Forensic Applications for 1,4-Dioxane and Solvent Stabilizers - Environmental Investigation and Remediation - page 443

9.3 SOLVENT STABILIZERS AS AGE MARKERS
The date when a chemical i rst became commercially available is important for establishing the
earliest possible date that a release could have occurred. Knowledge of the dates that chemicals
were produced must be coupled with evidence that the facility used the chemical in question. An
excellent compilation of dates of production and use patterns for chlorinated solvents is found in
Richard Doherty's solvent history articles in the Journal of Environmental Forensics (Doherty,
2000a, 2000b). A brief summary of the history of solvent use is proi led in Section 1.1. A tabulation
of the dates of introduction of the most widely used solvent-stabilizer packages for the major chlo-
rinated solvents could be similarly useful. Section 1.2.6 reviews the available sources of information
on solvent-stabilizer packages, and Tables 1.21 through 1.24 list the formulations. The dates listed
in these tables unfortunately do not correspond to when the stabilizer was i rst used; rather, the dates
refer to the date of publication of the citation for the inclusion of the listed stabilizer in the solvent.
In the case where there is documentation available for stabilizer use in a particular solvent, then
the earliest patent claiming its use can be helpful for bracketing its introduction for commercial
application. However, this information must also be integrated with the general pattern of commer-
cial use for the major chlorinated solvents. For example, 1,4-dioxane was i rst patented as a stabi-
lizer for methyl chloroform in 1957. But it was not until the early 1960s that methyl chloroform
found somewhat wider use in cold-cleaning and vapor degreasing applications and not until the mid-
1970s that it displaced TCE as the most widely used vapor degreasing solvent. In 1970, TCE
accounted for 82% of all chlorinated solvents used in vapor degreasing (Morrison, 2006). By 1974,
TCE accounted for only 46% of vapor degreasing solvent consumption (USEPA, 1977), and by
1976, TCE's share had declined to 42% (Morrison, 2006).
By the mid-1960s, the Navy and NASA were already using 1,4-dioxane-stabilized methyl chlo-
roform. The Navy analyzed four commercially available methyl chloroform products and identii ed
16 compounds, including stabilizers and impurities. The report notes that most of the compounds
(listed in Table 9.9 ) were previously found in submarine, spacecraft, and environmental test cham-
ber atmospheres (Saunders, 1965). A chromatogram from the report ( Figure 9.2 ) shows a distinct
peak for 1,4-dioxane.
Similarly detailed composition proi les of technical grade methyl chloroform can be found in the
toxicological literature in which scientists analyzed the composition of technical grade solvents to
determine all of the toxic agents to which laboratory animals are exposed. For example, Table 9.10
lists the analysis of pre-1986 technical grade methyl chloroform from a study on the toxicity of
methyl chloroform to male and female Sprague Dawley rat pups (Maltoni et al., 1986).

9.4 SOLVENT STABILIZERS AS MARKERS OF SOLVENT APPLICATIONS
Solvent stabilizers were tailored to prevent solvent breakdown in the demanding environments in
which solvents were used. The use of certain stabilizers to prevent solvent-breakdown reactions that
occur in unique applications—such as PCE used in phosphatizing baths for automotive coatings or
high temperatures encountered by PCE used in transformer l uids—can provide unique associations
that may allow the interpretation of solvent origins. The following circumstances occurring together
would favor the use of solvent stabilizers as marker chemicals to distinguish the origins of the same
solvent used in different applications:

• Stabilizer is unique to a specii c application employed by only one of the potentially

responsible parties assumed to have contributed to the solvent spill(s)
Stabilizer is added in sufi cient quantity to favor detection, or stabilizer is concentrated in

•

the application so that the mass released is sufi cient to favor detection
Stabilizer that would serve as a unique marker is sufi ciently mobile and persistent to favor •

its migration to the region in which plumes of the common solvent have commingled