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Table 8 Microscopic findings in the lungs of male and female rats 24 h and 90 days after a 90-day exposure to Graphistrength© C100

From: 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

  Males Females
Target concentration (mg/m3) 0 0.05 0.25 5.0 0 0.05 0.25 5.0
Number examined 10/10 10/10 10/10 10/10 10/10 10/10 10/10 10/10
(24 h/90 days)
Black particle deposition         
trace - -/10 - - - -/10 - -
minimal - 9/- -/10 - - 10/- 2/10 -
slight - - 10/- - - - 8/- -
moderate - - - -/2 - - - 4/3
marked - - - 10/8 - - - 6/7
Mean severitya - 0.9/0.5 2.0/1.0 4.0/3.8 - 1.0/0.5 1.8/1.0 3.6/3.7
Alveolar macrophages         
minimal - - 8/10 -/1 - - 9/10 -
slight - - - -/3 - - - 1/8
moderate - - - 10/6 - - - 9/2
Mean severitya - 0.0 0.8/1.0 3.0/2.5 - - 0.9/1.0 2.9/2.2
Alveolar eosinophilic material         
minimal - - - 6/8 - - - 4/4
slight - - - 2/2 - - - 4/5
moderate - - - 1/- - - - 1/-
Mean severitya - - - 1.3/1.2 - - - 1.5/1.4
Alveolar granulocyte infiltration         
minimal - - - 10/8 - - - 10/7
Mean severitya - - - 1.0/0.8 - - - 1.0/0.7
Interstitial inflammation         
minimal - - - -/1 - - - 4/5
slight - - - 10/9 - - - 6/5
Mean severitya - - - 2.0/1.9 - - - 1.6/1.5
Bronchiolar cell hypertrophy/hyperplasia         
minimal - - - 10/- - - - 10/-
Mean severitya - - - 1.0/- - - - 1.0/-
Focal/multifocal collagen depositions, alveolar septa         
minimal - - - - - - - -/2
slight - - - -/2 - - - -
Mean severitya - - - -/0.4 - - - -/0.2
Increased lymphocytes, BALT b         
minimal - - - 2/- - - - 2/-
slight - - - 1/- - - - -
Mean severity - - - 0.4/- - - - 0.2/-
  1. Histopathological findings were graded in severity using a five point system of minimal (grade 1), slight (grade 2), moderate (grade 3), marked (grade 4) or severe (grade 5). An additional grading unit, trace (grade 0.5), was used to describe a trace amount of black particle deposition in the lungs
  2. a: mean severity is ∑ number of animals x severity / number of examined organs in the group
  3. bbronchus associated lymphoid tissue
  4. - : no animal affected