Effect-directed identification of naphthenic acids as important in vitro xeno-estrogens and anti-androgens in North sea offshore produced water discharges.

Produced water from offshore oil production platforms represents the largest direct discharge of effluent into the offshore environment. Produced water effluents contain a complex mixture of substances which are known to bind to the estrogen receptor (ER) and antagonize the androgen receptor (AR). Short-chain petrogenic alkylphenols have been identified as responsible for around 35% of the ER agonist activity measured in vitro while the compounds responsible for antagonizing the androgen receptor are unknown. For the first time we report that petrogenic naphthenic acids are weak ER agonists that account for much of the 65% of the "unknown" ER agonist potency in North Sea produced waters while also disrupting the binding of AR agonists to the AR ligand receptor. We also report other known petrogenic components such as polycyclic aromatic hydrocarbons (PAHs) and alkylphenols as environmental AR antagonists. Our investigation shows that these petrogenic components are responsible for the majority of the ER and AR receptor mediated activity in produced waters. This hypothesis is supported by data from an effects-directed analysis of produced water using normal-phase high-performance liquid chromatography (HPLC) fractionation in combination with the yeast estrogen and androgen assays as well as androgen receptor binding assays of commercially available mixtures of naphthenic acids.