The LNT model is being challenged particularly in relation to the environment because it is now clear that at low doses of concern in radiation protection, cells, tissues and organisms respond to radiation by inducing responses which are not
readily predictable by dose. These include adaptive responses, bystander effects; genomic instability and low dose hypersensitivity. The phenomena contribute to observed radiation responses and appear to be influenced by genetic, epigenetic and environmental factors, meaning that dose and response are not simply related and the modeling of dose response relationships based on the number of irradiated cells may not be a valid approach (Little, 2003).