Explain the Fluoride Toxicity?
Fluoride is a cumulative toxin. Ingestion of fluoride 1.0-1.5 mg/L for several years may produce dental fluorosis, i.e. browning and pitting of teeth known as mottling, as you may recall studying in the Public Nutrition Course (MFN-006). Chronic high level of fluoride in the range of 2-5 mgL can cause skeletal fluorosis. Crippling skeletal fluorosis can occur where drinking water containing higher than 10 mg/L is consumed over several. years. The severe forms of skeletal deformity in toxic fluorosis include kyphosis (abnormal curvature of the spine), fixed spine and other joint deformities. Hyper parathyroidism secondary to high fluoride intake has been reported, which induces calcification of soft tissues. You may recall that PTH is a hormone involved in calcium homeostasis, releasing calcium from the bone into the blood when blood calcium levels tend to fall. An abnormal increase in PTH can add calcium to the soft tissues, hardening them in the process.
A form of severe skeletal flourosis known as "Genuvalgium" (knocked knees) has been reported from part of India, China and African countries. The condition is characterized by severe skeletal fluorosis and osteoporosis of the limbs. Chronic ingestion of excess fluoride coupled with low calcium and high molybdenum intakes appear to increase fluoride retention in the bone. While hyper-parathyrodism and increased levels of PTH result in calcium removal from the bone, explaining the osteoporosis of the limbs.