For years the news has been the same: Honey bees are being hammered by some mysterious environmental plague that has a name — colony collapse disorder – but no established cause. A two-year study now provides evidence indicting one likely group of suspects: pesticides. It found “unprecedented levels” of mite-killing chemicals and crop pesticides in hives across the United States and parts of Canada.

Scientists here at the American Chemical Society spring annual meeting, which kicked off today, will report on the findings of this study later in the week. But if you want an early peak at their results, or can’t make it to the meeting, check out a 19-page synopsis of the data that has just been published online in the March PLoS ONE.

In it, Christopher Mullin of Pennsylvania State University in University Park and his colleagues describe widespread pesticide tainting in 749 samples of bee-dom, some of those chemicals at levels that would be toxic if they occurred alone. Except that most bees aren’t exposed to just a single pesticide.

In beeswax, they report, “87 pesticides and metabolites were found with up to 39 different detections in a single sample.” The average number of pesticides identified per wax sample (and they analyzed 259 samples): eight. Among 350 pollen samples retrieved from hives, each harbored an average of seven such chemicals – but at times up to 31 pesticide contaminants (or their breakdown products, some of which are far more toxic to bees than the parent chemical would have been).

Overall, the 140 bees they analyzed tended to be less contaminated. Their bodies contained, on average, a little over two pesticides. At least one poor bug hosted 25.

The researchers have several suspicions why the bees looked cleaner than their dwellings. In some cases, detoxifying systems within the bees might have broken down the chemicals, fostering their excretion. But an even likelier explanation: The sampling focused primarily on live bees extracted from the hives. These tended to be the queens, brood nurses and adolescents – hive residents that aren’t on the chemical frontlines, foraging in pesticide treated fields. Indeed, the fact that researchers found so few healthy worker bees in many of the hives from which they received samples suggests that sickened foragers probably die before they get home.

In fact, some of the pesticides that were detected in hive materials can disorient bees. Which suggests many foragers that had been unwittingly carrying home such contaminants at last become too confused to find their front door.

Mullin’s team didn’t just sample hives clobbered by colony collapse disorder. They also analyzed all aspects of hives and their inhabitants from ostensibly healthy communities of bees as well. And that’s what makes the next stat so troubling. Out of all of those many hundreds of samples analyzed, “Only one of the wax, three pollen and 12 bee samples had no detectable pesticides.”