OBJECTIVES:
This project addresses the need to develop and utilize mixed field irradiation protocols that approximately
represent the shielded tissue environment in space and that can be combined with single-beam studies to validate
and further improve cancer risk models. Extensive studies have been carried out on the induction of chromosomal
aberrations by low- and high- linear energy transfer (LET) radiation in human lymphocytes, fibroblasts, and
epithelial cells exposed in vitro. The results, which are consistent with computational modeling predictions,
establish chromosome aberration models as an LET-sensitive tool for predicting damage from single ion
exposures. However, there is a lack of data on chromosome aberrations induced by low dose rate chronic
exposure and mixed field beams such as those expected in space.

This investigation will define a simplified mixed field and make model predictions of the effects of dose rate,
mixed fields, and shielding on expected biological damage. Chromosome aberration studies at NASA’s Space
Radiation Laboratory (NSRL) will provide the biological validation needed to extend the computational models
over a broader range of experimental conditions leading up to the galactic cosmic radiation (GCR) simulator,
which will help to reduce uncertainties in radiation quality effects and dose-rate dependence in cancer risk
models. These models can then be used to answer some of the open questions regarding requirements for a full
GCR reference field, including particle type and number, energy, dose rate, and delivery order.
This study has the following specific aims:

1) Evaluate the effects of dose rate on biological damage using acute and chronic exposures with single ion
and mixed field beams to irradiate normal human fibroblasts and to measure chromosome aberrations.
2) Compare the external field versus local tissue field approach by measuring chromosome aberrations in
normal human fibroblasts using shielded and unshielded.


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Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) investigates and mitigates the highest risks to human health and performance, providing essential countermeasures and technologies for human space exploration. Risks include physiological and performance effects from hazards such as radiation, altered gravity, and hostile environments, as well as unique challenges in medical support, human factors, and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify the approach and research activities planned to address these risks, which are assigned to specific Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.

The Human Research Roadmap is located at: https://humanresearchroadmap.nasa.gov/