SEM Basics—Introduction

Particles Everywhere!

Microscopic particulate matter is a major component of environmental and occupational exposures. Obvious examples of such exposures are:
  • Atmospheric aerosols
  • Fugitive dusts
  • Unconsolidated soils
  • Suspended waterborne sediments
  • Industrial process emissions

At times, such expoures may prove hazardous. Consequently, it may be necessary to ask certain questions about the particulate material which may pose an exposure threat. These questions may be very basic.

  • Is unrecognized particulate material present in the medium? (Such as a low level contaminant in air or water)
  • What types of particles are present, and do they pose a potential hazard? (Such as airborne asbestos fibers, or lead particles in dust)
  • What is the source of the material? (Is it of natural origin, or is it man-made from a nearby industrial process?)
  • Can particle identification be made from tissue samples? (Such as inhaled silica paticles or asbestos fibers in lung tissue)

An obvious way of addressing such questions, is to examine the particulate material directly. One of the most powerful analytical tools available for characterizing microscopic particulate material is the electron microscope. Principally, this is because the electron microscope makes it possible to examine particles which are too small to be resolved in the light microscope. Scanning Electron Microscopy (SEM) used in tandem with Energy Dispersive X-ray Microanalysis (EDX) is a combination of instrumentation which is capable of providing detailed information on the nature, origin and transformations of environmental samples at the individual particle level. The strength of SEM/EDX analysis is its ability to gather data on the size, morphology and composition of the particles in a time efficient manner.