1,4-Dioxane Chemistry, Uses, and Occurrence - Environmental Investigation and Remediation - page 94

(e.g., alcohol) in the reactor. 1,4-Dioxane forms when two molecules of ethylene oxide are cleaved
from the parent ethoxylated alcohol. 1,4-Dioxane formation is favored by an excess of sulfur triox-
ide, high temperatures, and moisture and longer ethylene oxide chains in the ethoxylated alcohol
feedstock (Kosswig, 2002; Dado et al., 2006). The level of 1,4-dioxane in the product remains rela-
tively low at 20-30 ppm until a critical point of oversulfation occurs. Once oversulfation occurs and
the mole ratio exceeds 1.04, 1,4-dioxane production increases rapidly to values measured in hun-
dreds of parts per million (Foster, 1997).
Vacuum stripping, steam stripping, drying, and other solutions were eventually successful
in achieving substantial reductions in the 1,4-dioxane content of i nished surfactant products
(Sachdeva and Gabriel, 1997). The recovered 1,4-dioxane is often condensed and used as a fuel for
on-site boilers or in other energy-recovery operations. Equipment specii cally designed for removal
of 1,4-dioxane in the production of lauryl ether sulfate achieves an eightfold decrease. Additional
equipment is designed to subsequently destroy 1,4-dioxane in the condensate. Destruction methods
include a catalyzed reaction with hydrogen peroxide to oxidize 1,4-dioxane, producing carbon
dioxide and water (Chemithon Corporation, 2006).

2.4.1.3 1,4-Dioxane in Contraceptive Sponges and Spermicidal Lubricants
The active spermicide nonoxynol-9 has been commonly used in contraceptive products since the
1970s. Nonoxynol-9 is among the surfactants that may contain 1,4-dioxane as an impurity of
production. The levels of 1,4-dioxane present were deemed to be less than the 10 ppm limit recom-
mended for polysorbates in food and applied to contraceptives by the FDA (FDA, 1997a). Protracted
debate over the safety of a contraceptive sponge in the 1980s and 1990s focused on the presence of
1,4-dioxane in nonoxynol-9 in the “Today” sponge. The FDA determined that there is no apprecia-
ble risk because of lack of vaginal absorption of nonoxynol-9 (Woodcock, 1997). Approximately
one-sixth of the nonoxynol-9 contained in the sponge is released during use. The process used to
create the contraceptive sponge is thought to drive off 1,4-dioxane, reducing its concentration
sevenfold (FDA, 1997b). The level of 1,4-dioxane present in nonoxynol-9, 7 ppm, would probably
not appear in the sponge (Medical Economics Publishing, 1983). Nonoxynol-9 is also used as a
spermicidal lubricant in condoms and related products.

2.4.1.4 1,4-Dioxane in Polyethylene Glycol
PEG compounds are used in a wide range of products (Union Carbide, 2001):

• Pharmaceuticals

• Cosmetics such as deodorant sticks, lipsticks, shaving creams, toothpastes, and lotions

• Detergents in laundry soaps and dish-washing soaps

• Textiles and leather processing

• Plastics and resins

• Paper

• Printing inks

• Lubricants

• Mold-release agents in the rubber industry

• Metal corrosion inhibitors in the petroleum industry

• Anticracking and preservation in woodworking

• Brake l uid lubricants

Pharmaceutical grades of PEG typically contain less than 10 ppm 1,4-dioxane.
Dow Chemical tested the 1,4-dioxane content of various grades of PEG. Some grades showed
no detection; all grades tested less than 1 part 1,4-dioxane per million parts PEG (Dow Chemical
Corporation, 1989). In 1988, Union Carbide notii ed its customers that its Carbowax line of
PEG products contained no more than 5 ppm 1,4-dioxane and was therefore in compliance with