Working out the 'Bugs': Establishing Efficacy of Honey and Other Hive Products as Biomonitors for Heavy Metal Distribution in Urban Environments

Western honeybees (Apis mellifera) and their products, including honey, bee bread (fermented pollen), and propolis, are useful biomonitors that elucidate small-scale distribution of pollutants within a city. We compare the utility of various hive products, collected throughout the Metro Vancouver region (BC, Canada), for assessment of heavy metal distribution in an urban environment using trace element concentrations and lead (Pb) isotopic compositions. This geospatially-constrained data fits well within the chemical context of more traditional environmental proxies we collected near the hives: topsoil (representing re-suspended solids), exchangeable Pb fraction of the topsoil, and air particulate matter (PM₁₀). Bee tissue, all hive products, and all soil and air particulates analyzed follow a similar trend: samples collected in urban and industrialized areas exhibit elevated trace element concentrations (i.e. Pb, Zn, V, Ti) and a less radiogenic Pb isotopic composition (i.e. elevated ²⁰⁸Pb/²⁰⁶Pb) relative to their suburban and rural counterparts. Generally, the results for all analyzed materials reflect their immediate zoning or land use setting in Metro Vancouver. Honey, bees, and topsoil are the best predictors of metal distribution (that is, the data are in good agreement with one another) whereas bee bread and propolis have a less robust correlation with the rest of the data, probably since the bees do not homogenize these products to the same extent as they do for honey. We suggest that managed honeybee colonies, which are prolific worldwide, may become essential tools in the near future as the field of urban geochemistry expands to accommodate its ever-changing scientific requirements. Developing a standard geochemical framework (i.e. field and analytical methods) for use of hive products in this context is essential for transferring the approach to other metropolitan centers, particularly cities where environmental monitoring is not standard practice. This study has benefited from partnerships with the general community and local industry. This work is the first in North America to measure Pb isotopes in hive products other than honey and demonstrates the value of interdisciplinary collaboration when addressing issues within geochemistry, urban ecology, and public health.