Heavy Metals in Honey
- Kyle Snare & Sukhjeet Singh (Hill Labs)
- 3 days ago
- 3 min read
Among several New Zealand labs’ suite of honey tests are those designed to detect heavy metals. Hill Labs scientists Kyle Snare and Sukhjeet Singh explain how the heavy metals make it into the sweet stuff and why the testing is needed.
By Kyle Snare & Sukhjeet Singh (Hill Labs)
What are “heavy metals”?
Heavy metals refer to trace metals that occur naturally in the Earth’s crust and are toxic to organisms at low concentrations. Heavy metals can become concentrated through various human activities, including industrial processes, mining, agriculture, and transportation.[1] Overseas purchasers of honey may have an interest in finding out the concentrations of heavy metals in honey. Lead and Zinc are the most widely requested heavy metals for testing, but other heavy metals that Hill Labs frequently tests in honey include Mercury, Cadmium, Arsenic and Chromium.
How do heavy metals get into honey?
Heavy metals can make their way into honey in various ways. When natural cycles are disrupted, heavy metals can accumulate in water and soil in both rural and urban areas.[2] If the soil or water near beekeeping areas is contaminated with heavy metals, plants can absorb these metals. Consequently, bees collect pollen and nectar from these plants, transferring the metals into the honey. Industrial processes and mining operations can also release heavy metals into the air, which then settle on flowers and plants.[3]
Certain pesticides and fertilisers can also contain trace levels of heavy metals, and overuse of these can lead to accumulation in crops where bees forage. Bees kept in urban environments may be exposed to pollution from traffic and industrial zones. Because of this, there is the risk that honey from urban areas can contain elevated levels of heavy metals.[4]
The storage of honey is also important to consider, as containers made from metals that leach can cause contamination. This is especially true if the equipment is old or poorly maintained.[5]
What are the implications of heavy metals in honey?
Heavy metals in honey can have various implications across health, environmental, and economic standpoints. Heavy metals like lead, cadmium, and mercury are toxic even at low concentrations. Long-term exposure can have negative effects and cause neurological and developmental issues as they accumulate in the body, especially in children and vulnerable populations.[4]
Environmentally, honey can serve as a natural bioindicator of environmental pollution. Traditional methods of environmental pollution monitoring can be expensive, time-consuming, and often reliant on samples from different geographic areas. Bees forage over wide areas and can bring back pollutants into the hive as they collect nectar, pollen, and other materials.[6] By analysing honey, pollution sources can be traced, and the overall health of ecosystems can be evaluated more effectively.
Economically, honey contaminated with heavy metals can lose market value. Consumers and importers expect purity and traceability, and countries with strict food regulations could reject honey imports that exceed heavy metal limits.[7]
Honey from New Zealand generally shows low levels of heavy metals, frequently below international safety limits. This is largely attributed to environmental regulations, clean agricultural practices, and comparatively low industrial pollution. New Zealand honey is often used as a benchmark for purity in global markets.[4]
How are the metals detected?
The technique employed by Hill Labs to measure heavy metals is Inductively Coupled Plasma – Mass Spectrometry (ICP-MS). In ICP-MS, a liquid sample (e.g. acid-digested honey sample) is introduced as an aerosol into an argon plasma. The plasma operates at approximately 8000 °C, a temperature hot enough to break down molecules into individual atoms, then ions. The positively charged ions are directed into a vacuum chamber, containing a quadrupole mass analyser, where ions are separated into their mass-to-charge ratio. An electron multiplier is used to amplify the signal from incoming ions, and this response correlates to the concentration of a given element.
While ICP-MS is a highly sensitive technique, the main challenge faced by trace metals laboratories is environmental contamination. When looking at elements in such low levels, dust and other airborne particles can pose a contamination risk. To overcome this challenge, Hill Labs utilises positive pressure, Highly Efficient Particulate Air (HEPA) filtered environments to minimise the risk of external contaminants that may interfere with analyses.
References:
[4] Honey as a Bioindicator: Pollution’s Effects on Its Quality in Mining vs. Protected Sites – DOAJ
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