The role of electron microscopy and microanalytical techniques in the understanding of the pathophysiology of environmental dusts associated with lung disease.

The purpose of this study has been to elucidate the usefulness of TEM/STEM/EDX system in the identification of environmental dust within the interstitial macrophages of the lung. The four cases chosen for this study gave variable history of exposure to occupational "dust". A review of literature with particular reference to clay associated pneumoconiosis has been made. Previous studies have given little prominence to the fate or behaviour of inhaled "dust" particles in the intracellular environment. It is here that it is believed that a TEM/STEM/EDX system has the potential of playing a significant role in promoting our understanding of "dust" associated pneumoconiotic disease of the lung. The results obtained from the three cases demonstrate the presence of clay particles in the form of granules, plates and needles or thin flakes within the phagosomes of the interstitial macrophages. On morphological grounds the thin needles or flakes appeared to undergo a process of stacking within the phagosomal matrix resulting in the formation of large closely stacked needle-like structures which lie free in the cytoplasm. The possibility of a physicochemical basis for such a morphological sequence is discussed. The fourth case, that of stainless steel associated pneumoconiosis, also showed evidence of breakdown of the original dust in the macrophages. From the evidence presented it is concluded that application of the TEM/STEM/EDX technique may advance our knowledge of the interaction of inhaled dust and the macrophages at the subcellular level.