New theoretical insight into indirect photochemical transformation of fragrance nitro-musks: Mechanisms, eco-toxicity and health effects.


Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China. Electronic address: [Email]


The ubiquitous presence of fragrance-associated synthetic musk is cause for serious concern due to their transformation and environmental impacts. In particular, nitro-musks are frequently detected in various matrices, including water, even though they were restricted because of carcinogenicity. Thus, using musk xylene as a model compound, the mechanism, eco-toxicity and health effects during OH-initiated transformation process were systematically studied using quantum chemistry and computational toxicology. Results indicate that musk xylene can be exclusively transformed via H-abstraction pathways from its methyl group, with total rate constants of 5.65 × 108-8.79 × 109 M-1 s-1, while the contribution of other pathways, including single-electron transfer and OH-addition pathways, were insignificant. The subsequent dehydrogenation intermediates (MX(H)) could further transform into cyclic, aldehyde and demethylation products. Based on toxicity assessments, all the transformation products exhibited decreased aquatic toxicity to fish in comparison with the parent musk xylene but they were still classified at toxic or very toxic levels, especially the cyclic products. More importantly, these products still exhibited carcinogenic activity during OH-initiated transformation and increased carcinogenicity relative to the parent musk xylene. This is the first time that the transformation mechanism and environmental impacts of nitro-musks have been explored through theoretical calculations.


Carcinogenic activity,Computational toxicology,Hydroxyl radical,Nitro-musks,Theoretical calculation,Transformation mechanism,