CONTRIBUTION OF ELECTRON PROBE X-RAY MICROANALYSIS (EPXMA) TO POLLUTION STUDIES.

This paper surveys the literature on the use of EPXMA in conjunction with (heavy metal) pollution studies. Metal-accumulating compartments are usually granules or vacuoles of 6 main types: (i) extracellular, soluble and fairly pure calcium carbonate granules; (ii) insoluble, calcium and phosphorus-rich granules, often containing several metal contaminants; (iii) multifunctional, calcium and phosphorus granules containing a high proportion of rather complex organic molecules; (iv) copper- (and sulfur-) rich granules; (v) iron- (and phosphorus) rich granules; (vi) Cd, Zn, Cu and Hg - containing vacuoles, where the metals are presumably complexed with cysteine-rich metallothionein proteins, or their derivatives. With a few exceptions, types (ii)-(vi) are intracellular. Many of these inclusions may be associated with the lysosomal system, and the metals are sequestered by the various compartments due to their ligand-binding properties (i. e. , whether they belong to Class A or Class B) and on the availability of pre-existing or inducible ligands within those compartments. It is concluded that EPXMA provides unique multi-element information concerning the metabolism of essential and toxic heavy metals within cells.