Toxicity hydrophobic organic compounds

Swackhamer, D.L. 1991. Bioaccumulation of toxic hydrophobic organic compounds at the primary trophic level. /. Environ. Sci. (China) 3 15-21. 

Pardos, M. and Blaise, C. (1999) Assessment of toxicity and genotoxicity of hydrophobic organic compounds in wastewater, Environmental Toxicology 14, 241-247. 

Dioxins are a family of the most toxic chlorinated organic compounds known to science, numbering around 75 dioxins and 135 related furans. These can cause cancer and are ECD for humans, even at very low exposure levels, since minute amounts, can bio-accumulate due to their ease of solubility in body fat (dioxins are hydrophobic, water-hating and lipophilic, fat-loving ). Number and position of chlorine atoms in the molecule has a considerable effect on toxicity, and 17 dioxins are classed as highly toxic. These include polychlorinated dioxins (PCDD) and dibenzofurans (PCDF) which are by-products of the chlorine bleaching of paper, the burning of chlorinated hydrocarbons (such as pentachlorophenol, PCB, and PVC) and the incineration of municipal/medical... 

Prepai ative isolation of nonvolatile and semivolatile organic compounds fractions (hydrophobic weak acids, hydrophobic weak bases, hydrophobic neutrals, humic and fulvic acids) from natural and drinking waters in optimal conditions was systematically investigated by solid-phase extraction method with porous polymer sorbents followed by isolation from general concentrate of antropogenic and/or toxic semivolatile compounds produced in chlorination and ozonation processes. 

The concentration of a compound in water is controlled by its equilibrium solubility or solubility constant (the maximum amount of a compound that will dissolve in a solution at a specified temperature and pressure). Equilibrium solubility will change with environmental parameters such as temperature, pressure, and pH for example, the solubility of most organic compounds triples when temperature rises from 0°C to 30°C. Each type of waste has a specific equilibrium solubility at a given temperature and pressure. The solubility of toxic organic compounds is generally much lower than that of inorganic salts. This characteristic is particularly true of nonpolar compounds because of their hydrophobic character. 

The partition coefficient Kq of an organic compound in the 1-octanol/water system is used to assess the bioaccumulation potential and the distribution pattern of drugs and pollutants. The partition coefficient of imidazole and ILs strongly depends on the hydrogen bond formed by these molecules and is less than one due to the high solubility in water. The low value of the 1-octanol/water partition coefficient is required for new substances, solvents, insecticides to avoid bioaccumulation. Kqw is an extremely important quantity because it is the basis of correlations to calculate bioaccumulation, toxicity, and sorption to soils and sediments. Computing the activity of a chemical in human, fish, or animal lipid, which is where pollutants that are hydrophobic will appear, is a difficult task. Thus, it is simpler to measure the 1-octanol/water partition coefficient. This parameter is used as the primary parameter characterizing hydrophobisity. 

Association of surfactant molecules onto humic substances is also termed sorption and has been given some attention. In the case of cationic alkyl trimethyl and dimeth-yldioctadecyl ammonium surfactants (Versteeg and Shorter, 1992), the presence of dissolved organic carbon in the water significantly reduced the toxicity of these compounds to fathead minnows. The effect of toxicity reduction increased with increasing hydrophobicity. For the anionic surfactant LAS, this mitigating effect was less pronounced (Traina et al., 1996). 

In addition to direct membrane analogs, many researchers have used Cg, Cis, and XAD resins to simulate the bioavailability of organic compounds. Lake et al. (1996) used Cig resins as a surrogate for benthic organism bioaccumulation of hydrophobic compounds from sediments. Gustafson and Dickhut (1997) and Ankley et al. (1991) also utilized resins to sorb compounds for the assessment of toxicity (and bioavailability) of contaminants in sediments. 

Explosive compounds are weakly hydrophobic and therefore their bioaccumula-tive potential is expected to be low [1-3]. Bioconcentration (net accumulation of chemical from water) of explosives was low in a variety of aquatic animals [2-9], Moreover, the dietary uptake of explosives in fish was minimal relative to aqueous uptake [7,8,10], Although food web transfer of explosive compounds is expected to be insignificant, the demonstrated toxicity of those compounds to a wide variety of aquatic organisms (see Chapter 4) warrants pursuing an adequate understanding of their fate in relevant aquatic species. 

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