Lung inflammation and lack of genotoxicity in the comet and micronucleus assays of industrial multiwalled carbon nanotubes Graphistrength© C100 after a 90-day nose-only inhalation exposure of rats

Table 1 Target and achieved aerosol concentrations and particles size of Graphistrength^© C100. Temperature, relative humidity and oxygen concentration measured over the 90-day exposure period

Groups	Control	Low	Mid	High
Target aerosol concentrations (mg/m³ air)	0	0.05	0.25	5.0
Achieved aerosol concentrations (mg/m³ air)	-	0.06 ± 0.04	0.28 ± 0.06	4.84 ± 0.41
Mean mass median aerodynamic diameter (MMAD, μm) (gravimetric determination)	-	nd^a	1.62 ± 0.39	2.30 ± 0.34
			(n = 5)	(n = 14)
Mean GSD (gravimetric determination)	-	nd^a	4.67 ± 4.81	2.47 ± 0.26
Mean percentage of particles < 3 μm (gravimetric determination)	-	nd^a	74.10 ± 14.00	63.49 ± 6.23
Count median aerodynamic diameter (CMAD, nm) (WPRS determination)	-	196.2 ± 54.7	231,5 ± 65.1	208.0 ± 62.0
		(n = 14)	(n = 14)	(n = 14)
Mean temperature (°C)	23.2 ± 0.9	23.3 ± 0.7	23.6 ± 0.7	23.8 ± 0.6
Mean relative humidity (%)	5.8 ± 1.5	6.1 ± 1.7	6.1 ± 1.7	6.3 ± 1.6
Mean oxygen concentration (%)	20.8 ± 0.0	20.8 ± 0.0	20.8 ± 0.0	20.8 ± 0.0

nd: not determined
^a at 0.05 mg/m³ due to the very low concentration, the particle size could not be determined by gravimetry at an air flow rate of 1 L/min. The aerosol concentrations at 0.05 and 0.25 mg/m³ were achieved by serial dilution with compressed, filtered, dry air of the 0.25 and 5.0 mg/m³ concentrations, respectively. Therefore, the MMAD and GSD at 0.05 mg/m³ are expected to be of the same order as at 0.25 mg/m³. This is also confirmed by particle size data from the 5-day study with sampling at an air flow rate of 9 L/min (see Additional file 1: Table S4 for details)

ISSN: 1743-8977