We've known for a long time that traffic fumes are very bad for our health. But according to new research, there are other sources of pollution that should also be a concern.
A new study, published in the journal Science, has found that household products such as shampoo, oven cleaner, and deodorant could all be a significant source of air pollution — the same form as that which is released by car fumes.
The team from the National Oceanic and Atmospheric Administration in Colorado collected air samples in Pasadena, Los Angeles valley, which is a particularly smoggy area. They then analysed data from the US and Europe, including research from other scientists.
They found that up to half of volatile organic compounds (VOCs) came from domestic products, including bleach, perfume, shampoo, and paint. When these particles degrade, they become a particulate matter called PM2.5, which is know to cause respiratory problems and is linked with 29,000 deaths in the UK each year.
According to the study, the use of household products could therefore make it harder for countries in Europe and America hit their targets, even if they are making headway with tackling traffic fumes.
But the researchers think it is also a sign of success, according to coauthor Brian McDonald who spoke during a news conference at the annual meeting of the American Association for the Advancement of Science.
"The sources of air pollution are now becoming more diverse in cities," he said, meaning action to clean up car exhaust pollution in recent decades has had a big effect.
It's also important to look at the findings in context. While the results show how pollution is changing in the US and Europe, the same probably isn't true for other countries.
For example, the emissions from consumer products are only significant now because of the effort to use cleaner fuel and reduce traffic fumes.
In countries such as China and India, coal-fired power plants and traditional ways of burning wood, coal, and dung are the main methods for heating and cooking. So in these places, pollution from shampoo is unlikely to be having much of an impact.
Rather than scare-mongering, the authors of the new paper say this is good news because other sources of pollution can be identified. It's more of a case of identifying what else we can to improve air quality, not an indication pollution is getting worse.