Until recently, perchlorate was detected only in a few places where it was manufactured or used in large quantities. In 1997, new techniques made it possible to detect perchlorate in water at very low levels — about 4 parts per billion (ppb). Because of these advancements, low levels of perchlorate have been detected in more places. Once perchlorate was detected at these low levels, industry and government began reviewing and studying the health effects of perchlorate, resulting in several new studies that showed these low levels have no measurable effect on human health. Treatment technologies have also been developed and implemented to address perchlorate in water.
Update: Perchlorate is less present in the environment today.