© 2006 by Taylor & Francis Group, LLC

5
Abrasive Blasting and
Heavy-Metal
Contamination
In the previous chapter, mention was made of the need to minimize spent abrasive
when blasting old coatings containing lead pigments. This chapter covers some
commonly used techniques to detect lead, chromium, and cadmium in spent abrasive
and methods for disposing of abrasive contaminated with lead-based paint (LBP)
chip or dust. Lead receives the most attention, both in this chapter and in the technical
literature. This is not surprising because the amount of lead in coatings still in service
dwarfs that of cadmium, barium, or chromium.
The growing body of literature on the treatment of lead-contaminated abrasive
seldom distinguishes between the various forms of lead found in old coatings,
although toxicology literature is careful to do so. Red lead (Pb 3O 4), for example, is
the most common lead pigment in old primers, and white lead (PbCO 3 • Pb[OH] 2)
is more commonly found in old topcoats. It is unknown whether or not these two
lead pigments will leach out at the same rate once they are in landfills. It is also
unknown whether they will respond to stabilization or immobilization treatments in
a similar manner. A great deal of research remains to be done in this area.
5.1 DETECTING CONTAMINATION
There are really two questions involved in detecting the presence of lead or other
heavy metals:
1. Does the old paint being removed contain heavy metals?
2. Will the lead leach out from a landfill?
The amount of a metal present in paint is not necessarily the amount that will
leach out when the contaminated blasting media and paint has been placed in a
landfill [1-3]. The rate at which a toxic metal leaches out depends on many factors.
At first, leaching comes from the surface of the paint particles. The initial rate,
therefore, depends most on the particle size of the pulverized paint. This in turn
depends on the condition of the paint to be removed, the type of abrasive used, and
the blasting process used [4]. Eventually, as the polymeric backbone of the paint
breaks down in a landfill, leaching comes from the bulk of the disintegrating paint
particles. The rate at which this happens depends more on the type of resin used in
formulating the paint and its chemistry in the environment of the landfill.
© 2006 by Taylor & Francis Group, LLC
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