VOC pollutants in car interiors are toxic to drivers’ health

New stricter VOC regulations for car interiors are driving a shift in focus beyond the "new car smell" towards off-gassed & external pollutants, as studies show typical driver exposure to VOCs can be harmful to health.

VOC POLLUTANTS IN CAR INTERIORS

This article examines these trends using an analysis of 21 key international scientific studies of VOC pollutants in automotive interiors, in the context of proposed new regulations from the EU and UN. It examines how:

1.    New regulations are enforcing lower VOC levels in Automotive Interiors
2.   The focus is moving beyond the "New Car Smell" to the toxicity of VOCs
3.    Studies show VOC Levels can remain unsafe for several years
4.    AqFresh™ technology eliminates VOCs from automotive interior trim

1. New Regulations are Enforcing Lower VOC Levels in Automotive Interiors

A number of countries mandate a maximum total VOC (TVOC) concentration in car interiors. In China the limit is 600 μg/m³[i], while Japan has an even stricter limit of 400 μg/m³[ii]. Some specific toxic VOCs have particularly low limits: notably Acetaldehyde and Formaldehyde, amongst others. In Europe, most car manufacturers already have their own standards similar to the VDA-278 for minimising VOCs. However, proposed new UN and EU regulations are bringing a greater focus on the most toxic of pollutants in car interiors, with the aim of improving Vehicle Interior Air Quality (VIAQ).

The European Union’s proposed new formaldehyde regulation[iii] requires cars to have <62 μg/m³ formaldehyde. A class I carcinogen, formaldehyde is commonly found in car interiors due to off-gassing from nonwovens, plastics, adhesives & coated textiles used in headliners, seat covers, carpets, door and dashboard trim.

Cars must be tested in a whole vehicle test chamber according to ISO 12219-1:2021 under 3 environmental conditions: ambient conditions (ambient mode) at 23 °C - 25 °C with no air exchange; a second only for the measurement of formaldehyde at elevated temperatures (parking mode); and a third for VOCs and carbonyl compounds simulating driving after the vehicle has been parked in the sun starting at elevated temperatures (driving mode).

The United Nations Economic Commission for Europe (UNECE) are working on a Draft Mutual Resolution (M.R.3) on Vehicle Interior Air Quality[iv] aiming for final publication in 2025 which will harmonise the testing of car interiors for the presence of Formaldehyde, Acetaldehyde, Benzene, Toluene, Xylene, Ethylbenzene, Styrene, and Acrolein (from the off-gassing of automotive interior trim materials). It will also cover the testing of car interiors for the presence of PM2.5, NO, NO2, and CO2 (typically from outdoor air pollution entering the cabin). The exact limits to be enforced will be set in each country’s national standards.

The proposed new EU End-of-Life Vehicles (ELV) directive[v] requires automotive OEMs to manufacture cars with at least 25% recycled materials by 2030. However, recycled materials are typically more malodorous with VOCs absorbed during their previous use.

2. The focus is moving beyond the "New Car Smell" to the toxicity of VOCs

Whilst the "new car smell" associated with VOCs is noticeable primarily in new vehicles, the focus is now shifting towards other harmful pollutants, in particular: formaldehyde, acetaldehyde and nitrogen dioxide (NO2), as well as Benzene, Toluene, Ethylbenzene, Xylene and Styrene. These can be present even in older cars and are linked to various health concerns, including:

• Formaldehyde: Classified as a carcinogen by the International Agency for Research on Cancer (IARC), who say that formaldehyde exposure can irritate the eyes, nose, throat, and skin, and potentially contribute to respiratory problems and cancer. In 8 out of the 9 studies reviewed measuring formaldehyde, detected levels (from 75 to 1550 μg/m³) in the worst car exceeded the national limits, even in non-new cars at lower temperatures (18°C).
• Acetaldehyde: Classified as a class IIb possible carcinogen, according to the EPA, Acetaldehyde also causes irritation of the eyes, skin, and respiratory tract and at higher exposure levels, erythema, coughing, pulmonary edema, and necrosis may also occur.
• Nitrogen Dioxide: Exposure to NO2 can irritate the airways, leading to coughing, wheezing, and shortness of breath. It can also worsen asthma symptoms and increase the risk of respiratory infections. While not directly measured in most of the reviewed studies, the upcoming UNECE Draft Part IV of the Mutual Resolution (M.R.3) on VIAQ aims to ensure the measurement of NO2 alongside other pollutants, highlighting its growing importance.
  
  

However, in half of the 21 studies measuring VOCs in car interiors reviewed, formaldehyde and acetaldehyde were not measured. The new EU & UN regulations are therefore driving a greater focus on these toxic pollutants.

3. Studies Show VOC Levels Can Remain Unsafe for Several Years

VOC pollutants in car interiors are toxic to drivers’ health. Research indicates that VOC levels in car interiors can remain at unsafe levels for several months, and even years after manufacture. While VOCs are mostly present initially due to off-gassing from car materials, other sources like outdoor air pollution, car exhaust, and passenger activity (tobacco, food, perfume, etc) contribute to in-car VOCs over time.

• A study by Yoshida and Matsunaga[vi] demonstrated that TVOC concentration can still be as high as 200 μg/m³ three years after vehicle delivery, highlighting the long-term presence of these pollutants.
• One study by Hafs et al[vii] found TVOCs of 5595 μg/m³ in cars 5 months after manufacture
• A study by Zhang et al[viii] found formaldehyde at 80 μg/m³ in cars up to 5 years old and another by Bakhtiari et al[ix] at 1550 μg/m³ in taxis 1-5 years old

Short-term exposure to VOCs >3000 μg/m³ is expected to cause discomfort and possibly headaches, as shown in Table 1 below, according to the study by Yingying Cha (2019)ⁱⁱ. 10 of the studies reviewed have detected TVOC levels >3000 μg/m³.

Whilst TVOC levels are an important measure, there are some common car interior VOCs with more severe health effects than others. Formaldehyde & Benzene are class I carginogens, whereas Styrene is a class IIa probable carcinogen and Acetaldehyde & Ethylbenzene are class IIb possible carcinogens.

Although opening the window or turning the AC on will reduce VOCs to a safer level, most national VOC standards are based on testing cars in parked/unventilated mode at c. 23°C.

Wang et al, 2023[x] measuring VOCs in a new car for 12 days under different environmental conditions detected formaldehyde with an average concentration of 82.7 μg/m³ and a peak concentration of 223.5 μg/m³, way above the new EU formaldehyde limit of 62 μg/m³ and the Chinese national standard limit for in-cabin formaldehyde concentration of 100 μg/m³. Increasing air & material surface temperature generally increases VOC concentrations. In this study, in-cabin temperatures ranged from 20 to 90°C, with the dashboard being the car part that experienced the highest temperatures, so this is a key car part to address.

The health risks of formaldehyde exposure for car drivers was revealed by a study by Reddam and Volz, 2021[xi]. It showed that driving for 4 hours a day in a car with the average level detected of 24.25 μg/m³ formaldehyde (just 30% of the average level found in the Chinese study) gives the driver a 74% probability of exceeding the Reference Daily Dose (ie. ‘safe’ level of exposure to avoid cancer).

Whilst reducing the new car smell to below 3.0 on the VDA-270 and minimising TVOCs according to VDA-278 and ISO 12219 is the current norm, there remains a VOC health concern in cars. Future regulation is likely to seek to improve VIAQ for human health.

 A new additive odour & VOC elimination technology, AqFresh™, has been incorporated into car materials to reduce the VOCs they off-gas. It can also be incorporated into car AC filters which play an important role in helping combat in-car pollution beyond the initial few months, to help keep car users safe.

4. AqFresh™ technology enables VOC elimination from automotive interior trim

AqFresh™ technology, from Cambridge-UK Chemtech Aqdot, offers a novel solution to address VOCs in car interiors. By incorporating AqFresh™ into car materials, such as fabrics, nonwovens, plastics, and air conditioning filters, it captures and eliminates both off-gassed VOCs from the materials themselves and external VOCs entering the car from the environment.

Benefits of AqFresh™ for Material Design Engineers and Car Manufacturers:

• Compliance with stricter VOC regulations: 
  • AqFresh™ can help car manufacturers meet the evolving regulatory landscape for VOC emissions in car interiors.
  • Recycled plastic dashboard material was proven to off-gas 43% less TVOCs when AqFresh™ was incorporated into it.

• Reduced health risks for drivers by eliminating the worst pollutants:  
  • Car interior materials with AqFresh™ reduce formaldehyde from the air enabling car manufacturers to meet new stringent regulatory limits
  • The EU's proposed new regulations require cars to have <62 μg/m³ formaldehyde, even lower than the current limit in China of 100 μg/m³
  • Studies have found that due to emissions from car interior materials, formaldehyde was present in some cars at levels as high as 1550 μg/m³
  • When impregnated into a typical nonwoven material used in car interiors, AqFresh™ was proven in independent testing to the Chinese standard QB/T 2761-2006 to reduce the formaldehyde concentration in the air by 97.9% - from 18 times higher than the limit to 61% below the limit.
  • AqFresh™ has been successfully integrated into a range of car interior materials including nonwovens, virgin & recycled plastic, films, and coated textiles.
  • This unique technology offers car interior material manufacturers an added-value, effective & comprehensive solution to the problem of VOCs from car materials.
  • By effectively reducing both VOC emissions from car materials and environmental VOCs in the air, AqFresh™ can be incorporated into a single car interior part to reduce VOCs emitted from all the other car interior parts.
  • By minimizing VOC exposure, AqFresh™ contributes to a healthier in-car environment.
  • AqFresh™ has been proven in independent analytical testing to reduce the level of acetaldehyde off-gassed by plastics by 92%.
  • AqFresh™ is enabling automotive interior materials to be used safely and to meet regulatory requirements.
  • For example, the acetaldehyde emissions of a typical car dashboard rigid plastic were reduced by AqFresh™ from 6 times higher than the regulatory limit in Japan to 28% below.

• Improved odour control: 
  • AqFresh™ has been proven to reduce the new car smell to below 3.0 on the VDA-270 contributing to a more pleasant driving experience.
    
    
• Versatility: 
  • AqFresh™ has been integrated into various car interior materials via finishing treatments such as spraying or padding or by compounding into plastic masterbatch for rigid plastics or nonwoven fibres.
  • This versatility allows for seamless integration without compromising design aesthetics or functionality.

 Looking to the future:

With growing awareness of the health risks associated with VOCs in car interiors, and stricter regulations on the horizon, AqFresh™ technology offers a valuable solution for material design engineers and car manufacturers seeking to create safer, healthier and regulatory-compliant driving experiences.

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References

[i] Tokumura, M., Hatayama, R., Tatsu, K., Naito, T., Takeda, T., Raknuzzaman, M., . . . Masunaga, S. (2016). Car indoor air pollution by volatile organic compounds and aldehydes in Japan. AIMS Environmental Science, 362-381 (https://www.aimspress.com/article/id/831).

[ii] Yingying, C. (2019). In-cabin VOCs: Sources, health effects, and control methods. https://www.researchgate.net/publication/336578692_In-cabin_VOCs_Sources_health_effects_and_control_methods#pf7.

[iii] European Union (EU). (2023, July 14). Eur-Lex. Retrieved from Official Journal of the European Union: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32023R1464

[iv] United Nations Economic Commission for Europe (UNECE). (2024, February 7). Retrieved from Working Party on Pollution and Energy (GRPE): https://wiki.unece.org/download/attachments/228622570/VIAQ-29-04-Draft%20Part%20IV%20of%20the%20Mutual%20Resolution%203%20on%20VIAQ.docx?api=v2

[v] European Union (EU). (2000, September 18). Eur-Lex. Retrieved from Official Journal of the European Union: https://eur-lex.europa.eu/EN/legal-content/summary/end-of-life-vehicles.html

[vi] Yoshida, T., & Ichiro, M. (2006). A case study on identification of air-borne organic compounds and time courses of their concentrations in the cabin of a new car for private use. Environ. Int., 58–79 (https://pubmed.ncbi.nlm.nih.gov/15993490/).

[vii] Hafs, N., Djeddou, M., Benabed, A., Fokoua, G., & Mehel, A. (2023). Experimental Study of the TVOC Distribution in a Car Cabin. Air 2023, 184-195 (https://www.mdpi.com/2813-4168/1/3/14).

[viii] Zhang, G.-S., Li, T., Luo, M., & Liu, J.-F. (2008). Air pollution in the microenvironment of parked new cars. Building and Environment, 315-319 (https://www.researchgate.net/publication/223322085_Air_pollution_in_the_microenvironment_of_parked_new_cars).

[ix] Bakhtiari, R., Hadei, M., Hopke, P. K., Shahsavani, A., Rastkari, N., Kermani, M., . . . Ghaderpoori, A. (2018). Investigation of in-cabin volatile organic compounds (VOCs) in taxis; influence of vehicle's age, model, fuel, and refueling. Environmental Pollution, 348-355 (https://www.sciencedirect.com/science/article/abs/pii/S0269749117346833?via%3Dihub).

[x] Wang, H., Guo, D., Zhang, W., Zhang, R., Gao, Y., Zhang, X., . . . Xiong, J. (2023). Observation, prediction, and risk assessment of volatile organic compounds in a vehicle cabin environment. Cell Reports Physical Science, (https://www.sciencedirect.com/science/article/pii/S2666386423001431).

[xi] Reddam, A., & Volz, D. C. (2021). Inhalation of two Prop 65-listed chemicals within vehicles may be associated with increased cancer risk. Environment International, (https://www.sciencedirect.com/science/article/pii/S016041202100026).