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Table 4 Sensitivity of results in dependence on modified input data (MPPD input parameters, steady state particle volume, clearance half time in humans) and different MPPD program versions: Estimated NOAEC in rats, calculated adaptation factors AF lung burden and AF clearance , and the derived human equivalent concentration (HEC) according to the second Model B procedure described by Equation (7) on p.182 and Equations (8), (9), (10) on p. 186 in [14]

From: Translational toxicology in setting occupational exposure limits for dusts and hazard classification – a critical evaluation of a recent approach to translate dust overload findings from rats to humans

MPPD Version

MPPD input parameters*

Alveolar deposition fraction in rats /%

Alveolar deposition fraction in humans/%

Critical steady state particle volume burden/μL per kg-rat

Alveolar clearance half time in humans/days

NOAEC/mg/m 3

AF lung burden /1

AF clear ance /1

HEC/mg/m 3

2.0

IA switched off OMB

7.5

16.4

1

400

0.53

0.93

0.93

0.53

2.0

IA ONA

6.3

8.4

1

400

0.63

1.52

0.93

1.03

2.11

3.3

8.8

1

400

1.21

0.76

0.93

0.98

2.0

IA ONA

6.3

8.4

4.2

400

2.66

1.52

0.93

4.33

2.11

3.3

8.8

4.2

400

5.07

0.76

0.93

4.14

2.0

IA ONA

6.3

8.4

1

250

0.63

1.52

0.58

1.65

2.11

3.3

8.8

1

250

1.21

0.76

0.58

1.58

2.0

IA ONA

6.3

8.4

4.2

250

2.66

1.52

0.58

6.93

2.11

3.3

8.8

4.2

250

5.07

0.76

0.58

6.62

  1. *IA, Inhalability Adjustment; OMB, Oronasal-Mouth Breather; ONA, Oronasal-Normal Augmenter; Other input data used invariantly and in accordance with [14] and [11]: reference body weights = 1 kg-rat, 70 kg-human; ventilation rates = 0.29 m3/kg-rat and day, 10 m3/70 kg-human and day; macrophage pool volumes = 7x1010 μm3/kg-rat and 50x1010 μm3/kg-human; alveolar clearance half time in rats = 60 days; MMAD = 1.8 μm, GSD = 2, density = 1 g/cm3 (particle characteristics); other MPPD input parameters as listed in the MAK document ([11], p. 57, 58 and Appendix).