QSARs for photo-induced toxicity of polycyclic aromatic hydrocarbons (PAHs)

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:37497

Mekenyan, O; Call, D ^[1]; Ankley, G; Veith, G ^[2]

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1. Univ. of Wisconsin, Superior, WI (United States)
2. Environmental Protection Agency, Duluth, MN (United States)

Photo-induced toxicity of polycyclic aromatic hydrocarbons (PAHs) was found to be a result of competing internal and external factors which interact to produce a complex, multilinear relationship between toxicity and chemical structure. The relationship between molecular electronic structure and photo-dynamic effects was studied in both ground and excited states. A measure of the energy required for an electron to be elevated from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), or HOMO-LUMO gap, provided a useful ground state index to explain the persistence, light absorption, and eventual photo-induced toxicity of PAHs to Daphnia magna. The derived QSARs clearly distinguished photo-induced toxicity differences between pairs of structurally similar PAHs, such as phenanthrene and anthracene, benzo[a]anthracene and tetracene, etc. Those PAHs exhibiting photo-induced toxicity were consistently within a specific HOMO-LUMO gap range. The relationship between the excited state electronic parameters and toxicity was also studied. Significant correlations were found with the measured energies of singlet and triplet states from spectroscopic data. An investigation of the effect of substituent additions on photo-induced acute toxicity of parent PAHs revealed that alkyl and hydroxy moieties did not significantly reduce the HOMO-LUMO gap of the parent PAHs. Nitro, alkene and chloro substituents cause gap reductions, whereby certain derivatives of parent chemicals that were close to the ``toxic region`` of the electronic gap could become phototoxic with such additions.

• OSTI ID: 37497
• Report Number(s): CONF-9410273--
• Country of Publication: United States
• Language: English

Related Subjects

56 BIOLOGY AND MEDICINE
APPLIED STUDIES
DAPHNIA
MOLECULAR STRUCTURE
PHOTOCHEMICAL REACTIONS
POLYCYCLIC AROMATIC HYDROCARBONS
SENSITIVITY
STRUCTURE-ACTIVITY RELATIONSHIPS
TOXICITY
WATER POLLUTION