Evaluation of contaminants in fluorosilicic acid used for public water fluoridation in the Santos region, Brazil

Fluorosilicic acid is one of the main products used in water fluoridation. As a by-product of the phosphate fertilizer industry, it may contain contaminants that are harmful to human health. The aims of this study were to assess the quality control analysis of fluorosilicic acid; to detect the presence of contaminants, such as arsenic, lead, cadmium, aluminum, barium, strontium, cobalt, iron, and sulfur in fluorosilicic acid samples by using inductively coupled plasma–optical emission spectrometry; and to collect data for water analysis performed at a water treatment plant. The results show the presence of all contaminants mentioned previously, except for lead, in fluorosilicic acid samples from all sources. No quality control was carried out or required for this product at any time. Although the water analyses indicate the water is potable, there are no minimum safe limits for human consumption regarding carcinogenic elements such as cadmium and arsenic and both were detected and released in the water. Therefore, the purity of fluorosilicic acid used for water fluoridation should be required and monitored by public administrations to avoid long-term public health problems.