We all love smelling good. I mean… why would we want to smell bad? As a variety of perfumes enter the market and become widely available to consumers, we should stop and think about the impact they can have on the environment. In this blog post, I will be discussing a study by McDonald et al. (2018) titled ‘Volatile chemical products emerging as largest petrochemical source of urban organic emissions’.
The study aims to identify and quantify the most important human-produced sources of Volatile chemical products (VCPs) emissions to effectively mitigate air pollution and improve human health. Surprisingly, the study found that consumer products such as shampoo, cleaning products and paint now contribute as much to urban air pollution as tailpipe emissions from vehicles. These products are known as VCPs and contain organic solvents, which lead to substantial emissions of VOCs to the atmosphere. This is because the oxidation of VOCs to form secondary organic aerosols (SOPs) in the environment is a major source of fine particulate matter (PM2.5) and react to produce ozone in the troposphere in cities and contributes significantly to urban air pollution.
Consumer products can cause high levels of not only indoor air pollution, but also contribute to outdoor air pollution. The researchers concluded that in the United States, the amount of VOCs emitted by consumer and industrial products is actually two or three times greater than estimated by current air pollution inventories, which also overestimate vehicular sources.
Although the sale of VCPs in the United States is substantially smaller than that of gasoline and diesel fuel, VOC emissions from VCPs (7.6 ± 1.5 Tg) are twice as large as from mobile sources (3.5 ± 1.1 Tg) because of differences in emission factors. In an interview (Fell, 2018), Jessica Gilman, one of the researchers of the study mentioned that
Gasoline is stored in closed, hopefully airtight, containers and the VOCs in gasoline are burned for energy, but volatile chemical products used in common solvents and personal care products are literally designed to evaporate. You wear perfume or use scented products so that you or your neighbor can enjoy the aroma. You don’t do this with gasoline.
This fundamental difference in how we use these substances reveals the true impact of consumer goods on the environment. This difference can be seen in the diagram below
The researchers also conducted models with Los Angeles as a case study to investigate the chemical footprint of these goods by assessing the importance of VCP emissions to ambient air pollution. The results have been summarised in the diagram below.
Los Angeles has extremely high ozone levels leading to poor air quality. Ozone formation remains sensitive to the reactivity of VOCs emitted and their secondary products with respect to the hydroxyl radical (OH). In the United States, ozone regulations do not address lower-volatility compounds (vapor pressure<0.1 mmHg at 20°C). However, these can evaporate and contribute to SOA. Disclosure of ingredients used to make fragrances like perfumes is not required in the United States, but terpenes are common and known aerosol precursors. Hence, the use of everyday consumer products continue to contribute to both indoor and outdoor air pollution, worsening air quality.
One way we can see this manifesting is the increase in festive products around Christmas. Popular scented candles with festive scents like cinnamon and mistletoe release VCP emissions, while even harmless-seeming party poppers cascade particulate matter into the air (Allen, 2016). Here, we can see how the use of consumer goods can lead to air pollution and worsen air quality.
In Allen (2016), air pollution expert Professor Ian Colbeck, of the University of Essex mentioned that
Christmas Day may well be the most toxic day of the year. It has the same effect as standing by the side of a busy London road for four hours, which is not something most people would choose to do.
Overall, I found this article to be a fascinating read. I had never really consider the environmental impact of scented products like perfumes. Now, I know that these products can result in both indoor and outdoor pollution. It also is a source of particulate matter in urban areas that can lead to poor urban air quality.
Allen, V. (2016). Why Christmas is the most TOXIC day of the year: Cooking, festive candles and party poppers release volatile chemicals that are harmful to humans. The Daily Mail. Retrieved from https://www.dailymail.co.uk/health/article-4059366/Why-Christmas-TOXIC-day-year-Smoke-cooking-candles-party-poppers-harmful-humans.html.
Fell, A. (2018). Consumer, Industrial Products Overtake Transportation as Source of Urban Air Pollution. The Regents of the University of California, Davis campus. Retrieved from https://www.ucdavis.edu/news/consumer-industrial-products-overtake-transportation-source-urban-air-pollution.
McDonald, B., de Gouw, J., Gilman, J., Jathar, S., Akherati, A., & Cappa, C. et al. (2018). ‘Volatile chemical products emerging as largest petrochemical source of urban organic emissions’. Science, 359(6377), 760-764. https://doi.org/10.1126/science.aaq0524.