There was a study last year that analysed diacetyl concentrations in common e-liquids. They found that 47% of 159 preparations examined were above the safety gu

There was a study last year that analysed diacetyl concentrations in common e-liquids. They found that 47% of 159 preparations examined were above the safety guidelines for daily consumption >The median daily exposure levels were 56 μg/day ... They were slightly lower than the strict NIOSH-defined safety limits for occupational exposure ... however, 47.3% of DA and 41.5% of AP-containing samples exposed consumers to levels higher than the safety limits. http://ntr.oxfordjournals.org/content/early/2014/09/23/ntr.ntu176 http://ntr.oxfordjournals.org/content/early/2014/09/23/ntr.n... Compared to this recent study, this shows that addition of diacetyl and in what concentration is decreasing.