Research shows paints, perfumes, sprays and other synthetic items contribute to high levels of ‘volatile organic compounds’ in air
Household cleaners, paints and perfumes have become substantial sources of urban air pollution as strict controls on vehicles have reduced road traffic emissions, scientists say.
Researchers in the US looked at levels of synthetic “volatile organic compounds”, or VOCs, in roadside air in Los Angeles and found that as much came from industrial and household products refined from petroleum as from vehicle exhaust pipes.
The compounds are an important contributor to air pollution because when they waft into the atmosphere, they react with other chemicals to produce harmful ozone or fine particulate matter known as PM2.5. Ground level ozone can trigger breathing problems by making the airways constrict, while fine airborne particles drive heart and lung disease.
In Britain and the rest of Europe, air pollution is more affected by emissions from diesel vehicles than in the US, but independent scientists said the latest work still highlighted an important and poorly understood source of pollution that is currently unregulated.
“This is about all those bottles and containers in your kitchen cabinet below the sink and in the bathroom. It’s things like cleaners, personal products, paints and glues,” said Joost de Gouw, an author on the study at the University of Colorado in Boulder.
“When you think about how much of those products you use in your daily life, it doesn’t compare to how much fuel you put in the car. But for every kilogram of fuel that is burned, only about one gram ends up in the air. For these household and personal products, some compounds evaporate almost completely.”
Globally, the greatest source of volatile organic compounds are plants and trees, but the natural background levels are bolstered by vapours released from hairsprays and perfumes; cleaning products and pesticides; paints and lacquers, and substances such as formaldehyde, which is used in glues, plywood and other building materials. Yet more synthetic VOCs come from burning fuels such as gas and wood.
“It’s hard to say how much pollution is down to VOCs, but a rough estimate is that between one quarter and a third of all particles are made up of organic compounds that originate as VOCs,” said Alastair Lewis, professor of atmospheric chemistry at the University of York. In Britain, one of the most harmful air pollutants is nitrogen dioxide, which is unrelated to VOCs.
Writing in the journal Science, De Gouw and others report that the amount of VOCs emitted from household and industrial products is two to three times higher than official US estimates suggest. The result is surprising since only about 5% of raw oil is turned into chemicals for consumer products, with 95% ending up as fuel.
“This paper is interesting because it shows that domestic use of VOCs is beginning to dominate, displacing the traditional sources from vehicles and industry,” Lewis told the Guardian. “It’s a challenge for regulators since many of these sources, including cleaning and personal care products, aren’t controlled.
“If the paper is right then many countries will need to rethink how they plan to meet their international obligations to reduce emissions. The UK is already thinking about how to tackle and reduce domestic emissions,” he said.
William Bloss, professor of atmospheric science at the University of Birmingham, said the work highlighted a continuing need to understand real world emissions. But he added: “We have a much higher proportion of diesel traffic in the UK and we know that diesel use is associated with a lot of different hydrocarbons and particulates. I suspect that in the UK, traffic in the form of diesel vehicles is still the most important.”
Even so, De Gouw believes VOCs from household products should still be factored into policies on emissions. “London is a little different to LA because of the higher diesel use, but I expect that even in London a significant fraction of VOCs will come from these kinds of emissions,” he said.
David Green, who studies air pollution at King’s College London, said: “Organic aerosols, which are produced when these volatile chemicals react in the atmosphere contribute significantly to UK PM2.5 concentrations as they do all over the world. In London, where we measure these routinely, approximately a third of PM2.5s can be attributed to organic aerosols which come from a range of sources including vehicle emissions, wood burning and even cooking. This paper highlights a previously poorly understood source which is currently unregulated.”