Abstract
Carcinogenic nitrated aromatic hydrocarbons (nitro-PAHs) are a group of nitro-derivatives of polycyclic aromatic hydrocarbons (PAHs), which have aroused increasing attentions due to their wide occurrence and potent toxicity. Though their concentration levels are lower than respective parent PAHs, nitro-PAHs exhibit higher cancer risks to human and are proven to be direct mutagens. Previous studies focused on analyzing nitro-PAHs in atmospheric samples and revealing their formation mechanisms or emission sources. Comparing to the well-documented parent PAHs, studies on nitro-PAHs are at the initial stage and regulations on them are still lacking. My thesis research is directed at developing sensitive and efficient analytical methods to estimate the exposure risks of representative nitro-PAHs via dietary intake.Firstly, I reported a novel ultraperformance liquid chromatography coupled with fluorescence detection (UPLC-FLD) method, which combined pre-column nitro-reduction and fluorescence detection, to analyze nitro-PAHs in meat products. A follow-up work was conducted on rice grains and vegetables, and QuEChERS based sample extraction was applied to determine nitro-PAHs. Dietary exposure risks of nitro-PAHs were evaluated based on the monitoring results and Hong Kong diet. The results suggested that more than 90% of the tested samples were detected with nitro-PAHs and the concentration levels were higher than expected.
Moreover, the fate of model nitro-PAH, 1-nitropyrene, was explored on a plant-soil system for the first time and compared with pyrene. The fate study revealed that the more carcinogenic nitro-PAHs might be more stable in the agricultural soil, and were susceptible to plant uptake, particularly in the root part of plant. Ultimately, biomarkers (DNA and protein adduct) associated risk assessment was conducted both in vitro and in Sprague Dawley rats. In contrast to the in vitro result, protein adduct level was more than 100 times higher than that of DNA adduct in vivo, which could be a more valuable biomarker for nitro-PAHs exposure.
It is anticipated that the food monitoring study and fate study of nitro-PAHs could contribute to the dietary exposure risk assessment via direct or modeling estimation.
Furthermore, we hope the development of biomarkers for 1-nitropyrene could help assess the toxicity of nitro-PAHs and thus facilitate implementing regulations on nitro-PAHs.
| Date of Award | 2018 |
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| Original language | English |
| Awarding Institution |
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