A survey of honey from around the world has found that 75 per cent of samples tested contain at least one or more types of pesticide.
Swiss scientists tested 198 honey samples sourced from every continent except Antarctica for the presence of five neonicotinoid pesticides, which are commonly used in agriculture.
Honey from North America, Asia and Europe contained the highest levels of pesticides, they reported in the journal Science.
The researchers stressed that the levels of contamination found in the honey were “below the maximum-residue level authorised for human consumption” by the European Union in all but two samples.
But they said that exposure to these pesticides, which target the nervous system, may harm bees and other pollinators.
“There are increasing concerns about the impact of these systemic pesticides [on] honey bees and wild bees,” they wrote.
“[The] average concentration [found in the honey] lies within the bioactive range, causing deficits in learning, behaviour, and colony performance.”
Colony collapse was first recognised 10 years ago, when beekeepers in the United States noticed that thousands of hives were completely empty of bees.
A number of factors have since been discovered to contribute to colony collapse, including pesticides ingested by bees at sub-lethal levels.
Study co-author Professor Edward Mitchell from the University of Neuchatel in Switzerland, said even at low levels neonicotinoids were cause for concern.
“These pesticides are so incredibly toxic that they have a considerable effect at concentrations that are barely measurable,” he said.
Australia’s most common pesticide on EU banned list
The researchers employed the help of citizen scientists to send samples of honey purchased in shops around the world back to their laboratory in Switzerland.
They excluded products where the source location of the honey could not be verified.
“Many of our samples were from very remote regions. We also aimed to [include] isolated oceanic islands and places in central parts of continents far away from big industrial areas,” Professor Mitchell said.
“In many of these places we had positive samples.”
While 30 per cent of samples contained a single pesticide, 45 per cent contained a minimum of two, and up to five different types of neonicotinoid.
Thiamethoxam, which was the most commonly detected pesticide in honey from Oceania including Australia, was put on a temporary ban by the EU in 2013 following concerns over colony collapse.
A French law passed in 2016 will see the banning of neonicotinoids by 2018.
Although colony collapse is yet to be detected in Australia, North America and Europe have still been experiencing high bee mortality over the winter months.
In the US 2015-16 winter, a national beekeeping database recorded more than 28 per cent of colonies were lost.