Water-based paints labelled as having ‘zero’ or ‘low’ levels of volatile organic compounds (VOCs), could still contain such chemicals, according to a new analysis. The researchers behind the findings are calling for further research into the risks associated with emissions of these chemicals in indoor environments.

In water-based paints, water is used as the main solvent for resin and pigment particles, instead of the organic solvents used in traditional paint products. As a result, they generally contain low levels of VOCs. However, to ensure comparable performance and quality to traditional products, other additives are used – such as coalescing agents and preservatives – many of which are semi-volatile organic compounds (SVOCs) that have been linked to potential health risks.

To find out more about the chemicals in water-based paint products, a team of researchers in China and the US, analysed 40 of the best-selling water-based paints of different brands from across the global market, most of which were labelled as ‘zero-VOC’ or ‘low-VOC’.

After extraction, filtration, and concentration, the samples were analysed using gas chromatography–mass spectrometry (GC–MS). Dry paint films were also prepared by applying paints on aluminium foil and drying them in a ventilated fume hood for up to two days.

‘We used organic solvents to extract the various compounds in the water-based paints and after filtration and concentration we analysed the samples with GC–MS,’ explains Yujie Fan , a researcher at Tsinghua University in China, who worked on the project. ‘We then confirmed the identified compounds using chemical [reference] standards and quantified the concentrations of these chemicals in the water-based paint.’

Open paint tins

Source: © Leon Harris/Getty Images

Overall, they detected 20 SVOCs with concentrations ranging from 10 to 6200 parts per million (ppm) in the wet films and from 10 to 35,000ppm in the dry films. The team notes that these compounds can persist indoors for years, often in dust.

Several coalescing agents – which help the paint form a strong, continuous film as it dries – were identified in many of the samples, while isothiazolinone preservatives, which have been linked to severe allergies and asthma, were identified in almost half of the paint products.

Finally, in 24 of the wet paint samples advertised as either zero- or low-VOC, 11 different VOCs were detected including ethylene glycol, which was detected in 15 samples at concentrations ranging from 800 to 20,000ppm.

The researchers said that the health risks of these products were not just related to toxicity but also to overall exposure levels. ‘We should be aware … these chemicals may persist in indoor environment – they emit slowly but once they are released they may [adhere] to different surfaces and may result in potential risks for humans,’ says Tsinghua University’s Ying Xu, who led the project.

Responding to the study findings, a spokesperson for the British Coatings Federation (BCF) said that all paint sold in the UK and the EU had ‘strict’ VOC limits that manufacturers had to comply with and that the VOC content was required, by law, to be communicated on the product label. They added that the BCF takes the position that the use of the terms ‘zero-VOC and ‘VOC-free’ were ‘false claims’.

‘There will always be a trace element of VOCs in paint, even if no raw materials containing VOCs have been added,’ they said. ‘It is impossible to ensure that every batch of paint is completely free of VOCs.’

Referring to the researchers’ detection of ethylene glycol in liquid paints at up to 20,000ppm, they highlighted that under EU regulations, the maximum allowed VOC content for an indoor matte paint was 30,000ppm.

‘The VOC content of the tested water-based paints is much lower than that found in solvent-based paints, which typically contain more than 60% VOCs. As such claiming “low VOC” on a product containing only 2% VOCs [or 20,000ppm] is not green washing as this is within allowed limits.’

They also explained that although preservatives were potentially hazardous, without them the paint would spoil quickly, making it unusable and that mixtures containing isothiazolinones above a specific concentration limit must be labelled properly given their potential to cause an allergic skin reaction. ‘Decorative paints are not toxic and not harmful when used appropriately,’ they added.