Review date
July 2023
Article publication date
May 2023
Summary
This experimental and observational study examined bee exposure to extremely low frequency (ELF) electric and magnetic fields (EMF). The study observed bee visitation to flowers around active and inactive power transmission towers. The study also placed caged bees under active and around inactive power transmission towers and exposed bees to ELF EMF in the laboratory using a solenoid. ELF EMF exposure in the field around the active power transmission towers was approximately 9.47 μT compared to 1.5 μT around the inactive towers. The exposure in the laboratory was approximately 7.8 μT. The exposed bees were tested for changes in mRNA levels of stress response genes such as heat shock proteins (HSP) and genes that relate to behavioural changes in bees such as the caMKII that relates to long term memory. The study also examined flower abundance around power transmission towers. The study reported that flower visits did not change based on ELF EMF exposure. However, flower abundance was reduced around active power transmission towers, and this reduced the number of bee visits to that area. The authors reported that bees exposed to ELF EMF both in the laboratory and in the field were showed increased expression of HSP70 and reduced expression in caMKII. The authors concluded that ELF EMF exposure impacts bee physiology and behaviour.
Link to
Electromagnetic fields disrupt the pollination service by honeybees
Published in
Science Advances
ARPANSA commentary
This paper reported an increase in the expression of HSP and genes related to behaviour in bees when exposed to ELF EMF. Very few studies have examined changes in expression related to ELF EMF exposures in bees or even in insects. A previous study exposed cockroaches to ELF EMF at 1000 μT and found no changes in expression of HSP70, however, the study did find an increase in HSP expression at 10,000 μT, which is 50 times greater than the international human safety limit of 200 μT (ILIJIN et al 2021). Another study exposed flies to ELF at 0.004 μT and reported increases, decreases and no changes in expression of HSP70 in different exposed fly groups when compared to controls (Tipping et al 1999).
The current study also reported changes in the expression of caMKII that may be associated with long term memory. However, despite this change in expression of this gene there were no behavioural changes observed in exposed bees. This may indicate that the level of expression change in caMMKII observed has no functional outcome in bees.
The study did not report on possible confounders, such as the presence of herbicides. They are commonly used to control vegetation around transmission lines and towers. The use of herbicide, specifically glyphosate also known as roundup, has been shown to change gene expression in bees (Battisti et al 2022). Glyphosate has been reported to increase the expression of HSP and effect learning and memory (Tan et al 2022). The use of herbicides would also explain the reduction in flower abundance around the power transmission towers.
Generally, most research has been at levels much higher than would normally be encountered by bees in the environment. The evidence on the effect of ELF EMF on insects remains weak with some conflicting results and further research is required (Vanbergen et al, 2019).
