BTEX hydrocarbons toxicity

In New York and Massachusetts where PCB contamination is always a possibility, the laboratory tests required by the state environmental protection agencies for analysis of a petroleum-contaminated soil are as follows (a) flash point (b) total petroleum hydrocarbon (TPH) (c) PCB screening (d) total organic halides (TOH) (e) reactivity of cyanide and sulfide (f) BTEX or equivalent (g) eight metals under TCLP (Toxicity Characteristics Leaching Procedure) for USTs and (h) full range of tests under TCLP for ASTs and spills. 

In the selection of a microbial system and bioremediation method, some examination of the degradation pathway is necessary. At a minimum, the final degradation products must be tested for toxicity and other regulatory demands for closure. Recent advances in the study of microbial metabolism of xenobiotics have identified potentially toxic intermediate products (Singleton, 1994). A regulatory agency sets treatment objectives for site remediation, and process analysis must determine whether bioremediation can meet these site objectives. Specific treatment objectives for some individual compounds have been established. In other cases total petroleum hydrocarbons total benzene, toluene, ethyl benzene, and xylene (BTEX) or total polynuclear aromatics objectives are set, while in yet others, a toxicology risk assessment must be performed. 

Significant concentrations of nonpolar, but toxic dissolved organic compounds, including benzene, toluene (up to 60 mg for BTEX), phenols (20 mg L ), and polyaromatic hydrocarbons... 

Aromatic hydrocarbons are cyclic, planar compounds that are stabilized by a delocalized tt electron system. Aromatics include the mono aromatic hydrocarbons such as BTEX (benzene, toluene, ethylbenzene, and o-, m-, and p-xylenes) and other alkyl-substituted benzene compounds (C -benzenes), and polycyclic aromatic hydrocarbons (including oil-characteristic alkylated PAH homologues and the other U.S. EPA priority PAHs). Benzene is the simplest one ring aromatic compound. The commonly analyzed PAH compounds range from two ring PAHs (such as naphthalene) up through six ring PAHs (benzo g, h, i) perylene). BTEX and PAHs are of concern because of their toxic properties in the environment. 

BTEX compounds can be released to surface water streams from, for example oil spills or industrial processes and get monitored on low levels. In particular, during the production of gasoline products, oil refineries generate a waste stream that contains petroleum by-products such as BTEX. These volatile, monoaromatic hydrocarbons can be toxic to receiving streams. 

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