title: Reply to the letters to the editor submitted by T. L. Ogden and K.T. Du Clos, and by R. Foster regarding the paper ‘SWeRF—a method for estimating the relevant fine particle fraction in bulk materials for classification and labelling purposes’.
abstract: The authors respond to the points raised in the Letters to the Editor raised by Ogden and Du Clos and by Foster. Ad 1: The debate of the classification of respirable cyrstalline silica is outside the scope of the technical paper. Ad 2: A standard for the determination of SWeRF is under development, in which indeed the provision is made that for a correct determination all quartz within the fine fraction needs to be liberated. Ad 3: Dustiness tests provide useful information for occupational hygienists, but are not suitable for fulfilling classification and labelling requirements. Ad 4: Pipette effects are not discussed in the paper because the difference between calculating the SWeRF from the particle size distribution and the SWeRF from sedimentation is very small.
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Pensis
authors.forename: Frank
authors.initials: F
authors.lastname: Luetzenkirchen
authors.forename: Bernd
authors.initials: B
authors.lastname: Friede
mesh_terms: D015197:Carcinogenicity Tests; D004784:Environmental Monitoring / Q000379:methods*; D006801:Humans; D011356:Product Labeling / Q000592:standards*; D012822:Silicon Dioxide / Q000032:analysis* / Q000633:toxicity*
chemical_list: D012822:Silicon Dioxide