[Needle-like nonasbestos particles in Bulgarian mineral raw materials]

The spreading of needle-like minerals in the country is studied, which are of no industrial importance, but are contained in some of course and nonmetallic mineral raw materials. On the basis of their classification are chosen standards: sepiolite, wollastonite, palygorskite, etc., and their dispersion in needle-like fine dispersive particles, is studied. On the basis of a preliminary prognosis are established needle-like particles in ore dust of one iron ore location. The importance of the needle-like nonasbestos components can be expressed with "dose" inhaled needles on the basis of the concentration of the needle-like components, the duration of one work shift and the work load in a definite work operation. The quantity of inhaled needles by an operator on a filling machine for mineral flour, containing minimum quantity of needles (0.5%) with pollution above MAC is near to that during packing of asbestos. The results received are useful for future classification of the biological activity of needle-like nonasbestos components.