NEHA July/August 2024 Journal of Environmental Health

ADVANCEMENT OF THE SCIENCE

participants, the mean age was 36.5 ± 10.2 years, the average body mass index (BMI) was 25 ± 3.71 kg/m , 20% of participants identified as current smokers or ex-smokers, and 37% of participants identified as current smokers or ex-smokers of cannabis. In response to survey questions about their physical activity, 93% of participants answered that they frequently rode bicycles in the city. When asked if they did other regular physical activity, 62% of the partici- pants answered yes. In response to questions about preexisting comorbidities, 11% of the participants reported they were asthmatic, and 3% reported high blood pressure. No participant reported having chronic obstruc- tive pulmonary disease (COPD), heart fail- ure, or another pathology. Characteristics of the participants by route of cycling are pre- sented in Table 1. A comparison of cyclists’ ages between the two routes was made using a non-para- metric Wilcoxon test and showed a nonsig- nificant di”erence ( p = .087). The distribu- tion of BMI in the sample was normal, and the di”erence in participant BMI measure- ments between both routes was not statisti- cally significant ( p = .504). Each participant had their blood pressure taken before start- ing the cycling trip. This measurement was taken twice. For the analysis, the average value of the two measurements was used. We did not detect any statistically signifi- cant di”erences in the blood pressure of participants in each route. Exposure to environmental pollutants (PM 2.5 , PM 10 , NO 2 , and noise) was explored in both routes. No statistically significant dif- ferences were found in PM 2.5 and PM 10 con- centrations between routes; however, the NO 2 concentration was higher in Route 1 and the noise level was higher in Route 2 (Table 2). Regarding potential inhaled doses per route, there were significant di”erences in PM 10 and NO 2 , with measurements for both being higher in Route 1 (Table 2). Even though exposure to PM 2.5 and PM 10 was not di”erent between routes, in most of the cycling trips we detected exposure lev- els above the threshold at least 14% of the time for all the variables analyzed. The mean exceedance exposure time for PM 2.5 was higher for Route 2 and the di”erence was sta- tistically significant ( p = .0005). The percent- age of time exposure to noise levels >70 dBA

TABLE 1

Demographics of Participants by Cycling Route ( N = 64)

Demographic Variable

Route 1 Participants ( n = 32)

Route 2 Participants ( n = 32)

p -Value

Age (years)

33.8 ± 7.5

39.2 ± 11.9

.08

Sex (#)

Female

13 19

13 19

1.00

Male

BMI

24.7 ± 2.9

25.3 ± 4.4

.50

Smoking status (#/participant response) Tobacco

2/30

2/30 9/23

1.00

Cannabis

14/18

.29

Regular physical activity (#) Yes

23

18 14

.44

No

9

Comorbidities (#) Respiratory

3 0

4 2

1.00

Cardiovascular

.47

Blood pressure Systolic

125 ± 12

123 ± 18

.18 .10

Diastolic

83 ±7

81 ±13

Note. BMI = body mass index.

was also di”erent and higher for Route 2 ( p = .0003), which is also statistically significant (Table 3). A wide range of exceedance times was detected during some cycling trips on spe- cific days; exceedance time in all variables was >60% (in Route 1 for days 8 and 17, and in Route 2 for days 5–8, 11, 12, 15, 17, and 34). For noise and PM 10 , exceedance time was >60% of the cycling time in >80% of the days. On the other hand, some cycling trips showed no exceedance time, mainly for PM 2.5 (Supplemental Figure 1, www.neha.org/ jeh-supplementals). CO saturation measurements are the per- centages of hemoglobin saturation with CO (%COHb) and the estimation of ppm of CO (CO-oximetry). These measurements were obtained from participants before and after completion of the cycling trips as a proxy of the short-term impact of air pollutants on the respiratory function of participants. We estimated the di”erences in concentra- tions before and after the cycling trips. The mean CO-oximetry before the trip was 2.98 ±

2.8 ppm, with 3.06 ± 3.34 ppm in Route 2 and 2.91 ± 2.2 ppm in Route 1 ( p = .831). After the trip, the CO-oximetry global mean was 2.32 ± 2.2 ppm, with 2.44 ± 2.79 ppm in Route 2 and 2.22 ± 1.43 ppm in Route 1 ( p = .69). The mean of the di”erences was -0.652 ± 0.9 ppm and when di”erentiating between the routes, the di”erences had a mean of -0.625 ± 0.94 ppm for Route 2 and -0.688 ± 0.93 ppm for Route 1. In both routes, on average the measurements decreased after the cycling trip compared with the measurements before the trip. There were no di”erences, however, between routes ( p = .975, Wilcoxon test). Multivariate Statistical Analysis To determine an association of various variables with the concentration of CO exhaled by the cyclist before and after completing the route, multivariate analyses were performed. Simple and multiple linear regression models were fit- ted for the di”erence between CO-oximetry (after versus before) and for the CO-oximetry measurement after. As explanatory variables, many scenarios were considered with di”erent

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Volume 87 • Number 1

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