The dawn of pollution
A walk in pre-sunrise hours may increase chances of asthma
health enthusiasts living near freeways should minimize their outdoor exercise timings during the early morning hours; they should also keep their windows closed through the night. A team of environmental health scientists found the levels of air pollution to be really high during the pre-sunrise hours in the Interstate 10 freeway in Santa Monica, California.
Researchers from the University of California, Los Angeles and California Air Resources Board equipped an electric vehicle with no emissions of its own, with instruments to measure gaseous and particulate air pollutants, a global positioning system, video monitor and instruments to measure temperature and winds. For pre-sunrise measurement, the vehicle was driven on a fixed route over two days in the summer and three days in the winter of 2008 between 4 and 7 am. Covering a distance of 3,600 m this route passed through a dense residential neighbourhood below the freeway. Air pollutant concentrations were also measured on the freeway and streets transecting the route.
During pre-sunrise hours, the traffic volume was found to be 30 to 80 per cent lower compared to the morning or afternoon hours. However, the ultrafine particle concentrations were significan tly higher. This, the key researcher Shishan Hu explained, was due to unique meteorological conditions that exist in dawn.
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