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 due to the usage of raw materials like sand, silt, cement, concrete, sawdust, etc and activities like excavation, drilling, bulk material transportation, loading and unloading, open-air material storage, concrete and mortar making, cutting and filling, and the movement of equipment. If unattended, particulate pollution is bound to surpassingly increase having greater health implications on 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. Moderate to high wind speeds carry away the particulates that endanger the workers, people in nearby proximity, roads, etc. Vehicular emissions ( from trucks, loaders, bulldozers, excavators) and diesel generator sets used for excavation purposes generate PM2.5 along with other pollutants (Carbon Monoxide, Nitrogen Oxides, unburnt hydrocarbons, etc). Heavy vehicles and excavators re-entrain the settled sand particles which keep the air particulate concentration well above the threshold limit. Maximum air particulate pollution is caused during this phase.
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. At the site, activities like sieving the sand, cement mixing, cutting, and shaping of bricks, tiles, marbles, woodcutting, and finishing, etc are carried out till the building is nearly finished. It generates fine particulate matter that can easily penetrate through the respiratory system.
Construction and Demolition (C&D) Waste
Demolition of older sites generate 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 which 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 which in return if not planned properly 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 for air quality monitoring are provided by various institutes and agencies across the world. 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.
The monitoring devices like the Oizom’s low-cost sensor 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. 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 to the particulates. 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.
It is also necessary to carry out air quality monitoring at the site before any construction activities are carried out. The baseline data hence generated helps in making of the compliance report, Environment Impact Assessment (EIA) and Environmental Clearance (EC). Baseline data further help 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 depending on the meteorological parameters. 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. Manually functioned sprayers, mist cannons, sprinklers are turned on that sprays the water to suppress the air particulate pollution. This is an orthodox and inefficient method. When to turn on or turn off the cannons or sprayer and it’s time duration totally depends on the particulate concentration.
These can be automated at construction sites by air quality monitoring using Oizom’s DustroidTM. Threshold limits are set in the system according to the exposure limits of OSHA and Ambient Air quality Standards so that whenever it is breached, the mist cannon or sprayers are automatically triggered to spray. An alternate method is to generate baseline data by baseline monitoring before the construction and considering it as the threshold value that should not be exceeded.
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.