EVALUATION OF TOXICITY OF CRACK/COCAINE TO MARINE ORGANISMS EXPOSED TO DIFFERENT SCENARIOS OF ACIDIFICATION BY ENRICHMENT OF CO2.

Abstract

Occurrence, fate and effects of illicit drugs in aquatic ecosystems are of environmental concern. In fact, the amounts of illicit drugs consumed worldwide are comparable with those of therapeutic drugs, as millions of individuals are current users of cocaine, heroin, amphetamine like stimulants, marijuana and other drugs. Once cocaine and its metabolites are excreted, they reach inland waters directly by sewage outfalls. Brazil has been identified by the United Nations Office on Drug and Crime as one of the emerging nations where the use of stimulants such as cocaine - used either intranasally ("powder") or smoked (crack) - is increasing. Considering the alkaline pH of marine waters and the pKa of the pharmaceuticals and drugs detected in coastal zones, some compounds could be more bioavailable to the marine biota when compared to freshwater environments. Taking cocaine as an example in Santos Bay, this illicit drug with a pKa = 8.5 tends to be partially found in its non-ionic form in the pH of the sampling area (ranging from 7.9-8.1), which increases cocaine octanol-water partition coefficient (log Kow) values from 0.10 (for the ionic form) to 2.30 (for the non-ionic form). Higher Kow values favor absorption and bioaccumulation processes in organisms exposed to these compounds, and an increased toxicity may therefore be expected. The inorganic carbon system is one of the most important chemical equilibria in the ocean and is largely responsible for controlling the pH of seawater. Dissolved inorganic carbon (DIC) exists in seawater in three major forms: bicarbonate ion (HCO3-), carbonate ion (CO32-), and aqueous carbon dioxide (CO2(aq)), which here also includes carbonic acid (H2CO3). When CO2 dissolves in seawater, H2CO3 is formed. Most of the H2CO3 quickly dissociates into a hydrogen ion (H+) and HCO3-. A hydrogen ion can then react with a CO32- to form bicarbonate. Therefore, the net effect of adding CO2 to sea water is to increase the concentrations of H2CO3, HCO3-, and H+, and decrease the concentration of CO32- and lower pH (pH = - log[H+]). The hypothesis of this work is that the acidification associated with enrichment of CO2 in the marine environment will provoke a modification in the bioavailability and toxicity of illicit drugs such as cocaine and its by products. The main objective of this project is to assess the toxicity of crack/cocaine to the mussel Perna perna combined with acidification by enrichment of CO2 in marine environments. Different toxicity tests to test lethal and sublethal endpoints were conducted during the execution of the project. This project is the first study on illicit drugs (cocaine and crack cocaine) behavior related to different acidification scenarios associated with enrichment of CO2 focusing specifically alterations in pathways of bioavailability and effects, to draw attention to these emerging contaminants in acidification of the marine ecosystem by enrichment of CO2. (AU)