Global construction activities have increased drastically in the last few decades. In the case of India, the Construction industry is expected to record a CAGR of 15.7% to reach $ 738.5 bn by 2022. How is the growth of construction activities related to air pollution monitoring? Actually, it is quite simple. Construction activities are major contributors to dust pollution. Apart from the usage of raw materials like sand, cement, concrete, etc., activities like excavation and drilling contribute to pollution. Bulk material transportation, loading/unloading, open-air storage, concrete and mortar making, cutting and filling, and the movement of equipment also have a fair share. If unattended, particulate pollution will surpassingly increase, impacting the health of labourers and workers at these sites.
Construction activities majorly account for dust or particulate pollution viz. metallic, gravel, cement/concrete, wooden, sand particles, etc. The airborne dust measurement ranges from the particle size of 1 micrometer (PM1) to 100 micrometers (PM2.5, PM10, PM100). Sources of dust generation due to construction activities are:
- Preparation of Raw Materials
- Construction & Demolition (C&D) Waste
- Road Construction
Excavation causes major particulate pollution in the entire lifecycle of constructing a building. Drilling and mining activities generate air particulates (dust) that remain in suspension for a longer duration. In addition, moderate to high wind speeds carry away the particulates that endanger the workers, people in nearby proximity, roads, etc. Vehicular emissions ( trucks, excavators) and DG sets used for excavation generate PM2.5 along with other pollutants (CO, NO, hydrocarbons). Heavy vehicles and excavators re-entrain the settled sand particles which keep the air particulate concentration well above the threshold limit. As a result, this phase causes the maximum air particulate pollution.
Sand and cement are abundantly utilized at the sites. Unloading from the trucks causes them to disperse due to the impact and create a surge in the air particulate concentration.
Preparing Raw Materials
Raw materials for construction are generally sand, cement, bricks, wood, high-density iron and steel roads, tiles, and marbles. Activities like sieving the sand, cement mixing, cutting, and shaping of bricks, tiles, marbles, woodcutting, and finishing, etc continue at the site till the completion of major construction. It generates fine particulate matter that can easily penetrate through the respiratory system.
Construction and Demolition (C&D) Waste
Demolition of older sites generates air particulate pollution. Construction and Demolition waste rule 2016, CPCB, India states that loading and unloading of C&D waste, incoming and outgoing vehicles, and machinery used in C&D operations causes air particulate pollution. This should be monitored and mitigated effectively.
Road construction including state highways, national highways also acts as fugitive sources for the dust pollution. Highway construction and widening are the activities that registered the highest growth. However, if unplanned, they will be responsible for the increased particulate pollution.
Why Air Quality monitoring at Construction Sites important?
Construction Dust Emission (CDE) is important as particulate matters pose a great threat to the workers on site and people in the nearby proximity. According to the World Health Organization (WHO), PM is capable of penetrating deep into lung passageways and entering the bloodstream causing cardiovascular, cerebrovascular, and respiratory impacts. Moreover, reduced visibility due to dust may cause accidents at nearby major roads and intersections. It is also mandatory for the construction companies to maintain the exposure limits issued by the Occupational Safety and Health Association (OSHA) and ambient air concentrations according to the guidelines of respective national agencies, boards, etc. Moreover, air quality monitoring helps in analyzing long term trends of the dust concentration and to plan mitigative strategies.
Air Particulate Monitoring
Guidelines provided by the United States Environmental Protection Agency (USEPA), Institute of Air Quality Management (IAQM, United Kingdom), Central Pollution Control Board (CPCB, India) can be used to plan the monitoring study.
Monitoring devices like the Oizom’s dust monitor DustroidTM (with variants – Light, Smart, and Pro) are stationed at the construction sites. A brief guideline regarding the selection of the correct model of DustroidTM can be found here. For instance, the devices are placed at the periphery for Periphery Air Monitoring (PAM) and fixed stations near the source where the workers are likely to be exposed. DustroidTM measures the concentration of various particulate matter with size ranging from 1 micron to 100 microns such as PM1, PM2.5, PM10, and PM100 in the ambient air. which can be further integrated with a weather station.
Carrying out air quality monitoring at the site before any construction is necessary. The baseline data hence generated helps in making of the compliance report, Environment Impact Assessment (EIA) and Environmental Clearance (EC). Additionally, baseline data helps in planning and executing the Environment Management Plan (EMP). The data also acts as base data to compare the air particulate concentration pre, mid/during, and post-construction activities.
Monitoring meteorological parameters like temperature, humidity, wind speed, wind direction, etc help in conducting the dispersion analysis of the dust particles. As discussed earlier wind easily carries away the dust particles i.e. sand, sawdust, cement particles, etc. This means that the dust generated at the construction site can also affect the people living in nearby areas and faraway places. Oizom provides an online platform that carries out the dispersion analysis based on the data generated through air particulate monitoring.
It has also become mandatory for the construction companies to provide water spraying as a mitigative measure for dust suppression. Operators turn ON sprayers, mist cannons, sprinklers manually to suppress the air particulate pollution. This is an orthodox and inefficient method. When to turn ON/OFF the cannons or sprayer and its time duration entirely depends on the particulate concentration.
Oizom’s Dust monitoring device – DustroidTM can automate these at construction sites by air quality monitoring. By setting threshold limits in the system, according to the exposure limits of OSHA and Ambient Air Quality Standards, the mist cannon or sprayers automatically trigger to spray in case of a threshold breach. An alternate method is to generate baseline data by monitoring before the construction and considering it as the threshold value.
Oizom devices update the air concentration data every 2 minutes so as soon as the ambient air concentration is below the threshold limits the mist cannon stops itself. It saves water and effectively performs dust suppression with minimum human interventions and errors.