Researchers Tune In to Bee Hives To Get the Buzz on Air Pollutants
Insects' daily sorties give scientists the scoop on toxic chemicals
For Jerry Bromenshenk and his colleagues, a summer's day isn't complete without a look at what the honey bees dragged into the hive - a touch of pollen, some nectar, a dash of water or dust, and perhaps some perchloroethylene, a dry-cleaning solvent.
Flying daily sorties at the US Army's Aberdeen Proving Ground in Maryland, hundreds of thousands of bees are part of an experimental system that uses the buzzing insects as living "sentinels" to provide early warning of toxic-chemical leaks.
Special high-tech hives allow the University of Montana research team to monitor hive activity moment by moment for signs of stress on the bees. Once such signs are detected, the team can analyze pollen and air samples from the hives to identify the offending chemicals without ever disturbing the insects.
In effect, the system turns the bees into tiny lab assistants who constantly sample the environment within a half-mile radius of the hives and return their "samples" for analysis.
Beyond their role as living pollution detectors, the researchers say, the bees are providing a vital reference point for computer models that try to determine the impact of pollutants on the food chain.
The general concept of using bees as the "king's tasters" has been around for years, says Dr. Bromenshenk, an entomologist. Groups like the National Academy of Science's National Research Council and the US Environmental Protection Agency have noted that bees make excellent air-quality monitors.
Bees' big advantage
Los Alamos National Laboratory in New Mexico has "routinely used bees to monitor its hazardous-waste burial sites," he says. But such approaches either require that the bees go belly up to signal a problem, or that they be captured and killed in order to analyze the pollutants that may be trapped in their tissue.
This fails to take advantage of the bees' big advantage: They bring home more "souvenirs" from their travels than an overeager tourist, according to Garon Smith, a University of Montana chemistry professor working with Bromenshenk.
"Bees are probably the only organism out there in huge numbers, that get into everything, and that return to a central convenient location," he says. They use water to cool their hives and control the viscosity of wax and honey, they forage on plants, and their body hairs exhibit a small-scale version of static cling, attracting and holding airborne pollen and dust.
In 1982, Bromenshenk and colleagues from the Department of Energy's Pacific Northwest Laboratory in Richland, Wash., used honey bees to map the distribution of arsenic, cadmium, and fluoride concentrations around Puget Sound. Their maps closely matched those drawn by state and local agencies using soil and vegetation samples.
As encouraging as the results were in showing that bees were cost-effective pollution monitors over a wide area, Bromenshenk wasn't satisfied. Gathering samples was labor intensive, too infrequent for effective early warning, too invasive of the hives, and fatal for the hapless bees selected for tissue analysis.
"We were not doing diagnostic studies" of a region, he recalls. "We were doing autopsies."
The set-up at Aberdeen, by contrast, represents "a real leap forward," Bromenshenk says.
Infrared detectors at the hive entrances monitor the insects' comings and goings down to the bee - a much more accurate way to track changes in a hive's population than counting the bodies of dead or diseased bees that the hive's housekeeping bees eject. Sensors monitor a hive's internal temperature, which tracks the reproductive health of a colony.
A 'real time' alarm
Monitored via computers from the comfort of an office, unusual changes in these data provide the "real time" alarm that something may be wrong, Dr. Smith says. Using that information, technicians can head to the affected hives. There they can activate small pumps to draw air from inside the hive. These samples can be analyzed for volatile compounds in about 25 minutes, he says.
Meanwhile, small screens at the hive entrance scrape pollen and other residue from the forager bees as they enter the hive. Collected in trays at the hive, this material can be analyzed for chemical contamination or compared with vegetation maps to determine where the bees have been. Ultimately, he says, the Montana team hopes to be able to so closely correlate specific changes in bee behaviors with specific chemical compounds that monitoring and analysis can be full automated.
Tom Shedd, program manager for the five-year, $800,000 project at Aberdeen and a research biologist at the US Army's Center for Environmental Health Research at Fort Detrick, Md., notes that using the insects is not the be-all and end-all for pollution detection and tracking.
But the approaches the Montana team is taking are so cost-effective compared with alternatives that the Defense Depart- ment is looking to adopt them at its facilities worldwide.