State of the Science Report for Ethylbenzene

Appendix A: Estimates of Exposure to Ethylbenzene from Consumer Products by Adult Canadians¹

Consumer product type	Assumptions	Estimated concentrations and daily intakes
Acrylic enamel aerosol spray paint2	Inhalation3 - based on a reported maximum concentration of 40% in a coating product (Environment Canada, 2001), a concentration of 40% in an acrylic enamel aerosol spray paint is assumed in the determination of an upper-bounding estimate of intake - assuming the amount of product used is 460 g per event, a 0.17-hour duration of exposure, a room volume of 20 m3, a breathing rate of 1.3 m3/hour for an average adult engaged in light-level activity and a frequency of use of 1 day per year (Versar Inc., 1986) - a body weight of 70.9 kg is assumed for an average Canadian adult (EHD, 1998)	Air concentration = 9200 mg/m3 Estimated daily intake = 78.6 µg/ kg-bw per day
	Dermal4 - assuming an estimated permeation coefficient (Kp) of 9.55 × 10-5 cm/h (U.S. EPA, 1992), a paint density of 0.9 g/cm3 (Versar Inc., 1986), a surface area of the hands of 910 cm2 (EHD, 1998) and significant coverage of 50% of the hands while painting	Estimated daily intake = 0.10 µg/ kg-bw per day
Latex wall paint5	Inhalation6 - using the Wall Paint Exposure Model (version 3.2; U.S. EPA, 2001) and its default values, unless otherwise stated - model assumes 38 exposure events in a 75-year lifetime - assuming an adult do-it-yourself painter in the painted area where only the walls are painted - based on a reported maximum concentration of 40% in a coating product (Environment Canada, 2001), a concentration of 40% in a latex wall paint is assumed in the determination of an upper-bounding estimate of intake - assuming a body weight of 70.9 kg for an average Canadian adult (EHD, 1998) - the model calculates the highest instantaneous concentration to which an individual is exposed (Cp) and the estimated lifetime average daily dose	Air concentration (Cp) = 250 mg/m3 Estimated lifetime average daily dose = 85 µg/kg-bw per day
	Dermal7 - assuming an estimated permeation coefficient (Kp) of 9.55 × 10-5 cm/h (U.S. EPA, 1992) - assuming a paint density of 1.22 g/cm3 (Versar Inc, 1986), a surface area of the hands of 910 cm 2 (EHD, 1998) and significant coverage of 50% of the hands while painting - assuming 38 exposure events in a 75-year lifetime with an average of 5.135 hours per event (WPEM, version 3.2; U.S. EPA, 2001) - assuming a body weight of 70.9 kg for an average Canadian adult (EHD, 1998)	Estimated daily intake = 2.13 µg/ kg-bw per day
Gasoline8	Inhalation while pumping gas9 - based on a maximum concentration of 1862 µg/m3 measured in samples taken while pumping gas (PACE, 1987) - assuming an event frequency of one gas fill-up per week, a duration of exposure of 15 minutes and a breathing rate of 1.3 m3/hour for an average adult engaged in light-level activity (Versar Inc., 1986; PACE, 1987) - a body weight of 70.9 kg is assumed for an average Canadian adult (EHC, 1998)	Maximum concentration =1.862 mg/m3 Estimated daily intake = 1.22 µg/ kg-bw per day
Cigarettes 10	Inhalation from tobacco smoke11 - based on a maximum concentration of 19.3 µg/m3 measured over a 4-hour period after 24- to 27-minute sessions of smoking in an environmental chamber with a volume of 225 mL - measurements were taken after the third cigarette was removed; therefore, an event frequency of 3 cigarettes per day was assumed - body weights of 59.4 kg, 70.9 kg and 72.0 kg are assumed for average Canadians 12-19 years old, 20-59 years old and 60 years old and more, respectively (EHD, 1998) 12-19 years old: 20-59 years old: 60+ years old:	Maximum concentration = 0.0193 mg/m3 Estimated daily intake = 2.19 × 10-4 µg/kg-bw per day Estimated daily intake = 1.84 × 10-4 µg/kg-bw per day Estimated daily intake = 1.81 × 10-4 µg/kg-bw per day

¹ Since these products are used primarily by adults (20-59 years old), estimated exposures have been derived for this age group only, with the exception of cigarettes, for which exposure for three age groups (12-19, 20-59 and 60+ years old) was considered.
² Exposure to an aerosol spray paint was considered representative of an acute exposure for paint products based on use pattern parameters (compare with latex paint, footnote 5).
³ For this scenario, it was assumed that exposure occurred only during the time the product was in use and that the total amount of ethylbenzene released during each event was present in the room air throughout the period of use (i.e., evaporation was assumed to be instantaneous). Thus, the user of the product was assumed to be exposed to the peak ethylbenzene concentration throughout the exposure period. It was also assumed that the ethylbenzene vapours were confined to the room where the product was used throughout the exposure period (i.e., household air exchange rate was assumed to be negligible throughout the exposure period). Also assumed is 100% absorption across the lungs.
⁴ Dermal exposure may occur during use of aerosol spray paints. A skin permeation coefficient (K_p) for ethylbenzene from water of 0.517 cm/h has been estimated according to the equation log K_p = -2.72 + 0.71 log Kow - 0.0061 MW, where K_ow is the octanol/water partition coefficient and MW is the molecular weight (U.S. EPA, 1992). Since ethylbenzene is assumed to comprise 40% of the paint product, a K_p for the neat substance is considered more appropriate. The relationship K_p(neat) = K_p(water) × (water solubility / density of neat substance) has been determined (U.S. EPA, 1992). Therefore, K_p(neat) was calculated to be 9.55 × 10^-5 cm/h. For this scenario, an acute exposure dose was calculated. It was assumed that exposure occurred only during the time the product was in use and that there was 100% absorption through the skin.
⁵ Exposure to a latex wall paint was considered representative of a chronic exposure for paint products based on use pattern parameters (compare with spray paint, footnote 2).
⁶ The Wall Paint Exposure Model was developed by the U.S. Environmental Protection Agency to estimate an individual's inhalation exposure to a chemical in a latex wall paint, during and after the time when a building is painted. It is a sophisticated model that may give a more realistic output than simple equations for inhalation exposure. The model's use of a certain number of exposure events over a lifetime makes it appropriate for estimating chronic exposure to a substance.
⁷ Dermal exposure may occur during use of wall paints. A skin permeation coefficient (K_p) for ethylbenzene from water of 0.517 cm/h has been estimated according to the equation log K_p = -2.72 + 0.71 log K_ow - 0.0061 MW, where K_ow is the octanol/water partition coefficient and MW is the molecular weight (U.S. EPA, 1992). Since ethylbenzene is assumed to comprise 40% of the paint product, a K_p for the neat substance is considered more appropriate. The relationship K_p(neat) = K_p(water) × (water solubility/density of neat substance) has been determined (U.S. EPA, 1992). Therefore K_p(neat) was calculated to be 9.55 × 10^-5 cm/h. For this scenario, a lifetime chronic exposure dose was calculated. It was assumed that there was 100% absorption through the skin.
⁸ Ethylbenzene occurs naturally in gasoline and may also be used as a fuel additive. Estimated exposures have been derived for the average Canadian adult (20-59 years old).
⁹ The study by PACE (1987) involved taking air samples from pump operators at full-serve stations and kiosk operators at self-serve stations. For this scenario, the maximum concentration used was measured for pump operators at full-serve stations. Samples from kiosk operators at self-serve stations were also taken in the study; however, they are not involved with filling the gas tank and are not considered representative of the average Canadian adult. The duration of exposure was assumed to be the same as the short-term sample times from the study. It is noted that the sample time may represent three to five gas fill-ups for a pump operator; therefore, the duration of exposure used in the scenario may overestimate the actual potential dose for an average adult.
¹⁰ Daisey et al. (1994) measured volatile organic compounds over a 4-hour period after 24- to 27-minute sessions of smoking in an environmental chamber. The average concentrations of ethylbenzene in environmental tobacco smoke ranged from 11.5 to 19.3 µg/m³ (detection limit not stated). The estimated daily intake was not included in the total intake estimate, as active exposure (i.e., smoking) to ethylbenzene from cigarettes may not be representative of the general Canadian population.
¹¹ Doses were calculated for three relevant age groups. Exposure resulting from cigarette smoking was not included in the calculation of total intake, as cigarette smoke may have contributed to measured indoor air levels.