First: The CSIC guys use the picogram as their measure unit. This fun word corresponds to one billionth of a gram. One billionth. Frankly if CSIC analyses the air they could probably find a picogram of kryptonite.
Second: Research has been conducted in areas next to drug supermarkets or directly inside abandoned buildings used by the most sordid junkies. Great. So it's like going to Burger King and declaring that there are some picograms of Whopper in the air.
Last and certainly not least: Research reveals that drug consumption is at its highest on weekends. Bravo! Did we need an investigation and our tax money to discover that?