Flo là nguyên tố nhẹ nhất trong Tập đoàn VII của bảng tuần hoàn, với số nguyên tử 9 và trọng lượng nguyên tử của 18,998. Nó có một đồng vị duy nhất, và hóa trị của nó trong tất cả các hợp chất tự nhiên là 1. Mặc dù có chứa chất florua không được liệt kê là một trong "Tiêu chuẩn về các chất ô nhiễm không khí" quy định của EPA, nó vẫn là một chất gây ô nhiễm môi trường rất quan trọng khí. Thật vậy, florua (F) là các chất gây ô nhiễm không khí. | CHAPTER 10 Environmental Fluoride INTRODUCTION Fluorine is the lightest element in Group VII of the periodic table with atomic number 9 and an atomic weight of . It has a single isotope and its valence in all naturally occurring compounds is 1. Although fluoride is not listed as one of the Criteria Air Pollutants regulated by the EPA it is nevertheless a very important gaseous air pollutant. Indeed fluoride F is the most phytotoxic air pollutant because it can damage plants at extremely low concentrations. Furthermore adverse effects of F are not limited to airborne F waterborne F at high levels is also injurious to both human and animal health. For example in China and India millions of people are suffering from dental and skeletal fluorosis an abnormal or poisoned condition caused by F. OCCURRENCE AND FORMS OF FLUORIDE Fluoride is ubiquitous it occurs in minerals and soils air natural waters and foods. The F content in rocks is about to by weight . The most important F-containing minerals and soils are fluorspar or fluorite CaF2 cryolite Na3AlF6 and fluorapatite Ca10F2 PO4 6 . The air in . residential and or rural communities contains less than to ppb to mg F m3 . Fluoride content in natural waters in the . ranges from to ppm. In 1969 there were 2630 communities in the United States with a drinking water supply with a natural F concentration of ppm or more Figure .1 River waters contain to ppm with an average of ppm. Ground waters contain from to ppm depending on the rocks from which the waters flow. The F level in seawater is about ppm. Virtually all foods contain trace amounts of F. Fluoride-containing foods and beverages are therefore the most important sources of F. The adult intake of F from 123 2001 by CRC Press LLC 124 ENVIRONMENTAL TOXICOLOGY Figure Distribution of communities in the United States with ppm or more natural fluoride in community water .
