The impacts of air quality and secondary organic aerosols formation on traffic accidents in heavy fog-haze weather.

This study estimated changes in the levels of three components of regional haze, namely fine particulate matter (PM2.5), relative humidity (RH), and secondary organic aerosols (SOAs), at the time of two severe traffic accidents on a coastal expressway and a freeway in the Jianan Plain in southwestern Taiwan to understand the impact of weather and air quality factors on the low visibility. Monitoring data and surveillance images from four nearby air quality monitoring stations were collected to determine the precise causes of the poor visibility-related accidents. The study applied a haze extraction method to the images to achieve demisting, and the processed data were used to assess the relationship between the haze components and visibility during the accidents. The correlation between visibility and the haze components was assessed. The results revealed that the RH levels dropped significantly at the time of the accidents, signifying that moisture was not the main haze-fog component. The haze components can be ordered as follows in terms of their correlation with (and thus effect on) local visibility: PM2.5 > SOAs > RH. The spatial distributions and evolutions of the three components indicated that the PM2.5 concentrations remained high from midnight until early morning but decreased slightly at the time of both accidents. By contrast, the concentration of ultrafine SOA particles, which can scatter and absorb light to reduce road visibility, increased rapidly before both accidents. Therefore, PM2.5 and SOAs were two non-negligible factors of low visibility during the accidents, especially SOAs.

Appraisal of regional haze event and its relationship with PM2.5 concentration, crop residue burning and meteorology in Chandigarh, India.

Air pollution affects not only the air quality in megacities but also in medium and small-sized cities due to rapid urbanization, industrialization, and other anthropogenic activities. From October 28, 2015 to November 3, 2015, the Indo-Gangetic Plains region, including Chandigarh encountered an episode of poor visibility during the daytime. The daily average PM2.5 concentration reached 191 µg/m3, and visibility reduced by ∼2.2 times in the Chandigarh region. PM2.5 concentration was found around 4 times higher than a non-haze day and more than 3 times higher than National Ambient Air Quality Standards for 24 h. A significant correlation between PM2.5 and CO (r: 0.87) during the haze period indicated similarity in their emission sources; which was attributed to the burning of solid organic matter. Further, satellite data and back-trajectory analysis of air masses showed large-scale rice stubble burning in the agricultural fields, adjoining to the city areas. The transboundary movement of air masses below 500 m and meteorological conditions played a major role in building the pollution load in the Chandigarh region. Moreover, the enhanced concentration of biomass burning tracers, i.e., organic carbon (∼3.8 times) and K+ ions (2∼ times) in PM2.5 and acetonitrile (∼2.3 times) in ambient air was observed during the haze event. The study demonstrates how regional emissions and meteorological conditions can affect the air quality in a city; which can be useful for proper planning and mitigation policies to minimize high air pollution episodes.

Road traffic crashes at night-time: characteristics and risk factors.

The study was to examine the nature and risk factors associated with road traffic crashes at night in Ghana and identify potential measures to control them. Crash and injury data for the period 2013-2017 were analyzed. The fatality index and fatal crash ratio measures were employed to assess the severity of injuries among traffic participants. Statistical analysis was carried out for the variables using contingency tables and the chi-square (χ2) tests to assess statistical significance. Generally, night-time traffic crashes resulted in severer injury outcomes than crashes in the hours of daylight (χ2(2)=292.7, p < 0.001). The relative risk of death in a night traffic crash was 1.3 times that during the daytime. The risk of death was highest among pedestrians (44%) and motorcyclist (18%) compared to bus/mini-bus occupants (16%) and car occupants (11%) and the observed percentage differences were significant (χ2(14)=2303.2, p < 0.001). Most of the collisions (67%) occurred at the early hours of the night, between 18:00 and 22:00 hours. Poor night visibility coupled with poor visual guidance on roads are the key contributory risk factors associated with night travels. Policies must be geared towards provision of functioning street lights in built-up areas, road line markings, delineators and signage for the highways and arterial roads.