As the public is getting aware of the health implications of Dust/Particulate Matter and other pollutants, governments are expecting better pollutant management from industries. This guide provides a brief overview of a dust pollution risk management plan for construction activities as well as some best practices to help mitigate the impacts.
Construction, an important industry for global economic growth, also contributes significantly to air pollution in the form of dust. Although the exhaust from the construction vehicles and machinery adds to the NO2 levels as well, its impact is not as strong as Dust.
In scientific terms, Dust is referred to as Particulate Matter or PM. Other than being an annoyance by soiling surfaces (explanation), PM has major health and environmental implications. The WHO and the governments all around recognize PM10 and PM 2.5 (size in microns) among the most harmful pollutants. While the larger and heavier PM more commonly affect the construction site vicinity, the wind carries the lighter PM10 and 2.5 thus affecting people and vegetation miles away. Construction vehicles on the open ground further dissipate PM and carry it to farther distances.
PM is emitted at all stages of construction:
- construction; and
- track out (The transportation of dust and dirt from the construction site onto the public road network, where it may be deposited or suspended by vehicles using the network).
The PM impact depends on factors such as the size of the construction site, duration of activity, weather conditions, the direction of the wind, proximity of people and vegetation, etc.
Harmful effects of PM
Health effects from some particles are immediate while others take years to develop. Particles greater than 10 microns cause eye, mouth, and skin irritations but PM10 and smaller are much more harmful. Europe and U.S. attribute hundreds and thousands of deaths every year to PM 2.5 and PM 10.
PM10 affects the upper respiratory system by aggravating asthma and bronchitis. PM 2.5 penetrates deeper into the respiratory tract, dissolves into the blood and compromises immunity. When dust originates from activities on a formerly contaminated site, PM10-2.5 combine with heavy metals present in soil and cause toxicity in addition. Lead and asbestos toxicity from PM is fairly common.
PM also affects the ecosystem by wilting plants as dust on leaves prevents photosynthesis.
Major construction projects over a long duration also increase the long-term PM10 concentrations in cities.
An effective assessment forms the basis of a well-planned and environment friendly construction.
But you can drastically reduce dust emission with proper measures. The mitigation controls depend on the effective assessment of dust emission prior to construction activities. An effective assessment forms the basis of a well-planned and environment friendly construction.
PM Assessment for construction
Source: Guidance on the Assessment of dust by Institute of Air Quality Management
The assessment should take into account all stages of construction for the following three effects:
The assessment involves three steps:
- Step-1: Assessing the magnitude of each construction activity
- Step-2: Assessing the sensitivity w.r.t Soiling, Health, and Ecology for all four activities separately
- Step-3: Combining the results of the above two steps to determine the impact risk
The mitigation measures that you should employ will depend on the impact risk you calculate for each construction activity.
To begin, you should first determine the magnitude of dust emission for all four activities separately; Demolition, Earthworks, Construction, Trackout.
Depending on factors like the construction site area, soil type and construction vehicles, the four construction site activities should be graded as Large, Medium, and Small accompanied with proper justification. For example, the UK government, identifies construction activities greater than 100,000 m3 as Large and demolition activities less than 50,000 m3 as Medium. While more than 50 Heavy Duty Vehicles definitely cause high emissions, less than 10 are comparatively safer and so the Track out can be graded as Small, keeping in mind other factors like unpaved road length and surface material.
Below is a table for guidance to grade the activities for emission but all construction sites are unique and therefore a competent and experienced person carrying out the assessment should use her/his own judgement.
Next you should grade the sensitivity of receptors, i.e. human health and ecosystem for each of the four construction activities as High, Medium, and Low.
Major factors to consider for grading are proximity of receptors from the construction site, heritage value of nearby buildings and sensitivity of vegetation. Other factors to keep in mind include the average PM concentration in the area, dust-generating activities in the nearby sites, the duration of the activities, etc.
After completion of grading, your table should look something like the sample below.
As a final step you should now combine the gradings of the above two steps to determine the impact risk of PM from each activity on Health, Soiling, and Ecology. Again judgement should be use for grading. For example, Demolition activities usually emit more PM than Trackout, therefore when receptor sensitivity is high, risk is Medium for Demolition but Low for Trackout even if the emission is Small for both Demolition and Trackout.
Below is a sample table for the final risk grading for your reference.
Now that the overall impact of each activity is graded for risk, you can plan appropriate dust mitigation measures.
Dust mitigation best practices highly recommended irrespective of risk
Your construction activity irrespective of risk should display the name and contact information of the head-office as well as the person in charge at the site for air pollution. You must record any complaint and determine the root cause and ways to mitigate the issues. You must also carry out and maintain a log of regular inspections to monitor compliance. Other best practices are removing dusty materials when not needed, imposing speed limits for construction vehicles (especially on unpaved roads), ensuring availability of equipment to clean spills, avoiding dry sweeping of large areas, erecting screens around dusty activities, and ensuring that vehicles carrying construction materials or equipment are properly covered.
Best practices for Medium and High risk
If your construction activities involve Medium to High risks then you must take additional measures like regular soiling checks within 100 m, continuous PM10 monitoring, wet methods to keep site fences and scaffolding clean, rigorous revegetation of exposed areas while ensuring only small areas are exposed at a time, ensuring construction materials are always sealed to avoid emissions and using sprinklers on unpaved routes.
The world medical debt is increasing and people are ascribing their health issues to pollution. The government is under pressure to be stricter with industries to continuously monitor and control PM10 and 2.5. Construction industry contributes a vast portion of these pollutants, but a thorough and effective dust management plan can widely control PM emissions.
To help, Nimonik has partnered with world-renowned Ecomesure labs to provide indoor and outdoor air monitoring devices that are simple, accurate and affordable. Check the devices here and contact us for more information.