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Lead Contamination Found in Bees and Their Honey

A new study published in Environmental Science & Technology is the first Australian research of its kind to trace the source of contaminating metals, including lead, in honey bees and their products.

Researchers from Macquarie University used an isotopic source-tracing method to analyse metal contaminants in soil and dust from Sydney and Broken Hill, and compared the results in bees as well as their honey and wax.

“The results were unequivocal. They showed clearly the different sources and origins of lead across the study areas,” said Prof Mark Taylor. “The lead isotopes showed that honey bees… from Sydney and Broken Hill were clearly contaminated by legacy petrol sources and ongoing mining emissions, respectively.”

The study found that bees located in inner-city regions of Sydney fared worse than those in other areas, with bees in the CBD, Surry Hills and Newtown possessing 230–440 µg/kg of lead. The coastal residential suburbs of Coogee and Randwick fared better, with their bees only possessing an average of 125 and 146 µg/kg of lead, respectively.

“The suburbs with the lowest lead levels measured in their bees were Galston and Gordon, with 50 and 56 µg/kg respectively, which is likely due to the fact that these suburbs are both located near national parks with less legacy contamination from traffic pollution and human activities nearby,” Taylor said.

Broken Hill bees possessed much higher levels of lead than those in Sydney, measuring concentrations of around 2570 µg/kg, and also produced honey with much higher amounts of lead due to the active mining operations in the region.

“Honey collected from hives across Sydney contained negligible amounts of lead and didn’t exceed a concentration of 22 µg/kg. However, the amount of lead found in the honey of Broken Hill city bees, which had an average concentration of 295 µg/kg, was more than ten times the maximum of the bees measured in Sydney,” Taylor said.

“The large difference in honey lead concentration demonstrates that local active sources, such as the ongoing lead mining in Broken Hill, can have a substantial impact on the level of metals measured in local food products and ecological systems. There are very limited contemporary lead emissions in Sydney, which means that air lead levels are approximately 30 times lower than those in Broken Hill, which is why bee contamination was markedly lower,” Taylor said.

The researchers also found that dead worker bees were more contaminated than live worker bees, and also that worker bees were more contaminated than drone bees, indicating that contamination accumulates in bees as they forage in the environment and age.

“The fact that their honey contains much less lead than their bodies tells us that the bees are filtering this contaminant and therefore limiting its passage into honey,” Taylor said.

“We do not know if the bees’ behaviour and activity was impaired by the levels of contamination found. This will form part of our follow-up research,” Taylor concluded.