BEE-L:
 
With regard to propolis, its composition, properties, and lead:
 
Propolis is a very complex material.  Its composition varies with
locality, time of year, plants surrounding apiary, etc.  Its
anti-bacterial and ability to suppress microbial pathogens affecting
humans is well known.  What the exact ingredients are, and whether these
properties are something in the propolis that the bee introduces
(modifies, etc.) or something in the resin that the plants produce is
still hotly debated.  In Montana, one medical Dr. has had success
treating venereal warts with a tincture of propolis.  Apparently, the
patients report that the tincture doesn't burn and sting as bad as some
of the more conventional medicines.
 
The daughter of the former Head of our Microbiology Dept won a state-wide
Science fair for her demonstration of the action of propolis against
microbes.
 
As for lead in the propolis and bees collecting caulking, etc.   We
specialize in using bees as monitors of contaminants in the environment.
Bees have evolved to be highly efficient scavangers.  Unfortunately, they
are not always as discriminating as they should be.
 
The good news is that the honey remains surprisingly "clean".  Our
friends at Cornell and other places have found pollutants in honey, but
usually at levels considerably below those of bees, pollen, propolis, etc.
Having said this, I should note that there are exceptions - but it would
take me many pages to cover this whole area of discussion.
 
Basically, the forager bees pick up and sample everything in their
surroundings - water, air, soil, vegetation, etc.  In spite of what you
might think, vegetation is not necessarily the primary route of entry of
contaminants into the beehive.  Many gaseous and particulate materials
are taken up by the bees directly from the air.  My working hypothesis is
that they are miniature, flying, electro-static dust mops.
 
Some contaminants get into the hive with the water used to evaporatively
cool the hive.
 
The health food folks won't like this next bit of information.  Pollen
can be a major contributor of particulate contaminants to the hive.  One
can see the particules of dust, including things like lead, mixed with
the pollen grains.  We have analyzed pollen from industrial areas that
has had as much as 18 ppm arsenic (dry weight of pollen), 90 ppm of lead,
and 7 ppm cadmium, not to mention high levels of copper and zinc.  Not
something I would like to eat on a regular basis.
 
Most pollen is okay, but think of it like a wet, sticky lollipop and you
will begin to appreciate why it can be so "dirty".
 
Our local pollen marketing firm has me periodically analyze their pollen
to certify its purity and they make an effort not to purchase pollen from
beekeepers located in industrial areas.
 
Unfortunately for the bee, it is the bee itself that often sustains the
highest exposure to chemicals (ranging from radionuclides to toxic metals
to pesticides to more exotic organic chemicals such as PCBs).
 
These  chemicals can and do harm bees and colonies.  However, they mostly
act as additional stressors which can sap the strength of the colony and
make it more vulnerable to other stressors such as poor diet, poor
management, and maybe things such as mites - the topic of our current
research.
 
Ok, as per the lead.  Yes, scapings from metal excluders, paint, etc. can
be a source of metal contamination.  For example, the old zinc coated
extractors for processing honey can be a significant contributor of zinc
into honey.  Beekeepers have to take responsibility for maintaining a
pure product.  Sloppy practices can easily undo what the bees try to do -
that is I assume the bees try to produce a pure product, for their own
well-being.  They sometimes miss the mark because lots of the junk we
produce wasn't around when they evolved their foraging behavior.
 
I suspect the reports of lead in propolis could be due to one or more of
the following:
 
lead in paint, solder joints, other hive components
lead in the environment from automobiles, smelters, mining, industry
lead in the resin used to make propolis
 
Contaminants in plants may be a result of uptake from soil, water, or
air.  Much of what we see passed on to the bees is aerially deposited on
the surfaces of leaves, etc.  Some probably is moved systemically up
through the plant from roots or in through leaf surfaces.
 
My guess is that one of the most likely sources of lead in hive products
is automobile exhausts.  We have seen this time and again near highways
and heavily travelled roads.  In one case, we even saw the levels
increase over a single weekend as a result of increased holiday traffic
going down a highway near an apiary -  and that highway was in Montana
where all of the cars in the state at one time hardly compares to the
traffic on a highway in some of our larger urban areas.
 
We certainly saw a lot of lead in Seattle and reported this in an article
in Science in 1985.
 
I hope the above answers some questions.  For some, it may open the door
to many more.
 
Our take home messages are:
 
1.  Bees are incredible samplers of contaminants in their surroundings
and serve as mult-media samplers that average the concentrations of
pollutants over time and large spatial areas.  Bees sample contaminants
in all forms - gaseous, liquid, particulate.
 
2.  Most of the contamination (at least as indicated by the
concentrations) ends up in the bees and pollen.  Some chemicals
concentrate in wax, especially the lipophillic ones.
 
3.  Except for tritium as some other special cases, levels in honey will
be an order of magnitude or lower than those in bees, pollen, and some
wax samples.
 
4.  Propolis, like wax, can contain high levels of contaminants, but due
to the complex composition, timing, locality, etc.  the levels tend of
any contaminants often change dramatically from one date to the next -
much more than we tend to see in bees or pollen.
 
5.  Levels of junk in honey tend to be so low as to not be of concern
with respect to human health and are as good or better than most food
products.
 
6.  Beekeepers are the first line of prevention.
 
7.  Given the ability of bees to pull garbage out of the environment and
bring it back to the hive, putting untested chemicals into hives (for
example to try to control mites) poses a very serious risk of
contamination of the hive and the products in it.
 
8.  Bees can detect chemicals in their surroundings at levels often
difficult if not impossible to detect using more conventional approaches
- i.e., instrumentation.
 
9.  Beekeepers should take the attitude that this is a valuable new
service that they can provide (bee watch) - note something that might
jeopardize their business.
 
10. Public reception and support of this concept has been good.  It makes
sense and people generally like bees - at least the European ones that
get good press.
 
11. Don't collect and consume pollen in industrial areas, near highways,
by chemical plants, or under your local nuclear reactor.
 
12. Support your bee industry by buying honey - still one of natures best
products.
 
Cheers
 
Jerry Bromenshenk
The University of Montana
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