Heavy metals and toxic soil contaminates that build up in plants may be killing bees and reducing their ability to pollinate crops and produce honey.
New research by entomologists at the University of California suggests selenium - a trace mineral used as a superconductor in the electronics industry - can kill bees foraging for pollen from plants in heavily polluted areas, such as disposal sites for fly-ash from coal-fired power stations.
The study, by Kristen Hladun and Professor John Trumble, is the first of its kind to look at lethal impacts of plant-accumulated pollutants on honey bee feeding habits and survival. Their findings are published online in the science journal PLoS One.
"We know very little about how soil-borne pollutants can affect pollinators," the research paper said.
"Our study has shown that fewer bees respond to sucrose when fed selenate. If a forager bee does survive the ingestion of selenate, she may be less responsive, forage and recruit less."
The paper argues that fewer foraging bees reduces the pollen and honey production needed to support co-workers and bee larvae. The findings have serious implications for food production in the United States, where managed pollination services are estimated to be worth $US 14 billion a year to the economy.
The PLoS paper builds on an earlier discovery by Ms Hladun and Professor Trumble that high levels of selenium were being detected in the pollen and nectar of two common plants in California's central valley - a region where much of the state's $US9 billion fruit and nut orchards occur. The scientists found nectar and pollen collected from plants grown in a laboratory contained between 108 and nearly 2,000 parts per million of selenium -- many times the lethal level for most insects.
"In insect systems we've studied, it's toxic at around 15 to 20 parts per million, so this is way too high," Professor Trumble said.
"Pollen and nectar with that much selenium will likely kill all pollinators that feed on it."