Historical Use of Chlorinated Solvents and Their Stabilizing Compounds - Environmental Investigation and Remediation - page 27

Occupational safety and health regulations for worker exposure to solvents and toxic stabilizer com-
pounds are discussed in Chapter 6. Proper operation of degreasers and periodic testing of solvent
stability prevents solvent-breakdown reactions and toxic reaction products such as phosgene gas.
1.2.2.2 Off-Spec Work
A solvent that has become acidic may stain or damage the work. Parts from which grease, soldering
l ux, cutting oils, bufi ng oils, and other oily wastes and debris must be removed can become dis-
colored or receive spots and insoluble deposits from a solvent that has deteriorated. A contaminated
solvent will discolor or stain metals, particularly brass and aluminum. Sensitive instruments, printed
circuit boards, thermal switches, or other parts may become damaged if the solvent has accumu-
lated too much oil that consequently vaporizes at a higher temperature. Temperature-sensitive parts
may melt when the solvent boils too hot. In addition to spots and stains, the work may become
corroded from the acid evolved during solvent-breakdown reactions.
A solvent that has deteriorated because of loss or imbalance of the stabilizer package may also
become malodorous, colored, or too acidic for dry-cleaning clothing and textiles. Fabrics cleaned
with decomposing solvent appear “dull and lifeless,” especially fabrics in pastel colors, and the odor
of the residual solvent in the fabric and cleaning plant becomes increasingly unpleasant.
Perchloroethylene that has become too acidic from decomposition reactions can damage the cloth-
ing by leaching dyes and fabric colors. The leached dye discolors the perchloroethylene and makes
it unsuitable for further use; its recovery is also difi cult (Skeeters, 1960b).
In order to clean dirt and grime from uniforms, clothing, shop overalls, and other items, dry-
cleaning solvent is often infused with detergent and water to remove both water-soluble and water-
insoluble fraction of the dirt (Skeeters, 1960a). However, some stabilized compositions are not fully
compatible with soaps and detergents, which leads to solvent failure in dry-cleaning applications.
Management of waste solvents has been the subject of a series of increasingly stringent regulations.
Problems with spotting, staining, discolored textiles, and malodorous solvents often led operators to
distill or discard the offensive solvent. Disposal or recycling of waste solvents was usually done in the
most cost-effective and expedient manner available or was not actively regulated. For example, until
1986, dry cleaners could legally discharge condensate water to sanitary sewers. Today, the connection
of dry-cleaning machinery to sewers is prohibited; all waste must be inventoried, manifested, and sent
to a licensed facility for recycling. Chapter 6 provides a full discussion on the evolution of waste-
handling regulations and their effect on the nature and chemical composition of waste discharges.
1.2.2.3 Production Line Shutdown
Chlorinated solvents have played an integral role in supporting production lines for a wide variety of
products such as automotive parts, armaments, aircraft, electronics, precision instruments, metal parts,
textiles, semiconductors, and printed circuit boards. The value of goods produced from these assembly
lines can be very high. The cost of a degreaser shutdown due to solvent that has lost its stability and
has become acidic can be enormous: the loss of production and the cost of repairing the damaged
degreaser far outweigh the cost of the solvent. The solvent must be drained from the degreaser, and
all the surfaces must be cleaned with an alkaline detergent. The tarry material may have deposited in
inaccessible components and surfaces, requiring the replacement of pipes and other equipment.
In addition to damage to products cleaned in degreasers from staining or spotting, the runaway
reaction of an out-of-balance solvent can damage the degreasing equipment itself. To prevent this,
operators test solvents frequently for indicators of stability versus impending breakdown. (Testing
protocols for determining solvent stability are described in Section 1.2.7 .) Preventing loss of produc-
tion and damage to degreasing equipment was presumably a strong motivation to discard and replace
solvents. Prior to regulation and wider understanding of the environmental and/or economic con-
sequences of releasing solvent to the ground, operators faced with the issue of discarding waste
solvent may have opted to dump it on-site or to contract with haulers to remove the waste to landi lls,
recyclers, or unknown destinations.