1,4-Dioxane Chemistry, Uses, and Occurrence - Environmental Investigation and Remediation - page 95

California's Safe Drinking Water and Toxics Enforcement Act of 1986 (Proposition 65) and Section
313 of Title III of the Superfund Amendments and Reauthorization Act of 1986 (SARA Title III)
(Union Carbide, 1988).
The PEG compounds of interest in the context of personal care products include ethers of
propylene glycol, propylene glycol stearate, propylene glycol oleate, and propylene glycol cocoate.
These compounds serve as cleansing, solubilizing, and emulsifying agents, skin-conditioning
agents such as humectants and emollients, and solvents in cosmetic formulations. Only a minor
percentage of cosmetic formulations use these compounds; some are not currently used. PEG,
propylene glycol cocoate, and propylene glycol oleate are produced by the esterii cation of poly-
oxyalkyl alcohols with lauric acid and oleic acid, respectively. Impurities include ethylene oxide
(maximum 1 ppm), 1,4-dioxane (maximum 5 ppm), polycyclic aromatic compounds (maximum
1 ppm), and the heavy metals lead, iron, cobalt, nickel, cadmium, and arsenic (maximum 10 ppm
combined) (Johnson, 2001).

2.4.1.5 1,4-Dioxane in Glyphosphate Herbicides (Accord ® , Roundup ® , Rodeo ® , Vision ® )
1,4-Dioxane may also be present as an impurity of polyoxyethyleneamine (POEA), the salt of gly-
phosphate [ N -(phosphonomethyl)glycine], which is the major component in widely used herbicide
formulations such as Roundup ® . The United Nations Food and Agriculture Organization has estab-
lished a limit of 1 ppm for 1,4-dioxane in POEA. The USEPA considers 1,4-dioxane as an “inert of
toxicological concern” in pesticide and herbicide formulations. The most popular herbicide,
Roundup ® , contained less than 0.03% 1,4-dioxane in 1990 ( 300 mg 1,4-dioxane per kilogram of

Roundup ® ) (Diamond and Durkin, 1997). Monsanto, the producer of Roundup ® , reported in 1997
that 1,4-dioxane contamination had been further reduced to 23 ppm (U.S. Forest Service, 1997).
Although 1,4-dioxane content was probably too low to cause groundwater contamination from
application to i elds, locations where glyphosphate-based herbicide was loaded into or washed from
spray equipment could be sources of low-level 1,4-dioxane contamination (Pesticide Action Network,
2006). The practice of rinsing herbicide containers prior to recycling may also cause detectable
1,4-dioxane contamination in groundwater.
Some urea herbicides could potentially contain 1,4-dioxane as a residue of production. 1,4-Dioxane
is reacted with 4-chloroaniline, anhydrous hydrogen chloride, and phosgene at 70-75°C to produce
p -chlorophenyl isocyanate, an intermediate used for the production of urea herbicides (Roig et al.,
2003). Another herbicide used in plantings of tomatoes and other crops, rimsulfuron, could contain
1,4-dioxane as an impurity of production. Technical rimsulfuron, also called Shadeout, is manufac-
tured in a two-step batch process in which a carbamic acid and an aniline compound are reacted
in a 1,4-dioxane solution (California Environmental Protection Agency, 1997). Rimsulfuron is
1-(4,6-dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2-pyridylsulfonyl)urea (CASRN 122931-48-0;
formula: C 14 H 17 N 5 O 7 S 2 ). Agricultural products that contain ethoxylated surfactants may also contain
traces of 1,4-dioxane. 1,4-Dioxane is listed as present but below reportable quantities in the insecti-
cide Dursban, which includes surfactants among its components (Dow Chemical Corporation, 1985).

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2.4.1.6 1,4-Dioxane in Pesticides
Some insecticidal formulations claimed in patents have used a solvent mixture comprising 30-50%
of the formulation. An example solvent mixture claimed in the patent literature is 20% 1,4-dioxane
along with methyl chloroform, methanol, and ethanol (Chang, 1999). It is unlikely that 1,4-dioxane
was widely used in commercial production as a carrier in insecticides in such high percentages
because of its high cost. 1,4-Dioxane was present in some pesticide formulations as a stabilizer of
methyl chloroform, which has been documented as an “inert” ingredient in pesticides. In 1989,
USEPA's Ofi ce of Pesticide Programs issued a notice concerning inert ingredients of pesticide prod-
ucts, in which 1,4-dioxane was included in the list of “inerts of toxicological concern.” Methyl chloro-
form is also a carrier solvent for pesticides; it was included on a list of “potentially toxic inerts”