5 different ways to measure air quality
The WHO Global Air Quality Guidelines mention five different pollutants, but what are they? Let's have a look.
Particulate matter (PM2.5 and PM10)
Particulate matter (PM) are inhalable particles smaller than 10 micrometer (PM10) and 2.5 micrometers (PM2.5) respectively. PM can consist of things like mineral dust, ammonia, nitrates and black carbon. The WHO limit is 15µg/m³ for PM2.5 and 45µg/m³ per 24 hours.
Carbon monoxide is produced by burning wood and fossil fuels like natural gas, petrol and kerosene. You can't see, taste or smell it, but in high levels it can kill you. The WHO limit is 4mg/m³ per 24 hours.
Nitrogen dioxide is reddish-brown in colour and is produced by fossil-fuel based heating, transport and power generation. It irritates airways and is linked to asthma and other respiratory diseases. The WHO limit is 25µg/m³ per 24 hours.
When nitrogen oxides (NOx) react photochemically, they form ground-level ozone, which is a major component of smog. Ozone causes problems breathing, triggers asthma and leads to lung disease. The WHO limit is 100µg/m³ per 24 hours.
Sulfur dioxide is yet another pollutant produced by the combustion of fossil fuels like coal. It is a colourless gas that easily dissolves in water to form sulfuric acid. The WHO limit is 40µg/m³ per 24 hours.
Interesting how many of these air pollutants are fossil fuel based, and if we just stop burning stuff, it helps to prevent climate change too. Who knew?