Changes

A value of aerodynamic diameter such that 50% of the activity in the aerosol is associated with particles of [[thermodynamic diameter ]] (dthd_th) greater than the AMTD. The AMTD is used when deposition depends principally on diffusion, typically when the AMAD is less than about 0.3 μm. (Adapted from [[ICRP Publication 130]], 2015)

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