We looked at uptake, transport, partitioning, and fate of a wide variety of inorganic and organic chemicals into honey bee colonies from 1974 till the current time.  In the 70s and 80s, EPA and DOE funded our work on using bees as sentinels and monitors for hazardous substances -and in the 90s we added harmful biological agents for DoD.

Simply stated, wax is a sink - all kinds of things end  up in wax, and some may persist for years or decades.  How does it get there?  Via numerous routes - directly from hive atmospheres (gaseous materials and fine particulates), from the bees themselves, from water, from nectar, from propolis.  Some contaminants sorb onto the surface of the bee body; a combination of electrostatic charge levels on the bee and particle size play a role - we've published models of this.

Chemical uptake into the hive and colony components can be very fast - in heavy metal laden areas near heavy industry, bee colonies moved onto a polluted site quickly change in terms of residues levels so fast that we couldn't really track the change - we expected it to take days, and thought we were being conservation by sampling hourly, but within a half day or less, the new colonies (hours of exposure) closely resembled the resident colonies (weeks of exposures).

A major pathway of entry and transfer was from foragers, especially pollen gatherers, to nurse bees, and into the brood nest. 

Contaminated wax is dynamic - partitioning can go both ways.  Wax has some benefits for pollution monitoring (whether industrial, urban, agrichemical, etc.) and some big downsides.  The plus is that wax can retain stable chemicals like metals and some organics for years, providing an historical (retrospective) viewpoint.  But, when that chemical came into the hive is hard to determine - last week, last month, last year, last decade?  Also, comb is EXTREMELY variable in terms of chemical dispersion across the comb surfaces and in cells.  Bees use cells over and over, and what's in any cell varies from week to week - brood, pollen, nectar, empty.  There are always sampling chemical HOT SPOTS in comb.  A few cells may have an extreme outlier value - this is a reason researchers shouldn't just publish the 95% outliers - ask instead what was the mean, mode, how many samples were outliers, what was the overall distribution of values - were the concentrations normally distributed or were they skewed?  I've often found a pocket of a few cells that are extreme outliers, clearly not representative of any comb in the hive.

We found it best to sample lots of places on combs and/or several combs, or often better, process whole combs for analysis, if you really want to get a profile of the chemical concentrations.

But sampling problems  and concentration values are even worse than  just differential concentrations over any comb.  The levels and chemicals can change from comb to comb - think about comb age and comb usage, and rotation, moving of combs by beekeepers.  Brood combs are different than honey combs.  Old versus new comb, bottom versus top of the hive, it all changes.

The most interesting data was that bees move wax.  When they need lots of comb fast, such as in the middle of a honey flow, they may harvest wax from new comb being drawn out and use it on old comb to rebuild, repair, or draw cells out deeper.  So, old contaminated comb may get a bit cleaner from dilution with newer wax (and  loss of contaminant is not necessarily going into the brood, although some may be) as a result of this reconstruction.  And, new drawn comb itself can disappear or be undrawn.  In the brood nest, the lining and re-lining of  brood cells, that most members of Bee-L know  can seal in biological agents like spores from foul brood, may help seal off some of the contaminants, but as with spores that can survive for years, at some time, as cells get smaller, the bees may decide to tear down and rebuild - releasing both pathogens and chemicals.  And then if you've got an intermittent exposure source, like emissions from a smokestack during an inversion or an incident like planting dust or chemigation, you can get a rapid influx of chemical into a colony, the hive, and wax.  So, keep track of time of year, weather, and what's going on in the surroundings.

For environmental monitoring, we concluded that the only valid way to use wax for monitoring was to use wax of a known source, chemistry, and age.  Old comb is nearly impossible to interpret - hot spots, age, stage of rebuild, partitioning, its just a messy system.  What is representative of true  values of exposure to bees?  How to sample, how to deal with the  huge variability, where and when did it get contaminated? - mostly unanswerable.  At best, a measured concentration of something says  at some time, the comb was exposed to x,y, z chemical.

About the only way comb and wax can realistically be used to assess the ebb and flow of chemicals into and out of wax is by starting the experiment with clean (chemically analyzed) wax, inserted into the hive on a known and recorded date.  Sometimes we used full foundation sheets, sometimes we use  wax foundation strips.  These then become the sampling matrix, a sort of trap, that will pick up things being brought in as well as some transfer of materials already resident  in the hive (from bees, from older comb).  Its generally cost prohibitive to start with all new comb, but if you are looking at wax contamination during a specific window of time, at least use new, clean wax.  It will get 'dirty' soon enough.

J.J. Bromenshenk
Bee Alert
Missoula, Mt



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