Gasoline Vapor Emissions during Refueling

Gasoline is a complex mixture of many chemicals, including several that are harmful to human health, such as volatile aromatic hydrocarbons like benzene, toluene, ethylbenzene, and xylene. These chemicals can be released in various ways, such as during vehicle refueling when gasoline vapors in a vehicle’s tank are pushed out into the atmosphere by the rising liquid gasoline level in the tank. To deal with this, vapor recovery systems have been created to direct vaporized gasoline into a canister on the vehicle, thereby reducing the overall escape of vapors into the atmosphere. From 1998 to 2006 the US Environmental Protection Agency (EPA) mandated that nearly all newly manufactured vehicles be equipped with onboard refueling vapor recovery (ORVR) systems, and in 2012 the EPA determined that the US vehicle fleet was sufficiently saturated with ORVR systems. This study aimed to examine the current magnitude of refueling-related emissions exposure in an ORVR-saturated fleet, as well as to determine the effectiveness of using an infrared camera to view vapor emissions from refueling events at gas stations.

The team used an infrared camera optimized for optical gas imaging of volatile organic compounds (VOCs), present in petroleum products, to record refueling for 16 vehicles at six gas stations in Northern Manhattan, NYC. Infrared cameras are frequently used to detect leaks in petroleum refining operations and were used in this study to record the fuel pump nozzle and external vehicle fuel tank filler pipe during each refueling session. Each infrared video was reviewed to identify the presence and magnitude of vaporized gasoline emitted during a refueling session as well as patterns of vapor emission. Gasoline Vapor Emissions During Vehicle Refueling Events in a Vehicle Fleet Saturated with Onboard Refueling Vapor Recovery Systems: Need for an Exposure Assessment.

The infrared camera was able to detect gasoline vapors emitted during vehicle refueling as well as identify vapor sources, the time of vapor release, and the movement of vapors after being emitted. Fuel vapor emissions were observed for 14 out of the 16 vehicles recorded, and the majority of vehicles had substantial fuel vapor emissions, especially at the end of refueling.  

This pilot study highlighted the value of using an infrared camera to complement traditional methods of exposure measurement for determining potential health risks from vehicle refueling, and visually showed large amounts of fuel vapor emissions that were being released, even within an ORVR-saturated vehicle fleet. The study raises a question about whether there is a breakdown in the overall functioning of the ORVR systems in the US vehicle fleet over time.

Overall, this study is important to public health and policy since the effectiveness of ORVR systems directly impacts the lifetime exposure of individuals to gasoline vapors during refueling events. Additionally, VOCs potentially released during refueling can chemically react in the atmosphere and contribute to ozone as well as other secondary pollution formation, indirectly leading to more human health concerns. The authors recommend that future studies be conducted with comprehensive exposure assessments as well as real-time monitoring of VOCs, along with infrared cameras, in order to improve the health and safety of the public.
 

Shearston J, Hilpert M.  Gasoline Vapor Emissions During Vehicle Refueling Events in a Vehicle Fleet Saturated with Onboard Refueling Vapor Recovery Systems: Need for an Exposure Assessment. Front Public Health. 2020 Feb 7; 8:18.