What’s in your honey? It depends where it came from

Jar of honey with a wooden honey dripper on a table Photo by showcake

It turns out fingers (and Pooh’s paws) aren’t the only things that stick to honey. A new study employing urban beekeeping in Vancouver shows how honey is a simple and accurate indicator of urban pollution, and how beehives in rural and remote areas can provide valuable background readings on industrial pollutants.

The study, “Honey As a Biomonitor for a Changing World,” published in Nature Sustainability, underscores the value of honey as a tool for tracking changes and disparities in pollutants between different geographical areas. The lead author, Kate E. Smith, is a doctoral candidate of Dominique Weis at the Pacific Centre for Isotopic and Geochemical Research in the University of British Columbia’s Department of Earth, Ocean, and Atmospheric Sciences. Working in collaboration with the community organization Hives for Humanity, the study gathered honey directly from hives in six areas of Vancouver to investigate the potential presence of pollutants from urban, industrial, residential, and agricultural areas.

Honey is an ideal pollutant trap because worker bees only forage for pollen on average about three kilometres from the hive, allowing researchers not only to identify individual pollutants but to also be confident that their source is highly local. While foraging, the bees inadvertently gather pollutants from pollen as well as airborne particulates they happen to pick up in their travels. The study employed hives at Galiano and Bowen Islands to provide comparison with the urban samples. It also used samples from tree rings taken from a western hemlock and a western red cedar that were uprooted in a storm in Stanley Park in the winter of 2006-07.

The researchers were looking for metals such as iron, copper, manganese, and zinc, which can all be toxic, and, especially, lead. Measuring trace metals in honey has been done for decades; what made this study unique is that the researchers used isotope analysis to show that lead in honey from downtown Vancouver was from anthropogenic—human—sources rather than from natural ones. The data for hives in the greater Vancouver study area also showed relatively higher concentrations of trace metals there than for Galiano and Bowen.

The authors stress that the pollutants did not appear at dangerous levels for honey consumers. The lead levels in downtown Vancouver were very low, compared to the worldwide average of lead in honey. An adult would have to eat more than 600 grams of honey a day from Vancouver hives to exceed the U.S. Food and Drug Administration’s guidelines for a tolerable intake of lead. As well, metals that are nutritionally essential (such as copper, zinc, iron, and manganese) were not present at a toxic level.

The fact that lead in the honey samples in downtown Vancouver hives had a unique isotopic composition, compared to that of those found in rural honey, pointed to an anthropogenic source. More research is needed, but the study suggests that the lead could be coming from a combination of diesel exhaust from cars and trucks, power station fuels, and marine industrial sources such as fuel oils, paints, and exhaust from around the port of Vancouver.

Beyond the insights the study provides into urban pollutants in Vancouver, it underscores the value of beekeeping in “citizen science,” and points to potential opportunities for hive owners in rural and remote areas like cottage country to participate in other research. As this study advises, “Honey sampling is low cost and metal free, requiring minimal training and no expensive equipment. Honey can be collected using a ‘citizen science’ approach where community members volunteer samples of their own backyard or rooftop apiary products to assess environmental conditions in addition to satisfying their own scientific curiosity—a model that has proven successful in this study and elsewhere.” One of the benefits of the citizen science in this study was that the collaborator, Hives for Humanity, trains people who were once part of Vancouver’s homeless or otherwise marginalized communities in apiary management.

“We were looking for particular anthropogenic industrial activity, in an urban setting,” says Kate Smith. But hives in rural or remote areas are useful study subjects too. They can provide background readings of pollutants for urban studies such as the Vancouver one, and Smith notes that they have sampled hives as far away as Lillooet. These hives outside urban areas can also be used to detect and monitor pollution from non-urban sources. “In rural settings,” Smith points out, “previous studies have used bees as sentinels of the improper use of pesticides.”

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