The hidden emissions: How everyday goods contribute to indoor air pollution

Amber Yeoman leads a research programme on consumer products emissions at the Wolfson Atmospheric Chemistry Laboratories at the University of York. She gives an overview of the pollution day-to-day product use releases into our homes.

Shampoo, deodorant, moisturiser – no one thinks twice about regularly using these products, and many others like them, so embedded are they into our daily lives. Whilst these products are extremely popular and frequently used, they’re also a source of pollutants that are emitted into homes during use.

Sources of indoor air pollution that traditionally come to mind are cookers, wood burners, candles, airborne viruses, mould, and allergens such as pollen, pet hair, and dust. But emissions from consumer products are often overlooked.

Defined as any personal care (cosmetic and hygiene) or household cleaning product that is available for the public to purchase for personal use, consumer products are frequent emitters of volatile organic compounds (VOCs). These are emitted as gases and are a significant component of indoor pollution, but a class that often goes unnoticed. Our homes are full of unique mixes of VOCs, being dependent on occupant behaviours and ventilation in the home. Anyone who breathes indoor air, which we do on average 90% of the time, will be exposed to a distinct mixture of VOCs that often differ between rooms even in the same building. Some will likely be more vulnerable to the negative health effects of breathing indoor VOCs, for example the very young, very elderly, and anyone with a significant pre-existing respiratory conditions such as asthma. In addition, VOCs can react indoors to produce secondary products, and some of these are known to be harmful to health, such as formaldehyde and fine particulate matter.

Quantifying any possible negative health effects from consumer product emissions is not straightforward, in part because their formulations are complicated and often undocumented. There are thousands of different consumer products on sale and each one has the potential to emit any number of VOCs. Even two products of the same type, but with different scents, will emit different VOC at different concentrations. For example, a body spray with a `vanilla` fragrance will have a different VOC emission to the exact same product with a `fruity` fragrance. Generalising how consumer product VOCs impact indoor air quality is near impossible, without products being tested for their emissions in the lab.

What we do know is that typically ethanol, propane, and butane are the VOCs found in the highest concentrations in UK homes, and these are commonly emitted from consumer products. Propane and butane are used as propellants in aerosol products; while it is well known that improper use of aerosol products is dangerous to health, even appropriate use can result in high VOC concentrations accumulating in a poorly ventilated room. There is little data on the long-term health effects of exposure to common everyday levels of aerosol propellants, or indeed many of the other common VOCs used in consumer products.

Ethanol is used in thousands of products – it’s a cheap and readily available solvent. On labelling its often called ‘denatured alcohol’ or ‘alcohol denat’. Whilst there are many indoor sources of ethanol – baking bread, breathing, and alcohol consumption – consumer products are a particularly large source. Fragrance compounds are also very commonly emitted and are the easiest type of VOC to detect without using specialist equipment – we can sense them with our noses. This doesn’t necessarily mean they are present in high concentrations, however; they just happen to be the most noticeable VOC to us as we can smell them even in tiny amounts.

Asides from propellants, solvents, and fragrances, consumer products are formulated to contain, preservatives, emollients, UV blockers, conditioning agents, and other compounds which enhance product delivery, all of which can be emitted to air both during and after use. There is also the possibility of VOC contaminants such as benzene and toluene being present in trace amounts in bulk solvents such as ethanol. These VOCs have been classified as hazardous to human health, and are banned in all consumer products, but sometime still find their way onto the shelves by accident.

The role of ventilation

The simplest solution to reducing indoor air pollution is often thought to be by improving ventilation, either by opening windows or mechanically ventilating using extractor fans, to move pollutants elsewhere. Whilst this is undoubtedly an important part of any good indoor air quality strategy, there are drawbacks to relying on it alone.

As some products are applied directly to our bodies, and sometimes the face, we will directly inhale a portion of the VOCs emitted before they can be removed from the room. We also have to consider that some homes do not possess adequate ventilation systems, be that in a lack of windows to the outdoors or outdated and inefficient mechanical extraction. It is also not widely known that extraction systems have to be regularly cleaned in order for them to work effectively. Additionally, any VOCs that are ventilated outside will ultimately contribute to outdoor air pollution, so it is only a partial solution.

It is vital, therefore, that indoor pollutants such as VOCs are also addressed at their source. Whilst it is an overreach to tell people what to do in their own private homes, consumers do have a right to know how their purchases and behaviours are affecting their exposure to indoor pollutants, and this includes the use of personal care and cleaning products.

How can we tell if a product is a high VOC emitter?

Unless you’re looking to buy paint, varnish, or other decorating materials, then unfortunately you can’t. DIY products have for years had a basic label showing VOC emissions (Low, medium high, very high), and there is evidence that the label helps to some degree guide consumer choice. For other types of VOC-containing products, at least in the UK, there is no labelling at all. Introducing this would be a quick and easy way for consumers to know what they’re purchasing and using.

The UK Clean Air Strategy 2019 floated the idea of a voluntary VOC product labelling scheme, but this could open the door to greenwashing, where companies make environmental claims with no scientific basis. To be effective, both labels and product testing procedures would need to be standardised and regulated. This would require the definition of what constitutes `low`, `medium`, and `high` emissions, and for the varying health and environmental impacts of individual compounds to be taken into account.

Green, natural, organic, and eco products

There are many descriptors used by manufacturers to boost the environmentally-friendly appearance of their products, and to make consumers feel that by using them they are being both environment and health conscious. Whilst eco labels may describe the provenance of ingredients, they are not indicative of the VOCs a product emits and cannot be used as a proxy for being `clean` or ‘healthy’ for indoor air. In fact, our research at University of York suggests that “eco” products can emit more VOCs than those without green marketing claims. The indoor air quality impact of a VOC is the same regardless of the chemical’s source. For example, a fragrance compound derived from a natural plant extract is chemically identical to one that has been synthesised in the lab; biologically produced ethanol from crops is identical to petroleum produced ethanol, once it is released to air.

Looking forwards

Where the responsibility lies for reducing indoor air pollution from consumer products is yet to be determined. Is it the responsibility of the occupant to control their behaviours around product use and ventilation, the manufacturers to reformulate with lower VOC content and provide testing and labelling, or the government to step in and regulate the maximum levels of VOCs that consumer products can emit? In reality, to effect long-term change, it will rely on all three. Right now, however, it’s up to consumers to take charge of their own indoor air quality by changing their consumer product buying and usage habits. In the absence of information, such as labelling, toxicology data, and government recommendations, they are left largely in the dark.

This article first appeared in the latest issue of Air Quality News Magazine