An aerosol is a suspension of fine solid particles or liquid droplets. They can be from natural sources such as desert dust, sea salt and volcanic emissions or they can come from anthropogenic sources such as industrial processes, biomass burning or vehicle emissions. Fine particles (PM2.5) can have adverse health impacts as they are small enough to be inhaled.

Nitrous oxides (NOx), including Nitrogen dioxide (NO₂), are major air pollutants, with sources coming from fossil fuel combustion, which is also a main driver of climate change, as well as cars, ships, airplanes, and heating. Natural sources of NO₂ include lightning, plants, soil and water, but this only accounts for 1% of the total NO₂ in cities. NO₂ is an important air pollutant because it contributes to the formation of photochemical smog, which can have significant impacts on human health.

In the UK 64,000 people die due to air pollution each year, according to a study by the Environment, Food and Rural affairs parliamentary committee[1]. The average volume of particulate pollution in the UK over the course of a year is 10.5 millionths of a gram per cubic metre, with central London recording the highest level, of 15.3. Data from the EEA found that the UK had the second highest number of deaths from NO₂ pollution in Europe, with Italy having the highest, in 2013 [2].

According to the World Health Organisation, ambient air pollution accounts for an estimated 4.2 million deaths per year[3]. The health effects of air pollution include heart disease, stroke, chronic obstructive pulmonary disease, lung cancer, and acute respiratory infections.

Featured Educator

• Dr Pepijn Veefkind, Senior Scientist, KNMI