Regulation and Risk Assessment of 1,4-Dioxane - Environmental Investigation and Remediation - page 304

from repeated exposure to low levels of 1,4-dioxane in contaminated shower water or in shampoos
and soaps. The majority of published 1,4-dioxane risk summaries conclude that the risk of adverse
health effects from dermal exposure to low concentrations in water or sundries is not signii cant.

6.5.5 R ISK FROM I NHALATION E XPOSURE TO 1,4-D IOXANE
Inhalation exposure to 1,4-dioxane may result from a variety of occupational and domestic activities
involving use of products that contain 1,4-dioxane as an additive or impurity. Chapter 2 proi les
the many products that contain 1,4-dioxane; use of these products indoors increases the chance of
1,4-dioxane being inhaled. 1,4-Dioxane may also be present in indoor air from adhesives and coat-
ings used in construction and interior i nishes. For example, wood parquet l oors may use adhesives
containing 1,4-dioxane up to 0.5%, whereas wood glues may contain 1,4-dioxane from 1% to 5%
(DAP Inc., 1994). Coatings and varnishes in ofi ce cubicles as well as draperies also emit measur-
able levels of 1,4-dioxane (see Section 2.3.8). A NASA survey of indoor air sources determined that
a minor percentage of commonly encountered home construction practices can introduce 1,4-
ioxane. By testing materials in closed containers at elevated temperatures not ordinarily encoun-
tered in the home, researchers were able to measure 1,4-dioxane present in 16 construction adhesives,
coatings, and rubber materials. Adhesives were the major source of 1,4-dioxane; their median emis-
sion rate was 4.3 μg/g of adhesive, and their maximum emission rate was 21 μg/g of adhesive
(McDonnell Douglas Corporation, 1986). Draperies and drapery linings emitted 1.3 μg/m 2 /h in one
study (Bayer and Papanicolopoulos, 1990). A German study identii ed 1,4-dioxane at less than
50 μg/m 3 (14 ppbv) among volatile organic compounds emitted in subcarpet construction coatings
(Fischer, 1998). Polyurethane foam insulation may emit 1,4-dioxane at elevated temperatures during
installation or incineration. At 80°C, the average 1,4-dioxane concentration of eight air samples of
emissions from one freshly sprayed and three cured polyurethane foams was 2400 ± 1500 ppbv; at

40°C (104°F), 1,4-dioxane was not detected (Krzymien, 1989).
A sampling survey of 12 homes in Woodland, California, found a geometric mean concentration
of 0.03 ppb 1,4-dioxane in indoor air, an arithmetic mean of 0.39 ppb, and a maximum value of
39 ppb (Sheldon et al., 1991; Hodgson and Levin, 2003). An earlier review of surveys estimated that
the geometric mean 1,4-dioxane concentration in indoor air was 0.02 ppb (Pellizzari et al., 1986).
A National VOC Indoor Air Database, with 585 measurements for 1,4-dioxane, lists the average
1,4-dioxane concentration at 1.03 ppbv (Shah and Heyerdahl, 1988; Shah and Singh, 1988). A survey
of indoor air in Los Angeles and Contra Costa County, California, found 1,4-dioxane present in
12-55% of the homes sampled. In Los Angeles, 112 homes sampled in the summer of 1984 had an
average 1,4-dioxane concentration of 0.15 ppbv; the maximum detected value was 1.2 ppbv. A win-
ter 1984 survey of 51 homes in Los Angeles detected 1,4-dioxane at an average concentration of
0.044 ppbv. The sampling of indoor air in Contra Costa homes occurred in the summer of 1984 and
found an average concentration of 0.042 ppbv and a maximum of 0.81 ppbv (Wallace, 1986).
Exposure to 1,4-dioxane emitted from architectural coatings and other sources mentioned in this
section is unlikely to pose a signii cant inhalation risk. The greatest inhalation risk from 1,4-dioxane
exposure is with its direct use without proper personal protective equipment and ventilation
measures. Unfortunately, 1,4-dioxane does not provide workers with warning properties such as a
distinct and low-threshold odor or an effect such as watery eyes or respiratory irritation. The odor
threshold for 1,4-dioxane in air is 24 ppm (Amoore and Hautala, 1983).
The greatest occupational exposure to 1,4-dioxane by inhalation is likely to have occurred during
degreasing operations in earlier decades. Degreasing with methyl chloroform containing up to 3%
1,4-dioxane will cause inhalation exposure from 3 to 15 ppm (12-60 mg/m 3 ). The scenario under
which such exposure would occur is an open-top vapor degreaser without supplied ventilation
(VROM, 1999). Since use of methyl chloroform was banned by the Montreal Protocol, this route of
exposure is no longer signii cant. Some occupational exposure to 1,4-dioxane may remain where it is
used in laboratories, as a solvent for producing cellulose acetate membranes, or where it occurs as a