CONSTRUCTION SITES AND NO2
It is well known that construction sites can generate and emit many different forms of pollution,
the most obvious being material waste, visible dust, noise and vibration. However, construction and demolition sites also produce less obvious pollutants which are of serious concern for human health and impact on the environment. Two of these pollutants are the gas nitrogen dioxide (NO2) and fine dust particles called 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 to be a similar situation in other major conurbations.
NRMM on construction sites generate NO2 from diesel or gasoline fuelled engines in 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 NO2. It is estimated that 15% of diesel fuel consumed per year in the UK is associated with NRMM, which equates to approximately 4 billion litres.
HOW IS NO2 GENERATED?
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 evident links short-term NO2 exposures with adverse respiratory effects including airway
inflammation in healthy people and increased respiratory symptoms in people with asthma. Studies also show a connection between short-term exposure and increased hospital admissions for respiratory illnesses. In addition to contributing to ground-level ozone effects on the respiratory system, NOx reacts with ammonia, moisture and other compounds to form small particles. These small particles can penetrate deeply into sensitives parts of the lungs. Recent research shows children exposed to diesel-dominated air pollution in London are showing poor lung capacity, putting them at risk of lifelong breathing disorders. The study was led by Kings College London, Queen Mary University of London and the University of Edinburgh.
WHAT IS NEW IN NO2 MEASUREMENT?
Aeroqual provide real-time dust sentry monitors for accurate measurement of dust and particulates, (PM) which are widely used across the UK on construction sites. These monitors now have the option of being upgraded to accurately measure NO2 in parallel with dust and particulates. The systems have advanced patented sensors and an active pumped air flow to sample NO2 to near reference standards giving a reliable picture of key pollutants on site. Data is stored and uploaded to a cloud each minute of alerting and reporting. In the past diffusion tubes have been used to measure NO2 concentrations in communities. These are passive devices which measure the average concentration typically over 1 month. NO2 concentrations are usually required as an hourly period, and for construction projects during working hours. These limitations of diffusion tubes make new real time NO2 monitoring an attractive proposition. Newer dust sentry and profiler monitors can be upgraded now and brand new AQS (Dust & Gas units) can be purchased or hired today.
The dust Sentry AQS can also measure Ozone and VOC’s. For more information on air quality monitoring click here.
