Mobile phones are used worldwide not only for telephony, but increasingly also for banking, news, social media and other applications, and the trend is rising. The constant communication to and from base stations causes more and more environmental pollution. Many researchers have found changes in plants and insects caused by radio-frequency radiation from wireless communication technologies. Since honey bees play an important role as pollinators (value of 200 billion dollars worldwide, 9.5% of total food production), together with wild bees and other insects, they are crucial to crop yield. In the last century, honey bees have repeatedly suffered heavy losses. This was called Colony Collapse Disorder (CCD) in the United States at the beginning of the 20th century, with the main causes being pests, malnutrition, management and pesticides. An important pest is the varroa mite, which appeared in the 1970s and 1980s in the West. Since its worldwide distribution, beekeepers have to take countermeasures; otherwise, the colonies collapse in a short time. Other contributing factors also include air pollution, nanomaterials, solar radiation, predatory insects and global warming. In 2007, radio-frequency radiation from wireless communication technologies was discussed for the first time as a possible factor. Some studies demonstrated drastic effects on the behavior and ability of bees to return to their hives. The health and productivity of a bee colony are directly dependent on the queen, which is the only one laying eggs and providing the worker bees every year. Therefore, we investigated in this experiment queen development and the subsequent mating success in the context of mobile phone radiation.
The beehives were set up near the institute of the University of Hohenheim, Germany. The experiment lasted from May to August 2018, using healthy colonies from their own population. The natural food sources consisted mainly of nectar from various plants including dandelion, blackberry and basswood. The average temperature during the experiment ranged from 15.2 to 20.1 °C and precipitation from 45 to 90 L/m2. Overall, the weather conditions for food collection and mating were good. A simultaneous double batch of 2 collector colonies was used in the experiment, one of each sham-exposed (control) and exposed. For the development and hatching of the queens, the boxes were set up at a distance of about 3 km so that the worker bees could not return to their original stock. The queens were exposed with a common 900 MHz mobile phone (GSM) for the entire time of development including pupation (14 days, SAR 0.59 W/kg at head and 1.16 W/kg at trunk). Both SAR values were below the current ICNIRP limit of 2 W/kg. There were fifteen 2-min phone calls every 24 hours over 2 weeks (downlink without conversation). The control group was sham-exposed. The mobile phone was mounted to the center of the box so that the animals were exposed to different SAR levels.
After the young queens had hatched, hatching rates were determined on day 13, preparing the animals for mating. On day 24, the mating success was evaluated. On day 88, the colony strength was measured by counting the number of bees as well as brood cells (open and closed). The counting was performed by the same person in the morning before the start of the bee flight. In addition, 5 full colonies of the sham-exposed and 4 full colonies of the exposed queens were established to investigate differences in their population dynamics.
The survival of the queens showed significant differences: exposed queens had a significantly higher mortality. A significant reduction in the animals during the pupal stage was witnessed; the difference between the groups was 44.4%. The mating success on day 24 was cut in half; however, compared to the total number of hatched queens on day 13, no significant differences were observed. The determination of the number of bees and brood cells on day 88 showed no significant differences. Chronic exposure to radio-frequency radiation significantly reduced the hatching of honey bee queens (44%). Mortality occurred during the pupal stage, but not the preceding larval stages. Mating success was not affected by exposure. After exposure, the queens were able to develop intact colonies.
Other factors such as pesticides or higher colony density may also play a role because beekeeping has become fashionable, especially in cities. A higher colony density allows for an easier transfer of pollutants or diseases. It also increases the risk of higher exposures to mobile phone and base station radiation, which is constantly rising, especially in cities. It remains unclear how much of this risk is attributable to electromagnetic fields.
The two authors were able to demonstrate that 900 MHz radiation of a common mobile phone clearly has negative effects on the queens of honey bees. Mobile phone radiation significantly reduced the percentage of hatched animals, but not mating success. If exposed queens mated successfully, colony formation was not impaired. The pupal stage can be adversely affected by mobile phone radiation, but if this stage develops normally, no disadvantages in the adult stage were observed. The researchers state the following about the results: “Even though detrimental effects on ontogenetic queen development were revealed by the outcome of our study, caution is needed in interpreting these results. So far, there have been no serious records of colony losses associated with mobile phone radiation. Moreover, we have created by far a worst-case operator scenario to which honey bee colonies would not be exposed under realistic beekeeping conditions. Duration and level were similar to average operator exposure by the use of a mobile phone, but not to those present at an apiary, neither in rural nor in urban areas. And yet, queens that survived the treatment were able to establish full functional colonies, demonstrating an immense recovering potential.” Therefore, the authors do not expect negative effects on bee health during the middle developmental stage. Acute effects of mobile phone radiation in bees can be ruled out; however, an effect of low-level, but permanent exposure levels cannot be ruled out, in particular chronic sublethal field strengths found in urban areas. Thus, further research with long-term exposure is urgently proposed to determine which impact this type of radiation has on bee health and to be able to perform an appropriate risk assessment.