Poor air quality

Impact 5
risk indicator
Impact & Likelihood
Impact key
5 Catastrophic
4 Significant
3 Moderate
2 Limited
1 Minor
Likelihood key
5 >25%
4 5-25%
3 1-5%
2 0.2-1%
1 <0.2%


Air quality has improved significantly over recent decades. However, air pollution remains the largest environmental risk to UK public health and is linked with reduced lifespans. Short-term surges in poor air quality occur primarily due to weather conditions preventing pollution from dispersing. These conditions include low winds or temperature inversion. Air quality is also worsened by the ultraviolet light from sunshine, as it reacts with the air to generate ozone. The government set out commitments to tackle all sources of air pollution and improve air quality for all through the Clean Air Strategy. The Environmental Improvement Plan sets out the actions that will support us to continue improving air quality and to meet our new interim and long-term targets for PM2.5 set under the Environment Act 2021. In addition, the UK Government has published a revised air quality plan for tackling nitrogen dioxide (NO2) emissions in urban areas.


The reasonable worst-case scenario is based on a 30-day period of elevated ground level ozone or fine particulate matter.

During a poor air quality event of this kind, the UK could experience significant health risks, including an increase in deaths from exacerbation of respiratory or cardiovascular conditions, with an associated increase in hospital referrals and pressure on emergency response services. The duration of an air quality episode would be heavily influenced by meteorological conditions. High ground-level ozone episodes in the UK occur most commonly in the summer months when high pressure weather systems dominate. Elevated ground-level ozone can also occur during springtime. At a national scale elevated fine particulate matter concentrations are most common in the spring. In urban centres however, high particulate matter events can occur at almost any time of year if emissions from road transport and domestic sources are released in certain weather conditions.

These episodes may be worsened when already polluted air from continental Europe is drawn over the UK. Fine particulate pollution events may also arise from other natural phenomena including the wind suspension of soil dust following drought, from long-range transport (for example Saharan dust), and from uncontrolled biomass combustion from wildfires.

Key assumptions

The main assumption is that the air pollution event would last for up to 30 days, with elevated ozone and/or particulate matter.


A less impactful but more likely variation involves a shorter 22-day air pollution event, although this would require the same response capabilities.

Response capability requirements

Communications networks to provide advice to those in affected areas (ensuring messaging reaches those who are most vulnerable, such as older adults) would be required. Access to healthcare professionals, including GPs to help individuals with less severe symptoms, and emergency services and hospitals to assist those with more severe symptoms would also be essential.


Poor air quality is known to have long-term health impacts, such as cardiovascular and respiratory conditions. Based on current evidence however, it is not possible to distinguish the relative contributions from air quality episodes and longer-term exposure to lower levels of air pollutants.