Cytogenetic markers, DNA single-strand breaks, urinary metabolites, and DNA repair rates in styrene-exposed lamination workers.

The effect of occupational exposure to styrene on frequencies of chromosomal aberrations and binucleated cells with micronuclei and on single-strand break levels in peripheral blood lymphocytes was studied in 86 reinforced plastic workers and 42 control individuals (including 16 maintenance workers with intermittent, low-dose exposure). In these individuals, the irradiation-specific DNA repair rates and the repair rates of 8-oxoguanines were investigated. We assessed the exposure by measuring the concentrations of styrene in air and in blood and of mandelic acid, phenylglyoxylic acid, 4-vinyl phenol conjugates and regioisomeric phenyl hydroxyethyl mercapturic acids in urine. All these parameters correlated with one another. No clear relationship was found between the styrene exposure and the frequencies of chromosomal aberrations. Binucleated cells with micronuclei were moderately related to the parameters of styrene exposure. We found a negative correlation between all exposure parameters and single-strand breaks. The positive correlation between exposure parameters and DNA repair rates suggests that particular DNA repair pathways may be induced by styrene exposure

Evaluation of the health effects of carbon nanotubes

Recent studies have suggested that some types of multiwalled carbon nanotubes (MWCNTs) have similar effects as asbestos. This report shows that rigid, long and needle-like MWCNTs induce inflammation and DNA damage in the lungs and in cultured cells, while flexible, long and tangled MWCNTs do not. It appears that the rigidity of MWCNTs is a key feature in triggering a specific inflammatory reaction and in causing cellular alterations involved in cancer formation. These results provide new information on the adverse effects of MWCNTs and are useful in assessing which forms of MWCNTs require regulatory attention and special safety measures in occupational settings

<i>In vitro</i> and <i>in vivo</i> genotoxic effects of straight versus tangled multi-walled carbon nanotubes

<p>Some multi-walled carbon nanotubes (MWCNTs) induce mesothelioma in rodents, straight MWCNTs showing a more pronounced effect than tangled MWCNTs. As primary and secondary genotoxicity may play a role in MWCNT carcinogenesis, we used a battery of assays for DNA damage and micronuclei to compare the genotoxicity of straight (MWCNT-S) and tangled MWCNTs (MWCNT-T) <i>in vitro</i> (primary genotoxicity) and <i>in vivo</i> (primary or secondary genotoxicity). C57Bl/6 mice showed a dose-dependent increase in DNA strand breaks, as measured by the comet assay, in lung cells 24 h after a single pharyngeal aspiration of MWCNT-S (1–200 μg/mouse). An increase was also observed for DNA strand breaks in lung and bronchoalveolar lavage (BAL) cells and for micronucleated alveolar type II cells in mice exposed to aerosolized MWCNT-S (8.2–10.8 mg/m³) for 4 d, 4 h/d. No systemic genotoxic effects, assessed by the γ-H2AX assay in blood mononuclear leukocytes or by micronucleated polychromatic erythrocytes (MNPCEs) in bone marrow or blood, were observed for MWCNT-S by either exposure technique. MWCNT-T showed a dose-related <i>decrease</i> in DNA damage in BAL and lung cells of mice after a single pharyngeal aspiration (1–200 μg/mouse) and in MNPCEs after inhalation exposure (17.5 mg/m³). <i>In vitro</i> in human bronchial epithelial BEAS-2B cells, MWCNT-S induced DNA strand breaks at low doses (5 and 10 μg/cm²), while MWCNT-T increased strand breakage only at 200 μg/cm². Neither of the MWCNTs was able to induce micronuclei <i>in vitro</i>. Our findings suggest that both primary and secondary mechanisms may be involved in the genotoxicity of straight MWCNTs.</p