Written by Adrian McConnell, Chief Executive, CO Research Trust
As a research charity, our mission has always been to turn evidence into action, especially when that evidence concerns the health and safety of those who dedicate their lives to helping others. The recent Measuring Air Pollution from Ambulances (MAPA) Pilot Study, funded by the CO Research Trust (CORT), is an example of how independent research can illuminate hidden risks and, more importantly, help us make meaningful improvements.
The findings from this pilot will be challenging reading for some. They suggest that ambulance crews, hospital staff, and even patients may be exposed to higher-than-expected levels of air pollution in and around emergency departments. That can understandably cause concern.
But rather than fuelling alarm, this study should serve as a catalyst for collective problem-solving. It gives us, for the first time, a reliable dataset about air quality in the ambulance environment.
Why the study matters
The MAPA Pilot was carried out in a collaboration between the East of England Ambulance Service NHS Trust (EEAST), and the University of Suffolk. The study monitored air quality both in and around ambulances at Addenbrookes Hospital in Cambridge over a three-month period spanning winter 2024–25.
It focused on common pollutants produced by idling diesel engines: particulate matter (PM2.5 and PM10), nitrogen dioxide (NO₂), carbon monoxide (CO), and volatile organic compounds (VOCs). These are well-known contributors to cardiovascular and respiratory illness. Yet until now, we lacked concrete data on how much of this pollution might be present in an ambulance bay, or even inside the vehicles themselves.
What did the study find?
The results showed that pollutant levels near emergency department ambulance bays were consistently higher than those measured at a nearby reference point. In some cases, particularly for fine particulate matter, readings approached or exceeded thresholds set by the World Health Organization (WHO) and the UK’s Department for Environment, Food and Rural Affairs (DEFRA).
Inside ambulances, the study found that average levels of fine particulate matter exceeded WHO annual guidelines, and occasional peaks of carbon monoxide and particulates were recorded across all activities, including when vehicles were parked or travelling. While these spikes were brief, they underline the need to understand both average and peak exposures more thoroughly.
Critically, no clinical cases of carbon monoxide poisoning were identified among staff tested. None of the 160 participants recorded CO levels suggesting acute danger. However, about one in five reported symptoms such as headache, fatigue, or dizziness while in the ambulance bay. These are symptoms that, although non-specific, reinforce the need to understand air quality as an occupational factor.
The report also found no simple link between the number of ambulances queuing and pollutant concentrations. A reminder that the relationship between air quality, architecture, and activity is complex. Temperature, airflow, and the design of the ambulance bay itself (in this case, a partially canopied courtyard) likely play a part.
What is the context?
It’s crucial to note that this was a pilot study, conducted in a single hospital during winter - the busiest and coldest part of the year, when ambulance idling is at its highest. The data, therefore, represent a snapshot, not a national picture. The findings should not be interpreted as evidence of immediate harm, but as an early warning that occupational exposure to air pollution deserves far more attention in healthcare settings.
We should also acknowledge the study’s sensitivity. Ambulance services already work under immense pressure. The men and women who staff them routinely make impossible choices under strain. The aim of this research is not to blame but to equip decision-makers with the knowledge they need to create safer environments. For staff, for patients, and for everyone working in emergency care.
From risk to opportunity
Every challenge revealed by the MAPA study comes with an opportunity. We now have a foundation of real-world data showing how air pollutants behave in and around emergency departments. This opens the door to new, practical interventions.
For example:
Designing safer ambulance bays. The architecture of ED bays varies widely: some open, some enclosed, some with full or partial canopies. The MAPA data suggests that airflow and ventilation design are key factors influencing pollution build-up. Future hospital developments can incorporate this knowledge to minimise exposure.
Reducing engine idling. Ambulances often idle to power life-saving equipment or maintain temperature control. But there are emerging solutions: electric hook-ups, battery support systems, and engine-off policies for stationary vehicles, that could drastically cut emissions without compromising patient care.
Protecting staff health. The study demonstrates a need for ongoing monitoring of air quality and staff health indicators. Simple tools, such as personal exposure sensors or regular CO checks, could help identify and mitigate risks early.
Collaborative innovation. The findings create opportunities for cross-sector collaboration - between NHS estates teams, ambulance trusts, researchers, and environmental technology providers, to design sustainable, evidence-based interventions.