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Raheja G, Nimo J, Appoh EKE, Essien B, Sunu M, Nyante J, Amegah M, Quansah R, Arku RE, Penn SL, Giordano MR, Zheng Z, Jack D, Chillrud S, Amegah K, Subramanian R, Pinder R, Appah-Sampong E, Tetteh EN, Borketey MA, Hughes AF, Westervelt DM. Low-Cost Sensor Performance Intercomparison, Correction Factor Development, and 2+ Years of Ambient PM 2.5 Monitoring in Accra, Ghana. Environ Sci Technol 2023; 57:10708-10720. [PMID: 37437161 PMCID: PMC10373484 DOI: 10.1021/acs.est.2c09264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 06/01/2023] [Accepted: 06/02/2023] [Indexed: 07/14/2023]
Abstract
Particulate matter air pollution is a leading cause of global mortality, particularly in Asia and Africa. Addressing the high and wide-ranging air pollution levels requires ambient monitoring, but many low- and middle-income countries (LMICs) remain scarcely monitored. To address these data gaps, recent studies have utilized low-cost sensors. These sensors have varied performance, and little literature exists about sensor intercomparison in Africa. By colocating 2 QuantAQ Modulair-PM, 2 PurpleAir PA-II SD, and 16 Clarity Node-S Generation II monitors with a reference-grade Teledyne monitor in Accra, Ghana, we present the first intercomparisons of different brands of low-cost sensors in Africa, demonstrating that each type of low-cost sensor PM2.5 is strongly correlated with reference PM2.5, but biased high for ambient mixture of sources found in Accra. When compared to a reference monitor, the QuantAQ Modulair-PM has the lowest mean absolute error at 3.04 μg/m3, followed by PurpleAir PA-II (4.54 μg/m3) and Clarity Node-S (13.68 μg/m3). We also compare the usage of 4 statistical or machine learning models (Multiple Linear Regression, Random Forest, Gaussian Mixture Regression, and XGBoost) to correct low-cost sensors data, and find that XGBoost performs the best in testing (R2: 0.97, 0.94, 0.96; mean absolute error: 0.56, 0.80, and 0.68 μg/m3 for PurpleAir PA-II, Clarity Node-S, and Modulair-PM, respectively), but tree-based models do not perform well when correcting data outside the range of the colocation training. Therefore, we used Gaussian Mixture Regression to correct data from the network of 17 Clarity Node-S monitors deployed around Accra, Ghana, from 2018 to 2021. We find that the network daily average PM2.5 concentration in Accra is 23.4 μg/m3, which is 1.6 times the World Health Organization Daily PM2.5 guideline of 15 μg/m3. While this level is lower than those seen in some larger African cities (such as Kinshasa, Democratic Republic of the Congo), mitigation strategies should be developed soon to prevent further impairment to air quality as Accra, and Ghana as a whole, rapidly grow.
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Affiliation(s)
- Garima Raheja
- Department
of Earth and Environmental Sciences, Columbia
University, New York, New York 10027, United States
- Lamont-Doherty
Earth Observatory of Columbia University, Palisades, New York 10964, United States
| | - James Nimo
- Department
of Physics, University of Ghana, Legon, Ghana, Ghana
- African
Institute of Mathematical Sciences, Kigali, Rwanda
| | | | | | - Maxwell Sunu
- Ghana
Environmental Protection Agency, Accra, Ghana
| | - John Nyante
- Ghana
Environmental Protection Agency, Accra, Ghana
| | | | | | - Raphael E. Arku
- Department
of Environmental Health Sciences, School of Public Health and Health
Sciences, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Stefani L. Penn
- Industrial
Economics, Inc, Cambridge, Massachusetts 02140, United States
| | - Michael R. Giordano
- Univ
Paris Est Creteil, CNRS UMS 3563, Ecole Nationale des Ponts et Chaussés,
Université de Paris, OSU-EFLUVE—Observatoire Sciences
de L’Univers-Envelopes Fluides de La Ville à L’Exobiologie, F-94010 Créteil, France
| | - Zhonghua Zheng
- Department
of Earth and Environmental Sciences, The
University of Manchester, Manchester M13 9PL, U.K.
| | - Darby Jack
- Department of Environmental Health Sciences, Mailman
School of Public
Health, Columbia University, New York, New York 10032, United States
| | - Steven Chillrud
- Department of Environmental Health Sciences, Mailman
School of Public
Health, Columbia University, New York, New York 10032, United States
| | | | - R. Subramanian
- Univ
Paris Est Creteil, CNRS UMS 3563, Ecole Nationale des Ponts et Chaussés,
Université de Paris, OSU-EFLUVE—Observatoire Sciences
de L’Univers-Envelopes Fluides de La Ville à L’Exobiologie, F-94010 Créteil, France
- Kigali Collaborative
Research Centre, Kigali, Rwanda
| | - Robert Pinder
- Environmental Protection Agency, Raleigh, North Carolina 27709, United States
| | | | | | | | | | - Daniel M. Westervelt
- Lamont-Doherty
Earth Observatory of Columbia University, Palisades, New York 10964, United States
- NASA Goddard Institute for Space Science, New York, New York 10025, United States
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Raheja G, Sabi K, Sonla H, Gbedjangni EK, McFarlane CM, Hodoli CG, Westervelt DM. A Network of Field-Calibrated Low-Cost Sensor Measurements of PM 2.5 in Lomé, Togo, Over One to Two Years. ACS Earth Space Chem 2022; 6:1011-1021. [PMID: 35495364 PMCID: PMC9036579 DOI: 10.1021/acsearthspacechem.1c00391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 02/18/2022] [Accepted: 02/23/2022] [Indexed: 05/07/2023]
Abstract
Air pollution is a leading cause of global premature mortality and is especially prevalent in many low- and middle-income countries (LMICs). In sub-Saharan Africa, preliminary monitoring networks, satellite retrievals of air-quality-relevant species, and air quality models show ambient fine particulate matter (PM2.5) concentrations that far exceed the World Health Organization guidelines, yet many areas remain largely unmonitored and understudied. Deploying a network of five low-cost PurpleAir PM2.5 monitors over 2 years (2019-2021), we present the first multiyear ambient air pollution monitoring data results from Lomé, Togo, a major West African coastal city with a population of about 1.4 million people. The full-study time period network-wide mean measured daily PM2.5 concentration is 23.5 μg m-3 m-3. The strong regional influence of the dry and dusty Harmattan wind increases the local average PM2.5 concentration by up to 58% during December through February, but the diurnal and weekly trends in PM2.5 are largely controlled by local influences. At all sites, more than 87% of measured days exceeded the new WHO Daily PM2.5 guidelines; these first measurements highlight the need for air quality improvement in a rapidly growing urban metropolis.
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Affiliation(s)
- Garima Raheja
- Lamont-Doherty
Earth Observatory of Columbia University, 61 Route 9W, Palisades, New York 10964, United States
- Department
of Earth and Environmental Science, Columbia
University, 1200 Amsterdam Avenue, New York, New York 10027, United
States
| | - Kokou Sabi
- Université
de Lomé (UL), 01BP, 1515 Lomé, Togo
| | | | | | - Celeste M. McFarlane
- Lamont-Doherty
Earth Observatory of Columbia University, 61 Route 9W, Palisades, New York 10964, United States
| | | | - Daniel M. Westervelt
- Lamont-Doherty
Earth Observatory of Columbia University, 61 Route 9W, Palisades, New York 10964, United States
- NASA
Goddard Institute for Space Studies, 2880 Broadway, New York, New York 10025, United
States
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