Air pollution is moving from outdoor to indoor - here's why

There are many sources of air pollution indoors—

• Cooking, particularly with natural gas, and when frying meat at high temperatures, produces nitrogen oxides and particulate matter.

• Cleaning can produce fragrance compounds, called volatile organic compounds (VOCs), as well as particulate matter.
  

• Burning candles can also produce nitrogen oxides and particulate matter, and also volatile organic compounds if scented.

—by Nicola Carslaw, Indoor Air Chemistry Professor, University of York and David Carslaw, Urban Air Pollution Scientist, Chemistry, University of York for The Conversation

You may have seen the before-and-after-lockdown photos of major cities that appear to show dramatic changes in air quality. In one, the India Gate war memorial in New Delhi is barely visible amid the smog. Then, during lockdown, it’s clearly visible in its red Bharatpur stone grandness.

Getting vehicles off the road may do wonders for smog, but there’s more to air pollution than that. The shift away from vehicles powered by fossil fuels and the improvement of outdoor air quality in urban areas, combined with changes to buildings and lifestyles, means that indoor air pollution will become much more important in the future. And there aren’t many easy answers about how much of a risk this will create – or how to address it.

Vehicles have been a dominant source of air pollutants for decades. But the century-long dominance of petroleum-based fuels is drawing to an end with the increasingly rapid rollout of electric vehicles. A consequence of this will be a fall in concentrations of highly reactive gases called nitrogen oxides, which actually neutralize another pollutant from industrial sources, ozone. So fewer petrol and diesel-fueled cars, coupled with lower emissions from those that remain, could actually result in higher ozone concentrations in urban areas.

Unlike way up in the stratosphere where ozone plays an important role in protecting us from harmful ultraviolet radiation, at the surface, it can act as a respiratory pollutant. This property makes life difficult for those with respiratory illnesses such as asthma and bronchitis.

But we are not just exposed to ozone outdoors, it can also move into buildings through windows, doors and cracks in buildings. So it follows that if ozone concentrations increase outdoors, they will also increase indoors. Indeed, computer models predicted that during lockdown, indoor ozone concentrations would increase by 50%. Read More  

Source: The Conversation