Honey bees don’t just bring home nectar — they also bring home pollution, making honey an excellent indicator of environmental contamination
As I stir a teaspoon of honey into my coffee, I humbly dwell on the effort that went into creating that sweet spoonful. How many bees touched that nectar? How many flowers? Across what distance? Some estimates say it takes the equivalent of one worker bee’s whole life to collect that teaspoon, and around 30,000 floral visits to sites several kilometers away. It turns out there’s even more than just honey in that jar, too. There are also trace amounts of lead, copper, cadmium, and other metals, which can all tell us a story of environmental pollution and where it’s coming from. And with the rising popularity of urban beekeeping, urban gardens, and citizen science initiatives, metropolitan hives are becoming ideal environmental monitoring stations.
Kate Smith (a PhD candidate at the University of British Columbia, Vancouver), her advisor (Dr. Dominique Weis), and their colleagues have analyzed four years’ worth of honey from hives throughout Metro Vancouver for this very reason. Smith is in the geological sciences program and has a background in analytical chemistry, studying rocks and other non-living environmental samples, so honey bees are quite a diversion for her. But she and Weis realized early on that they could capitalize on honey bees’ incessant foraging. They recently published the results of their city honey study in Nature Sustainability,1 where they describe how their honey analyses are letting them learn more about urban pollution, including what pollutants exist in our cities, where it’s all coming from, and if it’s building up over time.
Vancouver, which is also where I have lived for the last ten years, is a bustling city and a major Canadian port. Ships arrive in Vancouver to offload cargo from all over the world, and there is a major train station downtown (the western end of the Trans-Canadian Railway). There are also nearby agricultural operations and isolated, pristine islands, making it a great place to compare pollution from different industrial sectors within a relatively small region.
Most chemical analyses of honey interrogate it for agrochemicals and hive treatments — pesticides, fungicides, and miticides, for example — or markers for authenticity (to distinguish real honey from ‘fake’ honey). But Smith and Weis are taking a different angle: They want to see what honey can tell us about pollution, not necessarily for the sake of honey bee health, but for our own, and for keeping tabs on our environmental footprint. They focus on metals because these substances are very stable over time and are indicative of many types of urban pollution. For example, vanadium (chemical symbol V) is released from oils burned by cargo ships. Antimony (Sb) comes from wear and tear on vehicle brakes. Cadmium (Cd) is emitted from metal refineries. Copper (Cu) and manganese (Mn) leach from agricultural pesticides. The list goes on. All of these metals, and many more, make up the urban chemosphere that we live and breathe every day.
Honey bees, as they flit from flower to flower, collect tiny environmental samples which collectively contain the pollution fingerprint of the region. “Honey bees fly through the air, drink water, land on soil and surfaces, and of course, interact with vegetation when they forage,” Smith explains. “As a result, the honey they produce can provide a geochemical snapshot of each hive’s immediate surroundings.”
Smith and Weis teamed up with a non-profit organization, Hives for Humanity, to sample colonies throughout Metro Vancouver, and analyzed the honey for metallic traces. Their union with the non-profit group grew organically from an initial collaboration initiated by Julia Common, the co-founder of Hives for Humanity, who wanted to test their honey for contaminants. People started worrying that honey from Hives for Humanity, whose colonies are worked by homeless people in Vancouver’s Downtown Eastside as part of a social empowerment program,2 might not be safe for consumption. Weis used her analytical techniques to demonstrate that this was a false accusation, but when this project ended, the partnership stuck. Since Hives for Humanity has apiaries all over the city, it was a great opportunity to begin their pollution mapping project.
Since 2014, Common sampled hives at the different locations, near different industrial sectors, banking the honey samples until Smith arrived from Wisconsin to begin her studies. Common would systematically examine frames of comb, finding patches of freshly capped honey, then sample it with what looks like a wooden popsicle stick and a small vial. The laboratory analytical methods are so sensitive, she can’t even scoop the honey with metal utensils for fear of contaminating it with metal traces. Smith joined the team in 2017 and they continued sampling in this way throughout that year, so they could see if their measurements were remaining stable over time.
Smith and Weis focused most of their analyses on lead (Pb), mainly because of public health concerns and an abundance of anthropogenic sources (that is, pollution originating from human activity). Lead is a toxic metal and gets into the environment from old paint, roadway construction, cosmetics, and plumbing. The word ‘plumbing’ is even derived from plumbum, which is the ….