Study shows Yom Kippur’s empty roads make for cleaner air

New research finds an immediate drop in air pollution when Israelis mark the calendar’s most solemn day

Israelis riding their bikes on the empty streets of Jerusalem on Yom Kippur. (Yonatan Sindel/Flash90)
Israelis riding their bikes on the empty streets of Jerusalem on Yom Kippur. (Yonatan Sindel/Flash90)

Israelis have long suspected that Yom Kippur is good not only for the soul, but for the environment — and now there is scientific proof. A new study by a researcher at the Technion shows that pollution levels throughout the country, and especially in the Tel Aviv area, fall significantly during the 25-hour period from the beginning of Yom Kippur, through the end of the fast.

The study, by Dr. Ilan Levy of the Technion’s Civil and Environmental Engineering, gives scientific credence to a phenomenon that has been studied only partially in the past. Israelis, especially those who live in the crowded center of the country, are right when they say that the air feels cleaner on Yom Kippur. The study, published in the latest edition of the scientific journal Atmospheric Environment, was also detailed by Brian of London, a Times of Israel blogger.

Few, if any, Israelis drive their cars on Yom Kippur, especially in large cities. For those not attending services in synagogue, the preferred method of transportation is biking (many of those bike riders aren’t eating; recent polls show that close to 60% of Israelis fast on the Day of Atonement). The bottom line is that the biggest source of air pollution, the exhaust generated by vehicles, disappears for the day.

According to Levy’s study, the impact on pollution levels is almost immediate. Levels of nitrogen oxide (the building block of smog) drop by 83–98% at different sites in the Tel Aviv area, ozone levels fall significantly, and nitrogen dioxide levels fall as well. The research takes 15 years’ worth of pollution data and analyzes it in order to come to its conclusions.

Yom Kippur’s arrival eliminates a great deal of primary pollution (besides cars, factories come to a halt as well, so smokestacks that usually belch pollutants into the air — except for those of the Israel Electric Company — are offline), although secondary pollution — the interaction of pollutants already in the atmosphere with other elements, including sunlight — can actually rise slightly, the paper shows.

Ilan Levy and family (photo credit: Courtesy the Technion)
Dr. Ilan Levy and family (photo credit: Courtesy Technion)

“The policy implications of this study are substantial,” Levy stated in the research, detailing how the Yom Kippur effect could impact the environment if replicated on other days of the year. “A change in vehicle fleet to low-emission vehicles will have a major impact on both primary and secondary pollution levels over large regions, while possibly increasing secondary pollution levels at the urban core. The health benefits associated with the large regional changes are expected to be far greater than the costs of increase in secondary pollutants (i.e., ozone) at the congested urban core. Moreover, the low levels of primary pollutants will benefit not only populations at risk (i.e., young children, the elderly and people with existing respiratory or cardiovascular conditions) but also the entire population,” Levy added.

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