ABSTRACT
Fluoride (F) is a ubiquitous element. It occurs naturally in the atmosphere through volcanic eruption, and in the earth's crust. It rarely occurs free in nature but combines with a variety of elements to form fluorides that exist in minute amounts in air, water, minerals and soils, vegetation, and body tissues. Fluoride content in natural waters in the northeastern part of the United States ranges from 0.02 to 0.1 ppm, whereas in the west and midwest river waters, it ranges from 0 to 6.5 ppm, with an average of 0.2 ppm. Virtually all foods contain trace amounts of F. Fluoride content in air in the US residential and/or rural communities varies markedly, and it depends on the location where samples are taken but is less than 0.04-1.2 ppb F. Fluoride emissions into the atmosphere are derived mainly from modern-day anthropogenic sources, particularly industrial sources.
