Questions raised over A350 air pollution monitoring

Questions have been raised with Wiltshire Council over the lack of PM2.5 pollution sensors along the busy A350 through Westbury.

The council has recently published its first update on the Wiltshire Community Air Network (WCAN), which uses more than 100 low-cost sensors to build “Wiltshire’s most detailed picture yet” of PM2.5 air pollution – small particles in the air that can increase health risks and damage the environment.

However, White Horse News has questioned why there are no WCAN sensors on the A350 through the town, given the volume of traffic using the route and the potential contribution of vehicle emissions and tyre and brake wear to particulate pollution.

Westbury has long been flagged for air-quality concerns. The town has an Air Quality Management Area covering parts of Warminster Road and Haynes Road, along the A350, due to annual mean nitrogen dioxide (NO2) levels.

The council does monitor NO2 along the route. However, none of the latest WCAN PM2.5 sensors in the Westbury area are located on the A350. They are located on Bratton Road and Neptune Road with another on the High Street in Dilton Marsh.

When asked by WHN why there are no WCAN sensors on the A350 through Westbury, Cllr Mel Jacob, deputy leader of the council, said, “The sensors were installed at locations offered by volunteer hosts, including schools, community groups, businesses, town and parish councils, healthcare settings and people’s homes.

“When selecting locations, we sought broad geographic coverage across Wiltshire and a mix of site types, including urban, suburban, rural and roadside environments.

“WCAN is the council’s first large-scale project focused specifically on monitoring PM2.5 and is intended to provide a better understanding of PM2.5 patterns, trends and potential hotspots across Wiltshire.”

New monitoring station

Last October, the council announced funding for a new automatic monitoring station in Westbury which would monitor nitrogen oxide and fine particulates including PM2.5.

Asked by WHN for an update, Cllr Jacob said plans for the station are “progressing”, but the final location and installation timetable have not yet been confirmed, with the council currently assessing potential sites.

A council spokesperson added, “Locations close to the A350 are being considered. As one of the main traffic routes through Westbury, the A350 is likely to influence local air quality, so it is important that the monitoring station is located where it can provide meaningful data on traffic-related pollution levels.”

WCAN update and interim findings

Interim data from October 2025 to March 2026 suggests PM2.5 levels across much of Wiltshire are “generally within good to fair range”, but that pollution varies considerably between communities and seasons.

Cllr Paul Sample, Cabinet Member for Environment, Climate and Waste, said the findings point to a “complex mix” of influences, including traffic, domestic solid fuel burning, weather conditions and long-range pollution events.

The WCAN programme is due to run until October 2026, with a final report to be prepared once a full year of data has been collected, with findings helping to inform the development of future air quality policies and strategies.

Live data from the low-cost sensors is available to the public via the PurpleAir real-time map, allowing residents to track local PM2.5 levels in near real time.