Can automotive air conditioners emit carcinogenic benzene?

Rumors: Do not open the air conditioner immediately after entering the car. Open the window for a few minutes before opening the air conditioner. Because according to research, the car's dashboard, sofa, and air filter will release benzene (smell the smell of plastic in your car at high temperatures), which is a carcinogenic toxin. Exposure can cause leukemia, which greatly increases the risk of cancer. In addition to causing cancer, benzene can also erode our bones, causing anemia and reducing the number of white blood cells. It can also cause miscarriage in the long term. The acceptable level of benzene is 50 mg per square foot. Vehicles parked indoors and with closed windows can produce 400-800 milligrams of benzene. When parked outdoors in the sun, the temperature exceeds 60 degrees Fahrenheit (15.6 degrees Celsius), and benzene rises to 2000-4000 milligrams, which is 40 times the allowable amount! People in the car will inevitably inhale excess toxins. Before entering the car, it is recommended to open doors and windows to convection the air. Benzene is a toxin that affects the kidneys and liver and is difficult to excrete from the body.

Crack: This rumor has itself been misunderstood very badly. Many readers had the impression that after reading this rumor: It warned drivers not to use car air conditioners because the air conditioning system itself emits benzene. In fact, the article wanted to express: Do not open the air-conditioner as soon as you get in the car. Instead, you should roll down the window and let the accumulated “benzene smell” (dispelled by dashboards, interior components, etc. in rumors). Disperse from the car, and then close the window to open the air conditioner.

In addition, we know that discussing the content of chemical substances in gases should be described as the mass per unit "volume" rather than the mass per unit "area". Rumours that the acceptable level of benzene is 50 mg per square foot is obviously wrong. The American Cancer Society’s website commented on this rumor: Although this is only a small technical problem, it also reflects that the rumors may have very limited knowledge of basic scientific concepts.

Regardless of the details of these two technologies, how many of the remaining contents are facts?

Benzene is indeed a carcinogen

The American Cancer Society pointed out that there is evidence that benzene is associated with an increased risk of leukemia [1]:

“A considerable amount of human research evidence indicates that there is a link between benzene and cancer. It was initially reported that leukemia, especially acute myeloid cells, are exposed to workers exposed to high levels of benzene (chemicals, shoes, and oil refining). The risk of leukemia has increased. More recent research has focused on workers exposed to relatively low levels."

Animal research has also achieved consistent results. There is sufficient animal experimental evidence to prove the carcinogenicity of benzene. Some important animal experiments support previous findings: Inhaled and ingested benzene can increase the risk of human leukemia. Reviewing the details of such studies, the relevance of benzene and cancer was confirmed.

Benzene's "acceptable level"

The US administration has not established so-called "acceptable levels of benzene." The National Institute of Occupational Safety and Health (NIOSH) of the United States has two limits for the benzene content in the workplace: short-term (in 15 minutes) 3.2 milligrams per cubic meter, and long-term average of 0.32 milligrams per cubic meter. The rumors of "50 mg/cubic foot" can be converted to 1765.7 mg/m3, which is hundreds of times larger than the short-term exposure limit! It can only be understood as a rumors creator mistaken the unit or made another mathematical mistake. The value of "50 mg per cubic foot" is meaningless.


Although the two benzene limit values ​​provided by NIOSH are for workers in some industries, we can also use it as a reference to measure the level of benzene in the car's internal air.

Is it really possible to produce benzene that is potentially carcinogenic in automobiles?

There is no scientific evidence for this. In 2001, a South Korean study investigated people with long commutes in urban areas (including sedans and buses). Although they did find that vehicle use would increase the exposure of benzene, their findings were similar to those in the above rumors. The description is obviously different [2]:

The study found that the use of vehicles increases the exposure levels of various harmful substances, and benzene is one of them. But the primary factor that led to this situation was the fuel used by the vehicle, not the interior components such as dashboards.

The study found that the benzene content of old cars was higher than that of new cars. This shows that the "new car smell" emitted by the dashboard, interior components and other components is not the primary factor affecting the level of benzene in the car.

The study found that the level of benzene exposure increased significantly during the winter months. This shows that the use of automotive air conditioning is not a major factor in benzene exposure.

The Korean study also found no connection between commuting-induced benzene exposure and the onset of cancer.

In 2007, a study in Germany focused on the "toxicity of the air inside a parked vehicle" [3]. The researchers set up a new car of the same brand and an old car that used three years, placed under 14,000 watts of light, raised the temperature to 150 degrees Fahrenheit (65.6 degrees Celsius), and collected gas inside the vehicle. They then exposed laboratory culture cells from humans and hamsters to extracts of these gases. This is a normal measure of toxicity testing.

Studies have shown that the gas from the new vehicle does not show toxicity, but only causes a slight immune response. In theory, these reactions may cause allergies in some people. Old cars do not have this phenomenon. The study concluded that: "The internal air of the parked vehicle has not found any obvious health hazard."

The study also found that the total amount of volatile organic compounds in the new car is 10.9 milligrams per cubic meter, and its main component does not include benzene. The rumors claim that the content of benzene in vehicles under the sun can reach 2000-4000 milligrams per cubic foot, which is 70.6 grams to 141.3 grams per cubic meter. This amount of benzene is collected, the volume is almost as much as a bottle of toilet water! Obviously absurd.

Even if we assume that the gossip creator has mistaken the unit, it is still unreasonable to “help him” change the “gram” from the above-mentioned value to “mg”. After such revision, the rumors of benzene, the substance, are still about 10 times larger than the total amount of volatile organic compounds measured in the above study. What's more, benzene is not even among the more than 40 organic compounds that have been detected.

The American Cancer Society also investigated several other studies in Germany, South Korea, and the United States, and concluded that:

“We have found no evidence in our published study that this can be confirmed (in rumors). In some studies on moving vehicles, the level of benzene exposure exceeds the recommended level of chronic benzene exposure in the workplace, but these levels of benzene It is unlikely to occur in maintaining an appropriate vehicle."

It is right to open the window first in hot days, but it has nothing to do with benzene.

There is a point of view in the rumors that is desirable: on hot days, when you return to a vehicle with doors and windows closed, you should open the window and let it air for a while. But the reason is not related to benzene, but because vehicles parked in the sun and closed doors and windows have a greenhouse effect, making the temperature inside the car much higher than outside the car. Opening the window for a while can speed up the temperature drop through gas exchange, which is more effective than cooling by air conditioning alone.

How to Avoid and Reduce Benzene Hazard

Although there is no scientific evidence to support the benzene content of the air in the car enough to cause cancer, there are other pathways in daily life that may be exposed to benzene. The American Cancer Society recommends:

If you are concerned about benzene contamination in your car, you can regularly open the window for ventilation, or set the air conditioning system to a circular state so that the air inside and outside the vehicle can circulate. The following methods can also reduce the amount of daily exposure to benzene:

Stay away from cigarettes. If you are a smoker, quit smoking. Smoking is the main source of benzene exposure.

If you have benzene in your work environment, consult with your employer to change the workflow (eg, use other solvents to replace benzene, or ensure that benzene is properly stored in closed conditions), or use personal protective equipment. If necessary, the Occupational Safety and Health Administration (OSHA) may provide information or go for an inspection.

Reduce your exposure to gasoline, be careful when refueling, or choose a gas station that has an oil and gas recovery system. Gasoline contains benzene and should avoid skin contact.

Finally, when confronted with some solvents, paints, pigments, and other chemical substances, use common sense to determine if they may contain benzene. Reduce and avoid coexistence with these substances, especially in unventilated areas.

Conclusion: This rumor of "car air-conditioner emits carcinogenic benzene" contains many mistakes in concepts and viewpoints. In fact, although studies have found that the use of vehicles will slightly increase benzene exposure, it has not been found that this level of exposure can lead to an increased risk of cancer. Other ways, including smoking, are the main source of benzene exposure in daily life, and we also have many methods to deal with, which can avoid and reduce the harm of benzene.



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