Abstract

  
  The area of Salina Cruz in Oax., Mexico is characterized by its intense oil activity in the last 30 years, with crude product being distributed to bulk plants in the center of the country for processing and refining. These industrial activities have generated environmental contradictions due to continuous emissions and discharges that are exhausted to the environment. One of the aquatic systems affected by this process is the La Ventosa estuary since one of its tributaries the Zanjón stream crosses the refinery.
   Polycyclic Aromatic Hydrocarbons (PAH) are important constituents of petroleum products and their mutagenic and carcinogenic potential are well known. In order to determine the effect of these substances on the activity the enzyme 7-Ethoxyresorufin-or-deethylase (EROD) , it was evaluated using the liver of Salmo trutta exposed to different mixtures of PAH present in the sediments of 8 stations located in the Zanjón-Ventosa system. The PAH concentrations were measured according to EPA8310 methodology and the mixtures were made with analytic standards dissolved in DMSO. The results showed an increment in the activity of EROD in the Zanjón stream where the higher PAH concentrations were present suggesting the technique to be a sensitive bio-marker of oil polluted aquatic systems.