Impact of Environmental Pollution at Gas Stations

Research Overview

Researchers in the United States have examined the environmental pollution effects at gas stations, specifically focusing on the emissions of carcinogenic substances such as benzene from vent pipes. While many individuals are aware that gasoline vapors are released from gas stations, they might not recognize vent pipes as a significant source of these emissions.

The Role of Vent Pipes

Gas stations are equipped with vent pipes connected to underground gasoline storage tanks. These vent pipes are essential because gasoline vapors can expand or contract in response to fluctuations in external temperature and barometric pressure, or due to pressure buildup from evaporation. As a result, vent pipes serve as the primary source of emissions at gas stations.

Health Implications of Emissions

This study aims to address the health effects associated with environmental pollution stemming from vent pipe emissions.

Study Methodology

Hourly Emission Analysis

The researchers conducted a study on gasoline vent pipe emissions from gas stations, marking what they believe is the first investigation to analyze hourly emission data and publish their findings in a peer-reviewed journal. Their research was documented in the publication “Science of the Total Environment.”

Gas Station Profiles

The study focused on two high-volume gas stations, each selling approximately 3.6 million gallons of gasoline annually. The first station, located on the U.S. Northwest coast, operated during the day from 6:00 AM to 9:30 PM on weekdays and 7 AM to 7 PM on weekends, selling around 700,000 gallons per month. The second station was situated in the U.S. Midwest and operated 24 hours a day, with monthly sales of 450,000 gallons.

Emission Measurement Techniques

The initial objective of the research was to perform a cost-benefit analysis comparing the financial losses from fuel emissions to the advantages of investing in technologies aimed at reducing these losses. A dry gas diaphragm flow meter was utilized to measure emissions through the vent pipes. Rather than directly measuring benzene levels, researchers predicted benzene concentrations using the AERMOD Modeling System developed by the U.S. Environmental Protection Agency (EPA).

Findings on Benzene Emissions

Emission Patterns

The data collected from the two gas stations revealed no consistent emission patterns. At the Midwest 24-hour station, emissions were typically higher during daytime and evening hours, likely correlating with increased gasoline dispensing. Conversely, the Northwest station showed higher emissions during late night and early morning hours when the station was closed. Possible reasons for this discrepancy include improper fuel deliveries or issues with piping and valves.

Exceeding Safety Thresholds

The model predicted that benzene emissions could occasionally surpass the one-hour Reference Exposure Level (REL) for this carcinogen, even at distances up to 160 meters from the station. Furthermore, the vent emission factors recorded were more than ten times higher than current estimates used to determine setback distances from other buildings.

Study Limitations

The authors acknowledged several limitations in their study, including:
– Data collection was limited to the fall and winter seasons, which may affect the results since vent pipe emissions can vary seasonally.
– Benzene levels were not directly measured.
– The study did not forecast indoor benzene levels.

Recommendations for Future Research

Revising Setback Distances

The primary conclusion of this study is the need to revise the setback distances for gas stations. Current American regulations are based on vent emissions data that is over 20 years old, indicating that it is time to incorporate new findings. Additionally, further research could explore more effective emission reduction technologies for gas stations.

Reference

Hilpert et al. “Vent pipe emissions from storage tanks at gas stations: Implications for setback distances.” Science of the Total Environment. 650 (2019) 2239–2250.