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Received Oct 16, 2017; Revised Jan 13, 2018; Accepted Jan 28, 2018
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Di-2-ethylhexyl phthalate (DEHP) is the most common member of the class of phthalates, which are used as plasticizers in polymer products to make plastic flexible. DEHP is also called bis(2-ethylhexyl) phthalate or dioctyl phthalate (DOP). This colorless viscous and lipophilic liquid is more soluble in materials such as paint removers, gasoline, and oils than in water and has almost no odor [1]. It does not evaporate easily, and little will be present in the air even near sources of production. DEHP is produced at more than 2 million tons annually worldwide [2].
DEHP consists of a pair of eight-carbon esters linked to a benzene-dicarboxylic acid ring with a molecular weight (MW) equal to 390.56 g-mol−1 and a chemical formula of C24H38O4. DEHP is used as a plasticizer in many products, especially in medical devices, such as intravenous (IV) bags and tubing, umbilical artery catheters, blood bags and infusion tubing, enteral nutrition feeding bags, nasogastric tubes, and peritoneal dialysis bags, and is utilized in manufacturing a wide variety of consumer products, such as packed food and beverages; soft plastic products, such as toys and infant products [3], building and furniture materials, including furniture upholstery, mattresses, wall coverings, floor tiles, and vinyl flooring; and cosmetics and personal care products to carry fragrances [4, 5]. Due to the overuse of DEHP in many products, it can be found in air, water, and soil. DEHP can bind to the dust particles in air and be carried back to earth when it is released; DEHP can also bind strongly to soil and dissolves very slowly in groundwater [6].
Due to its ubiquity in the environment, DEHP has raised concerns pertaining to continuous exposure of the human population. When DEHP enters the body, it is metabolized into different metabolites. The primary monoester metabolites of DEHP are di-n-octyl phthalate (DnOP), di-n-butyl phthalate (DnBP), benzyl butyl phthalate (BBzP), and diethyl phthalate (DEP) [7]. The secondary oxidation DEHP metabolites are mono-(2-ethyl-5-hydroxyhexyl) phthalate (5OH-MEHP), mono-(2-ethyl-5-oxohexyl)...