22 of the world’s 30 most polluted cities are in India – Greenpeace
There is a plethora of scientific reports & research by WHO, Global burden of disease, IPCC(Intergovernmental Panel on Climate Change) on the harmful effects of air pollution. Day by day increasing pollution level mandates some air standards to be in place looking at the dire need of air quality management. We need to try and recede the pollution below the ‘threshold effect level’ – a level at which air poses no risk to human health. This procedure requires a network of continuous ambient air monitoring systems to generate routine pollution or air quality report.
Currently, one air pollution monitoring station is available for every two million people in India. There are more manual stations than real-time air quality monitoring systems. As per a report by CSE India, out of the 5,000 cities and towns in India, a regulatory monitoring network exists only in 268. Out of these 5000 cities, only 24 cities have the potential and means to perform real-time monitoring. The rest rely on manual monitoring.
As of September 2018, four key pollutants—Sulphur Dioxide (SO2), Nitrogen Dioxide (NO2), PM10, and PM2.5—are monitored at 703 AQ stations across 307 cities and towns.
Air quality varies over a relatively small span – even between and within city blocks. Hence, the pollution concentration in a specific region depends primarily on the local emissions and ambient conditions. The current air quality monitoring systems cannot solve this problem as they are sparsely located due to the large capital cost and resources required for creating a high-density network of such systems.
So, what can we do to solve this problem? To get more realistic air quality data?
Low-cost Air Quality Monitors
All low-cost sensors consist of a few basic elements:
- The sensor element that senses the parameter of interest
- A transducer that converts the response from electrical signals
- Data storage or link to a communication device
- Source of power (e.g. battery or solar energy)
The biggest advantage of a low-cost Continuous Ambient Air Quality Monitoring System (CAAQMS) over conventional ones is that it is compact, lightweight and cost-effective.
In fact, US EPA has categorized the low-cost air monitors into different tiers based on their cost.
What Makes Low-Cost Air Monitors Compact?
These low-cost sensors use micro-fabrication techniques and contain micro-electro-mechanical systems (MEMS) made of optical and nanostructured elements, making them lighter and inexpensive. The compactness is complemented by low-power consumption and energy-efficient sensor circuits.
How can a Low-Cost Sensor Benefit Us?
Well, it can overcome almost all the problems which could not be solved with bulky conventional air monitoring systems. Here are some of the instances:
Advanced technologies with AI used in new sensor-based air quality monitors have enabled real-time data collection and analysis. Real-time monitoring of major pollutants and the continuous dissemination of the data is important for both policy and public opinion. Most cities are facing a data vacuum today due to delayed response.
Manual monitoring is much less efficient in capturing pollution levels compared to automatic real-time monitors. For instance, to arrive at an annual average in India, at least 104 measurements in a year are necessary. The measurements must be taken 24-hourly, twice a week, at uniform intervals. Real-time low-cost air monitors can provide more accurate data leading to more robust and reliable conclusions about air quality levels.
Low-cost compact air monitors or CAAQMS enables small-scale environmental data monitoring. It can be deployed in large numbers across urban and rural scape to generate local data. The advanced IoT technology has made environmental monitoring possible even in remote areas, which was not possible earlier. In fact, the network of these sensors can be remotely controlled for data transmission.
The idea of ubiquitous monitoring is attracting attention from the air quality management community, which is possible due to the low cost and miniaturization of sensors. These low-cost air monitors can be installed on any smart pole to collect ambient air data. This allows for hyperspatial data acquisition encompassing a wider area for high-resolution exposure mapping of the city.
Deploying these sensors in large numbers can also assist in detecting pollution hotspots and creating emission inventories. These steps allow actual exposure assessment to devise effective mitigation strategies.
High Precision Data
The airflow in urban environments is usually turbulent and can be difficult to predict without a sophisticated modelling method. This requires real-time high-resolution pollutant concentration mapping, which is not possible with the conventional monitors. It requires a large amount of data, computing facilities and input details that are not available for many cities with the existing monitors. Advanced IoT based air quality monitors can provide higher environmental data accuracy through appropriate maintenance like sensor calibration, sensor drift and cross-sensitivity corrections, robust hardware, periodic sensor replacement, etc. See how Oizom Environmental Sensors provide 13% higher data accuracy than other low-cost CAAQMS using its Active Sampling method.
Retrieving data from these sensors is simple. The sensors provide granularity, which helps in the identification of pollution sources. These data banks can support in providing more detailed studies on the effects of air pollution on quality of life.
360-Degree Environment Monitoring
The data acquired from the low-cost air quality sensors monitor dust particles, toxic & odor gases, along with weather parameters within a single enclosure. For instance, a single air quality monitor can measure PM1, PM2.5, PM10, SOx, NOx, CO2, CO, TVOCs, etc. along with meteorological parameters like wind speed and direction, relative humidity, ambient temperature, pressure, light intensity, rainfall, UV Radiations, etc.
It is possible to carry out exposure mapping across the microenvironment and make that data accessible to people. Thus, they provide a complete picture of what’s happening in the air around us.
With the conventional monitors, public awareness can be achieved only after collecting all the data, and generating reports or index to be presented over website or portals etc. But the low-cost sensors have made data handling very easy, which allows wide options of data visualization.
The data can be visualized by a number of mobile and web-based applications and is readily available for use by citizens. Online air monitors enable access and quick treatment of data for presenting it publicly via different media.
Many of these sensors do not require specialized knowledge, which encourages public participation in the process. This has given birth to community-based monitoring, which is driven by local information needs and community values. The low-cost air quality monitors also allow opportunistic sensing by data acquired for one purpose to be used for other purposes as well.
This is a powerful tool to connect people with the problem, demystify the smog and demand action. These technologies have provoked intense public interest as it is now possible for people to own and monitor the surrounding air and understand the level of actual exposure.
Too Good to be True?
Although the low-cost Continuous Ambient Air Quality Monitoring Systems (CAAQMS) seem near perfect, they have some setbacks of their own. The sensor devices require frequent calibration and suffer from drift due to temperature and humidity changes. Sensor Drift refers to the deviation in the response of the monitor with time.
The metal oxide sensors also have electrical noise which can be due to drift and cross-sensitivity. The cross-sensitivity refers to the sensor responding to the parameters other than the targeted ones. Poor selectivity is one of the main issues with low-cost sensors. These readings can be influenced by multiple pollutants, temperature, and humidity. The life of sensors is also limited, and hence, need to be replaced periodically. However, these obstacles can be overcome by accurate sensor calibration and algorithms for setting the drift and compensate temperature, humidity as well as cross-sensitivity.
Some Recent Low-Cost Air Quality Monitor Deployment
As of June 2019, the scientists at the University of Southampton deployed low-cost air pollution sensors in Southampton to achieve cost-effective pollution monitoring on a wider scale.
San Jose State University installed a network of 20 Low-Cost Air Quality Monitors in the Imperial Valley of Southern California to analyze fine particulate matter (PM2.5) in the region using dispersion modelling.
Since April 2019, Granada province in Spain has started monitoring Granada’s ambient air quality using Oizom’s low-cost air quality monitor Polludrone to provide data-driven better healthcare suggestive actions.
Public health challenges and risk assessment requires more refined and varied monitoring approaches to reduce exposures and risks. Hence, more stringent pollution control measures are required. This can be achieved by widespread air monitoring at the microscale, which is only possible through compact, highly scalable CAAQMS.
Currently, there are no set government regulations for low-cost CAAQMS as they are still subjective to interference by ambient conditions. But looking at the huge success and rising demand of these low-cost air quality monitors, governments across the globe have started considering to include these sensors under the Air Regulations. Currently, guidelines are underway for air quality sensor technology standards in the European Union, the United States, and China. In India, Council of Scientific & Industrial Research (CSIR)-National Physical Laboratory (NPL) is tasked by the government with certifying air quality monitoring instruments. CSIR-NPL is designated a national verification agency for the purpose and they shall develop the necessary infrastructure, management system.