Health risk assessment of ambient air concentrations of benzene, toluene and xylene (BTX) in service station environments.

Benjamin Edokpolo,Des Connell,Qiming Yu

doi:10.3390/ijerph110606354

Abstract

A comprehensive evaluation of the adverse health effects of human exposures to BTX from service station emissions was carried out using BTX exposure data from the scientific literature. The data was grouped into different scenarios based on activity, location and occupation and plotted as Cumulative Probability Distributions (CPD) plots. Health risk was evaluated for each scenario using the Hazard Quotient (HQ) at 50% (CEXP50) and 95% (CEXP95) exposure levels. HQ50 and HQ95 > 1 were obtained with benzene in the scenario for service station attendants and mechanics repairing petrol dispensing pumps indicating a possible health risk. The risk was minimized for service stations using vapour recovery systems which greatly reduced the benzene exposure levels. HQ50 and HQ95 < 1 were obtained for all other scenarios with benzene suggesting minimal risk for most of the exposed population. However, HQ50 and HQ95 < 1 was also found with toluene and xylene for all scenarios, suggesting minimal health risk. The lifetime excess Cancer Risk (CR) and Overall Risk Probability for cancer on exposure to benzene was calculated for all Scenarios and this was higher amongst service station attendants than any other scenario.

Highlights

Petrol vapour emissions constitute one of the main sources of air pollutants in service stations (Table 1)
Exposure to benzene at CEXP50 was higher than National Institute for and Health (NIOSH) Recommended Exposure Limit (REL) but lower than ACIGH Threshold Limit Values (TLVs), OSHA Permissible Exposure Limit (PEL), EC Limit Value (LV) and SAOHS Occupational Exposure limit (OEL)
Of the BTX compounds, benzene is the compound of most concern because levels higher than the exposure limits were observed in some scenarios

Summary

Introduction

Petrol vapour emissions constitute one of the main sources of air pollutants in service stations (Table 1). There are a wide range of Volatile Aromatic Hydrocarbons (VAHs) present in the atmosphere of service stations as a result of emissions of vapours during dispensing, loading, unloading and transportation of petrol [2]. The data sets used in this scenario were obtained from the following references and had the means and standard deviations for benzene (B), toluene (T) and xylene (X) as indicated: [3], B (910 ± 140); T (1580 ± 180); X (890 ± 110); [4], B (4 ± 1);. The data sets for exposure to concentrations of BTX in the air were based on personal monitoring and from static sampling. The Lifetime Average Daily Doses (LADD) (μg/kg/day) for exposure to BTX concentrations in air through inhalation were calculated for occupational and non-occupational exposure using Equation (2): (2).

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