The impact of COVID-19 lockdown restrictions on the short-term association between in-vehicle particulate pollutants and the respiratory health of Parisian taxi drivers

Objective This study assessed the short-term associations between in-vehicle ultrafine particles (UFP) and black carbon (BC) concentrations and irritation symptoms and lung parameters of taxi drivers, pre- and post-lockdown. Methods As part of PUF-TAXI project, 33 taxi drivers were followed up during two typical working days. In-vehicle UFP and BC were continuously measured by monitoring instruments. Irritation symptoms during the working day were reported via an auto-questionnaire and lung function was assessed by a portable spirometer, pre- and post- work shift. Generalized estimating equations, adjusted for potential confounders, were used to study the association between air pollutants and health outcomes. Effect modification by measurement period (pre- and post-lockdown) was investigated. Results UFP and BC concentrations inside taxi vehicles decreased significantly post- compared to pre-lockdown. Incidence of nose irritation was positively associated with in-vehicle UFP and BC levels pre-lockdown, when pollutant levels were higher, whereas no significant association was found post-lockdown. The decrease in the FEF25–75% (forced expiratory flow at 25–75% of the forced vital capacity) during the working day was significantly associated with in-taxi UFP levels before but not after lockdown. No association was found with BC. By contrast, incidence of eye irritation was significantly inversely associated with in-vehicle humidity, regardless of pollutant concentrations and the measurement period. Conclusions Our findings indicate that an upgrade in in-vehicle air quality could improve respiratory health. This study showed that the magnitude of the incidence of nasal irritation and decrease in lung function depends on UFP concentrations the commuters are exposed to.


TABLES AND FIGURES
Table S2.Baseline characteristics of Parisian taxi drivers, in the PUF-TAXI study (N= 33).BMI: body mass index; GERD: gastroesophageal reflux disease; SD: standard deviation; SPT: skin prick test.a. Smoker: current smoker or had quit smoking for less than twelve months b.Ex-smoker: have quit smoking for at least twelve months c.SPT is considered positive if the wheal diameter ≥ 3 mm and at least half the size of the positive histamine control (1) d.Asthma ever is defined as having a childhood asthma (diagnosis between 5 -14 years 'old) e. Allergic rhinitis is defined as having at least one of the following symptoms: congestion, rhinorrhea, sneezing, nasal itching, and nasal obstruction without any infectious triggers and having a hay fever or an allergy to pollen or other allergens (2) f.Nose irritations: sneezing, stuffy or runny nose, itchy nose without any infectious triggers g.Eye irritations: redness, watery or itchy eyes without any infectious triggers h.Throat irritations: hoarseness, irritation, and itching without any infectious triggers i. Chronic cough is defined clinically as having cough every day for at least 3 consecutive months (3) j.Chronic phlegm is defined clinically as having phlegm every day for at least 3 consecutive months (3) None of the participants have chronic bronchitis, emphysema, chronic obstructive bronchopneumopathy

EXPOSURE ASSESSMENT
During each sampling day, the taxi driver carried a carry case containing the measuring instruments (Figure 1).Ultrafine particles (UFP) and black carbon (BC) were measured by the Diffusion Size Classifier Miniature (DiSCmini ® -DM, Wohlen, Switzerland and commercialized by Testo SE &Co.KGaA, Titisee-Neustadt, Germany) and the microAeth ® Model AE51 (MA, Aethlabs, San Francisco, California, USA), respectively.Since the aerosol sampling is distant from the DiSCmini ® and the microAeth ® original inlets, the sampling was made by tubes, supplied by the manufacturer, placed outside the case, and connected to the devices (Figure 1S).CP11 ® (Michel Instruments, Lyon, France) was used to monitor temperature, humidity, and carbon dioxide (CO2) inside the vehicle.All the devices were logged at one min intervals.We should note that the same set of devices was given to all the taxi drivers.

QUALITY ASSURANCE AND DATA PROCESSING
Exposure measurement: Before the beginning of each survey day, the proper functioning of all the devices was checked according to the manufacturers.They were turned on for several minutes to stabilize before placing them in the vehicle.After each sampling day, DM and MA tubes were rinsed with filtered water and dried by pure air using a compressor.MA quartz filter was changed, and DM impactor was cleaned for one hour in an ultrasonic bath (Branson Model 1800, Fisher Scientific Co.L.L.C., Pittsburgh, PA, USA) with pure water to maintain measurement integrity.DM and MA were sent to their manufacturers on their calibration due dates.

Figure S1 .
Figure S1.Study population flowchart of the PUF-TAXI study

Figure S2 .
Figure S2.Photographs of the field measurement setup from PUF-TAXI study in Paris.A: Carry case containing four measuring devices.B: Carry case placed inside a taxi vehicle.

Figure S5 .
Figure S5.Variation of lung function parameters in Parisian taxi drivers between pre-and postlockdown, in the PUF-TAXI study (N=33) FEF25-75%: forced expiratory flow at 25-75% of the forced vital capacity; FEV1: forced expiratory volume at 1 second; FVC: forced vital capacity Each bar represents a participant.

Table S1 .
General characteristics of the measurement campaigns, in the PUF-TAXI study

Table S3 .
Comparison of the measurement campaign characteristics pre-and post-lockdown in the Paris area, in the PUF-TAXI study AC: air-conditioning; AR: air recirculation; OP: opening windows; SD: standard deviation a. Paired sample T-test b.Atmo index is based on four air pollutant concentrations: SO2, NO2, O3, and PM10.For each of these pollutants, a subindex is calculated and the Atmo index of the day is equal to the highest of the four sub-indices, scaled from 1 (very good) to 10 (very bad) (https://www.airparif.asso.

Table S4 .
Comparison of the incidence of the reported symptoms in Parisian taxi drivers preand post-lockdown, in the PUF TAXI study (N=33).An incident irritation was defined as the nasal or eye irritation occurring during the working day or getting worse compared to the start of the day (the symptom intensity scale during the working day > the symptom intensity scale at the start of the working day).