Scientists at the Empa Research Institute say it’s due to industry shutdown - as well as less air travel.
The study began in mid-March as the country went into lockdown - and shows levels of nitrogen dioxide and nitrogen oxide have decreased by up to 50% in some areas of the country.
The most significant reductions were in Lugano, Bern and Lausanne.
Some areas of the country didn’t fare so well.
Levels actually went up in Beromünster, Luzern - but researchers believe that may be due to weather conditions rather than an increase in emissions.