Add selenium to the growing list of compounds that may affect honey bee health.

A group of University of California, Riverside, researchers has found that selenium—found in four different forms in plants—can kill bees and delay their development.

They published their work in the October issue of the journal, "Environmental Toxicology and Chemistry," according to a news release

Selenium occurs naturally, but it also can be magnified by human activities, such as petroleum refining and cold-power production.

In agriculture, runoff can collect and concentrate selenium from surrounding soils, as it did at the Kesterson National Wildlife Refuge in California.

In minute amounts, selenium can be beneficial as part of an antioxidant enzyme.

But in higher concentrations, it is toxic.

With honey bees, they may eat contaminated pollen and nectar.

“It is not clear how selenium damages the insect’s internal organs, or if the bee has the ability to detoxify these compounds at all,” Kristen Hladun, lead author and a postdoctoral entomologist, said in the release. “Further research is necessary to examine the cellular and physiological effects of selenium.”

Honey bees also may be more susceptible to selenium than some other insects because they lack detoxification enzymes.

The researchers are conducting studies where bees are fed selenium-laden food. They will monitor the insects for changes in survival and behavior.

The researchers also are looking at other heavy metals, including cadmium, copper and lead.

Also involved in the study are Osman Kaftanoglu, a research apiculturalist at Arizona State University; David Parker, a professor in the UCR Department of Environmental Sciences; and a UCR undergraduate student, Khoa Tran. John Trumble, a UCR distinguished professor of entomology, is the principal investigator on the project.