Application of Thermodynamic Activity to Assess the Cumulative Environmental Risks of Phthalate Ester Mixtures

Phthalate esters (PEs) are a family of chemicals widely used in many consumer products to provide plasticity. This research uses an activity-based approach to assess the environmental risk of exposure to individual PEs and exposure to multiple PEs. The approach expresses exposure and toxicity data in terms of one thermodynamic quantity (i.e., activity), making it possible to include exposure and toxicological endpoint concentrations from multiple media in a single risk analysis; thereby improving the lines of evidence. The activities of 8 PEs in 5 abiotic (N=3886) and 3 biotic (N=407) media from sources worldwide, were compared to the 5th percentile of PE aquatic toxicity values and to the lower threshold of Critical Body Residue (CBR) associated with non-polar narcosis. Individually, PEs pose negligible risk, but cumulatively there is 0.1% probability that PE exposure concentrations will elicit non-polar narcosis. Guidelines to protect organisms from PE-induced non-polar narcosis are proposed