There has been constant debate over the past decade revolving around the cause or many causes for the decline in the number of bumblebees situated in the British countryside. Many scientists believe this decrease is caused by ubiquitous contrails which contain water vapour, carbon dioxide, oxides of sulphur and nitrogen along with metal particles such as aluminium. These nanoparticles are released from the jet’s exhaust at such a high altitude with lower vapour pressure that the water vapour condenses and may freeze (deposition) forming tiny ice crystals. This mixture of crystals and particles forms a sort of cloud. Scientists therefore assume that the nanoparticles of aluminium found in these artificial clouds or contrails is inhaled directly via the olfactory nerves by animals in this case or insects as the particles begin to disperse and descend due to gravity and eventually absorbed by the plants.
This may be a very valid theory, however recently, there has been dispute as to whether the industrial discharge containing aluminium is also implicating the aetiology of sporadic Alzheimer’s Disease (AD) and affecting the mental functioning of bumblebees. The bumblebees fail to differentiate between normal nectar and nectar that contains aluminium.
Scientists at Keele and Sussex University found that there was a large amount of aluminium in the pupae collected, between 13 and 200 ppm whilst a minimum of chronic exposure of 3ppm would be harmful to the human brain. At high levels in the brain, aluminium acts as a neurotoxin and thus causing a myriad of problems due to it inhibiting or altering the chemical impulses between neurones (delivering messages to the brain and back). Excess aluminium promotes formation and accumulation of insoluble A beta and hyperphosphorylated tau. Insoluble amyloid beta protein (A beta) leading to defective phosphorylation-dephosphorylation reactions and reduced glucose utilization, all contributing to the appearance of neurological disorders such as AD.
Since this is the destructive effect on humans with such a little dosage, there must be some sort of correlation with animals and insects such as a bumblebee that had x70 as much aluminium in its system.
Scientists believe that this detrimental quantity of aluminium would cause cognitive decline, the theory being simultaneous to how it affects the human brain causing Alzheimer’s Disease. The figures farming the bewildering and intriguing spectre suggest that aluminium-induced cognitive dysfunction may be catalysing the decline in the bumblebee population. Injections of aluminium in animals produce behavioural, neuropathological and neurochemical changes that partially model AD.
Sara Belazregue spent two weeks in Professor Maria Fitzgerald’s group in UCL’s Department of Neuroscience, Physiology & Pharmacology, supervised by Dr Madeleine Verriotis.