Pseudo-persistent Organic Pollutants: Present Status and Future Perspectives
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Introduction: Pseudo-persistent organic pollutants (P-POPs) are synthetic organic chemicals that possess relatively lower potential of environmental persistent, bioaccumulative and toxic properties than that of classical POPs. In recent years, there is a growing concern regarding the environmental contamination and health impact of trace levels of P-POPs on a global scale. This overview deals with ‘Compounds of Concern’ with POP-like properties for future environmental and health issues. During the past century, a large number of organic chemicals have been manufactured and used in industrial, agricultural, consumer products, human and animal health applications. Widespread manufacture, use, and disposal of these man-made chemicals containing halogenated groups (chlorinated, brominated, and fluorinated compounds), lead to environmental contamination and human exposure. These classical organohalogen compounds are commonly known as persistent organic pollutants (POPs) and known for their global distribution and toxic effects on wildlife and humans. For this reason, most organohalogens are banned and/or severely restricted for production and use. Further, the United Nations Environment Program (UNEP) implemented the Stockholm Convention of POPs in 2004 to protect human health and environment. As a result, several classical POPs levels in environmental and biological matrices exhibited gradual declining trends in most developed countries. However, in the recent years, several new pollutants are discovered that exhibit POP-like properties (pseudo-persistent organic pollutants –P-POPs) causing environmental and health concern on a global scale. The P-POPs include: pharmaceuticals, personal care products, degradation by-products, food contaminants etc.
P-POPs of Concern and their Physico-chemical Properties: The classical persistent organic pollutants such as polychlorinated biphenyls (PCBs), organochlorine pesticides and dioxins, etc., have physico-chemical and biochemical properties such as water solubility, vapor pressure, lipophilicity, biodegradability and particle affinity at appropriate magnitude to make them stable in the environmental media, bioaccumulate and biomagnify in the food chain causing chronic toxic effects. Several of the P-POPs discovered in the recent years also exhibit POP-like properties. The P-POPs of emerging concern may be grouped as (i) Pharmaceuticals (Antihistaamine, antiplatelet, antihypertension, antidepressents, etc.) and metabolites (ii) Illicit drugs (cocaine, amphetamines, etc.) (iii) Personal Care Products (UV-Filters, insect repellents, etc.) and (iv) Food contaminants (melamine, ammeline, ammelide, phthalates, etc).
Temporal Trends of POPs and P-POPs: Classical persistent organic pollutants, due to their recalcitrant properties, exposure pathway is complicated involving environmental contamination, bioaccumulation and biomagnification in the food chain and ultimately reach top predators such as humans in the terrestrial ecosystem and marine mammals in the aquatic ecosystem. This process takes relatively longer time to reach top predators from the time of application or use of these chemicals. Whereas, P-POPs, (emerging new compounds of concern) are used or applied directly to the human skin or consumed via contaminated water and/or food. Particularly, human exposure pathway for pharmaceuticals and personal care products are direct and intimate.
Conclusions
Based on their use (emerging compounds of concern), and their POP-like properties, it is possible that the environmental contamination as well as human exposure and health impacts by these compounds will continue to increase for several decades in both developed as well as developing countries. Further research is needed to determine whether accumulative and toxicological properties of P-POPs resemble those of POPs.