The formation and occurrence of polynuclear aromatic hydrocarbons associated with food

Polynuclear aromatic hydrocarbons are common contaminants of processed food, usually at trace levels. These hydrocarbons are products of combustion and pyrolysis, and are present in petroleum and coal, and in products derived from them. Most polynuclear aromatic hydrocarbons are not carcinogenic, but some of them are, and a few are potent inducers of skin and lung tumors in mice. Their carcinogenic properties have not been fully explored, but they seem to be less potent by ingestion or inhalation, and they are known as a group to produce cancer in humans. The most effective carcinogens among them are those with 5 or 6 fused rings, and these tend to be less prevalent in mixtures than the 3- and 4-ring hydrocarbons, most of which are not carcinogenic. Sophisticated analytical methods, using solvent extraction and chromatography have been developed to detect and measure polynuclear aromatic hydrocarbons at levels of 1 in 10(9) (1 part per billion) or less, and these have been applied to the measurement of individual compounds in foods, as well as in products of combustion and pyrolysis. Wood smoke and smoked foods contain the carcinogenic benzo[a]pyrene at levels of 1 ppb, and other hydrocarbons; liquid smoke has lower levels. Crude vegetable oils have higher concentrations, but purified 'deodorized' oils have benzo[a]pyrene levels near 1 ppb. Sausages cooked over burning logs had as much as 200 ppb benzo[a]pyrene. Charcoal-broiled steaks and ground meat had benzo[a]pyrene concentrations up to 50 micrograms/kg, while less fatty pork and chicken had lower concentrations (up to 10 micrograms/kg). It was probable that the rendered fat dripped on to the hot charcoal and pyrolyzed to form quantities of polynuclear aromatic hydrocarbons, which rose with the smoke to deposit on the meat. Therefore, oven cooking or cooking with a heat source above the meat, or segregation of the meat from the smoke resulted in food containing negligible amounts of polynuclear aromatic hydrocarbons. Modifications of cookings practices accordingly would greatly reduce exposure to this group of carcinogens.     

High-pressure liquid chromatography of polycyclic aromatic hydrocarbons and some of their derivatives.

The separation of polycyclic aromatic hydrocarbons and their derivatives by means of high-pressure liquid chromatography on Permaphase ODS is described. The method consists of the (isocratic) elution of compounds from the column with a methanol-water mixture of constant composition and is particularly suited to the identification of metabolic products of polycyclic hydrocarbons.     

Public Health Risks from Illegally Imported African Bushmeat and Smoked Fish

Large-scale importation of bushmeat from West and Central Africa into Europe was reported in 2010. We sampled 18 illegal African bushmeat consignments seized at Charles de Gaulle airport, Paris, France and tested for the presence of bacteria. Additionally, five smuggled smoked fish were analysed for polycyclic aromatic hydrocarbons, which are known carcinogens. All bushmeat samples had viable counts of aerobic bacteria above levels considered safe for human consumption. We also identified zoonotic bacterial pathogens in bushmeat and unsafe levels of carcinogens in fish. The illegal importation of meat is a potential risk for the introduction of pathogens.     

Identification of polycyclic aromatic compounds in mutagenic emissions from steel casting

Workers in ferrous foundries show increased risk of lung cancer. In the steel casting process hot metal is poured into sand moulds solidified with organic binders, producing a plume of smoke containing a variety of organic compounds and showing strong mutagenicity in the Salmonella/S9 assay. We have collected the emissions produced when steel is poured into an experimental sand mould solidified with oil, clay and cereal, a widely used binder system. The organic constituents of these emissions have been fractionated by preparative reverse-phase high performance liquid chromatography (HPLC) and mutagenic fractions have been analysed by capillary column gas chromatography/mass spectrometry (GC/MS). Of the 65 compounds for which mass spectra are reported, 54 have been tentatively identified as alkyl derivatives of polycyclic aromatic compounds. Many compounds of this class are known to be carcinogenic and mutagenic. In addition, several unsubstituted polycyclic aromatic hydrocarbons, including the carcinogenic benz[a]anthracene and benzo[a]pyrene, were found to be present.     

Differential exposure biomarker levels among cigarette smokers and smokeless tobacco consumers in the National Health and Nutrition Examination Survey 1999–2008

Assessment of biomarkers is an appropriate way to estimate exposure to cigarette mainstream smoke and smokeless tobacco (SLT) constituents in tobacco consumers. Using the US National Health and Nutrition Examination Survey (NHANES, 1999–2008), biomarkers of volatile organic compounds, halogenated aromatic hydrocarbons (HAHs), polycyclic aromatic hydrocarbons (PAHs), acrylamide, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and metals were evaluated. In general, biomarker levels in SLT consumers were significantly lower than in smokers (excluding NNK and some HAHs) and were not significantly different compared with nonconsumers (excluding NNK and some PAHs). These results provide useful information for science-based risk assessment and regulation of tobacco products.     

Carcinogen: DNA adducts in tobacco smoke-associated cancer of the upper respiratory tract.

Mortality connected with tobacco smoke-associated laryngeal cancer in Poland markedly exceeds the relevant epidemiological data from other European countries. The main groups of genotoxic agents considered as potential carcinogens present in tobacco smoke are polycyclic aromatic hydrocarbons, aromatic amines, N-nitrosoamines and reactive oxygen species. Aromatic DNA adducts, N7-alkylated guanosines and oxidative DNA damage derived from tobacco smoke exposure were detected in laryngeal and oral (tumour and non-tumour) biopsies, and white blood cells of cancer subjects. Further, DNA lesions were analysed to estimate the significance of such confounders as intensity of smoking, subject's sex, age, topography of larynx, cancer staging and genetic factor. The number of cigarettes smoked per day was found to be the main determinant of an individual's DNA adduct level. The occurrence of DNA lesions was established as a reliable marker of former exposure to tobacco smoke genotoxicants. On the other hand, a comparison of DNA lesion levels in various regions of larynx indicates limited usefulness of DNA adduct analysis as an estimate of cancer risk. For a better risk estimation one has to take into account DNA lesions in proto-oncogenes and tumour suppressor genes and the efficacy of DNA repair. Altogether, DNA adducts formation and removal has to be considered as a single stage in the multistep carcinogenesis.     

水体沉积物中微生物厌氧呼吸耦合多环芳烃降解的研究进展

多环芳烃(Polycyclic aromatic hydrocarbons,PAHs)是一种具有致癌、致畸、致突变的持久性有机污染物。本文在分析国内外主要水体沉积物中PAHs污染状况的基础上,综述了近几年有关厌氧水体沉积物中微生物以硝酸盐、Fe(III)以及硫酸盐为电子受体进行呼吸耦合PAHs降解的研究概况。此外,还总结了基于微生物的PAHs降解基因组、蛋白质组、代谢组以及菌群水平上互作网络的研究进展,以期为进一步加速PAHs污染水体沉积物原位生物修复提供科学理论参考。     

Biodegradability of Erika fuel oil

The biodegradation of the fuel oil resulting from the Erika wreck was studied by computerized gas chromatography in laboratory cultures over 80 days. The total extent of biodegradation was around 11%. The degraded compounds were the molecules of the light cracking fraction used to dilute the distillation residue, as well as n-alkanes and part of the branched alkanes. Part of the polycyclic aromatic hydrocarbons PAH and alkyl PAH was also degraded. The very low biodegradability of the Erika fuel is attributable to its chemical composition. The product is rich in components that are inherently resistant or refractory to microbial metabolism such as resins, asphaltenes and polycyclic saturated and aromatic hydrocarbons.     

SULT1A1 Arg213His polymorphism, smoked meat, and breast cancer risk: a case-control study and meta-analysis

SULT1A1 is involved in both detoxification of estrogens and bioactivation of carcinogens in smoked meat. SULT1A1 Arg213His polymorphism's effect on breast cancer risk is still unclear. We recruited 400 case-control pairs to investigate the association between SULT1A1 genotypes and breast cancer risk, and the combined effect of SULT1A1 polymorphism and daily intake of smoked meat. Participants were questioned about their dietary habits and other risk factors, and their SULT1A1 genotypes were determined. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were estimated by multivariable unconditional logistic regression. We also performed a meta-analysis of relevant published studies to test these associations. In the case-control study, no significant associations were observed between SULT1A1 polymorphism and breast cancer risk. In the meta-analysis, SULT1A1 His/His genotype slightly increased risk among both overall and postmenopausal women (OR(pooled-overall)=1.12, 95% CI: 1.02-1.24; OR(pooled-post)=1.17, 95% CI: 1.03-1.32). A larger positive association was observed in Asian populations (OR(pooled-Asian)=2.01, 95% CI: 1.24-3.26). In our case-control study, high energy-adjusted daily intake of smoked meat was significantly associated with breast cancer risk in overall, pre- and postmenopausal women (aORs: 2.31-3.13, OR 95% CIs exclude 1). High smoked meat intake interacted positively with the His variant allele (all γ>1). These results correlated with those of the meta-analysis (γ(pooled-overall)=1.27). The SULT1A1 His/His genotype may increase the risk of breast cancer among Asian women, and dietary exposure to heterocyclic amines and polycyclic aromatic hydrocarbons, along with the SULT1A1 His/His variant genotype, may synergistically increase the risk of breast cancer.     

Inhibition of hepatic aryl hydrocarbon hydroxylase by 3-methylcholanthrene, 7,8-benzoflavone and other inducers added in vitro.

A close correlation has been observed between the ability of aromatic polycyclic hydrocarbons and 7,8-benzoflavone (7,8-BF) to induce hepatic aryl hydrocarbon hydroxylase (AHH) in vivo and to inhibit the induced enzyme system in vitro. The activity of this mono-oxygenase was measured by the conversion of 14C-labeled dimethylbenz(a)anthracene (DMBA) or benzo(a)pyrene (BP) to water-soluble products by rat liver preparations (8000 X g supernatant). DMBA as substrate had the advantage over BP in giving a wider range of ethyl acetate-soluble metabolites and allowing the observation of changes in the pattern of these products following injection or addition of the inducing agents. This property was used to detect low concentration (0.1 muM) of polycyclic hydrocarbons which are strong AHH inducers and which may also be carcinogenic. The liver preparation was active for several months when stored at --20 degrees. A possible mechanism of action for the in vitro behaviour of polycyclic hydrocarbons and 7,8-BF towards AHH is proposed.     

Quantum chemical studies of polycyclic aromatic hydrocarbons and their metabolites: correlations to carcinogenicity.

In the context of the bay region hypothesis for polycyclic aromatic hydrocarbon (PAH) carcinogenesis, molecular properties were calculated for seventeen polycyclic aromatic hydrocarbons related to (1) intrinsic substrate reactivities towards activating and detoxifying metabolism and (2) the stabilities of the putative carbocation ultimate carcinogens. All-valence electron methods were used, avoiding the inherent difficulties found in the pi-electron methods. The calculated substrate reactivities were found to predict major metabolites successfully, supporting the validity of their use in attempted correlations with observed carcinogenic potencies. Positive correlations were found between observed carcinogenic potencies and (1) the reactivities of the parent polycyclic aromatic hydrocarbons towards the initial distal bay region epoxidation and (2) the stabilities of the diol epoxide carbocations. The reactivities of the distal bay region diol epoxides, were high for both carcinogenic and non-carcinogenic compounds, implying that the second epoxidation does not determine relative carcinogenic activity. Support for a possible alternative hypothesis, that polycyclic aromatic hydrocarbons are activated by one electron oxidation, was also found.     

Association of 1 hydroxypyrene glucuronide in human urine with cigarette smoking and broiled or roasted meat consumption

Humans are exposed to polycyclic aromatic hydrocarbons PAHs from various occupational, dietary, environmental and medicinal sources. We measured 1 hydroxypyrene glucuronide 1 OHP gluc concentration in urines from male non smokers n = 50, smokers of blond tobacco n = 31, smokers of black tobacco n = 16, and pipe smokers n = 3 . Immunoaffinity chromatography was used as a preparative step and synchronous fluorescence spectroscopy as the quantitation method. The concentration of 1 OHP gluc in urine from smokers mean SE: 1.04 0.13 pmol ml-1 urine was significantly higher than in urine from non smokers 0.55 0.05 pmol ml-1 urine by the Wilcoxon rank sum test non smokers versus all smokers, p = 0.001; vs black tobacco smokers, p = 0.001; vs blond tobacco smokers, p = 0.007 . Urinary 1 OHP gluc concentration among subjects who had consumed roasted, grilled or broiled meat within the past 24 h was elevated compared with those who had not p = 0.025 . Multiple linear regression showed significant associations of urinary 1 OHP gluc with number of cigarettes smoked p = 0.002 and consumption of roasted, grilled or broiled meat p = 0.028 . Systemic CYP1A2 activity estimated by caffeine metabolism was significantly correlated with urinary 1 OHP gluc concentration. However, this association was probably due to cigarette smoking, since adjusting for cigarette smoking by multiple linear regression made the association between urinary 1 OHP gluc and CYP1A2 phenotype non significant. These results further support the use of urinary 1 OHP gluc as a biomarker of recent pyrene exposure through inhalation or diet.     

Biodegradation of polycyclic aromatic hydrocarbons

The intent of this review is to provide an outline of the microbial degradation of polycyclic aromatic hydrocarbons. A catabolically diverse microbial community, consisting of bacteria, fungi and algae, metabolizes aromatic compounds. Molecular oxygen is essential for the initial hydroxylation of polycyclic aromatic hydrocarbons by microorganisms. In contrast to bacteria, filamentous fungi use hydroxylation as a prelude to detoxification rather than to catabolism and assimilation. The biochemical principles underlying the degradation of polycyclic aromatic hydrocarbons are examined in some detail. The pathways of polycyclic aromatic hydrocarbon catabolism are discussed. Studies are presented on the relationship between the chemical structure of the polycyclic aromatic hydrocarbon and the rate of polycyclic aromatic hydrocarbon biodegradation in aquatic and terrestrial ecosystems.     

Association of 1 hydroxypyrene glucuronide in human urine with cigarette smoking and broiled or roasted meat consumption

Humans are exposed to polycyclic aromatic hydrocarbons PAHs from various occupational, dietary, environmental and medicinal sources. We measured 1 hydroxypyrene glucuronide 1 OHP gluc concentration in urines from male non smokers n = 50 , smokers of blond tobacco n = 31 , smokers of black tobacco n = 16 , and pipe smokers n = 3 . Immunoaffinity chromatography was used as a preparative step and synchronous fluorescence spectroscopy as the quantitation method. The concentration of 1 OHP gluc in urine from smokers mean SE: 1.04 0.13 pmol ml-1 urine was significantly higher than in urine from non smokers 0.55 0.05 pmol ml-1 urine by the Wilcoxon rank sum test non smokers versus all smokers, p = 0.001; vs black tobacco smokers, p = 0.001; vs blond tobacco smokers, p = 0.007 . Urinary 1 OHP gluc concentration among subjects who had consumed roasted, grilled or broiled meat within the past 24 h was elevated compared with those who had not p = 0.025 . Multiple linear regression showed significant associations of urinary 1 OHP gluc with number of cigarettes smoked p = 0.002 and consumption of roasted, grilled or broiled meat p = 0.028 . Systemic CYP1A2 activity estimated by caffeine metabolism was significantly correlated with urinary 1 OHP gluc concentration. However, this association was probably due to cigarette smoking, since adjusting for cigarette smoking by multiple linear regression made the association between urinary 1 OHP gluc and CYP1A2 phenotype non significant. These results further support the use of urinary 1 OHP gluc as a biomarker of recent pyrene exposure through inhalation or diet.     

Profiles of polycyclic aromatic hydrocarbon metabolites after treatment with various inducers of microsomal rat liver monoxygenases (author's transl)

The microsomal oxidation of 12 frequently occurring environmental polycyclic aromatic hydrocarbons after incubation with rat-liver microsomes has been studied and their metabolites characterized by means of gas-liquid chromatography/mass spectrometry. The method enables the detection and characterisation of phenols, diols, triols, and tetrols as trimethylsilyl ethers beside the original hydrocarbons. Moreover, the induction properties of some carcinogenic and non-carcinogenic hydrocarbons (benz[a]anthracene, pyrene, chrysene, benzo[a]-pyrene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene) have been studied. Except pyrene and benzo[e]pyrene, all compounds investigated significant but different induction factors. The relevance of the induction for an estimation of the biological effect of environmental polycyclic aromatic hydrocarbons is discussed.     

Ellipticines as potent inhibitors of microsomes-dependent chemical mutagenesis.

9-Hydroxyellipticine (9-OHE), an inhibitor of microsomal monooxygenase activities has been shown to exert a large or even complete decrease of the mutagenicity, on the Salmonella strains of a great number of compounds (aromatic amines, polycyclic aromatic hydrocarbons, fungal toxins, azo compounds, tobacco smoke condensate). 9-OHE and 9-fluoroellipticine are more potent inhibitors than ellipticine itself. The inhibitions exerted by 9-OHE are not even equalled by 10-fold higher doses of 7,8-benzoflavone (7,8-BF). There is a good correlation between these data and the interaction properties of ellipticines with microsomal cytochromes P-450.     

Biomonitoring of tobacco smoke carcinogenicity by dosimetry of DNA adducts and genotyping and phenotyping of biotransformational enzymes: a review on polycyclic aromatic hydrocarbons

In this review article, we summarize the data on tobacco smoke carcinogenicity in relation to DNA adduct dosimetry and genotyping and phenotyping of biotransformational enzymes. A major class of carcinogens, polycyclic aromatic hydrocarbons, present in substantial quantities in tobacco smoke, is discussed. The historical background and an overview of the metabolic pathways are given. The epidemiological and biological data in particular on dosimetry of the representative DNA adducts and genotyping and phenotyping of the respective activating and detoxifying enzymes are presented. The salient findings are highlighted, the uncertainties are underlined and, finally, recommendations for future research are made.     

Biomonitoring of tobacco smoke carcinogenicity by dosimetry of DNA adducts and genotyping and phenotyping of biotransformational enzymes: a review on polycyclic aromatic hydrocarbons

In this review article, we summarize the data on tobacco smoke carcinogenicity in relation to DNA adduct dosimetry and genotyping and phenotyping of biotransformational enzymes. A major class of carcinogens, polycyclic aromatic hydrocarbons, present in substantial quantities in tobacco smoke, is discussed. The historical background and an overview of the metabolic pathways are given. The epidemiological and biological data in particular on dosimetry of the representative DNA adducts and genotyping and phenotyping of the respective activating and detoxifying enzymes are presented. The salient findings are highlighted, the uncertainties are underlined and, finally, recommendations for future research are made.     

DNA damage induced by cigarette smoke condensate in vitro as assayed by 32P-postlabeling. Comparison with cigarette smoke-associated DNA adduct profiles in vivo.

Cigarette smoke induces a multitude of bulky/aromatic DNA adducts in vivo as revealed by 32P-postlabeling assay. The formation of such adducts is thought to involve metabolic activation of aromatic chemicals especially polycyclic aromatic hydrocarbons (PAHs) present in tumor-initiating cigarette tar fractions, via cytochrome P450-associated monooxygenases. Because radicals are present in both the gas and particulate (tar) phase of cigarette smoke and in aqueous extracts of cigarette smoke condensate (CSC), we addressed the question as to whether cytochrome P450-independent, possibly free radical-mediated reactions may contribute, also, to formation of cigarette smoke-associated bulky DNA adducts. Rat-lung DNA was incubated with aqueous extracts of CSC in the absence of microsomes under various conditions and analyzed by 32P-postlabeling. Radioactively labeled bulky reaction products were found to accumulate in a time- and CSC concentration-dependent manner. The resulting chromatographic profiles resembled cigarette smoke-associated DNA-adduct patterns observed in vivo. Pretreatment of aqueous CSC extract with radical scavengers/reducing agents (ascorbic acid, glutathione) diminished adduct formation in a concentration-dependent manner. Adduct formation in vitro may involve oxygen-free radicals, which are known to be present in aqueous CSC extracts and could (i) attack DNA directly to produce bulky adducts, (ii) induce radical sites on DNA covalently binding CSC components, or (iii) convert CSC components to DNA-reactive electrophiles. In addition, DNA may react with direct-acting mutagens in CSC. Adduct fractions derived from in vitro and in vivo experiments showed similar chromatographic behavior, suggesting that metabolic activation as well as processes not involving metabolism lead to formation of smoking-induced bulky DNA adducts in vivo.     

Induction of choline kinase by polycyclic aromatic hydrocarbon carcinogens in rat liver

The administration to rats of polycyclic aromatic hydrocarbons such as 3-methylcholanthrene, 3,4-benzo(a) pyrene and β-naphthoflavone caused a significant elevation of hepatic choline kinase activity. On the other hand, phenobarbital-type inducers (phenobarbital, 1,1,1-trichloro 2,2-bis (ρ-chlorophenyl) ethane (DDT) and hexachlorobenzene) did not stimulate the activity at all. The administration of either cycloheximide or actinomycin D completely depressed the elevation of choline kinase activity induced by polycyclic aromatic hydrocarbons, indicating that the elevated activity by these chemicals could be due to the change in the enzyme level. These results strongly suggest that induction of choline kinase are involved in the sequence of events leading to the induction of hepatic drug metabolism by polycyclic aromatic hydrocarbons.