Heavy metal pollutants: The hidden pervasive threat to honey bees and other pollinators

Urbanisation and industralisation has increased heavy metal pollution globally. In this chapter we consider what we currently know of how heavy metal pollutants impact insect pollinators, especially honey bees. Heavy metal pollutants are a complex ecological challenge. Heavy metals often occur as cocktails of pollutants. Both mining and the burning or refining of fossil fuels release mixtures of metal pollutants into the environment. These can cause widespread and long-lasting damage to animals at tissue, cellular and epigenomic levels. Most of what we know of the effects of heavy metal pollutants has been derived from studies of humans or mammalian model systems. What we currently know from the studies of metal pollutants of insects suggests that insects are more exposed to environmental heavy metal pollutants. There is evidence that insects bioaccumulate them quickly, and they may be harmed by levels of pollution that would be considered safe for humans. This is a serious cause for concern, but we are limited by too few studies. Taxonomic coverage of insects is poor, with studies biased toward a few pest or beneficial species, including honey bees, a few wild bee species and mosquitos. Very few studies have considered how cocktails of metal pollutants might impact insects. For these reasons we need more data to accurately determine the “safe” and harmful levels of heavy metal pollutants for insect pollinators, and establish guidelines for their protection.