Ionizing radiation exposure to the lens of the eye is a known cause of cataractogenesis. Historically, it was believed that the acute threshold dose for cataract formation was 5 Sv, and annual dose limits to the lens were set at 150 mSv. Recently, however, the International Commission on Radiological Protection has reduced their threshold dose estimate for deterministic effects to 0.5 Gy and is now recommending an occupational limit of 20 mSv per year on average. A number of organizations have questioned whether this new threshold and dose limit are justified based on the limited reliable data concerning radiation-induced cataracts. This review summarizes all of the published human epidemiological data on ionizing radiation exposure to the lens of the eye in order to evaluate the proposed threshold. Data from a variety of exposure cohorts are reviewed, including atomic bomb survivors, Chernobyl liquidators, medical workers, and radiotherapy patients. Overall, there is not conclusive evidence that the threshold dose for cataract formation should be reduced to 0.5 Gy. Many of the studies reviewed here are challenging to incorporate into an overall risk model due to inconsistencies with dosimetry, sample size, and scoring metrics. Additionally, risk levels in the studied cohorts may not relate to occupational scenarios due to differences in dose rate, radiation quality, age at exposure and latency period. New studies should be designed specifically focused on occupational exposures, with reliable dosimetry and grading methods for lens opacities, to determine an appropriate level for dose threshold and exposure limit.

Thermal discharges released from industrial cooling water systems represent a potential environmental risk to fish species that spawn in nearshore waters. We investigated the impacts of in situ incubation of lake whitefish (Coregonus clupeaformis) embryos in the vicinity of a nuclear generating station. Over 3 consecutive years, fertilized embryos were deployed in Lake Huron using custom-built incubation chambers coupled with data loggers to monitor water temperature. Temperatures at sites in the vicinity of the thermal discharge were significantly elevated compared with reference locations, with mean winter temperatures up to 3 °C warmer. Temperatures were also more variable at these sites, with a significantly greater daily temperature range and rate of change. Embryos developing at discharge sites were significantly larger with smaller yolks than those from the reference stations, suggesting an advanced growth. This increased growth was supported by thermal data, with discharge sites predicted to be more than 10% advanced based on growth rate modelling. These temperature changes and increase in development rate are below thresholds for embryonic mortality but could potentially impact posthatch larval survival.

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Reliable human data on the effects of prenatal exposure to ionizing radiation are largely based on high-dose exposures. Exposure to low doses may produce effects that are not easily observable at birth, and may persist over the course of the offspring's postnatal life. This is important when considering fetal programing, a phenomenon characterized by changes in offspring phenotype due to a stress experienced in utero. In this review, we briefly summarize the known effects of both high- and low-dose exposure to ionizing radiation during pregnancy in humans. There is a major consensus that the atomic bomb survivors' data shows increased incidence of microcephaly and reductions in IQ of A-bomb survivors, whereas, with diagnostic radiography in utero there is no conclusive evidence of increased cancer risk. Due to the relatively limited data (particularly for low-dose exposures) in humans, animal models have emerged as an important tool to study prenatal effects of radiation. These animal models enable researchers to manipulate various experimental parameters and make it possible to analyze a wider variety of end points. In this review, we discuss the major findings from studies using mouse and rat models to examine prenatal ionizing radiation effects in postnatal development of the offspring. In addition, we broadly categorize trends across studies within three major stages of development: pre-implantation, organogenesis and fetal development. Overall, long-term effects of prenatal radiation exposure (including the possible role on the developmental programing of disease) are important factors to consider when assessing radiation risk, since these effects are of relevance even in the low-dose range.