Dibutyl phthalate is an organic compound which is commonly used as a plasticizer because of its low toxicity and wide liquid range. With the chemical formula C6H42, it is a colorless oil, although commercial samples are often yellow.
Production and use
DBP is produced by the reaction of n-butanol with phthalic anhydride. These precursor compounds are produced cleanly and cheaply. DBP is an important plasticizer that allows major engineering plastics, such as PVC, to be used. Such modified PVC is widely used in plumbing for carrying sewerage and other corrosive materials.
DBP has a low vapor pressure of 2.67 x 10−3 Pa. Thus DBP does not evaporate readily. I Henry’s Law constant is 8.83 x 10−7 atm-m3/mol. As reflected by its octanol-water partition coefficient of around 4, it is lipophilic, which means that it is not readily mobilized water. Nonetheless dissolved organic compounds increase its mobility in landfills.
Biodegradation
by microorganisms represents one route for remediation of pollution by DBP. For example, Enterobacter species can biodegrade municipal solid waste—where the DBP concentration can be observed at 1500 ppm—with a half-life of 2–3 hours. In contrast, the same species can break down 100% of dimethyl phthalate after a span of six days. The white rot fungus Polyporus brumalis degrades DBP.
The use of this substance in cosmetics, including nail polishes, is banned in the European Union under Directive 76/768/EEC 1976. The use of DBP has been restricted in the European Union for use in children's toys since 1999. An EU Risk Assessment has been conducted on DBP and the final outcome has now been published in the EU Official Journal. To eliminate a potential risk to plants in the vicinity of processing sites and workers through inhalation, measures are to be taken within the framework of the IPPC Directive and the Occupational Exposure Directive Also includes the 2004 addendum. Based on urine samples from people of different ages, the European Commission Scientific Committee on Health and Environmental Risks concluded that total exposures to DBP should be further reduced. Under European Union Directive 2011/65/EU revision 2015/863 , DBP is limited to max 1000 ppm concentration in any homogenous material.
United States
Dibutyl phthalate is one of the six phthalic acid esters found on the Priority Pollutant List, which consists of pollutants regulated by the United States Environmental Protection Agency. DBP is leached from landfills. However, due to the fact that DBP has a density less than that of water, a thin surface film forms at the air-water interface. DBP was added to the California Proposition 65list of suspected teratogens in November 2006. It is a suspected endocrine disruptor. It was used in many consumer products, e.g., nail polish, but such usages has declined since around 2006. It was banned in children's toys, in concentrations of 1000 ppm or greater, under section 108 of the Consumer Product Safety Improvement Act of 2008. An example of DBP’s endocrine disruption is shown in one study, in which pregnant female rats were exposed to varying doses of DBP orally from gestational day 12.5 to 21.5.^ Results showed that DBP down regulates the expression of BcI-2 and up-regulates the expression of Bax in male offspring, decreasing the BcI-2/Bax ratio.^ This results in the increase of apoptosis in the seminiferous tubule cells early in male rat development. In these male offpsrings, in-utero expression of DBP resulted in decreased anal-genital distance, decreased Sertoli cell and Leydig cell number in seminiferous tubule, and decreased sperm production.
