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New study finds gasoline stations vent up to 10x more benzene fumes than previously thought

A study led by environmental health scientists at Columbia University Mailman School of Public Health examined the release of vapors from gasoline station vent pipes, and found benzene emissions were 10 times higher than estimates used in setback regulations that determine how close schools, playgrounds, and parks can be to the facilities. The findings appear in the journal Science of the Total Environment.

At gas stations, fuel vapors are released into the atmosphere from storage tanks through vent pipes. Little is known about when releases occur, their magnitude, and their potential health consequences. Our goals were to quantify vent pipe releases and examine exceedance of short-term exposure limits to benzene around gas stations.

… Recorded vent emission factors were >10 times higher than estimates used to derive setback distances for gas stations. Setback distances should be revisited to address temporal variability and pollution controls in vent emissions.

—Hilpert et al.

Gasoline vapors contain a number of toxic chemicals—notably benzene, a carcinogen.

The researchers attached gas flow meters to venting pipes at two large gas stations in the Midwest and Northwest and took measurements over a three-week period. They report average daily evaporative losses of 7 and 3 gallons of liquid gasoline, respectively, or 1.4 pounds and 1.7 pounds per 1,000 gallons dispensed at the pump.

By comparison, the California Air Pollution Control Officers Association (CAPCOA) used an estimate of 0.11 pounds per 1,000 gallons. Based on CAPCOA emission estimates, the California Air Resources Board (CARB) determined their setback regulation of 300 feet (91 meters) from large gas stations. Similar laws exist in many, but not all states and localities. In urban areas like New York City, some gas stations are located directly adjacent to apartment buildings.

The study also simulated how the fuel vapor was carried in the air to assess the potential for short- and medium-term benzene exposures, comparing their measurements to three established thresholds.

The California Office of Environmental Health Hazard Assessment one-hour Reference Exposure Level (REL) for benzene—defined as a continuous hour of exposure to the chemical—was exceeded at both gas stations at distances greater than 50 meters. At the Midwest gas station, REL was exceeded on two different days at distances greater than 50 meters, and once as far as 160 meters.

The Agency for Toxic Substances and Disease Registry’s Minimal Risk Level (MRL) for benzene exposure over a period between two weeks and a year was exceeded within 7 or 8 meters of the two gas stations. A less stringent measure used for short-term exposures of first responders, the American Industrial Hygiene Association’s Emergency Response Planning Guidelines (ERPG), was not exceeded.

We found evidence that much more benzene is released by gas stations than previously thought. In addition, even during a relatively short study period, we saw a number of instances in which people could be exposed to the chemical at locations beyond the setback distance of 300 feet.

Officials should reconsider their regulations based on these data with particular attention to the possibility of short spikes in emissions resulting from regular operations or improper procedures related to fuel deliveries and the use of pollution prevention technology.

—first author Markus Hilpert, PhD, associate professor of Environmental Health Sciences at the Columbia Mailman School

In previous work, Hilpert and colleagues documented the release of gasoline as fuel is stored and transferred between tanker trucks, storage tanks, and vehicle tanks, and how these spills can contaminate the surrounding environment. Next, the researchers will explore additional short-term measures of vapor spread to determine the bounds of safe setbacks.

Co-authors of the new study include Ana Maria Rule at Johns Hopkins, Bernat Adria-Mora formerly at Columbia, and Tedmund Tiberi at ARID Technologies, Inc. In a competing interest statement, the authors note that Tiberi directs a company that develops technologies for reducing fuel emissions from gasoline-handling operations. The research is supported by a grant from the National Institutes of Health (ES009089).

Resources

  • Markus Hilpert, Ana Maria Rule, Bernat Adria-Mora, Tedmund Tiberi (2018) “Vent pipe emissions from storage tanks at gas stations: Implications for setback distances,” Science of The Total Environment, Volume 650, Part 2, Pages 2239-2250 doi: 10.1016/j.scitotenv.2018.09.303

Comments

HarveyD

It seems obvious that we have been had once more by the Oil and Car industries? No wonder that cancer cases have been going up at a fast rate for the last 100+ years

SJC

Petrochemical residue is a hazard all over the world, benzene is a carcinogen.

Peter_XX

Not all fuels are equal... Diesel fuel is inherently clean regarding vapour emissions.

Engineer-Poet

Diesel fuel can produce explosive fuel/air mixtures in storage tanks.  Saturated gasoline mixtures are generally too rich to ignite.

What appears to be needed here is some kind of vapor capture system on the fuel tanks.  Vehicles use charcoal canisters to hold hydrocarbons, and the canister is "purged" with air while the engine is running and the hydrocarbons are pulled out again and burned.  Problem is, there's no readily available "purge" stream for gasoline storage tanks.

Maybe what we need is application of heat to regenerate the charcoal and a flare stack to burn off the vapors.  The flare stack would also operate while the storage tank is being filled and air is being pushed out.

Bernard

E-P,

FYI, the problem is not "while the storage tank is being filled and air is being pushed out."
In most jurisdictions, the air that is pushed-out is sent to the tanker to replace the equal volume of fuel that is pushed-in.

Engineer-Poet

That assumes that the volumes are in fact equal.  If you're evolving light molecules into vapor in the receiving tank due to e.g. splashing, you're going to have more volume going out than coming in.

I watched a tanker unloading at a gas station once and noticed that I was standing in a light mist of falling droplets of gasoline from the vent pipe nearby.  This was before any requirements for recapture of vapor so I don't know what the situation is today.

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