Yom Kippur (Day of Atonement) has a reputation for air pollution “celebration” day in Israel, as for 25hr there is no traffic, industry and the country goes into silence.
There is indeed a significant reduction in emissions of pollutants from transportation and industry: 95% -80% of the concentrations of nitrogen oxides drops immediately in the beginning of the day.
But there are pollutants that aren’t emitted directly from manufacturing or transportation, but influenced from the concentration of other pollutants in the air like nitrogen oxides . These pollutants are called “secondary pollutants”, means pollutants generated from other air pollutants.
The most famous secondary pollutant in Israel and in various countries such as the United States is the ozone gas (yes, the same gas that protects us up there, is a little dangerous down here, and in fact constitutes a significant health risk …).
Ozone is heavily influenced by the concentrations of nitrogen oxides. Extreme drop in nitrogen oxide concentrations may actually lead to an increase in the concentration of ozone in the air we breathe.
This phenomenon has been extensively studied in recent years throughout the Western world and has received the nickname “the weekend effect”, since studies have shown that globally weekends in cities, where emissions of vehicles is lower, higher ozone concentrations are measured.
Since Yom Kippur is even more extreme in reducing concentrations of nitrogen oxides, there are many areas with high concentrations of ozone, just like a normal day at least!
Using BreezoMeter platform, which analyzes air pollution levels, we could see how last Yom Kippur ozone levels, in 2013, appeared in major cities in Israel. The results – weekend effect indeed: Moderate air quality levels was seen in Gush Etzion, Kiryat Tivon, Afula, Haifa, Modi’in, Givatayim and more. In fact, ozone levels were pretty similar both in trends throughout the day and in concentration.
Will we see it this year? It is very possible. But do not be alarmed, now that you know in advance, you should just have fun with the kids at home during noon…
Do not believe? We made some real graphs of engineers for you!