Biodegradation mechanisms of polycyclic aromatic hydrocarbons: Combination of instrumental analysis and theoretical calculation.

Polycyclic aromatic hydrocarbons (PAHs) are a common class of petroleum hydrocarbons, widely encountered in both environment and industrial pollution sources. Owing to their toxicity, environmental persistence, and potential bioaccumulation properties, a mounting interest has been kindled in addressing the remediation of PAHs. Biodegradation is widely employed for the removal and remediation of PAHs due to its low cost, lack of second-contamination and ease of operation. This paper reviews the degradation efficiency of degradation and the underlying mechanisms exhibited by algae, bacteria, and fungi in remediation. Additionally, it delved into the application of modern instrumental analysis techniques and theoretical investigations in the realm of PAH degradation. Advanced instrumental analysis methods such as mass spectrometry provide a powerful tool for identifying intermediates and metabolites throughout the degradation process. Meanwhile, theoretical calculations could guide the optimization of degradation processes by revealing the reaction mechanisms and energy changes in PAH degradation. The combined use of instrumental analysis and theoretical calculations allows for a comprehensive understanding of the degradation mechanisms of PAHs and provides new insights and approaches for the development of environmental remediation technologies.

Determination, exposure and risk assessment of PAHs in natural vitamin E isolated from vegetable oil industry.

Natural vitamin E, which is mainly extracted from vegetable oil deodoriser distillate (VODD), is likely contaminated by carcinogenic polycyclic aromatic hydrocarbons (PAHs). A total of 26 commercial vitamin E products from six countries were investigated for 16 EPA PAHs using QuEChERS combined with gas chromatography triple quadrupole mass spectrometry (GC-QQQ-MS). The concentrations of total PAHs in the samples ranged from 46.5 µg kg-1 to 215 µg kg-1, while the concentrations of PAH4 (BaA, Chr, BbF and BaP) ranged from 4.43 µg kg-1 to 20.1 µg kg-1. Risk assessment indicates that maximum intake of PAHs is 0.2 mg day-1, which is less than the LD50 and no observed adverse effect levels (NOAEL) of PAHs. However, chronic carcinogenicity of PAHs needs to be considered. The results suggested that PAH concentrations as well as toxicity equivalent should be considered as important indicator of risk of vitamin E products.

Simultaneous Determination of Typical Chlorinated, Oxygenated, and European Union Priority Polycyclic Aromatic Hydrocarbons in Milk Samples and Milk Powders.

An increasing number of studies have suggested that PAH contamination in dairy products demands high concern. This study established an efficient determination method for the European Union 15 + 1 PAHs and four PAH derivatives in dairy samples using a QuEChERS method coupled with GC-QqQ-MS. The optimized method obtained a recovery of 63.38-109.17% with a precision of 3.82-15.62%, and the limit of detection and limit of quantification were 0.08-0.78 and 0.27-2.59 µg/kg, respectively. The validated method was then successfully applied to identify the 20 PAHs in 82 dairy samples, including 43 commercial milk samples and 39 milk powders. The total PAH concentrations ranged from 2.37 to 11.83 µg/kg, and benzo[a]pyrene was only quantified in one milk and one milk powder sample at 0.35 and 0.42 µg/kg, respectively. The concentrations of PAH4 in milk samples and milk powders were not quantified (nq)-3.99 and nq-4.51 µg/kg, respectively. The results confirmed the appreciable occurrence of PAHs in dairy products, especially in infant formula. The data in this study provide a scientific basis for assessment on origin tracing, dietary exposure, and health risk of PAHs and their derivatives.

Polycyclic aromatic hydrocarbons in edible oils and fatty foods: Occurrence, formation, analysis, change and control.

Numerous studies have demonstrated that dozens of polycyclic aromatic hydrocarbons (PAHs) are mutagenic, genotoxic and strongly carcinogenic. PAHs are found to be widely present in foods contaminated through multiple paths. Due to their lipophilic nature, these compounds easily accumulate in edible oils and fatty foods where they can range from no detection to over 2000µg/kg. Compared to precursor PAHs, researchers have seldom studied the presence of PAH derivatives, especially in food matrices. This chapter includes the physical and chemical characteristics of PAHs and their types, occurrence, sample pretreatment and instrumental determination methods, and their formation, change and control in edible oils and fatty foods. The occurrence and formation of PAH derivatives in foods are much less investigated compared to those of their precursor PAHs. Although the removal of matrix effects and accuracy remain difficult for current rapid determination methods, a prospective research direction of PAH analysis for large-scale screening is in demand. To date, physical absorption, chemical oxidation and biodegradation have been widely used in PAH removal techniques. Specific types of bacteria, fungi, and algae have also been used to degrade PAHs into harmless compounds. However, most of them can only degrade a range of LPAHs, such as naphthalene, anthracene and phenanthrene. Their ability to degrade HPAHs requires further study. Moreover, it is still a great challenge to maintain food nutrition and flavor during the PAH removal process using these methods.

A new approach of specific determination for 6-chlorobenzo[a]pyrene and 7-chlorobenzo[a]anthracene in six different oils.

This study developed a new method for analysing 6-ClBaP and 7-ClBaA in six oil samples using liquid-liquid extraction and solid-phase extraction followed by GC-QQQ-MS. The recoveries of 6-ClBaP and 7-ClBaA were 44.26 ± 2.81% and 92.61 ± 4.09%, respectively. Both the instrument and method LODs were lower than 0.2 µg kg-1, while the intra-day and inter-day RSD were less than 5%. Five waste frying oils and one peanut oil were tested with the validated determination method. The concentrations of 6-ClBaP and 7-ClBaA in the tested samples ranged from no detection to 0.29 µg kg-1 and no detection to 0.20 µg kg-1, respectively. The data of 6-ClBaP and 7-ClBaA detected in this study suggest that a large scale of investigation on Cl-PAHs in foods is necessary.

Determination of Parent and Oxygenated Polycyclic Aromatic Hydrocarbons (PAHs) in Waste Cooking Oil and Oil Deodorizer Distillate by GC-QQQ-MS.

Background: Polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) are classes of contaminants that are present in the environment and food. They pose a great threat to human health because of their carcinogenicity and mutagenicity. Very few studies have focused on their concentration in waste cooking oil (WCO) and oil deodorizer distillate (ODD). Objective: This study aimed (1) to design a reliable method to determine 16 PAHs and 4 OPAHs in both WCO and ODD and (2) to determine and analyze PAH and OPAH concentrations in actual samples to provide references for further research. Method: The PAH determination approach included double liquid-liquid extraction, double solid-phase extraction, and GC-triple quadrupole tandem MS determination. Oxidation indices were determined by titrimetry. Results: The method reached good linearity (R² > 0.99) and an acceptable recovery rate (55.01-126.16% for WCO and 57.48-128.97% for ODD). Ten WCO and five ODD samples were determined, and the total concentration of 16 PAHs varied from 16.34 to 239.01 and 101.08 to 198.04 µg/kg in WCO and ODD, respectively. Among the 16 PAHs, three-ring PAHs typically contributed the most. It was also found that the acid value has a strong correlation with the concentration of OPAHs, probably because of the contribution of free fatty acids to OPAH formation. Conclusions: The proposed method was effective in the analysis of PAHs and OPAHs in WCO and ODD.

Influences of Light Intensity and ß-Carotene on Polycyclic Aromatic Hydrocarbons and Aldehydes in Vegetable Oil: A Case Study Using Palm Oil.

This study investigated the effects of three light intensities on four types of palm oils during consecutive storage for 12 months at 4 °C. The concentrations of 4-hydroxy-2- trans-hexenal (4-HHE), 4-hydroxy-2- trans-nonenal (4-HNE), polycyclic aromatic hydrocarbon (PAH)4, and PAH8 in the oils significantly increased with the increasing light intensity after storage. The red palm oil had the lowest rate of increase of 4-HNE, while 5° palm oil had the highest rate of increase of the PAH, OPAH, 4-HNE, and peroxide values during storage. For the same type of oil, OPAHs increased significantly under a light intensity of 6000 lx (lx) after storage. The increasing concentrations of 9FO, ATQ, and BaPO in the oils stored at 6000 lx showed a positive relation to their corresponding parent PAHs, indicating that PAH oxidation occurred at 6000 lx. The results suggest that light intensity and ß-carotene may control PAHs, OPAHs, and 4-hydroxy-trans- alkenals for vegetable oil storage, transportation, and retail.

Effect of storage time and temperature on parent and oxygenated polycyclic aromatic hydrocarbons in crude and refined vegetable oils.

Changes in polycyclic (PAH) and oxygenated (OPAH) aromatic hydrocarbon concentrations in vegetable oils during storage for 270days at 25°C or 4°C were investigated. The concentrations of OPAHs and PAHs increased with storage time. The increase in PAH concentration was mainly caused by light PAHs. Total PAH concentrations increased from 33.11-36.77µg/kg to 45.12-58.04µg/kg in 26 crude oil samples, while those in 26 refined oil samples increased from 16.52-20.02µg/kg to 25.73-40.01µg/kg. Acid value (AV) and peroxide value (POV) also showed an increase during the storage process from 0.08-0.92mg/kg to 0.33-2.98mg/kg, and from 0.08-0.12mmol/kg to 0.33-3.45mmol/kg in 52 tested oils, respectively. AV and POV were within the regulatory limits of China after storage for 270days. However, concentrations of 16 PAHs in all tested oils exceeded 25µg/kg. The results indicated PAHs and OPAHs formation was better inhibited in oils stored at lower temperature.