Occurrence of the potent mutagens 2- nitrobenzanthrone and 3-nitrobenzanthrone in fine airborne particles

Abstract

Polycyclic aromatic compounds (PACs) are known due to their mutagenic activity. Among them, 2-nitrobenzanthrone (2-NBA) and 3-nitrobenzanthrone (3-NBA) are considered as two of the most potent mutagens found in atmospheric particles. In the present study 2-NBA, 3-NBA and selected PAHs and Nitro-PAHs were determined in fine particle samples (PM 2.5) collected in a bus station and an outdoor site. The fuel used by buses was a diesel-biodiesel (96:4) blend and light-duty vehicles run with any ethanol-to-gasoline proportion. The concentrations of 2-NBA and 3-NBA were, on average, under 14.8 µg g^-1 and 4.39 µg g^-1, respectively. In order to access the main sources and formation routes of these compounds, we performed ternary correlations and multivariate statistical analyses. The main sources for the studied compounds in the bus station were diesel/biodiesel exhaust followed by floor resuspension. In the coastal site, vehicular emission, photochemical formation and wood combustion were the main sources for 2-NBA and 3-NBA as well as the other PACs. Incremental lifetime cancer risk (ILCR) were calculated for both places, which presented low values, showing low cancer risk incidence although the ILCR values for the bus station were around 2.5 times higher than the ILCR from the coastal site.

Figure 1

Chromatograms of 3-NBA and 2-NBA. (a) Bus station real PM sample, (b) ambient particulate sample from the coastal site. Limits of detection are 2.0 pg and 2.4 pg for 2-NBA and 3-NBA, respectively.

Figure 2

Electron impact mass spectra of (a) 3-nitrobenzanthrone and (b) 2-nitrobenzanthrone.

Figure 3

Box-and-Whisker plots for selected nitro-PAHs and PAHs in PM2.5, (a,b) diesel exhaust directly-emitted levels (bus station) and (c,d) ambient levels (coastal area). In this figure mean values are indicated by the red crosses, central horizontal bars are the medians, and the box lower and upper limits are the 1^st and 3^rd quartiles, respectively. Open circles and asterisks are outliers and closed circles are minimum/maximum values. The box plot width has no statistical meaning.

Figure 4

Ternary correlations among selected substances, top left: bus station, top right and bottom: coastal area.

Figure 5

Principal component analysis among active variables (or species determined in the samples, red circles) and active observations (or sampling days, blue circles) at 95% confidence level, for (a) bus station and (b) coastal site.

Figure 6

Agglomerative hierarchical clustering plots for (a,b) bus station and (c,d) coastal site datasets.