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Which paint ingredients make indoor air toxic?

Published 16.02.2022


Products used at home often have strong impact on the indoor air quality, sometimes causing short term health problems or even leading to chronic diseases. While the chemistry of paint products might seem too complex and challenging to grasp (often even the paint product label does not include full information), it is strongly advisable to get acquainted with at least the part explaining possible impacts these products might have on the health of the paint user and other people spending their time in the freshly painted room.

This blog post introduces to some chemical substances, which are better to avoid, if possible, when purchasing or using paint products. Namely, they can be present in paint products and contribute to making indoor air toxic leading to health risks for professionals working with these products on a daily basis as well as children growing up with painted walls in their closest environment.

Volatile Organic Compounds (VOC)

VOCs are present in nearly all traditional and commercially available paints. Simply put they are the wide array of gases or fumes that come off of paints and are potentially hazardous from the first moments of exposure till, in some cases, years after, while doing repair works, namely they can emit toxins in the indoor air, which are later inhaled by people being in the room.

The health impacts from the VOCs are somewhat linked to the duration of exposure and the environment, where it takes place, as well as age, pre-existing health conditions and individual levels of sensitivity, where groups most at risk are young children, elderly people and pregnant women. Unborn babies and newborn babies are especially vulnerable to the adverse effects of the toxin exposure because their organs and central nervous system are at the early stages of development.

The health problems directly linked to the exposure to VOCs are many, starting from irritation of eyes and respiratory tract and dizziness to nervous system damage, internal organ damage and several forms of cancer, such as leukaemia.

It is possible to recognise VOC in a paint product by the product label. Namely, the safest choice is, when the label indicates that the product is VOC free or that it has low amounts of VOC. Although the “low” or “safe” amount of VOC is disputable since these amounts can vary greatly from country to country and responsible institutions introduce new rules to be followed in order to protect the consumers after enough new studies provide new data.

The best measures anyone can take to protect their health and the health of their children is to use products that are free from these toxins altogether, since such options are available on the market. It is also advisable to avoid painting with traditional paints in cases when the paint ingredients list is unavailable, especially if higher risk groups – pregnant women, infants and young children – are involved (a).

Read more about volatile organic compounds in our blog post link


Formaldehyde is one of the most dangerous VOCs thus deserving its own place on the list of indoor air pollutants. Formaldehyde is a gaseous compound that escapes the paint as fumes and lingers in the indoor air, additionally it can stay "trapped" in the paint film and escape during the home renovation.

As formaldehyde is a gas, its main exposure route is through inhaling the indoor air. However, it could also cause damage from contact to the mucus of eyes and nose as well as contact to the skin.

Formaldehyde is an extremely irritant chemical with regard to skin and eyes, it could damage the respiratory system and it is classified as carcinogenic by the International Agency for Research on Cancer (IARC). Therefore the allowed amount of formaldehyde in the EU should not exceed 0.10 ppm or otherwise the product should be labelled as hazardous.

Those most at risks from formaldehyde exposure are people with pre-existing respiratory system problems, chemically sensitive people, newborns and small children, elderly people and pregnant women.

The consumers can recognise formaldehydes presence in a paint product at "safe" amounts through the product labelling – the European E1 Standard label and the GreenGuard label, while OSHA Hazard communication label would indicate that the "safe" amounts of formaldehyde are exceeded in the particular product. Safer product choice is available under labels "formaldehyde free". In addition some of the biocide containing products are known to emit formaldehyde, thus also should be used with caution (b).

Read more about formaldehydes in our blog post link


Biocides are paint additives that serve the purpose of controlling and limiting organic life in the product either in the in-can or the dry film stage, thus being used as paint preservatives in most commercially available paints. Most biocides used in paint formulation are either fungicides or antimicrobials.

Most biocides used in paint products belong to a group of semi-volatile organic compounds, meaning they have a potential to become an indoor pollutant as a result of off gassing through the paint application and drying stage. Later, as paint degrades, the biocidal active ingredients have a potential to become a pollutant of the indoor air due to addition to the dust particles.

Considering the fact that biocides belong to the poisonous substances, the impact biocides have on human health is surprisingly uncertain, although with more deliberate approach it is possible to find out that the chemical components of biocidal products have known health implications that vary from skin and eye irritation to endocrine disruption and risks of developing cancer. Additionally, the environmental risks linked to the biocidal product use, manufacture and end of life stage has been linked to antimicrobial resistance. Consequently, it could lead to increased resistance that bacteria, viruses and fungi develop in response to certain biocide exposure, thus increasing the risk of spreading various diseases. This eventually leads to an increased biocide use and potentially could create more problems since it becomes somewhat of a vicious cycle of man against nature.

Avoiding biocides is possible by not using antifungal and antimicrobial paints or using them in limited amounts. In case of absolute necessity only those biocide-containing paints should be used that have gone through the regulation process, preferably have ecolabel marking as well as are being used and disposed of following the safety guidelines (c ).

Read more about biocides in our blog post link

Heavy metals in paint

Traditional paints contain inorganic, coloured pigments that are known for containing heavy metals including titanium dioxide, iron oxides, aluminium and mica flakes. Other heavy metals present in paint may include cadmium, mercury and lead.

Heavy metal residues can persist in an indoor environment for a very long time, thus mostly through inhalation leading to long-term health effects in the people living there. The health effects of heavy metal accumulation in a body are numerous, some are linked to organ damage, respiratory system damage and nervous system damage, some are linked to tumour development and fetal development complications. For example, mercury exposure is known to lead to birth defects, cadmium is a known carcinogen that may have toxic effects on the kidney, skeletal and respiratory system, exposure to iron oxide fumes may lead to an illness called iron fever (d;e;f;g).

Since the potential harm of different heavy metals present in paints has been an object of quite many studies, this blog post highlights few of them.

  • Lead

Regarding heavy metals in paint pigments, lead use is either banned or limited. However, it should not be underestimated that lead has been used for a significant period of time in the past thus it still might have a lasting impact on the quality of the indoor air in residential and non-residential buildings. As lead-containing paint chips and brushes off, its smaller particles eventually contributes to the lead pollution in indoor air.

Lead exposure and uptake in the human body causes lead distribution in the blood and its accumulation in the bone consequently leading to numerous health problems including damage to nervous, immune, reproductive systems and also affecting oxygen carrying capacity of the blood. According to the EPA, the most common lead exposure effects are linked to neurological effects in children, potentially contributing to  behavioural problems, learning deficits and lowered IQ (h). 

  • Titanium Dioxide

One more noteworthy common paint pigment is the white titanium dioxide. While its hazardous health effects might be not so common, its nanoparticles have a potential of causing oxidative stress resulting in cell damage, genotoxicity, inflammation, immune response etc.

More significantly titanium dioxide is known for its possible environmental impact from the manufacturing stage. During the manufacturing process the so-called titanium waste is created. It consists of significant amounts of dilute sulfuric acid and large quantities of other harmful by-products acting in the environment as PH destabilisers and having harmful effects on soil and marine life (i;j;k).

These chemical substances, as well as other chemical substances mentioned above, can be identified by checking the product label or avoided by choosing natural or eco paints.




The traditional paint products consist of many hazardous chemicals. Getting acquainted with the known health effects of different paint ingredients it becomes clear that there are quite many substances that better should be avoided. While some of the poisonous substances mentioned in this blog post may be present in paint in small and seemingly insignificant amounts, their potential harm to individuals may vary greatly.

When aiming to protect the human health, especially the most vulnerable groups, it is advisable to use products that are free from substances mentioned in this blog post, since there are numerous alternatives available in the market and their number tends to grow. In addition, there are measures anyone can take to lower the health risks associated to dangerous substances present in the traditional paints:

  • Check, if the paint you purchase and use has full ingredient list available, pay attention to the product labelling;
  • Choose paints without or with possibly low amounts of VOCs, formaldehyde, biocides and heavy metals;
  • Wear protective clothing, while working with paint;
  • Choose to work with paint outdoors or in well-ventilated spaces;
  • Avoid using paints in the presence of the most vulnerable groups - pregnant women, newborns, young children, chemically sensitive people, elderly people and people with pre-existing health conditions;
  • Dispose of paint cans, brushes and other tools that have old paint on them and make sure to dispose of them in accordance with the safety guidelines.


Author: written by Anse Romančuka, edited by Linda Kikuste



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