I'm a little confused - can someone knowledgable in the area help out? In the introduction they assert:

"Once inhaled, ultrafine particles and the oxidant species located on their surface can translocate into the vascular space (13), resulting in a state of chronic vascular inflammation and oxidative stress noxious to endothelial function."

However in the conclusion they state:

"Inhaling nicotine-free electronic cigarette aerosol transiently impacted endothelial function in healthy nonsmokers"

It sounds like in the introduction they are aware of studies that concluded the aerosol inhalation causes chronic issues with endothelial function, but they concluded that it only has a transient effect. Are they refuting those claims? Did I miss something?