The number of criminal and gang-related assaults involving acid or other corrosive substances has risen sharply in some Western countries. As of July 2017, police statistics in England indicate assaults and threats involving corrosives have risen from 183 in 2012 to more than 500 this year, according to open source reporting. Although there has been minimal specific interest by terrorists in acid attacks to date, we judge the increase in criminal incidents coupled with recent English-language terrorist messaging encouraging attacks using acid may spur opportunistic terrorist use of the tactic, underscoring the potential threat and importance of an immediate on-scene emergency response.