Well, I'm impressed they actually did test JUST the vape liquid, even though they're still calling them e-cigs.

Quoting from the journal itself:

There were no significant differences in changes of BAL inflammatory cell counts or cytokines between baseline and follow-up, comparing the control and e-cig groups. However, in the intervention but not the control group, change in urinary PG as a marker of e-cig use and inhalation was significantly correlated with change in cell counts (cell concentrations, macrophages, and lymphocytes) and cytokines (IL8, IL13, and TNFα), although the absolute magnitude of changes was small. There were no significant changes in mRNA or miRNA gene expression. Although limited by study size and duration, this is the first experimental demonstration of an impact of e-cig use on inflammation in the human lung among never-smokers.

The way I read this, it seems like there's a small correlation with inflammation, but there's no measurable risk of developing lung cancer from it (they were doing cancer research after all). Personally for an adult, I feel like "inflammation" is kind of a nothingburger, just stop vaping for a while and you'll be fine. But for kids developing habits, I can understand the concern.