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The issue of potential long-term or hereditary effects for both humans and wildlife exposed to low doses (or dose rates) of ionising radiation is a major concern. Chronic exposure to ionising radiation, defined as an exposure over a large fraction of the organism's lifespan or even over several generations, can possibly have consequences in the progeny. Recent work has begun to show that epigenetics plays an important role in adaptation of organisms challenged to environmental stimulae. Changes to so-called epigenetic marks such as histone modifications, DNA methylation and non-coding RNAs result in altered transcriptomes and proteomes, without directly changing the DNA sequence. Moreover, some of these environmentally-induced epigenetic changes tend to persist over generations, and thus, epigenetic modifications are regarded as the conduits for environmental influence on the genome. Here, we review the current knowledge of possible involvement of epigenetics in the cascade of responses resulting from environmental exposure to ionising radiation. In addition, from a comparison of lab and field obtained data, we investigate evidence on radiation-induced changes in the epigenome and in particular the total or locus specific levels of DNA methylation. The challenges for future research and possible use of changes as an early warning (biomarker) of radiosensitivity and individual exposure is discussed. Such a biomarker could be used to detect and better understand the mechanisms of toxic action and inter/intra-species susceptibility to radiation within an environmental risk assessment and management context., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The effects of chronic exposure to (137)Cs gamma radiation (dose rate ranging from 6.6 to 42.7 mGy h(-1)) on growth and reproductive ability were carried out over three generations of Caenorhabditis elegans (F0, F1, and F2). Exposure began at the egg stage for the first generation and was stopped at the end of laying of third-generation eggs (F2). At the same time, the two subsequent generations from parental exposure were returned to the control conditions (F1' and F2'). There was no radiation-induced significant effect on growth, hatchability, and cumulative number of larvae within generations. Moreover, no significant differences were found in growth parameters (hatching length, maximal length, and a constant related to growth rate) among the generations. However, a decrease in the cumulative number of larvae across exposed generations was observed between F0 and F2 at the highest dose rate (238.8 ± 15.4 and 171.2 ± 13.1 number of larvae per individual, respectively). Besides, the F1' generation was found to lay significantly fewer eggs than the F1 generation for tested dose rates 6.6, 8.1, 19.4, and 28.1 mGy h(-1). Our results confirmed that reproduction (here, cumulative number of larvae) is the most sensitive endpoint affected by chronic exposure to ionizing radiation. The results obtained revealed transgenerational effects from parental exposure in the second generation, and the second non-exposed generation was indeed more affected than the second exposed generation., (Copyright © 2014 Elsevier Ltd. All rights reserved.)