Priority Substances List Assessment Report for 2-Ethoxyethanol

2.0 Summary of Information Critical to Assessment of "Toxic" under CEPA 1999

2.1 Identity, and physical/chemical properties¹

2-Ethoxyethanol, one of the class of substances referred to as glycol ethers, has the empirical molecular formula C₄H₁₀O₂, the structural formula CH₃CH₂OCH₂CH₂OH and a molecular weight of 90.12. Its Chemical Abstracts Service (CAS) registry number is 110-80-5. 2-Ethoxyethanol is a colourless liquid with an estimated water solubility of 300 000 mg/L² (DMER and AEL, 1996), a log octanol/water partition coefficient (K_ow) of -0.32 (Hansch et al., 1995), a vapour pressure of 710 Pa (Riddick et al., 1986) and a calculated Henry's law constant of 0.213 Pa·m³/mol (DMER and AEL, 1996).

Synonyms for 2-ethoxyethanol include 2-ethoxy-1-ethanol, ethylene glycol monoethyl ether and ethyl Cellosolve.

2.2 Entry characterization

2.2.1 Production, importation and uses

2-Ethoxyethanol was not produced in Canada in 1995 or 1996, according to data reported to Environment Canada by 14 companies in a survey carried out under the authority of Section 16 of the Canadian Environmental Protection Act, 1988 (CEPA) (Environment Canada, 1997b). According to these data, importation of 2-ethoxyethanol totalled 4.7 kilotonnes in 1995 and 3.0 kilotonnes in 1996. There was no export of 2-ethoxyethanol in 1995, and 2.3 tonnes were exported in 1996.

2-Ethoxyethanol has been used in paints, coatings, inks, cleaners, polishes, brake fluids and jet fuels and has been widely used as a solvent, chemical intermediate and solvent coupler of mixtures and water-based formulations (Stemmler et al., 1997). Data reported to Environment Canada in the survey conducted under the authority of Section 16 of CEPA indicated that 68.2 and 42.8 tonnes of 2-ethoxyethanol were used in Canada in 1995 and 1996, respectively, mainly as a component of formulated products (Environment Canada, 1997b). 2-Ethoxyethanol is present as a minor ingredient (<1.25%) in 26 Canadian registered pest control products (wood preservatives) (Ballantine, 1997; Health Canada, 1998a).

2.2.2 Sources and releases

2.2.2.1 Natural sources

2-Ethoxyethanol has not been reported to occur as a natural product (U.S. EPA, 1986; WHO, 1990). There are no known reactions that would lead to the in situ production of glycol ethers in the atmosphere (Rogozen et al., 1987).

2.2.2.2 Anthropogenic sources

Total on-site environmental releases of 2-ethoxyethanol reported to the National Pollutant Release Inventory (NPRI) in 1994 amounted to 2.36 tonnes. Most of this (at least 81%) was released into the atmosphere from four facilities (producing plastics and synthetic resins, paint and varnish, petroleum products and printing ink) in Quebec (NPRI, 2000). (Facilities with more than 10 full-time staff and that use or manufacture more than 10 tonnes of substances on the NPRI are required by law to report to Environment Canada.)

In 1995, total on-site environmental releases of 2-ethoxyethanol reported to the NPRI amounted to 8.1 tonnes (NPRI, 2000). Almost all of this was released into the atmosphere as emissions from storage from one facility (plastics manufacturing) in Ontario.

In 1996, total on-site environmental releases of 2-ethoxyethanol were 0.20 tonnes, released about equally from two facilities (producing motor vehicle stampings and industrial and household chemicals) in Ontario and Quebec (NPRI, 2000).

Releases reported to date for 1997 totalled 9.32 tonnes, from two printing ink industries in Ontario and Quebec (NPRI, 2000).

According to data reported under the CEPA Section 16 survey (with different reporting requirements from the NPRI), 5.8 tonnes of 2-ethoxyethanol were released to landfills in 1996, while 3.9 tonnes were released as waste and 0.9 tonnes were released to air from several facilities in Ontario and Quebec (Environment Canada, 1997b). (Industries surveyed by Environment Canada with commercial activities involving more than 1000 kg of 2-ethoxyethanol were required to supply data on uses and releases and other relevant information.)

The Canadian Chemical Producers' Association (1999a) reported total environmental emissions of 2-ethoxyethanol of 0.3, 0.015, 0.015 and 0.013 tonnes from member companies in 1992, 1993, 1994 and 1995, respectively, all of which were released to air by a single company. Reported emissions fell to 0 tonnes in 1996 (Canadian Chemical Producers' Association, 1999a), totalled 0.003 tonnes in 1997 and returned to 0 tonnes in 1998 (Canadian Chemical Producers' Association, 1999b).

2.3 Exposure characterization

2.3.1 Environmental fate

2.3.1.1 Air

An atmospheric half-life of 9.8 hours was determined in a smog chamber with irradiation at a 2-ethoxyethanol:NO_X ratio of 2:1 (Joshi et al., 1982). A half-life of about 4 days was calculated for the reaction of 2-ethoxyethanol with atmospheric hydroxyl radicals, assuming an ambient concentration of hydroxyl radicals of 10⁶ molecules/cm³ (U.S. EPA, 1985). This calculation was based on the rate constant in water of 1 x 10⁹ L/mol per second (Anbar and Neta, 1967), converted to a gas-phase reaction by the method of Guesten et al. (1981). Howard et al. (1991) estimated a half-life of 2-ethoxyethanol in air of 5.35-53.5 hours, based on reaction with hydroxyl radicals.

2.3.1.2 Water

Howard et al. (1991) estimated half-lives of 2-ethoxyethanol of 168-672 hours and 336-1344 hours in surface water and groundwater, respectively, based on unacclimated aerobic biodegradation.

2.3.1.3 Soils

A soil sorption coefficient (K_oc) of 113 was calculated for 2-ethoxyethanol using the method of Sabljic (1984), indicating moderate mobility in soil (U.S. EPA, 1985). Retention values for 2-ethoxyethanol of 21 New Zealand and Fijian soils ranged from 8 to 178 mg/g; these values were well correlated with the cation exchange capacity and a number of measures of moisture content of these soils (Churchman and Burke, 1991).

There is little information available on the biodegradation of 2-ethoxyethanol in soil. Howard et al. (1991) estimated a half-life of 2-ethoxythanol in soil of 168-672 hours, based on unacclimated aerobic biodegradation.

2-Ethoxyethanol underwent biooxidation to 2-ethoxyacetic acid (EAA) by the soil bacterium, Alcaligenes MC11, for which 2-ethoxyethanol was a source of carbon (Harada and Nagashima, 1975). Pseudomonas sp. 4-5-3, Xanthobacter autotrophicus EC1-2-1 and a bacterium identified only as "strain MC2-2-1" could also use 2-ethoxyethanol as a source of carbon for aerobic growth (Kawai, 1995).

2.3.1.4 Biota

A bioconcentration factor (BCF) of 0.5 was estimated for 2-ethoxyethanol, based on a log K_ow of -0.10 and using the equation proposed by Lyman et al. (1982) (i.e., log BCF = 0.76 log K_ow - 0.23) (U.S. EPA, 1985). Bioaccumulation of 2-ethoxyethanol in aquatic organisms would therefore not be significant.

2.3.1.5 Environmental distribution

Because of the high water solubility of 2-ethoxyethanol and its low log K_ow, physical adsorption to suspended solids and sediments should not be significant (U.S. EPA, 1985).

The environmental partitioning of 2-ethoxyethanol when released into air, water or soil was estimated by a Level III fugacity model (DMER and AEL, 1996). Values for input parameters were as follows: molecular weight, 90.1 g/mol; vapour pressure, 710 Pa; water solubility, 300 000 mg/L; log K_ow, -0.32; Henry's law constant, 0.213 Pa·m³/mol; half-life³ in air, 55 hours; half-life in water, 550 hours; half-life in soil, 550 hours; and half-life in sediment, 1700 hours. Modelling was based upon an assumed emission rate of 1000 kg/hour, although the emission rate used would not affect the estimated percent distribution. If 2-ethoxyethanol is emitted into air, EQC (Equilibrium Criterion) Level III fugacity modelling predicts that about 50% would be present in air, while approximately 25% would be present in soil and about 25% in water. If 2-ethoxyethanol is emitted into water, more than 99% would be present in water. If 2-ethoxyethanol is released to soil, about 75% would be present in the soil, while approximately 25% would be present in water (DMER and AEL, 1996).

2.3.2 Environmental concentrations

Few data on levels of 2-ethoxyethanol in the environment have been identified for Canada or elsewhere. One study was conducted to determine concentrations of 2-ethoxyethanol in multiple media in Canada to which humans are exposed, including drinking water and indoor and outdoor air (Conor Pacific Environmental Technologies, 1998), as outlined below in Section 2.3.2.1. Additional data on levels of 2-ethoxyethanol in specific media are presented in the subsequent sections where identified.

2.3.2.1 Multimedia exposure study

In a multimedia exposure study, exposure to a number of volatile organic chemicals was measured for 50 participants across Canada in 1997 (Conor Pacific Environmental Technologies, 1998). Thirty-five participants were randomly selected from the Greater Toronto area in Ontario, six from Queens Subdivision in Nova Scotia and nine from Edmonton, Alberta. For each participant, samples of drinking water, beverages and indoor, outdoor and personal air were collected over a 24-hour period; however, samples of food were not analysed for 2-ethoxyethanol. While confidence in the results of this survey was low (see Section 3.3.4), the concentration of 2-ethoxyethanol was below the method detection limit (0.05 µg/L) in all samples of drinking water. Similarly, it was not detected (detection limit 3.6 µg/m³) in any samples of indoor, outdoor or personal air. 2-Ethoxyethanol was not detected in composite beverage samples (method detection limit 3.3 µg/L).

2.3.2.2 Ambient air

In the Windsor Air Quality Study, the concentrations of 2-ethoxyethanol in 24 samples of ambient air collected in the vicinity of an automotive plant and 7 samples in downtown Windsor (OMEE, 1994) were measured. Concentrations of 2-ethoxyethanol were less than the limit of detection (0.81 µg/m³) in all the samples collected in downtown Windsor. Of the 24 samples collected at the automotive plant, concentrations of 2-ethoxyethanol were above the limits of detection (which ranged from 0.18 to 0.34 µg/m³) in 16 (over 66%); the mean value for these samples was 0.43 µg/m³ when concentrations in samples where 2-ethoxyethanol was not detected were assumed to be equivalent to one-half the limit of detection (maximum 0.86 µg/m³). The authors stated that the probable source of 2-ethoxyethanol in ambient air samples downwind of the plant was from paints and lacquers in which 2-ethoxyethanol is used as a solvent. In all of the samples from downtown Windsor or in the vicinity of the automotive plant, concentrations of 2-ethoxyethyl acetate, the acetate moiety of 2-ethoxyethanol, were below the limits of detection (range 0.55-2.9 µg/m³).

2-Ethoxyethanol was not detected in samples of ambient air collected at six locations in the United States in 1984-1985 (limit of detection 0.25 µg/m³) (Sheldon et al., 1988).

2.3.2.3 Indoor air

In northern Italy, six indoor air samples collected from homes in 1983-1984 contained 2-ethoxyethanol concentrations of up to 60 µg/m³ (De Bortoli et al., 1986). 2-Ethoxyethanol was detected at concentrations of up to 18.3 µg/m³ in indoor air samples collected in new buildings (hospital, office, nursing home) in the United States. In older buildings (office, nursing home, school), concentrations were lower (i.e., up to 4.15 µg/m³) (Sheldon et al., 1988).

2.3.2.4 Surface water

Samples of water from a polluted river in Japan contained 250-1200 µg 2-ethoxyethanol/L (Yasuhara et al., 1981).

2.3.2.5 Consumer products

Limited available recent data do not indicate that 2-ethoxyethanol or its acetate⁴ are commonly present in consumer products in Canada, although such applications are not regulated (Health Canada, 1998b). 2-Ethoxyethanol was not detected in the emissions of 13 consumer products, including window cleaners, all-purpose cleaners, paints, nail polish removers and hair dye, purchased in the Ottawa, Ontario, area (Cao, 1999). (These products were selected on the basis of other data presented here that suggested that 2-ethoxyethanol was present in similar products.) Glycol ethers, including 2-ethoxyethanol, are not registered for use as an active ingredient in therapeutic products used in Canada (Health Canada, 1998c). Of the cosmetic products registered for use in Canada, one nail polish contained 2-ethoxyethanol in the range of >0.3-l%, while 2-ethoxyethyl acetate was present in an eye makeup product and skin moisturizer at >30 to 100% and >1 to 3%, respectively (Health Canada Cosmetic Notification System, 2001). (The Food and Drugs Act stipulates that manufacturers and importers of new cosmetic products are required to notify Health Canada concerning the ingredients.) 2-Ethoxyethanol is a component in 26 wood preservatives registered for use in Canada (<1.25%) (Ballantine, 1997; Health Canada, 1998a).

Earlier in the United States, concentrations of 2-ethoxyethanol of up to 5% were reported in various consumer products, including hard surface cleaners and windshield washing fluid (Flick, 1986). However, in a more recent listing of ingredients in "advanced" cleaning product formulations, none of the products contained 2-ethoxyethanol or 2-ethoxyethyl acetate (Flick, 1994). (These data were submitted voluntarily by numerous companies and other organizations and may not represent a comprehensive list of formulations of consumer products available in the United States.) Additional data on emissions of 2-ethoxyethanol and its acetate from several consumer products tested in the United States prior to 1990 are presented in Table 1 (although no information was provided in the secondary account regarding the number of products examined). A European patent application for hair dye lists a 2-ethoxyethanol concentration of 12% (Cotteret, 1995). According to the 1993 Products Register in Sweden (reporting of the composition of products manufactured or imported in Sweden is mandatory), 2-ethoxyethanol and its acetate were ingredients in 137 and 170 products, totalling 105-242 and 172-270 tonnes/year, respectively, of pure substance (Johanson and Rick, 1996).

Table 1 Emissions of 2-ethoxyethanol and its acetate from consumer products in the United States

Product category	Number of products with detectable emissions1	Amount emitted (µg/g product)	Source
Cleaning compounds	4 (as 2-ethoxyethanol)	na2	Clinical Toxicology of Commercial Products database (CARB, 1991)
Spot / stain remover	1 (as 2-ethoxyethanol)	na	Clinical Toxicology of Commercial Products database (CARB, 1991)
Window / glass cleaner	2 (as 2-ethoxyethanol)	na	Clinical Toxicology of Commercial Products database (CARB, 1991)
Rug / upholstery cleaner	3 (as 2-ethoxyethanol)	na	Clinical Toxicology of Commercial Products database (CARB, 1991)
Coatings / inks	10 (as 2-ethoxyethanol) 4 (as 2-ethoxyethyl acetate)	na	Clinical Toxicology of Commercial Products database (CARB, 1991)
Coating thinners / strippers	6 (as 2-ethoxyethanol) 1 (as 2-ethoxyethyl acetate)	na	Clinical Toxicology of Commercial Products database (CARB, 1991)
Herbicide and fungicide	1 (as 2-ethoxyethanol)	na	Clinical Toxicology of Commercial Products database (CARB, 1991)
Medical / personal hygiene	1 (as 2-ethoxyethanol)	na	Clinical Toxicology of Commercial Products database (CARB, 1991)
Adhesives	3 (as 2-ethoxyethanol) 5 (as 2-ethoxyethyl acetate)	0.1-200 0.1-900	NASA/McDonnell Douglas Materials Testing Data Base (CARB, 1991)
Coatings	14 (as 2-ethoxyethanol) 66 (as 2-ethoxyethyl acetate)	0.09-450 0.05-1578	NASA/McDonnell Douglas Materials Testing Data Base (CARB, 1991)
Fabric	1 (as 2-ethoxyethanol) 3 (as 2-ethoxyethyl acetate)	0.23 0.07-0.7	NASA/McDonnell Douglas Materials Testing Data Base (CARB, 1991)
Pens / inks	6 (as 2-ethoxyethanol) 5 (as 2-ethoxyethyl acetate)	0.1-2800 0.49-4.3	NASA/McDonnell Douglas Materials Testing Data Base (CARB, 1991)
Foam / plastic products	2 (as 2-ethoxyethyl acetate)	0.095-0.7	NASA/McDonnell Douglas Materials Testing Data Base (CARB, 1991)

1. No information on the number of products tested was provided in the secondary account of these studies (CARB, 1991).
2. na = not available.

2.3.2.6 Fugacity modelling

Environmental concentrations of 2-ethoxyethanol were estimated by ChemCAN4 modelling. This model is a Level III fugacity-based regional model developed to estimate the environmental fate of chemicals in Canada. ChemCAN calculates the distribution of chemicals in environmental media, the transport and transformation process rates, and average concentrations in any of 24 regions or ecozones of Canada. The highest reported recent release of 2-ethoxyethanol in Canada is 8 tonnes/year, released into the air by one facility in southern Ontario in 1995 (NPRI, 1998). "Ontario - Mixed Wood Plain" was therefore selected as the geographic region for ChemCAN modelling of 2-ethoxyethanol. The input rate was 0.913 kg 2-ethoxyethanol/hour, all to the atmosphere. Chemical input values were as follows: molecular weight, 90.1 g/mol; vapour pressure, 710 Pa; water solubility, 300 000 mg/L; log K_ow, -0.32; Henry's law constant, 0.213 Pa·m³/mol; half-life in air, 55 hours; half-life in water, 550 hours; half-life in soil, 550 hours; and half-life in sediment, 1700 hours. For Ontario - Mixed Wood Plain, environmental characteristics were as follows: total surface area, 169 000 km²; percentage covered by water, 43.8%; average air height, 2 km; average water depth, 20 m; average soil depth, 10 cm; residence time in air, 1.71 days; residence time in water, 618 days; environmental temperature, 7.4°C.

Environmental concentrations of 2-ethoxyethanol in southern Ontario predicted by ChemCAN4 modelling are as follows: 6.9 x 10^-2 ng/m³ in air; 2.2 ´ 10^-5 µg/L in water; 4.15 x 10^-4 ng/g dry weight in soil; and 1.05 x 10^-5 ng/g dry weight in sediments. The ChemCAN model estimates average concentrations throughout the region; therefore, actual concentrations in the vicinity of releases will be higher than those estimated by the model.

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¹ See the environmental Supporting Document (Environment Canada, 1999) for a more complete listing of ranges of values reported and criteria for selection of physical and chemical properties.

² This estimated value was based on reported values for structurally similar or homologous compounds (DMER and AEL, 1996).

³ For each environmental compartment, DMER and AEL (1996) use a series of ranges of half-life times (<10 hours, 10-30 hours, 30-100 hours, etc.), and the half-life of the particular substance is assigned to the appropriate range, based on a consideration of available persistence data. The geometric mean of this range is then used as an input parameter for the fugacity model. For example, the atmospheric half-life of 2-ethoxyethanol in air is judged to be between 30 and 100 hours. The geometric mean of this range, 55 hours, is used as an input parameter in the model. Conservative values for persistence were selected, i.e., longer rather than shorter half-lives, to ensure that persistence is not underestimated.

⁴ The acetate moiety of 2-ethoxyethanol, 2-ethoxyethyl acetate, is often used in consumer product formulations. Since the acetate is rapidly converted to the parent 2-ethoxyethanol in the body, data on the presence of the acetate in consumer products are considered relevant to estimation of population exposure to 2-ethoxyethanol.