, \ should be described, [t should he rememberod that our Intorest is on the yearly average Lacluding pariads of eating and slooping as well a8 time spent on the water, The AMAD of 0.5 pm seems small, particularly when the main source appears to be mechanical disturbance, 14. P. 12, Lines 19+20, The statement that 20% of that on the filter is usually regarded as raspirable raises the quostion of how thig was included in the calculations, The definition of the AMAD of 0.5 ttm implies Fractions deposited and, fore, the "respirable" Fraction. 15. P, 19, par. 2. there- Tt should be noted that such a program is iu progross at Battelle and that numbers From their studies are not as extreme as those picked from reviews or articles for another purpose (i.e, Larsen). It would be well to draw such conclusions from the published experiments rather than from an interpretation.