Diethylhexylphthalate belongs to the family of phthalates: industrial chemicals used as plasticizers, softeners, adhesives or solvents used by a variety of industries. They are used in PVC, paints, printing inks, cosmetics, coatings of cars,... 
In 1997, 476.000 tonnes of DEHP was used in the EU. Due to these large quantities large amounts of DEHP are spread in the environment. DEHP is found in all environmental compartments, including remote areas. It mainly enters the marine environment through waste water from production sites, and through leakage from end products.
DEHP has a low water solubility (0,003 mg/l), a very low tendency to vaporize and a high adsorption rate to particles. DEHP is a very stable chemical, it takes 2000 years to degrade it by inorganic mechanisms. It can however more easily be biodegraded. In areas with a high amount of biomass, the DEHP level can be halved in 50 days. Therefore, DEHP is not considered a persistent chemical.
DEHP has a tendency to bioaccumulate. It mainly accumulates through direct uptake from the water and not by food intake. Therefore, there is little risk for biomagnification through food chains and the same concentrations can be found in zooplankton as in fish. There might however be risks for sea birds and marine mammals which eat large amounts of mollusks, crustaceans or krill.
DEHP is not considered a PBT substance (according to the OSPAR DYNAMEC or EU-TGD PBT criteria) although it is a borderline case. It is not considered persistent, but has a potential for bioaccumulation which does not meet the EU-TGD Bcriterion but exceeds the OSPAR DYNAMEC criterion for bioaccumulation. It has also potential of reprotoxicity for mammalian species. At given environmental concentrations, there is no apparent risk for marine organisms, in particular in open marine waters. However, there might be potential endocrine disrupting effects. DEHP is listed as priority substances under the Water Framework Directive (Annex X) and is subject to a review for identification as a possible “priority hazardous substance”. Risk assessment under Regulation 793/93 is still ongoing.