jones_supa (887896) writes "Researchers at Tampere University of Technology, Finland have been surprised of their finding about engine braking creating significant amounts of toxic nanoparticles (Google translation). 'Traffic exhaust fumes carrying nanoparticles are distributed all around where people go. Whether we are indoors or outdoors, there is an exposure to them. According to current knowledge, nanoparticles are the biggest health concern in our environment', tells associate professor Topi Rönkkö from the aerosol physics laboratory. The metal-based particles are released when gasoline injection is stopped during driving when performing engine braking. When they analyzed a heavy diesel engine vehicle rolling downhill with the foot lifted from the gas pedal, the amount of generated toxic particles shot through the roof, even though previous research claims otherwise. This was a surprise also to car manufacturers and oil companies. After the finding, Rönkkö himself cringes driving especially behind large trucks and recommends keeping a good safe distance."