| Abstract | Široka primjena radiofrekvencijskog elektromagnetskog zračenja (RF-EMZ)
uzrokovala je zabrinutost javnosti o mogućim štetnim učincima na zdravlje ljudi i životinja.
Naime, rezultati mnogih istraživanja pokazali su da izloženost RF-EMZ-u na radnoj
frekvenciji mobilnih telefona može uzrokovati različite biološke učinke, primjerice,
oksidacijski stres, promjene vrijednosti pokazatelja antioksidacijskog sustava te
genotoksični učinak. No, vrlo je važno istaknuti da su spomenuti učinci RF-EMZ-a još
uvijek dvojbeni osobito kada je riječ o rezultatima istraživanja utjecaja RF-EMZ-a na
pčelinje zajednice. Stoga je cilj ove disertacije utvrditi stupanj aktivnosti ili koncentracije
pojedinih pokazatelja oksidacijskog stresa i genotoksičnosti u različitim razvojnim stadijima
pčelinjeg legla, kao i u odraslim pčelama nakon kratkotrajnog i kroničnog izlaganja pčelinjih
zajednica RF-EMZ-u u laboratorijskim i terenskim uvjetima kao i ponašanje te uzgojnobiološke
osobitosti pčelinjih zajednica izloženih RF-EMZ-u stacionarnih baznih postaja
mobilne telefonije.
Istraživanje je načinjeno na pčelinjim ličinkama i kukuljicama te odraslim jedinkama
medonosne pčele (A. mellifera) u poljskim uvjetima na petnaest pčelinjih zajednica
smještenih u blizini antene stacionarnog odašiljača mobilne telefonije na tri lokacije. Za
provedbu analiza u laboratorijskim uvjetima korišteni su samo uzorci ličinki koje su bile
izložene RF-EMZ-u s različitim jakostima električnog polja tijekom dva sata. U svim uzetim
uzorcima ličinki, kukuljica i srednjih crijeva odraslih pčela određivana je koncentracija
lipidnih peroksida, aktivnost enzima super-oksid dizmutaze, katalaze i glutation-Stransferaze,
dok je u uzorcima ličinki izloženih radiofrekvencijskom zračenju u
laboratorijskim uvjetima određivano još i oštećenje molekule DNK. Rezultati su pokazali da
RF-EMZ na frekvenciji od 900 MHz i jakosti električnog polja od 10, 23, 41, 120 V m-1
nemoduliranog vala kao i pri modulaciji od 217 Hz i 1 kHz (80%) uzrokuje promjene
aktivnosti antioksidativnih enzima, oštećenje molekule DNK i lipidnu peroksidaciju u ličinki
medonosne pčele u laboratorijskim uvjetima ozračivanja. Također je zanimljivo da je
zabilježen pozitivan učinak samo unutar određenih istraživanih uvjeta.
Rezultati načinjenih pokusa u terenskim uvjetima pokazali su da aktivnost
antioksidacijskih enzima kao i koncentracija proizvoda lipidne peroksidacije ovise u stadiju
razvoja pčele, mjestu uzimanja uzoraka te o godišnjem dobu. Rezultati uzgojno-bioloških
osobina tj. jačina pčelinjih zajednica, agresivnost odraslih pčela, mirnoća pčela na saću te
izgradnja novih matičnjaka nakon izlaganja košnica s naseljenim pčelinjim zajednicama RFEMZ-
u na frekvenciji od 900 MHz, podrijetlom od stacionarnih antena mobilne telefonije,
pokazali su odstupanja ponašanja pojedinih pčelinjih zajednica bilo unutar iste, odnosno
različite lokacije promatranja. Radiofrekvencijsko zračenje povećavanjem jakosti polja ne
uzrokuje linearni odgovor biokemijskih, antioksidativnih pokazatelja niti stupanj
genostoksičnosti u medonosne pčele. Nadalje, nemodulirano polje RF-EMZ-a uzrokuje
promjene aktivnosti katalaze i lipidne peroksidacije na malim jakostima električnog polja,
dok modulacija RF-EMZ-a frekvencije od 900 MHz pri 1 kHz pokazuje povećanje oštećenja
molekule DNK kod pčelinjih ličinaka |
| Abstract (english) | The use of devices that emit radiofrequency electromagnetic fields (RF-EMF), such
as mobile phones, has arisen rapidly in recent years. With increasing usage of mobile phones,
public concern about possible adverse health effects from exposure to mobile phone signals
have occurred. The results of many studies have shown that exposure to radiofrequency
radiation at the operating frequency of mobile phones can induce various biological effects
in different species. One of the major effects could be possible genotoxicity and oxidative
stress. However, it is very important to emphasize that the mentioned effects of RF-EMF are
still controversial because there are several studies that have not found biological effects
after exposure to RF-EMF or have some shortcomings, especially in genotoxic effects.
Previous studies regarding effects of RF-EMF at frequencies from 900 MHz to 2.4 GHz in
honey bee colonies investigated mostly adult honey bees in unnatural conditions i.e. after
direct exposure to the mobile phone handset. Although few studies found no effect on
aggression and navigation of honeybee, brooding, honey production and foraging behavior,
the majority of results have shown effects such as decreased colony strength and egg laying
rate of the queen, induction of “worker piping” which is associated with swarming and the
alteration of some biochemical parameters (total carbohydrates, glucose, glycogen, total
lipids, cholesterol, protein, hexokinase, alkaline phosphatase, glucose 6-phosphatase and
free amino acids) in the hemolymph of the drone. However, there are still many uncertainties
and controversies about the effects of RF-EM radiation in honey bee. Furthermore, the
results of some experiments suggest that radiation produced by mobile phone base station
towers is actually frying the navigational skills of the foragers and preventing them from
returning back to their hives, and there are some reports of sudden unexplainable
disappearance of adult honeybees, syndrome called Colony Collapse Disorder (CCD). In the
light of mentioned literature data, the aim of this study was to investigate the oxidative stress
parameters and genotoxicity in honey bee larvae, pupae and adult bees after long-term
exposure in nature condition as well as short-term exposure to RF-EMF under controlled
laboratory conditions at the operating frequency of mobile phones with different field levels
and modulation. Next, aim of this study was to determine some behavior patterns regarding
biological-rearing status, strength of honey bee colonies, situated at different distances from
two mobile phone base stations, in field conditions.
Fifteen honeybee colonies (A. mellifera) were selected, and situated at three locations
in nature: O (n═5; 65,41 m and 159,46 m distance from mobile phone base tower,
respectively); H (n═5; 790 m and 700 m distance from mobile phone base tower,
respectively); K (n═5; 1630 m and 1520 m distance from mobile phone base tower,
respectively). Before transportation of hives with honey bee colonies to selected locations
the average frequency and electric field level were measured at each location using power
density meter NARDA SRM 3000 (NARDA, USA). Under laboratory conditions exposure
of honey bee larvae to a homogeneous electromagnetic field was carried out in the Gigahertz
Transversal Electromagnetic Cell. The four to six days old honeybee brood in original combs
were exposed to continuous radiofrequency electromagnetic field (RF-EMF) and modulated
signal (80% AM 1 kHz sinusoidal) at frequency of 900 MHz and field level of 10, 23, 41
and 120 V m-1 for 2 hours. All antioxidant parameters such as catalase (CAT), superoxide
dismutase (SOD), glutathione S-transferase (GST) as well as lipid peroxidation (TBARS)
were measured spectrophotometrically. Genotoxicity was mesuared using alkaline Comet
assay (single cell gel electrophoresis assay) while few clinical inspections of honeybee
colonies were conducted to recorde biological aspect: colony strength - the total area under
honeybee brood and comb surface covered with adult bees was measured according to
Liebefeld method; presence of queen cells on combs; and aggressiveness as well as
composure as rearing parameters.
Under laboratory conditionsthe GST activity in the honey bee larvae exposed to
unmodulated RF-EMF at frequency of 900 MHz and field levels of 10, 23, 41, 120 V m-1
was not statistically different when compared to the control. The lowest GST activity was
measured in the larvae exposed to modulated (80% AM 1 kHz sinus) field at 23 V m-1, and
it was significantly lower than in the larvae exposed to unmodulated field at 23 V m-1. The
CAT activity was significantly decreased in the honey bee larvae exposed to unmodulated
RF-EMF at field level of 10 V m-1 when compared to control group, as well as with group
exposed to unmodulated RF-EMF at field level of 23, 41, 120 V m-1 and modulated (217
Hz) field at 23 V m-1. The SOD activity in the honey bee larvae exposed to RF-EMF at
frequency of 900 MHz and field levels of 10, 23, 41, 120 V m-1 was not statistically different
compared to control. However, the lowest SOD activity was measured in the larvae exposed
to unmodulated RF-EMF at field level of 10 V m-1 and it was significantly lowerthan in the
larvae exposed to a modulated (217 Hz) field at 23 V m-1. The TBARS concentration was
significantly decreased in honey bee larvae exposed to unmodulated RF-EMF at a field level
of 10 V m-1 when compared to the control group. Although the content of TBARS in all
other exposed groups was lower than in the control group, there was no significant difference
between the groups. DNA damage was significantly increased in honey bee larvae exposed
to modulated (80% AM 1 kHz sinus) field at 23 V m-1 in comparison to the control and all
other exposure groups. Other treatments did not trigger significant DNA damage in
comparison to the control.
Under natural condition the results showed that the activity of antioxidant enzymes
as well as lipid peroxidation concentrations depend on the stage of bee development,
sampling site, and seasonality. The most significant differences in honeybee colonies
behavior, as well as in biological parameters, was observed during first two months after
colonies exposure and changes were visible only for colonies situated at location at nearest
distance from mobile phone base tower.
The results suggest that RF-EMF effects in honey bee larvae appeared only after
exposure to a certain EMF conditions; they did not follow a linear dose-response relationship
and they strictly depended on the measured parameters, field levels and modulation.
Modulated RF-EMF produced more negative effects than the corresponding unmodulated
field. Next, it is important to emphasize that RF-EMF at 900 MHz, which is used in GSM
communication and is modulated at 217 Hz, did not cause any statistically significant
changes in all observed parameters in cases when their results were compared to the control
group. But, despite this, the modulation at 1 kHz showed the increase of DNA damage.
Likewise, it can be concluded that exposure of honeybee colonies in vicinity to
mobile phone base stations in field conditions, as unfavorable environmental factor, may
induce alteration in the honeybee behavior and biological activities, probably as adaptation
process consequence. |
