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Road traffic noise exposure has been associated with auditory and non-auditory health effects, but few studies report noise characteristics. This study determines 24-h noise levels and analyzes their frequency components to investigate associations between seasons, meteorology, land-use types, and traffic. We set up 50 monitoring stations covering ten different land-use types and conducted measurements at three times of the year to obtain 24-h-average A-weighted equivalent noise levels (L Aeq , 24h ) and frequency analyses from 2013 to 2014 in Taichung, Taiwan. Information on land-use types, road parameters, traffic flow rates, and meteorological variables was also collected for analysis with the annual averages of road traffic noise and its frequency components. The annual average L Aeq , 24h in Taichung was 66.4 ± 4.7 A-weighed decibels (dBA). Significant differences in L Aeq , 24h and frequency components were observed between land-use types (all p-values < 0.001), but not between seasons, with the highest two noise levels of 71.2 ± 1.0 dBA and 70.0 ± 2.6 dBA measured in stream-channel and commercial areas, with the highest component being 61.4 ± 5.3 dBA at 1000 Hz. Road width, traffic flow rates, and land-use types were significantly associated with annual average L Aeq , 24h (all p-values < 0.050). Noise levels at 125 Hz had the highest correlation with total traffic (Spearman's coefficient = 0.795) and the highest prediction in the multiple linear regression (R 2 = 0.803; adjusted R 2 = 0.765). These findings reveal the spatial variation in road traffic noise exposure in Taichung. The highest correlation and predictive capacity was observed between this variation and noise levels at 125 Hz. We recommend that governmental agencies should take actions to reduce noise levels from traffic vehicles. [ABSTRACT FROM AUTHOR]

Land-use regression (LUR) models have been used to estimate particle mass concentration (PMC), but few studies apply it to predict particle number concentration (PNC) at different sizes. This study aimed to determine both PMC and PNC throughout one year to establish predictive models in Taichung, Taiwan. The annual averages of PM 10 , PM 2.5 , and PM 1 were 71 ± 46 μg/m3, 44 ± 35 μg/m3, and 32 ± 28 μg/m3, respectively. The PNC at size ranges of <0.5 μm, 0.5–1 μm, 1–2.5 μm, 2.5–10 μm, and ≥10 μm were 715098 ± 664879 counts/L, 29053 ± 30615 counts/L, 1009 ± 659 counts/L, 647 ± 347 counts/L, and 3 ± 3 counts/L, respectively. The model-explained variance (R2) values of PM 10 , PM 2.5 , and PM 1 were 0.42, 0.53, and 0.51, respectively. The magnitude of the R2 values ranged from 0.31 to 0.50 for the PNC with the highest R2 between 0.5 and 1 μm. The differences between the model R2 and the leave-one-out cross-validation R2 ranged from 4% to 8% for PMC and from 3% to 10% for PNC. This study developed LUR models with moderate performance to estimate PMC and PNC at different sizes in an Asian metropolis. The built LUR models may be improved by combining with other open data to increase the predictive capacity. [Display omitted] • Both particle mass and number concentrations are measured over one year. • The model explained variance (R2) is 0.53 for PM 2.5 and 0.51 for PM 1. • The magnitude of R2 ranged from 0.31 to 0.50 for particle number concentrations. • The built model has the highest R2 for particle number concentrations at 0.5–1 μm. • Models with moderate performance are developed to estimate particle concentrations. [ABSTRACT FROM AUTHOR]

Few studies have applied land-use regression to predict road traffic noise exposure, and there are few predictive models for different frequencies. This study aimed to measure 24-h average road traffic noise levels and to analyze the frequency components over one year to establish land-use regression models of noise exposure. Fifty monitoring stations were set up to conduct 3 measurements for A-weighted equivalent sound pressure levels over 24 h (L eq,24h) and night equivalent sound pressure levels (L night), as well as octave-band analyses, during the 2013–2014 period. Noise measurements were integrated with land-use types, road and traffic information, meteorological data and geographic information systems to construct land-use regression models. Leave-one-out cross-validation was performed to test the validity of the predictive models. The annual means of L eq,24h and L night were 66.4 ± 4.7 A-weighed decibels (dBA) and 62.1 ± 6.0 dBA, respectively. Octave-band frequency analyses revealed that the highest means over 24 h and at night were 61.4 ± 5.3 decibels (dB) and 56.7 ± 6.6 dB (both at 1000 Hz), respectively. The model-explained variance (R2) of the full-frequency noise was 0.83 for L eq,24h and 0.79 for L night. The R2 values for octave-band-frequency noise ranged from 0.67 to 0.88 for L eq,24h and 0.65 to 0.85 for L night , with the highest R2 at 250 Hz for L eq,24h and at 125 Hz for L night. The differences between the model R2 and the leave-one-out cross-validation R2 ranged from 5% to 15% for both L eq,24h and L night at all frequencies. In the validation, the root mean squared error was 2.09 dBA and 2.80 dBA for the full-frequency L eq,24 and L night , respectively, and ranged from 1.89 to 2.62 dB and from 2.51 to 3.28 dB for the octave-band-frequency L eq,24h and L night , respectively. This study observed that the annual means of the measured L eq,24h and L night in Taichung were both above 60 dBA and had the highest level at 1000 Hz. The developed land-use regression models of L eq,24 and L night both had good predictive capacity for the full frequency spectrum and within octave bands and can therefore be applied for epidemiological studies. Unlabelled Image • The highest annual means of L eq,24h and L night both are measured at 1000 Hz. • The model-explained variance (R2) is 0.83 for L eq,24h and 0.79 for L night. • The highest R2 is 0.88 at 250 Hz for L eq,24h and 0.85 at 125 Hz for L night. • The root mean squared error is 2.09 dBA and 2.80 dBA for L eq,24 and L night. • Models with good performance are built to estimate levels of road traffic noise. [ABSTRACT FROM AUTHOR]

Exposure to volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, xylene, and formaldehyde from long-distance buses has been reported to adversely affect human health. This study investigates the concentrations of these five VOCs and evaluates their health risks to drivers and passengers on board. Ten trips from Taipei to Taichung were performed during the warm and cold seasons of 2021–2022. Two locations inside the bus were established to collect air samples by a 6-liter canister for drivers and passengers. Exposure concentrations of benzene, toluene, ethylbenzene, and xylene were analyzed via gas chromatography with a flame ionization detector and the formaldehyde concentration was monitored using a formaldehyde meter. Subsequently, a Monte Carlo simulation was conducted to evaluate the carcinogenic and non-carcinogenic risks of the five VOCs. Formaldehyde emerged as the highest detected compound (9.06 ± 3.77 μg/m3), followed by toluene (median: 6.11 μg/m3; range: 3.86–14.69 μg/m3). In particular, formaldehyde was identified to have the significantly higher concentration during non-rush hours (10.67 ± 3.21 μg/m3) than that during rush hours (7.45 ± 3.41 μg/m3) and during the warm season (10.71 ± 2.97 μg/m3) compared with that during the cold season (7.41 ± 4.26 μg/m3). Regarding non-carcinogenic risks to drivers and passengers, the chronic hazard indices for these five VOCs were under 1 to indicate an acceptable risk. In terms of carcinogenic risk, the median risks of benzene and formaldehyde for drivers were 2.88 × 10−6 (95% confidence interval [CI]: 2.11 × 10−6 – 5.13 × 10−6) and 1.91 × 10−6 (95% CI: 4.54 × 10−7 – 3.44 × 10−6), respectively. In contrast, the median carcinogenic risks of benzene and formaldehyde for passengers were less than 1 × 10−6 to present an acceptable risk. This study suggests that benzene and formaldehyde may present carcinogenic risks for drivers. Moreover, the non-carcinogenic risk for drivers and passengers is deemed acceptable. We recommended that the ventilation frequency be increased to mitigate exposure to VOCs in long-distance buses. • Formaldehyde was found to have the highest level in the long-distance bus. • BTEX concentrations were higher during the cold season, rush hour, and on weekdays. • Drivers had possible cancer risks from exposure to benzene and formaldehyde. • Non-carcinogenic risks for drivers and passengers were acceptable levels. [ABSTRACT FROM AUTHOR]