Sensitivity is an individual’s or subpopulation’s increased responsiveness, primarily for biological reasons, to that exposure.[5] Biological sensitivity may be related to developmental stage,[6] pre-existing medical conditions, acquired factors, and genetic factors. Socioeconomic factors also play a critical role in altering vulnerability and sensitivity to environmentally mediated factors by increasing the likelihood of exposure to harmful agents, interacting with biological factors that mediate risk, and/or leading to differences in the ability to prepare for or cope with exposures or early phases of illness. Populations living in certain regions may be at increased risk due to location and the environmental characteristics of a region.