High Benzo[a]pyrene Research Articles

Dose-dependent benzo(a)pyrene [B(a)P]–DNA adduct levels and persistence in F-344 rats following subchronic dietary exposure to B(a)P

In order to investigate the relationship between BaP–DNA adduct formation and long-term exposure to benzo(a)pyrene (BaP), DNA adduct levels in liver and lung tissues of male and female F-344 rats subchronically exposed to BaP were determined. Doses of 0, 5, 50, and 100 mg/kg BaP, representing control, low, intermediate, and high doses, respectively, were administered in the animal diet over a 90-day period. After dosing, animals were sacrificed, liver and lung tissues were removed, DNA was isolated and analyzed for BaP-induced DNA adducts by the 32P-postlabeling method using a four-directional thin-layer chromatography system. At low and intermediate BaP doses, DNA adduct levels in the tissues were significantly correlated with exposure. However, at high BaP doses, the dose-DNA adduct relationship became non-linear. Similarly, the relative DNA adducts persistence at intermediate and high doses were significantly higher than that measured at low dose. The low and intermediate dose linearity and high dose non-linearity may be due to saturation of metabolic activation and detoxification enzymes, and DNA repair processes.

Applicability of the black slug Arion ater for monitoring exposure to polycyclic aromatic hydrocarbons and their subsequent bioactivation into DNA binding metabolites

The applicability of terrestrial black slugs Arion ater (Mollusca, Gastropoda) was studied for biomonitoring environmental exposure to polycyclic aromatic hydrocarbons (PAHs). In laboratory experiments, slugs were orally exposed to benzo[a]pyrene (BaP) for a short term (3 days) or a long term (119 days) period. Test animals were collected in the field, or were reared under laboratory conditions to ensure that they had no history of PAH-exposure. Benzo[a]pyrene hydroxylase (BPH) activity was measured in the digestive gland as a biomarker for BaP exposure. Bulky DNA adduct formation in kidney was measured as an effect biomarker for BaP bioactivation into DNA-binding metabolites. Although success of clutching was relatively low (5 out of 18 slugs produced egg packages), sufficient number of slugs were obtained to perform exposure experiments due to high hatching (89%) and survival rates (79%). After a short exposure to a relatively high BaP doses of 20 and 200 μg/g fresh feed, a dose-dependent and significant increase of BPH activity and bulky DNA adduct levels could be demonstrated in A. ater. Induction factors were low (two times control level), but optimization of the test conditions yielded a higher BPH induction factor of 4.8 times control level. BPH activity and bulky DNA adduct levels, however, did not increase after a long-term exposure to environmentally relevant BaP doses (upto 0.25 μg/g fresh feed). Based on this lack of response after realistic exposure it is concluded that A. ater is not sensitive to BaP exposure and, therefore, not suitable for monitoring environmental exposure to PAHs.

Newsagents’ daily personal exposures to benzo(a)pyrene in Genoa, Italy

Abstract Daily personal exposures to benzo(a)pyrene (BaP) of 31 newsagents working in Genoa, Italy, were evaluated throughout 1998 during two different seasonal periods (February–April and May–June). Exposures of smoker and non-smoker subjects were compared. The highest BaP exposures were those of smokers during the cold period (2.20±0.84 ng/m3). During this same period, the BaP exposure for non-smoker subjects was 1.00±0.32 ng/m3. Both smoker and non-smoker exposures showed a seasonal dependence, with the lowest values occurring in the warm period (smokers: 1.46±0.72 ng/m3, non-smokers: 0.65±0.25 ng/m3). Compared to the cold period, the warm period produced a nearly 35% reduction in BaP exposures in both smoker and non-smoker subjects. A linear correlation was observed between personal exposures and number of cigarettes smoked daily. An increase in average daily BaP exposure of 0.071±0.009 ng/m3 for every cigarette, due to passive smoke, was calculated. Mean BaP concentrations calculated from fixed monitoring stations were nearly 40% higher than mean personal exposures of non-smoker newsagents.

Benzo[ a]pyrene and β-Naphthoflavone Mutagenic Activation by European Eel ( Anguilla anguilla L.) S9 Liver Fraction

Is Anguilla anguilla L. (eel) liver ethoxyresorufin O-deethylase (EROD) induction absolutely necessary in order to convert promutagens as benzo[ a]pyrene (BaP) into a mutagenic compound? Eels were exposed for 8 h to clean (control) and 0.3 μM β-naphthoflavone (BNF)-contaminated water. The 8-h exposure to 0.3 μM BNF brought about a very high EROD induction (10 pmol/min/mg protein) compared to control animals (1 pmol/min/mg protein). The Ames test (Maron and Ames, 1983) was carried out with Salmonella typhimurium TA 98 strain (TA98 His −) and eel isolated S9 liver fraction was used as a metabolic BaP activator. The BaP and BNF dose range concentrations tested were 0 (blank), 0.015, 0.08, 0.15, 0.38, 0.75, 1.5, 3.8, and 7.5 μM/plate and 0 (blank), 0.412, 1.235, 3.704, 11.1, 33.0, and 100 nM BNF, respectively. A dose–response relationship between BaP concentration and mutagenic activity was observed in the presence of S9 fractions in control and 0.3 μM BNF-exposed eels. Significant positive results, as TA98 His + revertants, were observed at 0.38, 0.75, 1.5, 3.8, and 7.5 μM BaP/plate induced by BNF S9 fractions. Significant BaP mutagenic activation by liver control S9 was detected only at 1.5, 3.8, and 7.5 μM/plate. The BaP 1.5, 3.8, and 7.5 μM/plate mutagenic activation by BNF S9 and control S9 were not significantly different. Relative to BNF activation, it was only possible to detect His + reversion at 11.1 nM BNF concentration with 0.3 μM BNF-induced S9. The above results demonstrate that the eel S9 liver fraction has the capacity to biotransform high BaP concentrations and convert it into a mutagenic compound with or without previous liver BNF biotransformation induction. The same does not apply to low BaP concentrations, where liver S9 induction by BNF is necessary to promote mutagenesis.

The effect of stress on toxicant‐dependent cytochrome P450 enzyme responses in the arctic charr (Salvelinus alpinus)

In the present study we investigated the effect of stress and cortisol on cytochrome P450 (CYP) expression in Arctic charr exposed to benzo[a]pyrene (BaP). Expression of hepatic CYP1A and CYP3A was monitored 8 d after a single oral dose of BaP (10 mg/kg fish) and compared to that in unexposed fish. During this period the fish were subjected to one of the following stress regimes: no stress, no stress and cortisol implantation, 10 min of daily handling and confinement stress, and confinement stress during the last 6 h before sampling. In BaP-exposed fish daily stress resulted in significantly lower (53%) CYP1A protein levels as compared to those in unstressed fish. For CYP1A catalytic activity (measured as 7-ethoxyresorufin-O-deethylase [EROD] activity), the suppressive response to stress was less pronounced. These results contrast to previous findings of a potentiation by corticosteroids on xenobiotic-dependent CYP1A induction in vitro in cultured fish hepatic cells. No effects of high cortisol levels or BaP were found on the steroid-metabolizing CYP3A enzyme levels. The lack of any alterations in the CYP3A protein level indicates that CYP3A expression is not inducible by cortisol in the Arctic charr under the conditions used here. The conclusion was made that short-term stress associated with sampling (i.e., 6 h of confinement stress before sampling) of wild charr does not compromise the EROD activity as a reliable biomarker.

Precision of Benzo(a)pyrene (BaP) Analysis in Mussel Tissue

The precision of sampling and analytical methods used to determine benzo(a)pyrene (BaP) concentrations in mussel tissue were tested. BaP concentrations in the whole tissue of 10 wild mussels, randomly collected from eight different sites along the Liguria coast, were measured two or three times. The mean coefficients of variation (and standard deviation (S.D.)) were 11.5 ± 2.4 in low contaminated samples (BaP < 2 ng/g) and 10 ± 1.6 in mussel samples with a higher BaP concentration. The same analyses carried out in four sub-samples of breeding mussels (10 mussels each), caged for 20 days in differently polluted seawaters, showed a mean coefficients of variation (CV) of 19.5 ± 2.4 in mussels from a clean site and of 12.2 ± 1.1 in mussels from a contaminated site. According to the evaluated precisions, the sampling and analytical method adopted in this study can define statistically different BaP concentrations detected in the tissues of mussels collected from two sites when their difference is greater than 27%.

Influence of cooking on benzo(a)pyrene content in smoked sausages

The changes in benzo(a)pyrene (BaP) content of smoked sausages were monitored during 1 h cooking. During this time, the BaP content decreased from 4·80 to 1·87 μg/kg. The maximum drop in BaP content was reached in the first 20 min of cooking. Two factors affected the course of BaP changes, viz. water-holding capacity and the fat content. After excluding these factors, there was a high correlation coefficient of 0·996 between time of cooking and BaP content, which confirmed an inverse relationship between the decrease in BaP content and time of cooking. The BaP decrease was directly proportional to the decrease of fat content during cooking, when the relatively high BaP content of 7·71 μg/kg was found in the cooked-out fat.

Dose-related carcinogenic effects of water-borne benzo[ a]pyrene on livers of two small fish species

Benzo[ a]pyrene (BaP) administered by water-borne exposures caused dose-related carcinogenic effects in livers of two small fish species, the Japanese medaka ( Oryzias latipes) and the guppy ( Poecilia reticulata). Medaka and guppies each were given two 6-h exposures. The first exposure was conducted on 6- to 10-day-old specimens. The second exposure was given 7 days later. The tests incorporated five treatment groups: (1) control, (2) carrier (dimethylformamide) control, (3) low BaP dose (not detectable-4 ppb), (4) intermediate BaP dose (about 8–47 ppb BaP), and (5) high BaP dose (200–270 ppb). Following the high-dose exposure, hepatocellular lesions classified as foci of cellular alteration (altered foci), adenomas, and hepatocellular carcinomas occurred in both species. In medaka, the lesions appeared to develop sequentially with the appearance of altered foci followed by adenomas and then hepatocellular carcinomas. Most lesions in guppies, however, were classified as altered foci although a few adenomas occurred in the early (24-week) sample and hepatocellular carcinomas occurred in the late (52-week) sample. When total lesions were combined, medaka had an 11% incidence at 24 weeks after the initial exposure and 36% incidence at 36 weeks. In guppies, 8% had liver lesions at 24 weeks 19% at 36 weeks, and 20% at 52 weeks. A single extrahepatic neoplasm, a capillary hemangioma in a gill filament, occurred in a medaka from the 36-week high-dose sample. The results suggest that the medaka and guppy are capable of metabolizing water-borne BaP to carcinogenic metabolites which initiate hepatic tumor development.