Question: How do you know if the air quality is good?

Sarah Naylor answered on 9 Mar 2018:

In the UK we have set pollutant levels (objectives) which we use to compare our air against. The air pollutants of most concern are nitrogen dioxide gas and particulate matter or PM10 (this is essentially very tiny dust particles, the size of it is approximately 1/5th the width of a human hair – https://www.researchgate.net/figure/Relationship-of-particulate-matter-to-the-size-of-a-human-hair_fig1_267866793). These pollutants are mainly caused by vehicle exhaust emissions, so air quality next to busy main roads is likely to be worse than air quality in the countryside for example. We are able to measure our air quality a few ways. We can use diffusion tubes. These are little plastic tubes that can be attached to lampposts and contain a chemical which attracts nitrogen dioxide. The tubes are left outside for a month to absorb nitrogen dioxide and then are sent to a laboratory for analysis which then tells us how much nitrogen dioxide was in the air in that location for that month. It can be quite frustrating to have to wait a full month to find out pollutant levels. As such, there are also automatic monitors available which are able to measure pollutant levels (including nitrogen dioxide and particulate matter) straight away. The reason we also use diffusion tubes is that these automatic monitors are very expensive and require a lot of space to accommodate them, plus they need an electricity supply. Defra (the Department for the Environment, Food and Rural Affairs) have their own network of automatic monitors located all over the country. Have a look at their website (https://uk-air.defra.gov.uk/networks/network-info?view=aurn) to see if they have a monitor near you (hint you need to scroll close to the bottom of the page for a dropdown menu of locations). If you decide to look at the concentrations you need to compare them against the pollutant levels I mentioned before for you to be able to determine if the air quality is good. If the levels are below the annual mean objective of 40ug/m3 (this is for both nitrogen dioxide and PM10) then the air quality is considered good, if the levels are above this value then the air quality is considered poor.
Your local council also has a duty to monitor the air quality in your town. I would suggest that you look at their website (search for air quality) to find out what levels they have monitored. As part of their duties each year they have to produce an Air Quality Annual Status Report which should tell you what the air quality is like in your town, whether there are any poor areas of air quality (called Air Quality Management Areas) and, if so, what actions they are doing to improve the air quality.