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Monitoring of exposure to PM2.5 in the city of La Paz, BCS, Mexico

Smability carried out an exhaustive monitoring of PM2.5 exposure in the city of La Paz, BCS, Mexico during the months of October to December 2019 and January 2020. The monitoring focused on the collection, analysis and evaluation of data for the Automobile, Public Transport, Bicycle and Walking as transportation modes. The following summary shows the methodology and the preliminary results of the analysis and evaluation for the month of November 2019. In relation to this, the following should be mentioned:

  1. The solution used for the PM2.5 monitoring was SMAA I.
  2. The technical team of Smability carried out a training session on the use and functionalities of the solution for the technical team of the Secretariat of Tourism, Economy and Sustainability, of the State of Baja California Sur (SETUES). 
  3. PM2.5 monitoring was carried out by the SETUES technical team for the months of October, November and December 2019 and part of January 2020.
  4. The SETUES technical team defined transport modes, routes and periods for monitoring PM2.5. The modes monitored were:
    • Private car (automobile)
    • Public transport
    • Bicycle
    • Pedestrian / Walking 
  5. The routes monitored for each mode and for all periods of the month of November 2019 are shown in the following figure. However, It should be noted.
    • Each point represents an observation of PM2.5.
    • Each route by color represents a mode of transport. 
    • The image shows all the routes for the month of November 2019 for all periods by type of mode.

6. Finally, through the Cloud Data Platform users can visualize, analize, evaluate and download the surveyed information. The information can be later post-processed in third party programs such as QGIS or ArcGIS.

Methodology for the Analysis

For the analysis by period and transport mode the following was considered:

  1. The analysis used route data by mode, collected for the month of November 2019
  2. Four periods of analysis were considered: AM 7:00 -11: 00 am, interpeak 11:00-15:00, PM 15:00-19: 00 and Night 19: 00-23:00
  3. The analysis is an aggregation on percentages of PM2.5 exposure by transport mode; private car, public transport, bicycle and pedestrian/walking
  4. Disaggregation by PM2.5 bands and exposure percentages.

PM2.5 by Period and Transport Mode

The following analysis shows the results by period, mode and percentage of exposure per PM2.5 band. It is observed that public transport, bicycle and pedestrian modes showed a higher percentage of PM2.5 exposure, particularly in the bands 12.1-35.4µg/m3 (moderate air), 35.5-55.4µg/m3 (unhealthy air for vulnerable groups). Likewise, public transport mode, in the AM period, showed a considerable exposure of unhealthy air, bands of 55.5-150.5 µg/m3. Finally,  the 0-12µg/m3 (good air) band showed a higher percentage of exposure for the car mode compared to the rest of the modes.

Average PM2.5 per day and transport mode

From the previous analysis, an average per day and mode of PM2.5 observations was generated for the month of November 2019. The following graph shows the result of the analysis. From this it is inferred that:

  1. Auto mode shows a higher percentage of exposure for the 0-12µg/m3 band (good air) in relation to the rest transport modes
  2. Public Transport mode shows a higher percentage of exposure for the band 55.5-150.5µg/m3 (unhealthy air)
  3. Bicycle and Walking modes showed a higher percentage of exposure in the band 12.1-35.4µg/m3 (moderate air).

For the spatial analysis of PM 2.5 the following considerations were taken:

  1. Maximum analysis resolution is at neighborhood level
  2. An average of PM2.5 was generated by mode and period (07:00 – 23:00 hrs) per neighborhood with PM2.5 valid observations. The average was generated from the aggregation of PM2.5 points observed in each neighborhood
  3. The analysis was disaggregated by transport mode; private car, public transport, bicycle and walking
  4. The month analyzed was November 2019.

The spatial visualization of PM2.5 by neighborhood, mode and PM2.5 exposure bands is shown in the following map.

From the previous spatial analysis it can be inferred that:

  1. Automobile mode showed lower exposure to PM2.5 in central neighborhoods of the city of La Paz.
  2. Public transport mode showed greater exposure to PM2.5, especially in neighborhoods north of the downtown of La Paz.
  3. Bicycle mode has the highest exposure of PM2.5 in neighborhoods north of downtown La Paz and southwest of downtown La Paz.
  4. Walk mode; a smaller number of sampling points were generated when compared to the rest of the modes. However, the central area of ​​the city of La Paz showed a degraded situation of air quality (PM2.5) for pedestrians.

Preliminary Conclusions

  1. The Public Transport Mode shows higher exposures to PM2.5, when compared with the rest of the modes, particularly in the band 55.5-150.5µg/m3 (unhealthy air)
  2. The Bicycle and Walking Modes, in general, present higher exposure to PM2.5 in the band 12.1-35.4µg/m3 (moderate air)
  3. The Automobile Mode presents a higher percentage of exposure to PM2.5 in the band 0-12 µg/m3 (good air)
  4. The Public Transport and Bicycle modes, in the northern neighborhoods of the city, downtown and southwest, showed a greater exposure to PM2.5 in the 55.5-150.5µg/m3 band (unhealthy air).

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