BTEX VOCs

Sources of BTEX/VOCs

BTEX is a term that encompasses a group of volatile organic compounds (VOCs), which include benzene, toluene, ethylbenzene, and xylene. BTEX is more common in indoor environments than outdoors, commonly originating from construction materials, cleaning products, and tobacco smoking. BTEX can also worsen air quality through oxidation reactions, creating secondary pollutants.

BTEX VOCs are grouped due to their similarities in structure, properties, and emission sources, and can all be described as monocyclic aromatics. They are also all especially harmful to humans.

BTEX can originate from natural sources (e.g., forest fires, organic matter decomposition); however, these sources affect the indoor air quality much less than anthropogenic sources. Benzene is a clear and colourless liquid, with a sweet petrol-like smell. Toluene shares the same properties but has a reported strong, solvent-like smell. Ethylbenzene is also clear and colourless, characterised by a petrol-like smell.

Commonly perceived as a pleasant scent, TVOCs are key ingredients in many perfumes and are responsible for the 'new car smell'. As TVOCs are commonly released from new materials, increased concentrations are found in new cars or indoor renovations/new builds. VOCs can even be emitted from human breath and skin. Oxidants within the air (Ozone or hydroxyl radicals) can produce VOCs on the surface of human skin, which can continue to generate VOCs even after an individual has left the indoor environment.

VOC emissions can also vary depending on an individual's choices of food, alcohol, and personal care products (e.g., perfume, deodorant). This type of emission falls under the umbrella term "Bio-effluence", in which pollutants are produced during the metabolic processes that take place within the human body.

There are thousands of VOCs, making it practically impossible to monitor them all, which is why we use TVOCs as a metric. TVOC aggregates the concentrations of various VOCs into a single value. No universally agreed-upon definition explains which VOCs are included in the aggregate, so standards must be explored and decided upon before drawing accurate comparisons about TVOC levels across multiple samples.

Typical Sources of BTEX

• Chemical Or Petrochemical Industries
• Motor Exhausts
• Paints & Varnishes
• Coal/Biomass Burning

Impacts of Indoor BTEX

Benzene is the most abundant and dangerous BTEX compound. As a carcinogen and mutagen, the compound is correlated with the development of non-lymphocytic leukaemia. Toluene, Ethylbenzene and Xylene are associated with adverse effects on the liver, nervous system, heart, and kidneys. They can act as irritants to the eyes and respiratory tract, also leading to headaches, dizziness, and impaired concentration. The WHO has stated that there is no safe level of benzene concentration; however, many countries use an annual average standard of 3.6 µg m-3.

Common Impacts of BTEX

• Carcinogen and Mutagen
• Adverse Effects on CNS, Kidneys and Heart
• Irritant to Eyes and Respiratory Tract
• Headaches, Dizziness, Loss of Concentration

Testing for VOCs

Testing for BTEX is an identical process to TVOC testing, as BTEX is a volatile organic compound. Tenax tubes can be used passively over a course of a week, or actively with the use of a pump and completed under an hour. Use of Sysco environmental monitoring kits for the individual components of BTEX (Xylene, Benzene, etc) can also be used.

• Passive Tenax Sampling
• Active Pumped Sampling
  

 

The EPA states the reference concentration (RfC) of BTEX is 0.03, 5, 1, and 0.1 mg/m3, respectively. RfC refers to the continuous inhalation of a chemical which is unlikely to cause negative health effects. Workplace exposure limits outlined in EH40/ (WELs) of BTEX within the UK are 3.25, 191, 441, 220 mg/m3, respectively, over an 8-hour period. The air quality directive (2008/EC/50) outlines the outdoor EU limit value for benzene; the annual mean value may not exceed 5 micrograms per cubic metre (µg/m3). BTEX limits are outlined in some regulatory bodies, but are not defined concretely within UK IAQ legislation, likely due to its limited exposure pathways and limited research into causal long-term exposure effects. Most commonly, BTEX may be experienced through occupational exposure incidents.    

• The EPA RfC (reference concentration) for BTEX is 0.03, 5, 1, and 0.1 mg/m3, respectively.
• WEL limit for BTEX is 3.25, 191, 441, 220 mg/m3, respectively, over an 8-hour period.
• The air quality directive (2008/EC/50); BTEX may not exceed 5 micrograms per cubic metre (µg/m3) in outdoor air per annum.