Atlas de l'exposition aux pollutions atmosphérique et sonore

Methodology

Trips made

Nineteen bicycle trips were made from February 27 to March 3, 2017 in five districts of Mexico City (Miguel Hidalgo, Cuauhtémoc, Álvaro Obregón, Benito Juárez et Coyoacán) for a total of 137 kilometres and 11 hours.  

Measuring noise and pollution

Data collection was based on the use of three types of devices: 1) an Aeroqual Series 500 Portable Air Quality Sensors, 2) an Brüel & Kjaer Personal Noise Dose Meter (Type 4448), and 3) a Garmin GPS watch (910 XT). The Aeroqual devices have two sensors—nitrogen dioxide (NO2) and temperature and humidity sensors—that record the average NO2 value (µg/m3), the temperature in degrees Celsius, and the percentage of humidity every minute. The Brüel & Kjaer devices record the average decibel levels (dB(A)) every minute (Laeq 1 min.).

Photo credits : Gophrette Power.
 

Measuring the inhaled dose of the nitrogen dioxide (NO2) pollutant

Due to their higher physical activity levels than car users, cyclists have higher ventilation rates. In other words, they breathe more litres of air per minute into their lungs and thus inhale more air pollutants. The cyclist’s ventilation rate also varies according to the speed and the slope of the street section. To measure ventilation, each participant wore a biometric Hexoskin T-Shirt. Finally, by simply multiplying the estimated ventilation (litres per minute) and the value for the concentration of the NO2 pollutant measured with the Aeroqual sensor, one can relatively precisely estimate the inhaled dose (I) in micrograms of NO2 every minute.


 

 

 
Travel videos

A Garmin VIRB action camera is attached on the bicycle’s handlebars, enabling us to obtain a video of the trip. We can then estimate, in a relatively accurately manner, the traffic encountered along the route. We are looking for the number of cars and heavy duty vehicles in motion, the number of stopped cars and heavy duty vehicles with their engine running, etc.