I. Updates to Exposure Assessments 

a. Dietary Exposure 

In evaluating dietary exposure, EPA considered exposure under the proposed exemption 

from the requirement of a tolerance. EPA conducted an updated dietary exposure assessment 

using food consumption information from the U.S. Department of Agriculture (USDA) National 

Health and Nutrition Examination Survey, What We Eat in America (NHANES/WWEIA). This 

dietary survey was conducted from 2003 to 2008. As to residue levels in food, no residue data 

were submitted for C9 rich aromatic hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 

rich aromatic hydrocarbons. In the absence of specific residue data, EPA has developed an 

approach which uses surrogate information to derive upper bound exposure estimates for the 

subject inert ingredients. Upper bound exposure estimates are based on the highest tolerance for a 

given commodity from a list of high-use insecticides, herbicides, and fungicides. A complete 

description of the general approach taken to assess inert ingredient risks in the absence of residue 

data can be found at http://www.regulations.gov in the document ‘‘Alkyl Amines Polyalkoxylates 

(Cluster 4): Acute and Chronic Aggregate (Food and Drinking Water) Dietary Exposure and Risk 

Assessments for the Inerts,’’ in docket ID number EPA–HQ–OPP–2008–0738. 

In the case of C9 rich aromatic hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 

rich aromatic hydrocarbons, EPA made specific adjustments to the dietary exposure assessment to 

account for data submitted to the Agency demonstrating evaporative loss, which is an important 

consideration for compounds such as C9 rich aromatic hydrocarbons, C10–11 rich aromatic 

hydrocarbons, and C11–12 rich aromatic hydrocarbons. Based on the submitted data, the loss of C9

rich aromatic hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 rich aromatic 

hydrocarbons due to evaporation, and therefore not available as potential residues in food 

commodities, was determined to be 98%. 

b. Residential exposures. 

There are no residential exposures associated with the use of C9 rich aromatic 

hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 rich aromatic hydrocarbons as inert 

ingredient in pesticide products. However, C9 rich aromatic hydrocarbons, C10–11 rich aromatic 

hydrocarbons, and C11–12 rich aromatic hydrocarbons may be used as additives for gasoline. 

Residential exposure is possible via the inhalation route and may occur during gasoline refueling 
activities for consumers. Drinking water exposures may also occur as the result of the presence of 

these substances in drinking water resulting from their use in gasoline additives. 

i. Inhalation Exposure Assessment 

Inhalation exposures to C9 rich aromatic hydrocarbons, C10-11 rich aromatic 

hydrocarbons, and C11-12 rich aromatic hydrocarbons resulting from gasoline refueling activities 

may occur. Such exposure would be considered of short-term duration. While there are no 

reliable data related to inhalation exposures to C9 rich aromatic hydrocarbons, C10-11 rich 

aromatic hydrocarbons, and C11-12 rich aromatic hydrocarbons as a result of such activities, some 

data relative to inhalation exposures exist for other gasoline additives which can be used to 

conservatively estimate potential inhalation exposure to C9 rich aromatic hydrocarbons, C10-11 

rich aromatic hydrocarbons, and C11-12 rich aromatic hydrocarbons. 

Available data on methyl-t-butyl ether (MTBE), a gasoline additive used at concentrations 

far in excess of the concentration of C9 rich aromatic hydrocarbons, C10-11 rich aromatic 

hydrocarbons, and C11-12 rich aromatic hydrocarbons used in gasoline, suggest a maximum air 

concentration of MTBE of 7.5 mg/m3 (ECETOC, 1997).1

Based on a conservative assumption that the concentrations of C9 rich aromatic 

hydrocarbons, C10-11 rich aromatic hydrocarbons, and C11-12 rich aromatic hydrocarbons would 

not exceed 5% in gasoline, it can be estimated that inhalation exposures resulting from gasoline 

refueling would not exceed 4.5 μg/kg/day. 

ii. Drinking Water Exposures 

While there are no reliable data related to concentration of C9 rich aromatic hydrocarbons, 

C10-11 rich aromatic hydrocarbons, and C11-12 rich aromatic hydrocarbons in drinking water as a 

result of their uses as gasoline additives, some data relative to concentrations of gasoline additives 

in ground and surface water can be used to conservatively estimate concentrations of C9 rich 

 

1 7.5 mg/m3

 (from ECETOC—maximum air concentration of MTBE @11%as additive in gasoline 

at service station) x 0.454 (adjustment factor for a 5% level of additive) x 0.64 m3

/hr (OPP 

residential SOP mean inhalation rate for adults) x 0.167 hr (10 min exposure for gasoline 

refueling) / 80 kg (Residential SOP body weight adult) = 4.5 μg/kg/day. 
aromatic hydrocarbons, C10-11 rich aromatic hydrocarbons, and C11-12 rich aromatic 

hydrocarbons in drinking water. 

An EPA Blue Ribbon Panel evaluated the uses of oxygenates in gasoline and in its report 

provided a summary of studies examining MTBE contamination of drinking water sources. The 

cited data demonstrate that concentrations of MTBE in drinking water range from <5 to 20 ppb 

(EPA, 1999). Based on the fact that the occurrence of C9 rich aromatic hydrocarbons, C10-11 

rich aromatic hydrocarbons, and C11-12 rich aromatic hydrocarbons in gasoline additives is at 

lower concentrations than MTBE is it reasonable to assume that drinking water concentrations of 

these substances would not exceed the <5 to 20 ppb range. While gasoline containing C9 rich 

aromatic hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 rich aromatic hydrocarbons 

may result in some potential exposure via drinking water, such drinking water exposures are 

already addressed by the conservative assumptions for estimated drinking water concentrations 

utilized in the chronic dietary exposure assessment. 

II. Updates to Aggregate Risk Findings 

a. Acute risk 

The acute dietary exposure from food and water to C9 rich aromatic hydrocarbons, C10–11 

rich aromatic hydrocarbons, and C11–12 rich aromatic hydrocarbons will occupy 11% of the aPAD 

for children 1 to 2 years old, the population group receiving the greatest exposure. Therefore, C9

rich aromatic hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 rich aromatic 

hydrocarbons are not expected to pose an acute risk. 

b. Chronic risk 

EPA has concluded that chronic exposure to C9 rich aromatic hydrocarbons, C10–11 rich 

aromatic hydrocarbons, and C11–12 rich aromatic hydrocarbons from food and water will utilize 2.1 

% of the cPAD for children 1 to 2 years old, the population group receiving the greatest exposure. 

This number captures the likely exposure in groundwater from use of C9 rich aromatic 

hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 rich aromatic hydrocarbons as 

gasoline additives. 

c. Short-term risk 
Short term aggregate risk takes into account residential exposure plus average (or 

background) exposure to food and water. There are no residential pesticidal uses for C9 rich 

aromatic hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 rich aromatic hydrocarbons 

so the short-term risks would be equivalent to the chronic risk discussed above and therefore not of 

concern. There is a potential for short-term inhalation exposure from use of C9 rich aromatic 

hydrocarbons, C10–11 rich aromatic hydrocarbons, and C11–12 rich aromatic hydrocarbons as 

additives in gasoline. The MOE of >10,000 for short-term risk from inhalation exposures does not 

exceed the Agency’s level of concern (MOE<100). However, these inhalation exposures cannot 

be aggregated with oral (i.e., food and drinking water) exposures because, based on a routespecific inhalation toxicity study, the endpoints selected for oral and inhalation exposure are not 

based on a common specific target organ toxicity effects. 

. 

d. Intermediate-term risk. 

Intermediate-term risk is assessed based on intermediate-term residential exposure plus 

chronic dietary exposure. C9 rich aromatic hydrocarbons, C10–11 rich aromatic hydrocarbons, and 

C11–12 rich aromatic hydrocarbons are not contained in pesticide products registered for any 

specific use patterns (nor are there any non-pesticidal uses) that could result in in intermediate -

term residential exposure. EPA considers the chronic risk assessment to cover intermediate-term 

risk and concludes that there are no intermediate-term risk concerns. 
References: 

 European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOX) (1997), TR 072 : 

Methyl tert-Butyl Ether (MTBE) Health Risk Characterisation, June 1997. Available from 

http://www.ecetoc.org/index.php?mact=MCSoap,cntnt01,details,0&cntnt01by_category=5&cntnt0

1template=display_list_reports&cntnt01order_by=Number%20Desc&cntnt01document_id=250&c

ntnt01returnid=89 accessed August 5, 2014 

U.S. Environmental Protection Agency (EPA) (1997) . Achieving Clean Air and Clean Water: The 

Report of the Blue Ribbon Panel On Oxygenates in Gasoline EPA Report EPA420-R-99-021 

September 15, 1999. Available from 

http://www.epa.gov/OMS/consumer/fuels/oxypanel/r99021.pdf accessed August 5, 2014 

https://www.ehp.qld.gov.au/management/coal-seam-gas/pdf/btex-report.pdf