. The subjects were assessed for the quantity of light scattering intensities found in each of the six layers of the lens. Multiple stepwise regression analyses were performed with the stepwise regression for six variables: age, radiation exposure, smoking, drinking, wearing glasses and workplace. In addition, an age-matched comparison between exposed and unexposed subjects was performed. Minimal increased light scattering intensity in the posterior subcapsular region showed statistical significance. Our results indicate that occupational radiation exposure in interventional radiologists may affect the posterior subcapsular region of the lens. Since by its very nature this retrospective study had many limitations, further well-designed studies concerning minimal radiation-related lens changes should be carried out in a low-dose exposure group.

The persistent risk of genital tumors among men treated with psoralen plus ultraviolet A (PUVA) for psoriasis

Background: In the general population, squamous cell carcinomas (SCCs) of the male genitalia are rare. Ten years ago, we documented a significant dose-dependent increase in the risk of malignant genital neoplasms among men treated with psoralen plus ultraviolet A (PUVA). Since that time, fewer cohort patients have used PUVA, and genital protection among PUVA users is likely to be frequent. Objective: Our aim was to determine the incidence and risk factors for genital neoplasms since 1989 and risk factors for these neoplasms among patients treated with PUVA. Methods: We conducted a prospective cohort study of 892 men first treated with PUVA in 1975-1976. Results: Twenty-four men (2.7%) had 51 genital neoplasms, including 10 patients with a first tumor after May 1, 1989 (the ending date for our 1990 report). Since May 1, 1989, the incidence of invasive penile and scrotal SCCs was elevated 52.6-fold (95% confidence interval, 19.3-114.6) compared with that expected for the general white population. Multivariate models revealed the highest genital tumor risk among men with high-dose exposure to both PUVA and topical tar/ultraviolet B, with an incidence rate ratio of 4.5 (95% confidence interval, 1.3-16.1) compared with the low-dose exposure group. Conclusion: Although use of PUVA has decreased and genital shielding in our cohort has increased, the dose-dependent increase in the risk of genital tumors in men treated with PUVA has persisted. Particularly high risks occur among those with high-dose exposures to both PUVA and topical tar/ultraviolet B. (J Am Acad Dermatol 2002;47:33-9.)

Radiation Hormesis and Cancer

Despite the long history of radiation hormesis and the public health concerns with low-level exposures to ionizing radiation, there has been surprisingly little formal evaluation of whether hormetic effects are displayed with respect to radiation exposure and cancer incidence (i.e., reduced cancer risk at low radiation doses compared to controls, enhanced cancer risk at higher doses) until relatively recently. This paper reviews data relevant to the question of radiation hormesis and cancer with particular emphasis on experimental studies in animal models exposed to low levels of ionizing radiation. Data exist that provide evidence both consistent with and/or supportive of radiation hormesis. Other biomedical research provides potentially important mechanistic insight: low dose exposures have the capacity to activate immune function to prevent the occurrence of tumor development and metastasis; low doses of radiation have been shown to reduce mutagenic responses and induce endogenous antioxidant responses. These findings are consistent with epidemiological data suggesting an inverse relationship between background radiation and cancer incidence and with occupational epidemiological investigations in which low-dose exposure groups display markedly lower standardized mortality rates than the referent or control group.