Polycylic aromatic hydrocarbons PAHs

On occasions, animal feed has been suspected of deliberate contamination. Incidents involving contamination of animal feed by industrial by-products such as polycylic aromatic hydrocarbons (PAHs) and combustion products such as dioxins are not uncommon. A problem with animal feed is that there is sometimes inadequate control over the provenance of feed constituents. For example, spent cooking oil from food-processing plants is a legitimate feed component. Unfortunately, the temptation for the unscrupulous to dispose of other unwanted oils in this way is too great for some. In many cases such adulterants are probably diluted to such an extent that they are undetectable by conventional chemical analyses. Nevertheless, they may still represent a longterm cumulative hazard to consumers of products from animals fed on such material. 

In addition to gaps in knowledge for currently existing classes of chemicals and ecotoxicological effects, other mechanisms of actions that are currently not yet studied, or other processes, may require further studies. For example, recently it has become clear that phototoxic effects may be a realistic problem for polycylic aromatic hydrocarbons (PAHs) in aquatic and benthic organisms. The amount of UV-light which is required for phototoxicity, is thus an example of a parameter which was not introduced earlier as an important environmental parameter to describe or predict toxicity [148]. Other examples are if the internal effect concept can be used for metals and organometals in risk assessment [149,150]. 

Valerio, F., and Lazzarotto, A. (1985) Photochemical degradation of polycylic aromatic hydrocarbons (PAH) in real and laboratory conditions, Int. J. Environ. Anal. Chem. 23, 135-151. 

A biosensor for detecting the toxicity of polycylic aromatic hydrocarbons (PAHs) contaminated soil has been successfully constmcted using an immobilized recombinant bioluminescent bacterium, GC2 (laCj g), which constitutively produces bioluminescence. This biosensor system using a biosurfactant may be applied as an in-situ biosensor to detect the toxicity of hydrophobic contaminants in soils and for performance evaluation of PAH degradation in soils [18],... 

Fig. 2. Contribution of the aromatic rings of two polycylic aromatic hydrocarbons (PAHs) to the quantum-connectivity index CRg(p) (left) and to aqueous solubility expressed as InC ) (right). The compound at the top is benzo[a]pyrene and the one at the bottom is benz[a]anthracene.

Unusual polycylic aromatic hydrocarbons (PAH)s supporting Mn(0)-Mn(0) bonded species were reported in 2005. These compounds were made from the chemical reduction of a Mn(I) PAH precursor with 1 equiv. of cobaltocene (Scheme 7.11) [33]. The molecular structure of these compounds is... 

Fetzer, J.C. The deternrination of aqueous solubility for several large PAHs, Polycylic Aromatic Hydrocarbons, 23(3-4) 321-326, 2002. 

Another way of detecting interstellar species is provided by vibrational emission spectra (Figure 3). Let us mention here the so-called Unidentified Infra-Red (UIR) bands, which have not been unambiguously assigned yet. The striking resemblance of the UIR from the Orion bar with the Raman spectrum of an auto soot clearly seems to indicate that the carriers are carbon compounds. Very certainly, it will not be possible to make a one-to-one correspondence between the observed bands and some given species. Very certainly, also, the carriers of these bands are hydrogenated carbonaceous species. Whether these species are Polycylic Aromatic Hydrocarbons [24,25,26] (thereafter PAHs), coals [27,28,29], or amorphous carbon [30] is still a matter of debates and controversies that we shall not discuss further here. The interested reader can refer to a recent series published in the Faraday Discussions (1998). 

Fossato VU, Nasci C, Dolci (1979) 3,4-benzopyrene and perylene in mussels, Mytilus sp., from the Laguna Veneta, north-east Italy. Mar Env Res 2 47-53 Foster GD, Crosby DG (1986) Xenobiotic metabolism of p-nitrophenol derivatives by the rice field crayfish Procambrus clarkii). Environ Toxicol Chem 5 1059-1070 Foster GD, Crosby DG (1987) Comparative metabolism of nitroaromatic compounds in freshwater, brackish water and marine decapod crustaceans. Xenobiotica 17 1393-1404 Foureman GL (1989) Enzymes involved in metabolism of PAH by fishes and other aquatic animals hydrolysis and conjugation enzymes (or phase II enzymes). In Varanasi U (ed) Metabolism of polycylic aromatic hydrocarbons in the aquatic environment. CRC Press, Boca Raton, Florida, pp 185-202... 

The continuum emission in this spectrum is due to thermal emission from hot dust that has been heated by absorbing starlight. The sharp emission lines are due to radiation from various atoms and atomic ions. Atomic designations with square brackets such as [Nell] indicate the emission is due to a forbidden transition. A forbidden transition is a transition via the atom s electronic quadrapole moment or magnetic dipole moment rather than the electronic dipole moment. The broader emission features designated by PAH (polycylic aromatic hydrocarbons) are emission by dust components. One of the major discoveries with ISO spectroscopy has been that these PAH emission features... 

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