Source and Fate of Perchlorate in the Environment: A Grave Concern for World

Abstract

Perchlorate (ClO4−) is an emerging contaminant and considered as a worldwide problem due to its longer persistence in different environments. ClO4− was first detected in 1985 in wells at industrial sites of California, USA. ClO4− is either naturally occurring or synthetic by origin. Natural atmospheric process is responsible for formation of natural ClO4−, and it is influenced by lightning and UV-mediated photo-oxidation. Another natural source is volcanic eruptions. The anthropogenic pathway of introduction of ClO4− into the environment is more dominant than the geogenic sources. Synthetic perchlorates are mainly produced for military purposes or as a propellant in solid rocket fuels. ClO4− ions are highly soluble in water and can contaminate all sources of water, soil, food, etc., and ultimately living organisms including human via food chain. In case of human, ClO4− is present in different human body fluids such as urine, breast milk, saliva and blood, and it is mainly due to the ingestion of ClO4− contaminated water and food. Due to same ionic charge and almost same ionic radius of ClO4− ions and iodide ion, iodide uptake by the thyroid follicle cells is hinderer by ingestion of ClO4−. Lack of iodine uptake decreases thyroid hormone production, and this hormonal disbalance results in hyperplasia, which ultimately may lead to hypothyroidism. The World Health Organization (WHO) established provisional maximum tolerable daily intake (PMTDI) of 0.01 mg/kg body weight for ClO4−. Ion chromatography is considered as the basic method of analysing ClO4− in drinking water and environmental samples. Many biological processes such as natural biodegradation, phytoremediation and bioreactor and physicochemical processes such as chemical reduction, adsorption, membrane filtration, ion exchange and electrochemical reduction or removal of ClO4− by iron nanoparticles, catalytic reactors, etc., are available for the remediation of ClO4− in contaminated environments.