Enhancement of DNA damage and involvement of reactive oxygen species after exposure to bitumen with UVA irradiation

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

Genotoxic effect of exposure to polycyclic aromatic hydrocarbons (PAHs) in asphalt workers

Asphalt workers are at risk due to exposure to asphalt fumes containing polycyclic aromatic hydrocarbons (PAHs). The main purpose of this study was to measure the urinary metabolite of PAHs and to determine its effect on micronucleus (MN) formation as an indicator of genotoxic damage. In this cross-sectional study, the MN frequency in 48 male asphalt workers exposed to PAHs was measured and compared with 48 male non-exposed employees. PAHs exposure was evaluated by determining urinary 1-Hydroxypyrene (1-OHP). The mean concentrations of 1-OHP in the exposed and non-exposed groups were 0.58 ± 0.41 μmol/mol creatinine and 0.38 ± 0.25 μmol/mol creatinine, respectively. 1-OHP concentration was significantly higher in smokers compared with non-smokers in both exposed and non-exposed groups. Moreover, the mean MN frequency in the exposed group was significantly higher than in the non-exposed group. The MN frequency was significantly higher in asphalt workers with a work history of ≥ 15 years compared to workers with lower work history. In a fully adjusted model, there was a statistically significant association between exposure to PAHs, with MN and 1-OHP concentration, and between smoking status with 1-OHP. The findings of the present study indicated that occupational exposure to PAHs was associated with increased urinary 1-OHP as well as DNA damage in the asphalt workers.

Cytogenotoxicity induced by PBDE-47 combined with PCB153 treatment in SH-SY5Y cells

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are important recalcitrant halogenated compounds that have been regarded as major environmental pollutants. Recently, their concurrent appearance in the environment and humans and their structural and toxicological profile similarities have sparked interest in the potential toxicologic consequences of their coexposure. The aim of the current study was to evaluate the cytogenotoxic effects induced by 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) combined with 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) treatment in human neuroblastoma cells (SH-SY5Y) in vitro. SH-SY5Y cells were exposed to different concentrations of PBDE-47 (0, 2, 4, 8 μM) with or without PCB153 (5 μM) for 24 h. Thereafter, the cell viability, DNA damage, chromosomal abnormalities, and DNA-protein crosslinks (DPC) were determined. The results show that PBDE-47 and PCB153 alone and in combination induce DNA damage, with an increase in the frequency of micronuclei (MN) and DPC formation with increasing PBDE-47 concentration. In cells coexposed to PBDE-47 and PCB153, the cell viability significantly decreased while the MN frequency, DNA damage and DPC formation were all obviously increased compared to those of cells treated with the corresponding concentrations of PBDE-47 or PCB153 alone. Factorial analysis suggests that there were interactions between PBDE-47 and PCB153. The results imply that PBDE-47 interacts with PCB153 to inhibit cell viability and induce DNA damage, DPC formation, and chromosome abnormalities.

Effects of UVA and visible light on the photogenotoxicity of benzo[a]pyrene and pyrene

This study investigated the role of UVA/visible light (U, 320-800 nm) and visible light (V, 400-800 nm) in the phototoxicity and photogenotoxicity of two ubiquitous polycyclic aromatic hydrocarbons (PAH): benzo[a]pyrene (BaP) and Pyrene (Pyr). These mechanisms were evaluated by the WST-1 test and the comet assay on normal human keratinocytes (NHK) and by the micronucleus test on CHO cells. The production of reactive oxygen species (ROS) was assessed through the induction of 8-oxodeoxyguanine (8-oxodG) lesions by immunofluorescence staining in NHK. Results of the WST-1 test revealed the phototoxic properties of BaP and Pyr after irradiation with U and V lights. BaP presented the highest phototoxic properties. Results of the comet assay showed that U- and V-irradiated BaP and Pyr induced increasing rates of DNA single-strand breaks in NHK, in a dose dependent manner. The tested PAH could also induce increased levels of micronuclei in CHO cells after U and V irradiations. Increasing 8-oxodG levels were detected after U and V irradiations in BaP- and Pyr-treated keratinocytes and confirmed the involvement of ROS in the photogenotoxicity of PAH. Overall, this study highlighted the existence of an alternative pathway of PAH genotoxicity that is induced by UVA and/or visible light. Visible light is suggested to photoactivate PAH by a mechanism which is mainly based on oxidative reactions.

Potential of chlorpyrifos and cypermethrin forming DNA adducts

DNA adducts consist of DNA monoadducts, DNA intrastrand crosslinks, DNA interstrand crosslinks, and DNA-protein crosslinks. If not repaired or mistakenly repaired, DNA adducts may lead to gene mutations and initiate carcinogenesis. Two insecticides, chlorpyrifos and cypermethrin, were studied for their potential of forming DNA monoadducts, DNA interstrand crosslinks, and DNA-protein crosslinks in primary mouse hepatocytes via the assays of bioluminescence, ethidium bromide fluorescence, and K+-SDS precipitation. DNA interstrand crosslinks were also measured on calf thymus DNA. It was shown that chlorpyrifos could not form DNA adducts. Cypermethrin formed DNA monoadducts and DNA interstrand crosslinks in hepatocytes. However, cypermethrin didn't form DNA interstrand crosslinks on calf thymus DNA and in hepatocytes treated with SKF-525A, a cytochrome P450 inhibitor, which suggests that active metabolites of cypermethrin instead of cypermethrin itself caused DNA interstrand crosslinks and that cytochrome P450 may be involved in the activation of cypermethrin.

Lack of genotoxicity of bitumen fumes in transgenic mouse lung

During hot application of bitumen containing materials, e.g. in hot paving or roofing, fumes are emitted that contain polycyclic aromatic compounds. Previous studies with rodents exposed to bitumen and coal-tar fume condensates showed formation of DNA adducts. In order to clarify the genotoxicity of bitumen fumes, we designed a study by using mice carrying a reporter gene for mutagenesis analysis and exposed by nose-only to a constant and reproducible aerosol of bitumen fumes. We analyzed the genotoxic activity of inhaled bitumen fumes generated under those controlled conditions through the induction of mutation and DNA adducts in Big Blue mice. Mice were exposed to bitumen fumes (100 mg/m(3) total particulate matter) 6 h per day during 5 days by nose-only in an inhalation chamber designed in our laboratory. Following a 30-day fixation period, the experiment was terminated and lung DNA was extracted for mutant frequency and adduct determinations. The mutant frequency was determined using the cII and the lacI mutant analysis systems. In, addition, 61 and 54 mutants were sequenced in control and exposed groups, respectively. The study did not show any mutation or adduct induction in the exposed group compared to the control group: cII mutant frequencies were 11.0+/-4.5x10(-5) and 11.0+/-4.8x10(-5) in control and exposed lungs, respectively. Identically, using the lacI mutation detection system, the mutant frequencies were 6.4+/-3.1x10(-5) and 5.8+/-2.0x10(-5). The mutation spectra of both series were quite similar with regard to transition and transversion frequencies. The absence of genotoxicity in the group exposed to 100 mg/m(3) bitumen is discussed with regard to dosage of inhaled polycyclic aromatic compounds and species.