Reduced commuter exposure to PM2.5 and PAHs in response to improved emission standards in bus rapid transit systems in Mexico

Long-term effects of PM2.5 constituents on childhood attention deficit hyperactivity disorder: evidence from a large population-based study in the Pearl River Delta Region, China

BACKGROUND

Evidence linking fine particulate matter (PM2.5) constituents to childhood attention deficit hyperactivity disorder (ADHD) was limited.

OBJECTIVES

To investigate the individual and joint effects of exposure to PM2.5 constituents on ADHD.

METHODS

We conducted a large population-based survey involving 110,818 school children aged 6-18 years across six cities in the Pearl River Delta region, China. The three-year average concentrations of PM2.5 constituents (black carbon (BC), organic matter (OM), sulfate, nitrate, and ammonium) were estimated using the ChinaHighAirPollutants dataset. Parents completed an ADHD checklist using the Diagnostic and Statistical Manual of Mental Disorders-IV criteria. The individual and joint associations between PM2.5 components and ADHD were estimated using generalized linear mixed models and the quantile g-computation regression model, respectively.

RESULTS

The exposure-response relationships between PM2.5 constituents and ADHD primarily exhibited a nonlinear pattern. Compared with the lowest tertile, the highest tertiles of PM2.5 and its components were linked to greater odds for ADHD (e.g., the adjusted odds ratio (OR) was 1.37 (95 % confidential interval (CI): 1.27, 1.47) for PM2.5, 1.51 (95 %CI: 1.40, 1.63) for OM, 1.29 (95 %CI: 1.20, 1.39) for BC, and 1.20 (95 %CI:1.08, 1.34) for sulfate). Similar positive associations were observed between BC and sulfate exposure and ADHD subtypes. Moreover, joint exposure to PM2.5 components was associated with ADHD (OR = 1.14, 95 % CI:1.10, 1.18), with OM and BC contributing more to the observed associations.

CONCLUSIONS

These findings highlight the varying contributions of PM2.5 constituents to ADHD and underscore the importance of reducing specific PM2.5 component emissions to mitigate the burden of PM2.5-associated neurodevelopmental diseases.

A first screening of black carbon concentrations whilst commuting by diesel-fuelled buses in Montevideo, Uruguay

Urban bus commuters are exposed to a range of traffic-related air pollutants, including black carbon (BC) particles, a major hazardous component of vehicle exhaust emissions. This study provides the first assessment of in-cabin BC concentrations aboard diesel-fuelled public buses in Montevideo, Uruguay. Our objective was to assess BC concentrations during evening peak commuting hours and to examine how specific traffic elements, such as bus stops, traffic lights and traffic volume, influence exposure levels. We implemented a structured sampling strategy to maximise the reliability of our findings by collecting data during four consecutive weekdays within the same timeframe (17:00-18:00 h) in May 2019. We measured BC concentrations at a high-frequency sampling rate using a handheld aethalometer, focusing on two bus routes. The mean in-cabin BC concentration was 14.28 ± 14.38 μg m⁻³, with considerable spatial variability. Notably, BC concentrations were significantly higher at traffic lights and bus stops, where stop-and-go driving patterns and idling contribute to increased emissions, while the constant opening and closing of doors allows outside air to infiltrate. We found a positive trend between traffic volume and median BC concentrations, consistent with previous studies conducted in other cities. Compared to similar studies in South America, BC concentrations were found to be intermediate, but considerably higher than those observed in North American and European cities. This study underscores the importance of implementing targeted interventions in urban transport policies, specifically addressing congestion points, like bus stops and traffic lights, to effectively reduce commuter exposure to harmful air pollutants. Whilst our study focused on Montevideo, interventions to combat traffic-related air pollutants should be expanded across Latin American cities, where reliance on diesel-powered public transportation remains prevalent.

Migration patterns and health risk assessment of polycyclic aromatic compounds in typical coal fire source

The Wuda coal fire in Inner Mongolia, China, is a global catastrophic event. It emits a huge volume of organic pollutants, including polycyclic aromatic compounds (PACs), which are widely concerning due to their physiological toxicity and environmental persistence. However, there is no systematic study on the enrichment and migration patterns of PACs emitted from coal fires. Here, we compared samples from coal fire sponges and surrounding soil, and analyzed 47 PACs using GC × GC-TOFMS. Data analysis showed that the average content of 16 polycyclic aromatic hydrocarbons (16PAHs) in the coal fire sponge was 15400.65 ng/g, which is about 4.2 times higher than that in the surrounding soil. Meanwhile, 31 PACs were detected at levels far exceeding those of 16PAHs. The distribution pattern of PACs showed that coal fire sources are more likely to produce and store 16PAHs while surrounding soils are more likely to be enriched with PAH derivatives. The cancer risk assessment revealed a significant cancer risk in both the coal fires and the surrounding soil. The formation mechanism of oxygenated PAHs was also explored, and it was found that coal fires emit 16PAHs and alkylated PAHs, which oxidize to form oxygenated PAHs during migration to surrounding soils. The value of naphthaldehyde/alkylated naphthalene (< 2) can be referenced as characteristic markers of coal fire pollution. This provides a new perspective on the sources of PACs in the current environment.