Distributions of neonicotinoid insecticides in the Commonwealth of Massachusetts: a temporal and spatial variation analysis for pollen and honey samples

Environmental context Neonicotinoids are a group of widely used insecticides that have been implicated in the deterioration of honeybee health and the declining number of honeybee colonies worldwide. We wanted to find out whether neonicotinoids are commonly present in pollen and honey, which are the main food sources for bees. The results show that neonicotinoids are ubiquitous in the environment where bees foraged, and therefore could pose risks to honeybee health. Abstract It is known that honeybees are exposed to a wide variety of pesticides, including systemic neonicotinoids, through different media. Pollen might be a better matrix for assessing exposure to neonicotinoid not only because it is the protein source for bees, but also because pollen collected from foraging bees could help to establish the field-realistic levels of neonicotinoids. In this study, we aimed to assess temporal and spatial variations of neonicotinoids in pollen collected across the Commonwealth of Massachusetts. Monthly pollen samples and a honey sample were collected between April and August 2013 from 62 volunteered hives and analysed for eight neonicotinoids. We utilised the relative potency factor (RPF) method to integrate individual neonicotinoids into a single measurement of imidacloprid(RPF). We then analysed the spatial and temporal variations of imidacloprid(RPF) in pollen using the response profile analysis. Overall, 73% of pollen and 72% of honey samples contained at least one detectable neonicotinoid. We found that 49, 20 and 4% of pollen samples contained one, two and three neonicotinoids respectively. In honey, we detected that 57 and 15% of samples contained one and two neonicotinoids respectively. Neonicotinoids as a group, or imidacloprid, in pollen exhibited no significant temporal or spatial variation, however, we found statistically significant spatial-temporal interaction differences of imidacloprid(RPF) concentrations. Considering the ubiquitous of neonicotinoids in the environment and their effects on bees at the sub-lethal levels, it is prudent to identify ways to minimise the uses of neonicotinoids in order to reduce the risk of neonicotinoid exposure to honeybees.