CONSTRUCTION SITES AND NO₂

It is well known that construction and demolition sites can generate and emit many different forms of pollution, the most obvious being material waste, visible dust, noise and vibration. However, construction sites also produce less obvious pollutants that are of serious concern for human health and have a wider environmental impact. Two of these pollutants are the gas nitrogen dioxide (NO2) and fine dust particles known as particulate matter (PM).

It is estimated that in London, NRMM (Non-Road Mobile Machinery) contributes to 7% of NOx, 14% of PM2.5 and 8% of PM10, and it is believed that a similar contribution exists across other major UK conurbations. This highlights the growing importance of construction site air quality monitoring.

NRMM used on construction sites generates NO2 emissions from diesel or gasoline-fuelled engines, including trucks, excavators, loaders, bulldozers, mobile cranes, off-road machinery and static engines such as pumps and electricity generators. Idling engines are a significant contributor to NRMM emissions and personal exposure to PM2.5, PM10 and nitrogen dioxide (NO2).

It is estimated that 15% of diesel fuel consumed annually in the UK is associated with NRMM, equating to approximately 4 billion litres, reinforcing the need for effective air quality monitoring on construction sites.

HOW IS NO2 GENERATED?

The combustion of fossil fuels produces oxides of nitrogen (NO₂). NOx is primarily made up of nitric oxide (NO) and nitrogen dioxide (NO₂). NO₂ is of most concern due to its impact of health. However NO easily converts to NO₂ in the air – so to reduce concentration of NO₂ it is essential to control emissions of NOx. National ambient air quality standards set NO₂ as a criteria pollutant and indicator of the larger group of nitrogen oxides.

HEALTH EFFECT OF NO₂

Scientific evidence links short-term NO2 exposure with adverse respiratory effects, including airway inflammation in healthy individuals and increased respiratory symptoms in people with asthma. Studies have also shown a clear association between short-term exposure and increased hospital admissions for respiratory illnesses.

In addition to contributing to ground-level ozone formation and its effects on the respiratory system, NOx reacts with ammonia, moisture and other compounds to form fine particulate matter. These particles can penetrate deeply into sensitive areas of the lungs, increasing long-term health risks.

Recent research shows that children exposed to diesel-dominated air pollution in London exhibit reduced lung capacity, placing them at risk of lifelong breathing disorders. This study was led by King’s College London, Queen Mary University of London and the University of Edinburgh, underlining the public health importance of monitoring NO2 emissions from construction activity.

WHAT IS NEW IN NO2 MEASUREMENT?

Aeroqual provides real-time dust sentry monitors for accurate measurement of dust and particulate matter (PM), which are widely used across the UK on construction sites. These monitoring systems can now be upgraded to provide real-time NO2 monitoring, allowing nitrogen dioxide measurements to be captured alongside dust and particulates.

The systems use advanced patented sensors and an active pumped airflow to sample NO2 at near-reference standards, providing a reliable picture of key air pollutants on construction sites. Monitoring data is uploaded to the cloud every minute, enabling continuous alerting, reporting and compliance monitoring.

Historically, diffusion tubes have been used to measure NO2 concentrations in surrounding communities. These passive devices typically measure average concentrations over a one-month period. However, NO2 monitoring on construction sites often requires hourly data, particularly during working hours, making diffusion tubes unsuitable for active site management.

These limitations make real-time NO2 monitoring systems an increasingly attractive and effective solution for construction and demolition projects.

Newer dust sentry and profiler monitors can now be upgraded, while purpose-built air quality stations (AQS) can be purchased or hired today. For more information on NO2 monitoring and construction site air quality, please contact Campbell Associates.