non-targeted effects of ionising radiation bystander effect NCRP Glossary (https://ncrponline.org/wp-content/themes/ncrp/PDFs/NCRP-Composite-Glossary.pdf) The term used to describe the effects on cells in proximity to irradiated cells, but through which radiation has not passed. In experimental radiation biology, the bystander effect can be investigated by targeting individual cells, or by using doses low enough that the probability for a given cell to be hit by a particle is less than one. The bystander effect can be studied by identifying cells that were traversed by a charged particle. Jack Miller