Synthetic phenolic antioxidants (SPAs) have received increasing attention due to the reports of toxicity and environmental contamination. Nevertheless, limited information was available on human burdens of these SPAs, with the exception of 2,6-di-tert-butyl-4-methylphenol (BHT). In our study, BHT as well as six other SPAs were analyzed in human urine samples from United States donors. Three SPA congeners were detected in human urine: BHT, 2,4-di-tert-butylphenol (DBP), and 3-tert-butyl-4-hydroxyanisole (BHA). BHT, which is the congener received most concerns, was detected at low concentrations [geometric mean (GM): 0.06 ng/mL], whereas four of its metabolites were detected at relatively high concentrations (GM: 1.68 ng/mL). Surprisingly, DBP was detected at extremely high concentrations (GM: 18.3 ng/mL). The concentrations of DBP (GM: 25.8 ng/mL), BHT (0.853 ng/mL), and metabolites (GM: 10.5 ng/mL) increased significantly after the urine samples were hydrolyzed by β-glucuronidase (p < 0.01), indicating the prevalence of the conjugated forms of SPAs and their metabolites in human urine. DBP, which has previously received little attention, was the predominant congener, contributing 88.2% and 63.6% to total target concentrations in the urine samples before and after β-glucuronidase hydrolysis, respectively. Thus, previous studies have vastly underestimated the burdens of SPAs to humans. To our knowledge, this is the first study revealing the presence of DBP in human urine.

The present study presented an inclusive analysis of engine exhaust emission characteristics of direct injection diesel engine fuelled with diesel and biofuel. Biofuel used in this investigation was obtained by steam distillation from pine oil. A single-cylinder, four-stroke diesel engine was used for this purpose. In this work, performance characteristics like brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC) were analysed. The engine pollutants, namely nitrogen oxide (NO), carbon monoxide (CO), hydrocarbon (HC), and smoke, were examined. In addition, combustion characteristics like in-cylinder pressure and heat release rate were presented. Two engine modification techniques, namely thermal barrier coating and the addition of antioxidant to biofuel, were attempted. The advantage of thermal barrier coating is to reduce heat loss from the engine and convert the accumulated heat into useful piston work. In this work, partially stabilised zirconia was used as the coating material. The usage of antioxidant-treated biofuel in a diesel engine was said to be the prominent approach for NOx emission reduction. Three different antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary-butyl hydroquinone (TBHQ), were exclusively dissolved at a concentration of 1% by volume with PO fuel. The obtained performance and emission characteristics of the uncoated engine were compared with the thermally coated engine. From the results, it was observed that the PO biofuel may be a promising alternative in the near prospect with the thermal barrier coating technique to enhance the performance, combustion and emission characteristics of diesel engine. The PO+TBHQ blend was considered as more beneficial than PO+BHT and PO+BHA on account of its performance, combustion and emission characteristics. The effectiveness of the antioxidant was shown in the order of TBHQ>BHA>BHT.

The present work analyzes the effect of antioxidants on engine combustion performance of a multi-cylinder diesel engine fueled with PB30 and PB50 (30 and 50 vol.% palm biodiesel (PB)). Four antioxidants namely N,N′-diphenyl-1,4-phenylenediamine (DPPD), N-phenyl-1,4-phenylenediamine (NPPD), 2(3)-tert-Butyl-4-methoxyphenol (BHA), and 2-tert-butylbenzene-1,4-diol (TBHQ) were added at concentrations of 1000 and 2000 ppm to PB30 and PB50. TBHQ showed the highest activity in increasing oxidation stability in both PB30 and PB50 followed by BHA, DPPD, and NPPD respectively, without any negative effect on physical properties. Compared to diesel fuel, PB blends showed 4.61–6.45% lower brake power (BP), 5.90–8.69% higher brake specific fuel consumption (BSFC), 9.64–11.43% higher maximum in cylinder pressure, and 7.76–12.51% higher NO emissions. Carbon monoxide (CO), hydrocarbon (HC), and smoke opacity were reduced by 36.78–43.56%, 44.12–58.21%, and 42.59–63.94%, respectively, than diesel fuel. The start of combustion angles (SOC) of PB blends was − 13.2 to − 15.6 °CA BTDC, but the combustion delays were 5.4–7.8 °CA short compared to diesel fuel which were − 10 °CA BTDC and 11°CA respectively. Antioxidant fuels of PB showed higher BP (1.81–5.32%), CO (8.41–24.60%), and HC (13.51–37.35%) with lower BSFC (1.67–7.68%), NO (4.32–11.53%), maximum in cylinder pressure (2.33–4.91%) and peak heat release rates (HRR) (3.25–11.41%) than baseline fuel of PB. Similar SOC of − 13 to − 14 °CA BTDC was observed for PB blended fuels and antioxidants. It can be concluded that antioxidants’ addition is effective in increasing the oxidation stability and in controlling the NOx emissions of palm biodiesel fuelled diesel engine.

The present study assessed the long-term daily administration of benzoic acid (BA), potassium sorbate (PS), chlorophyll (CPL), tartrazine (TAZ), and butylated hydroxyanisole (BHA) on hepato-renal changes and DNA damage in rats. Animals were orally administered with the 10 times of the acceptable daily intake (ADI) from each tested substance daily for 60 consecutive days. Blood, liver, and kidney samples were collected to evaluate hematological, biochemical, histopathological, and genotoxic alterations. The extent of liver and kidney damage was evaluated by comet assay and histopathologically. Significant reduction of leukocyte numbers and lymphocytes % in CPL- and TAZ-treated rats. However, significant increases in platelet count in all treated groups after 60 days were detected. The levels of serum transaminases enzymes (ALT, AST), alkaline phosphatase (ALP), and creatinine were significantly increased in all treatments except with BHA group, but no substantial differences were found in urea after 60 days. Aside from BHA, results of DNA damage revealed significant increases in tailed nuclei, tail moment, DNA% in the tail, and tail length in liver and kidney at different degrees. Moreover, the histopathological figures of liver and kidneys affirmed destructive and degenerative changes. The study indicates that most of the tested food additives may provoke genotoxicity and hepato-nephropathy, which could be serious for human health. Therefore, it is necessary to be informed about the hazardous effects of food additives and more attention should be focused towards using natural substitutes.

This manuscript presents the impact of addition of antioxidant additives to rice bran biodiesel blend on the performance and emission characteristics of compression ignition (C.I) engine. Rice bran methyl ester (RBME) was produced from rice bran oil by transesterification using sodium hydroxide as catalyst. An experimental investigation was conducted on a single-cylinder four-stroke C.I engine to analyze the performance and emission characteristics of rice bran methyl ester (RBME) blended with diesel at 20% by volume (B20) with and without addition of 1000 ppm of two monophenolic antioxidant additives, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The results showed that the BHA- and BHT-treated B20 blend decreased the brake specific fuel consumption (BSFC) by 2.1 and 1.2% and increased the brake thermal efficiency (BTE) by 1.04 and 0.5% compared to B20. The BHA- and BHT-treated B20 blend produced mean reductions in NOx emission of 12.2 and 9.6%, respectively, compared to B20. The carbon monoxide (CO) and hydrocarbon (HC) emissions of BHA- and BHT-treated B20 were increased by 14.8–16.6% and 10.6–11.2%, respectively, compared to B20. However the emission levels were lower than those of diesel.

The use of reclaimed water for agricultural irrigation has emerged as a new strategy for coping with water scarcity in semiarid countries. However, the incorporation of the organic microcontaminants in such water into the diet through crop uptake poses a potential risk to human health. This paper aims to assess the presence of organic microcontaminants in different crops irrigated with groundwater and reclaimed water (secondary or tertiary effluents) in a greenhouse experiment. The determination of microcontaminants in water and vegetation samples was performed by solid-phase extraction and matrix solid-phase dispersion procedure with GC–MS/MS, respectively. The presence of nitrates in the groundwater used for irrigation increased biomass production by a higher proportion than the harvest index. The concentration of microcontaminants in lettuce, carrots, and green beans ranged from less than the limit of quantitation to 571 ng g⁻¹ (fresh weight). Tributyl phosphate and butylated hydroxyanisole exhibited the highest concentration levels in crops. The concentration and frequency of detection of microcontaminants were lower in green bean pods than in green bean roots and leaves. Although the concentrations were generally low, the simultaneous presence of a variety of microcontaminants should be taken into consideration when assessing the risk to human health.