Reducing Toluene-Related Air Pollution: Strategies For Improvement

Toluene is a colourless liquid with a distinctive smell that is used in the production of paints, paint thinners, fingernail polish, lacquers, adhesives, rubber, and some printing and leather tanning processes. It is also added to gasoline to improve octane ratings. Toluene is released into the air, water, and soil at places where it is produced or used, and it is commonly found in outdoor air, especially in areas with heavy vehicular traffic. Given its widespread use and associated health risks, it is important to explore ways to reduce air pollution caused by toluene.

Using modified natural zeolite and titanium dioxide nanoparticles to remove toluene vapours from the air

Toluene is a colourless, flammable liquid with the same solubilizing capacity as benzene. It is often used as a substitute for benzene due to uncertainty over whether it is carcinogenic. Workers can be exposed to toluene through inhalation, which can cause adverse effects on the nervous system.

To avoid the negative health effects of toluene exposure, various solutions are applied, including adsorption, thermal oxidation, membrane separation, and photocatalytic processes. One such method is the use of modified natural zeolite and titanium dioxide nanoparticles to remove toluene vapours from the air.

In this process, natural zeolite is modified using chemical and thermal methods to increase its specific surface area and Si/Al ratio, improving its ability to adsorb toluene vapours. Titanium dioxide nanoparticles are then stabilized and coated onto the modified zeolite. The resulting composite material is highly efficient at adsorbing toluene vapours and can be reused repeatedly.

The modified zeolite-titanium dioxide composite offers a promising solution for the removal of toluene vapours from the air, reducing the health risks associated with toluene exposure.

Avoiding inhalation and dermal effects by using solutions such as adsorption, thermal oxidation, membrane separation and photocatalytic processes

Adsorption is a process where gases or solutes are adhered to a solid or liquid surface. It is an effective method for removing volatile organic compounds (VOCs) from the air. One study found that activated carbon is an effective adsorbent for toluene due to its large specific surface area and pore volume. The study also found that the pore structure of the activated carbon affects its toluene adsorption capacity.

Membrane separation is another method that can be used to reduce air pollution caused by toluene. Membrane separation is a more energy-efficient process compared to heat-driven separation processes such as distillation. A novel ionic liquid-polymer gel membrane has been prepared to separate toluene from n-heptane. This membrane showed good separation performance and was stable at temperatures above 300°C.

Photocatalytic processes can also be used to reduce air pollution caused by toluene. One study used N-doped TiO2 to create more Ti3+ and oxygen vacancies, which act as active sites for the selective oxidation of toluene. The N-doped TiO2 exhibited excellent photo-assisted thermal performance, with a toluene conversion rate of 10960.0 μmol·gcat^-1·h^-1.

Thermal oxidation is a process where a fuel source, such as natural gas or propane, is burned to produce heat. This process can be used to reduce air pollution caused by toluene by burning the toluene before it is released into the atmosphere. One study found that TiO2 is an effective catalyst for the thermal oxidation of toluene, with the optimal performance achieved when the temperature was increased to 160°C.

Reducing exposure to products that contain toluene, such as paints, paint thinners, adhesives, and gasoline

Toluene is a common ingredient in paints, paint thinners, adhesives, and gasoline. Here are some ways to reduce exposure to these products and, by extension, toluene:

Paints

• Opt for water-based paints instead of oil-based, enamel, or alkyd paints. Toluene is a common solvent in these types of paints and is often used for thinning and removing them.
• When using oil-based, enamel, or alkyd paints, consider substitute products for toluene, such as acetone, ethyl acetate, or isopropyl alcohol. These alternatives are less toxic and can serve as effective paint thinners and cleaners.
• If you must use products containing toluene, ensure the work area is well-ventilated. Open windows, use exhaust fans, or work outdoors if possible. Proper ventilation is crucial to reducing inhalation of toluene vapors.
• Wear appropriate personal protective equipment (PPE) when working with paints containing toluene. This includes gloves, goggles, and a respirator.
• Dispose of paint products responsibly and in accordance with local regulations for hazardous waste.

Paint Thinners

• Choose water-based paint thinners that do not contain toluene.
• If using toluene-based paint thinners, ensure adequate ventilation in the work area. Use exhaust fans or work outdoors if possible, to reduce the concentration of toluene vapors.
• Wear PPE, including gloves, goggles, and a respirator, when handling paint thinners containing toluene.
• Follow safety guidelines and data sheets provided by the manufacturer. These sheets should disclose the presence of toluene and offer instructions for safe use.
• Store toluene in cool, dry, and well-ventilated spaces, as recommended.

Adhesives

• Opt for water-based adhesives instead of solvent-based ones, as toluene is often used as a solvent.
• When using solvent-based adhesives, improve ventilation in the work area. Use exhaust fans or work outdoors if possible, to reduce the concentration of toluene vapors.
• Wear gloves and work in a well-ventilated area when using contact adhesives that contain toluene. Toluene evaporates slowly and is more likely to be inhaled when using these types of adhesives.
• Dispose of adhesive products and containers responsibly, following local hazardous waste guidelines.

Gasoline

• Be cautious when working at gasoline service stations or handling gasoline. Gasoline typically contains toluene, and workers in these environments may be exposed to higher levels of toluene than the general population.
• When pumping gasoline, especially in enclosed spaces, wear a respirator to reduce inhalation of toluene vapors.
• If your occupation involves regular exposure to gasoline, such as tanker drivers or aircraft maintenance personnel, consult safety guidelines and use appropriate protective equipment.
• Avoid using gasoline-contaminated water for showering, cleaning, or other household activities to minimize exposure to toluene.

Preventing the release of toluene into the air, water, and soil by properly managing and containing it at production and usage sites

Toluene is a highly volatile, flammable organic compound that is used in a variety of industrial processes and is found in many household products. It is released into the environment primarily through the use of petroleum fuels and toluene-based solvents and thinners, as well as from motor vehicle exhaust. To prevent the release of toluene into the air, water, and soil, proper management and containment practices must be implemented at production and usage sites. Here are some strategies to achieve this:

Preventing Toluene Release into the Air

• Adsorption and filtration methods: Adsorbent materials such as activated carbon, natural zeolite, and photocatalytic titanium dioxide nanoparticles can be used to capture toluene vapors from the air. Zeolite, a natural mineral, can be modified chemically and thermally to increase its surface area and improve its adsorption capacity. Photocatalytic processes using titanium dioxide can break down toluene into harmless compounds like water vapour and carbon dioxide.
• Biological methods: Biotrickling filters create a biofilm that facilitates the degradation of toluene in the air. Acinetobacter genospecies, a toluene-degrading bacteria, has shown excellent degradation capabilities in this process.
• Non-thermal plasma techniques: These techniques use electrical discharges to remove toluene from the air, achieving high removal efficiencies.
• Controlling emissions from vehicles: As automobile emissions are a major source of toluene in the air, implementing stricter emission standards and promoting the use of electric vehicles can significantly reduce toluene pollution.
• Reducing industrial emissions: Industries that use toluene in their processes, such as printing, painting, and petroleum refining, should implement measures to minimise emissions. This includes proper ventilation, containment, and treatment of waste streams.

Preventing Toluene Release into Water

• Proper waste disposal: Toluene should not be disposed of in water bodies or poured down drains. Instead, it should be collected and treated as hazardous waste.
• Spill prevention and containment: In areas where toluene is stored or transported, such as petroleum refining facilities, spill prevention measures should be implemented. Containment systems, such as berms or catch basins, can be used to capture any spills and prevent them from reaching water bodies.
• Treatment of wastewater: Wastewater streams containing toluene should be treated before discharge. Advanced treatment methods such as granular activated carbon filtration, in combination with packed tower aeration, can effectively remove toluene from wastewater.

Preventing Toluene Release into Soil

• Containment and collection: In areas where toluene is handled, stored, or transported, secondary containment systems should be used to capture any spills. Spill kits and absorbent materials can be deployed to collect and contain spills, preventing them from soaking into the soil.
• Proper disposal of contaminated soil: Soil contaminated with toluene should be excavated and properly disposed of as hazardous waste. In some cases, bioremediation techniques can be applied to treat contaminated soil and break down toluene.
• Preventing groundwater contamination: As toluene can leach into groundwater, proper containment and spill prevention measures are crucial. Regular monitoring of groundwater near toluene handling facilities is necessary to detect any potential contamination.

Implementing regulations and recommendations to limit exposure to toluene, such as workplace air quality standards and drinking water guidelines

Toluene is a known health hazard, causing eye, nose and throat irritation, headaches, dizziness, and feelings of intoxication. It has also been linked to negative effects on memory, attention, concentration, and colour vision. As such, it is important to implement regulations and recommendations to limit exposure to toluene.

Workplace Air Quality Standards

Workplaces are a primary source of toluene exposure. The Occupational Safety and Health Administration (OSHA) has outlined several standards and documents to limit exposure to toluene in the workplace. These include:

• 1910 Subpart H - Hazardous Materials: A spill or uncontrolled release of liquids containing toluene may be considered an emergency, requiring an emergency response plan, training for responders, personal protective equipment, and medical surveillance.
• 1910 Subpart I - Personal Protective Equipment: Employers must conduct a formal assessment of personal protective equipment needs, such as gloves and respirators, and provide the equipment and training to employees at no cost.
• 1910 Subpart J - General Environmental Controls: Employers must evaluate the hazard of toluene in confined spaces and institute a program of training, ventilation, stand-by, and pre-entry air testing.
• 1910 Subpart Z - Toxic and Hazardous Substances: The Permissible Exposure Limit for toluene is 200 ppm 8-hour time-weighted average, with a ceiling concentration of 300 ppm and a peak of 500 ppm over 10 minutes. Employers must provide employees with access to air sample results, safety data sheets, and training about toluene.

Drinking Water Guidelines

Toluene is considered in the World Health Organization's (WHO) Guidelines for Drinking-water Quality (GDWQ). Health Canada has also established guidelines for toluene exposure in indoor air, recommending maximum exposure limits of 4 parts per million (15 mg/m³) for short-term exposure (8-hour average) and 0.6 parts per million (2.3 mg/m³) for long-term exposure (24-hour average).

To reduce exposure to toluene in indoor air, Health Canada recommends:

• Not allowing smoking indoors
• Not running cars or other gas-powered engines in attached garages, and keeping the door between the house and garage closed
• Properly storing gasoline and other fuels, preferably not in the home
• Using chemical products according to label instructions and disposing of leftover products properly
• Increasing ventilation when using chemical products indoors

Frequently asked questions