BTEX Analysis: The Complete Guide to Understanding, Detecting and Managing Pollution

Before delving into the details of the analysis, it is crucial to know precisely what BTEX are and why they represent a threat.

BTEX is an acronym for a group of four monocyclic aromatic hydrocarbons: benzene, toluene, ethylbenzene, and xylenes. These substances are classified as Volatile Organic Compounds (VOCs) because of their ability to evaporate readily into the air at room temperature. They are generally colorless, flammable liquids that occur naturally in crude oil.

The presence of BTEX in the environment is linked to natural sources and, predominantly, to human (anthropogenic) activities.

• Natural sources: These include oil seeps, forest fires, and volcanic eruptions.
• Anthropogenic sources: These are the most concerning. They include industrial emissions (oil refining, petrochemical plants), gasoline combustion, and, most importantly, leaks from underground storage tanks. According to the Maryland Department of the Environment (MDE), the primary source of BTEX contamination is leaks from these tanks , contaminating soil and groundwater.

Because of their high solubility in water, BTEX spread easily and can contaminate vast areas of groundwater, which sometimes serves as a source of drinking water.

BTEX compounds are considered toxic and ecotoxic . Their effects on human health vary depending on the compound, the dose, and the duration of exposure.

• Benzene (C₆H₆) is the most dangerous of the group. It is classified as a known human carcinogen . Prolonged exposure can cause serious blood disorders, such as leukemia, and affect the nervous system.
• Toluene, ethylbenzene, and xylenes are primarily toxic to the central nervous system. They can cause eye and skin irritation, as well as damage to the respiratory and nervous systems.

From an environmental perspective, BTEX are hazardous air pollutants (HAPs) that contribute to the formation of tropospheric ozone. Their presence in soils and waters threatens aquatic and terrestrial ecosystems.

BTEX analysis is a fundamental step in the management of contaminated sites and the protection of health. It is required in many contexts to assess a potential or actual risk.

• Diagnosis of polluted sites and soils: Before the rehabilitation of an industrial wasteland, a former service station or any site that has housed risky activities.
• Real estate transactions: To assess the environmental quality of a plot of land before its purchase or sale.
• Excavated soil management: To determine whether soil can be reused on site or if it needs to be removed to specific treatment centers.
• Environmental monitoring: Regular monitoring of groundwater, ambient air or indoor air quality in at-risk areas.

In France, the regulatory situation is nuanced. There are no universally applicable soil pollution thresholds . However, limit values ​​are set in specific contexts, particularly for the acceptance of waste at Inert Waste Storage Facilities (ISDI).

The decree concerning these installations sets a limit value for BTEX at 6 mg/kg of dry matter. This value serves as a reference for deciding whether excavated soil can be considered inert.

The graph above compares the limit values ​​for the admission of several organic pollutants to landfills, showing the relative position of BTEX compared to other contaminant families such as Polycyclic Aromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs). Note that the limit for Total Hydrocarbons (THCs) is much higher, while that for PCBs is stricter. Data from the decree on landfills .