Urban Honeybees Are Precise Pollution Detectives, Lead Study Finds

Hives are indicators of urban pollution levels.

A new study on pollution reveals that proof isn’t in the pudding — it’s in the honey. Research carried out in partnership between the nonprofit Hives for Humanity and the University of British Columbia showed that honey collected from urban beehives can accurately measure how polluted a city is. This means that honey isn’t just a byproduct of bee regurgitation — it’s also a way to closely monitor changes in the environment.

Writing in Nature Sustainability, the study’s authors explain that this study is the first of its kind in North America. They specifically analyzed honey collected from beehives in six Metro Vancouver neighborhoods — testing for levels of lead, zinc, copper, and other elements. The good news for Vancouver was that the chemical composition of this Canadian honey demonstrated that the city is “extremely clean.” But that doesn’t mean that human influence didn’t affect the honey at all — they found that the closer a hive was to the downtown metro, the higher the chance the hive’s honey contained elevated concentrations of lead, which is toxic at high concentrations.

bee hive
An urban hive in Vancouver.

Honey can act as a snapshot of an environment, namely because bees forage within a one- to two-mile radius around their hive. When pollutants enter an environment, they accumulate in plants — whatever enters soil, air, and water will show up in a plant’s pollen. Bee honey has previously tested positive for pollutants like zinc, nickel, and naphthalene — the toxic compound found in coal tar. In Germany, scientists regularly test the honey near the Frankfurt Airport to keep track of the air pollution caused by jet engines.

In this new study, honey samples showed that the concentration of elements linked to pollution increased when the hives were closer to areas with heavy traffic, higher urban density, and shipping ports. The hives at the edge of Vancouver — like the ones located in the agricultural town of Delta, a thirty-minute drive from Vancouver — had honey with higher levels of manganese, which the scientists write is largely indicative of the pesticide use in the area.

They also determined that the lead fingerprints in the honey didn’t match the lead found in other local environmental samples — save for traces of lead found in the trees of Stanley Park, a public park that borders downtown Vancouver. Subsequent isotope analysis revealed that the lead in the honey and the lead in the trees could come from the same anthropogenic origin: shipping ports.

bee
The scientists analyzed the honey produced by local bees.

“We found they both had fingerprints similar to aerosols, ores, and coals from large Asian cities,” senior author Dominique Weis, Ph.D., explained Monday. “Given that more than 70 percent of cargo ships entering the Port of Vancouver originate from Asian ports, it’s possible they are one source contributing to elevated lead levels in downtown Vancouver.”

Still, Vancouver residents shouldn’t worry about lead in their honey — Weis and her colleagues note that an adult would have to eat more than two cups of honey every day to exceed tolerable lead levels. That doesn’t mean that honey shouldn’t continue to be monitored: The team writes that they hope citizens and scientists in other cities will work together to analyze local honey, in turn monitoring the environmental health of their homes.

Abstract:

Urban geochemistry is an emerging field in which key scientific and societal challenges, including rapid urbanization and population growth, compel investigation of readily accessible biomonitors to determine the source, transport and fate of heavy metal pollutants in cities. Lead isotopic analyses of honey have recently proven its efficacy as a biomonitor for Pb source apportionment applications. We collected honey directly from hives in six geographical sectors in Vancouver, British Columbia (Canada) to investigate the presence of potential pollutants from varying zoning districts: urban, industrial, residential and agricultural. Systematic variations in trace element concentrations and Pb isotopic compositions of the honeys reflect proximity to anthropogenic land-use activities such as shipping ports and heavy traffic. Honey sampled from downtown hives, near the Port of Vancouver, shows elevated trace element concentrations compared with suburban and rural honey, and distinctly higher 208Pb/206Pb (that is, less radiogenic) compared with local environmental proxies (for example, oysters, Fraser River sediment and volcanic rocks), indicating possible input from Asian anthropogenic sources. This study presents the first Pb isotope data for North American honey, and supports the combined use of trace elements and Pb isotopic compositions in honey as a geochemical biomonitor.