Medicine. The length of time over which continuous or intermittent contacts occur between an agent and a target. For example, if an individual is in contact with an agent for 10 min a day, for 300 days over a 1-year time period, the exposure duration is 1-year. Valerie Zartarian, Tina Bahadori and Tom McKone. Adoption of an official ISEA glossary. Journal of Exposure Analysis and Environmental Epidemiology (2005) 15, 1-5. doi: 10.1038/sj.jea.7500411 Published online 24 November 2004