If you didn't read it, why are you criticizing it? Study papers will have a whole methodology section in which they tell you all about the data, the assumptions, the analysis, etc. You can't just go on conclusions without understanding what the conclusions are about.
The abstract was ONE paragraph. It says there were 90 kids who went to the ER in a Mediterranean city (Barcelona). Parent(s) of 85 of the 90 kids also provided hair samples (even druggies will help save their kids' lives sometimes, you know - this is not surprising).