How Does Molekule Remove the VOC Toluene?

Toluene is a very common substance in our modern world. You have probably encountered it mixed with paint or as an ingredient of a manufactured product. However, exposure to toluene, even in the short term, can lead to serious health issues. Fortunately, the PECO technology in Molekule not only removes toluene from the air, but it also destroys it. After passing through the PECO-filter, little remains of toluene apart from carbon dioxide and water.

Toluene: a common VOC

Toluene is classified as an aromatic hydrocarbon. The term “aromatic” means it has a six-carbon double bonded ring shape integrated into its structure. Like most other hydrocarbons, toluene was originally discovered by distilling tree oils, specifically the Tolu Bantam from which it gets its name. It also occurs naturally in crude oil, which was originally living plant matter. Burning plant-based substances such as gasoline and cigarettes often emits toluene into the air.

As the term “aromatic” suggests, toluene, like all aromatic hydrocarbons, has a characteristic odor that you would probably recognize as the smell of paint or paint thinner. Toluene is also a VOC, or volatile organic compound, which means it tends to evaporate into the air.

Does Molekule remove toluene?

The short answer is: Yes. Molekule not only removes toluene from the air, it also oxidizes it. The oxidation of a molecule like toluene essentially converts it into harmless substances like carbon dioxide and water. The process is very similar to completely burning toluene—only byproducts will remain. Thus toluene processed by a Molekule device ceases to be toxic.

How does Molekule remove toluene?

Molekule’s PECO-filter is coated with a catalyst activated by light inside the device. The activated catalyst interacts with water molecules in the air and produces what is known as hydroxyl radicals on its surface. Hydroxyl radicals are very unstable and tend to rapidly disappear as they recombine with water molecules. But if a pollutant like toluene is on the surface of the filter the hydroxyl radicals will preferentially combine with the toluene and transform it into carbon dioxide and water.

The actual chemical reaction is very complex and can proceed by many different paths, but the same toluene oxidation process occurs in the upper atmosphere so it is very well-studied.

Where is toluene found?

Toluene’s inherent properties make it an excellent solvent, which is a substance that dissolves other substances. This is why it is often used in paints and lacquers. Most paints have three basic components: a pigment, binder and solvent. The dry and dusty pigment is what gives paint its color, and the binder is a lot like glue that becomes hard when it dries. The solvent, also known as paint thinner, is used to dissolve the binder and the pigment together and to keep them soft and workable for normal use. After application, the solvent evaporates and leaves behind the binder and pigment in a thin, hardened coating we think of as a layer of paint. The ability to dissolve a material and evaporate after application has made toluene useful in inks, adhesives, lacquers, fragrances, cleaning supplies and other similar products.

In addition to being a solvent, toluene is useful as an industrial feedstock (also known as raw material). The chemical nature of toluene lends itself to the formation of many substances, including:

Foam: Toluene is made into millions of pounds of TDI (toluene diisocyanate) each year in the US, which in turn is made into spray sealants, polyurethane, and other foams. The EPA does not consider TDI safe and regulates the use and sale of any products that contain it.

Explosives: One of the most well-known explosives is trinitrotoluene, or TNT, and is made from toluene. Its stability and insensitivity make it much more practical than other explosives like dynamite and is primarily used for military purposes. Most of the TNT produced goes into shells, bombs and grenades.

Fuel: As you may have guessed from its role in the synthesis of explosives, toluene contains a lot of energy that is released when it burns. As a result it can be mixed with gasoline and used in high-performance vehicles or with other hydrocarbons for use as jet fuel.

Materials: Toluene’s reactive nature makes it ideal for manufacturing. Nylon, plastics, and many other synthetic materials are made with toluene as a starting point.

Sources of toluene in the home

Sources of toluene in the home are most likely to be solvent-based products such as paints and lacquers. The smell of toluene is detectable at a concentration of 8ppm, which is far below any dangerous levels (200 ppm is considered hazardous by OSHA). This means that if you think the smell is strong, it is definitely best to leave the room and increase ventilation by opening a door or window. You should also always keep substances containing solvents in tightly sealed containers or in a shed outside the home, if possible.

Another common source of toluene is gasoline and cigarette smoke. Unfortunately for bystanders, secondhand smoke contains hundreds of times more toluene than the mainstream smoke directly inhaled by the smoker. Toluene is also emitted as a component of car exhaust, so if you live near a parking lot or freeway your exposure may be higher.

The health effects of toluene

Exposure to toluene primarily affects the central nervous system. Short term exposure to low or medium levels of toluene causes fatigue, sleepiness, headaches, euphoria, and nausea, most of which should subside after time, as toluene is generally processed out of the body in about one day. However, even short-term exposure to high levels of toluene can lead to death.

Because it has a tendency to cause euphoria, some people abuse toluene by inhaling it, which is commonly known as “huffing” or “sniffing.” This is particularly dangerous and can lead to memory loss, poor coordination, loss of muscle control, and decreased mental abilities.

Longer term exposure to low levels of toluene can lead to irritation of the respiratory tract and eyes, sore throat and prolonged experience of the short-term symptoms. Because inhaling small amounts of toluene can be considered intoxicating, the EU has banned the sale of products with more than 0.1% toluene. This effectively restricts toluene to use only as an industrial feedstock rather than a solvent.

There has not been any evidence of toluene causing cancer to date and the EPA does not classify it as a possible carcinogen. However, the accepted long-term effects are still dire and can lead to permanent loss of hearing or vision, cognitive impairment, coordination problems, or damage to the kidney, liver, immune system or reproductive system.

Perhaps most importantly, toluene causes birth defects, including central nervous system dysfunction, ADD/ADHD, and minor physical abnormalities.

How to avoid toluene in the home

The best way to avoid toluene exposure in the home is to not buy any products that off-gas toluene. If you cannot tell if a product has toluene, then you should use any products with a strong chemical smell in a well-ventilated area.

To be safe, you can remove toluene and other VOCs in your air with an air purifier. Carbon filtration is a safe and fairly effective method to reduce VOC concentrations, but you should ensure that the carbon filter is changed on time. If you use a carbon filter to remove toluene, it will also subsequently be full of it. Slight changes in humidity or temperature can cause chemicals like toluene to become unstuck from a carbon filter and reenter the environment in potentially high concentrations.

Another option is to use a photocatalytic purifier, like the PECO-filter in Molekule. The PECO-filter does not just stick to VOCs like toluene, it breaks them down on the molecular level into carbon dioxide and water. When challenged with a mixture of VOCs including toluene, the current Molekule device was able to remove a concentration of about 194 ppb toluene to undetectable levels in about an hour.

To learn more about toluene and other VOCs, check out our blogs on the how VOCs affect your children, how Molekule destroys VOCs, or the best air purifiers for VOCs.

Written by

Haldane King is a molecular biologist by education, a statistician by training, and a researcher by nature. He spent 15 years in the market research world helping to grow all types of companies from pharmaceuticals to software to insurance. Haldane has researched the world of air quality, air pollution, and air purifiers at Molekule and now proudly attends to the Molekule.Science blog.