Construction sites are well known to produce and release many different types of emissions. The most noticeable being waste material, visible dust, vibration,noise and air pollution. So it is very important to consider air monitoring in construction sites, along with other pollution.
Nevertheless, construction and demolition sites often generate less apparent contaminants; which are of significant concern to human health and environmental impact. Two of these contaminants are a gas called nitrogen dioxide (NO2), and Particulate Matter (PM) called fine dust particles.
In this article we will explain:
- how such air pollution occur on construction sites
- how these air pollutants impact our health and climate
- what is air monitoring
- what laws relate to air monitoring
Air pollution emissions
Construction equipment’s key environmental problem is emissions of air pollution; which affect air quality, climate change and pose a significant health burden for construction workers. Construction machines such as diggers, caterpillars, and power generators make up over a quarter of the traffic-related particulate matter emissions in inner-city areas. The pollution caused by them is considerably higher, in specific locations.
Air pollutant #1: Nitrogen Dioxide (NO2)
Combustion of fossil fuels from cars, power stations and manufacturing processes creates nitrogen oxides (NOx). NOx consists mainly of Nitric Oxide (NO) and NO2.
NO2 is of utmost concern in air monitoring because it affects health. NO quickly transforms to NO2 in the air. Therefore in air monitoring it is important to check NOx emissions level in order to reduce NO2 concentrations. Global ambient air quality standards set NO2 as polluting criteria and clear indication of the larger nitrogen oxide category.
In heavy trucks, excavators, loaders, bulldozers, mobile cranes, off-road equipment, and static engines such as pumps and power generators; construction and demolition sites produce NO2 from diesel or gasoline-fueled engines. Idling engines add greatly to the air pollution and direct exposure to NO2.
Scientific evidence ties short-term NO2 exposures to harmful respiratory effects in healthy people; including irritation of the airway and increased respiratory signs in people with asthma. Also, studies show a correlation between short-term exposures and increased hospital admissions for respiratory diseases.
Apart from having ground-level ozone effects on the respiratory system; NOx reacts with ammonia, moisture, and other chemicals to form small particles. Such tiny particles can penetrate deep into sensitive parts of the lungs.
Air pollutant #2: Particulate Matter (PM)
Particle contamination or particulate matter (PM) is a complex combination of extremely tiny particles and liquid droplets; comprising all the floating particles in the air. The two PM-related issues of main importance in the construction sites are PM2.5 and PM10. The emissions from diesel-fueled construction machinery contains small particles which are nearly all PM2.5 (2.5 micrometers or smaller in diameter).
Primary and Secondary PM2.5
Particulate exhaust is also called primary PM2.5. Small particles such as PM2.5 are also chemically produced from various contaminants in the atmosphere. Some of which are emitted by diesel-fueled machinery and these particles are called secondary PM2.5. There are many air monitoring systems that can measure this type of emission.
Construction-related dust contains larger particles or coarser ones often known as PM10 (between 2,5 and 10 micrometers).
PM10 is produced from bulk material operations on construction sites, such as crushing and grinding, demolition, soil and aggregate storage, earthworks, and from smaller activities such as cutting of building materials.
Such activities lead to wind-blown dust issues, sometimes called fugitive dust; and the transfer of dust from the construction or demolition site to nearby roadways. When dirt or dust is ‘tracked out’ onto a road from a site, passing vehicles may cause the dirt to be held in the air as re-entrained road dust. Particles of fugitive and re-entrained dust can stay in the air for days, or even weeks. So in air monitoring concept, this type of emission is important too.
Impacts of air pollution on health
Particle exposure is associated with a variety of health problems including:
- impaired lung capacity
- attacks on asthma
- heart attacks
It’s also related to early death. The small particulate matter (PM2.5) in diesel engine exhaust is listed as carcinogenic to humans. In 2004, the World Health Organization (WHO) stated that there was no indication of a safe level of PM exposure or a limit at which no negative health effects could occur.
In short, construction sites, as hotspots, lead significantly to elevated local NO2and PM emissions concentrations. The health effects may include:
- Respiratory problems, cardiovascular disease, lung cancer and death
- Early onset dementia and autism
- Decreased lung capacity (particularly in children)
Monitoring regulations for air quality in construction sites
While road transport has been subject to several steps to reduce harmful NO2 and PM emissions; there has been inadequate control of the emissions from construction sites. Environmental organizations set air quality guidelines and regulations for monitoring; which are usually defined by local authorities when planning construction and development site operations.
However, this Main guideline should be applied everywhere: “Continuous site monitoring is an effective method for developers to control dust production during construction and demolition including PM10 and PM2.5 and NOxemissions.”
Besides construction sites, there are many other manufacturing plants which may affect air quality by releasing gas or some other emissions. One of these are glass manufacturing plants that are important in gas emissions & pollution issue.
The purpose of air monitoring
Air quality control at construction sites achieves a range of goals:
- Makes sure that the construction operations do not result in excess of the NO2, PM10 and PM2.5 air quality target/limit values and dust deposition.
- Ensures that the negotiated mitigation methods are applied to monitor dust and gas emissions and are successful.
- Provides a “warning system” for increased dust emissions; and a mechanism for the cessation of site work or the implementation of additional removal controls.
- Provides a collection of facts to support the possible emission of NO2, PM10 and PM2.5 from site works in case of complaints.
- Helps to link any elevated air pollution levels to particular on-site operations so that effective steps can be taken.
- Will assist in allocating the emission source to the individual polluter; particularly in areas where several construction or industrial operations coexist.