మొబైల్ ఫోన్ రేడియేషన్ వల్ల కలిగే రోగాలు

Research on cancer risk in cell phone users
Researchers and public health experts worldwide are engaged in a vigorous debate about whether cell phone radiation can lead to brain cancer (American Cancer Society 2008; FDA 2003; Hardell 2009; IARC 2008, 2009b; Kundi 2009). While earlier, short-term studies did not find an increased risk of brain cancer (Ahlbom 2009; Croft 2008; FDA 2003), studies of long-term cell phone use, published over the last four years, have found an increased risk of developing two types of brain tumors on the ipsilateral side (the side of the brain on which the cell phone is primarily held) among people who used a cell phone for longer than 10 years (Hardell, Carlberg 2006b; Hours 2007; Lahkola 2007; Lonn 2005; Schoemaker 2005; Schuz, Bohler, Berg 2006; Takebayashi 2008):
Glioma – a typically malignant tumor of the brain that arises from glial cells that provide physical support for the central nervous system;
Acoustic neuroma – a benign tumor of the vestibulocochlear nerve that innervates the ear.
Two recent studies also reported increased risk of salivary gland (parotid gland) tumors among cell phone users (Lonn 2006; Sadetzki 2008).
In the late 1990s, the International Agency for Research on Cancer (IARC) developed a multinational case-control study, INTERPHONE, to address strong public concerns about cell phone safety (Cardis 1999). The goal of the INTERPHONE study was to investigate whether the radiofrequency radiation emitted by cell phones is carcinogenic (IARC 2009b). Thirteen countries participated in the project (Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden and the UK). The study ran from 2000 to 2006, cost 30 million U.S. dollars (Economist 2008) and involved 14,078 study participants, among them 2,765 glioma, 2,425 meningioma, 1,121 acoustic neurinoma, 109 malignant parotid gland tumour cases and 7,658 controls (Cardis 2007).
The publication of final results and conclusions of the entire INTERPHONE study has been delayed for three years since the conclusion of the study (IARC 2009a; Microwave News 2009). Scientists have questioned whether the study design methods were adequate for detecting increased cancer risk, and whether recall biases might have impacted the quality of the data and resultant conclusions (Cardis 2007; Kundi 2009; Vrijheid, Armstrong 2009; Vrijheid, Cardis 2006; Vrijheid, Deltour 2006; Vrijheid, Richardson 2009). Meanwhile, scientists from different international centers have begun to publish their findings independently (Cardis 2007; Lonn 2005; Schlehofer 2007; Schoemaker 2005; Schuz, Bohler, Schlehofer 2006; Takebayashi 2006).
As described in the article published by the Economist in September 2008:
“Delays in releasing the report have been due to “the difficulty of interpreting the findings due to potential biases” and to the “conducting of additional analyses to try and disentangle the potential impacts of selection and recall errors on the risk estimates”. The Interphone researchers are split into three camps. One believes any increased incidence of tumours shown in the study is purely the result of the biases. Another thinks it really has found increased risks of certain tumours and wants to call for precautionary measures. A third group is just keeping quiet. One person who knows many of the scientists, but prefers not to be named, describes the relations between members of the three groups as “strained”—harsh language in the world of scientific research.”(Economist 2008)
The latest update of the INTERPHONE study results, published on October 8, 2008 (IARC 2008), included 6 publications that found some increase in the risk of glioma for long-term cell phone users, especially on the ipsilateral side (Christensen 2005; Hours 2007; Lahkola 2007; Lonn 2005; Schuz, Bohler, Berg 2006). This side of the head absorbs 97-99% of the total electromagnetic energy deposited in the brain during calls (Cardis 2008), which supports the link between cell phone use and ipsilateral brain tumor development. Only two of the INTERPHONE studies did not find an increased glioma risk (Hepworth 2006; Takebayashi 2008). Increased risk of glioma associated with long-term cell phone use has been also reported by the Hardell group in Sweden (Hardell, Carlberg 2006b; Hardell 2009).
INTERPHONE results for acoustic neuroma are more varied. Of the 7 INTERPHONE reports on acoustic neuroma, 5 publications based on less than 10 years exposure did not detect an increased risk (Christensen 2004; Hours 2007; Klaeboe 2007; Schlehofer 2007; Takebayashi 2006). In contrast, two publications that were based on longer than 10-year exposure reported an increased risk of acoustic neuroma (Lonn, Ahlbom 2004; Schoemaker 2005). Similar to glioma, the risk for developing acoustic neuroma appears to be strongest for tumors on the ipsilateral side and long-term exposures (Hardell, Carlberg 2006a; IARC 2008).
A meta-analysis that combined results from all brain tumor studies published to date reported that among people who had used cell phones for more than 10 years, the risk of ipsilateral brain tumor increased by 90% for glioma and 60% for acoustic neuroma (Hardell 2009; Kundi 2009). Some studies have also reported an increased risk of the benign brain tumor meningioma, although the risk appears to be smaller and thus much harder to detect (Hardell 2009; Kundi 2009; Takebayashi 2008). Authors of the study noted that the risk appears to be higher in rural areas where phones typically radiate at higher intensities to allow signals to reach distant transmission towers (Hillert 2006).
While the publication of the final INTERPHONE summary is pending (IARC 2009a), detailed post-study analysis suggested that some of the negative findings may have been related to the study design and methods for determining past personal patterns of cell phone use (Hardell and Hansson Mild 2006; IARC 2008; Vrijheid, Cardis 2006; Vrijheid, Deltour 2006; Vrijheid, Mann 2009; Vrijheid, Richardson 2009). For example, among studies where the observed effects were weak, an increased risk of brain tumor was nevertheless reported for long-term users, users with the largest number of calls, and users with the largest numbers of telephones (Hours 2007; Schoemaker 2009).
Recently, a large-scale, multi-center study in Israel also found an association between salivary (parotid) gland cancer and heavy use of cell phones, especially for rural areas where cell phones typically transmit at higher power (Sadetzki 2008). As reported by the team of Israeli scientists, the anatomic location of the parotid gland just below the ear would makes it vulnerable to cell phone radiation exposure. Parotid tumor occurs at a relatively young age (43-55 years of age), so that many current cell phone users may already be at risk for these tumors (Sadetzki 2008).
Researchers found a 48-58% increased risk of salivary gland tumors among people who make the greatest total number of calls or who log the most time on the phone without a hands-free device compared to others in the study group, on the side of the brain on which the cell phone was held (ipsilateral). No increased risk was seen for tumors on the other side of the head (Sadetzki 2008). The Israeli findings are in close agreement with an earlier study conducted in Sweden and Denmark; this study, based on a cohort about 1/3rd the size of the Israeli cohort, observed a 40% increased risk of ipsilateral benign tumors (Lonn 2006).
The fact that scientists have observed increased tumor risk in so many studies of cell phone users is even more powerful given that people have used cell phones widely for only about a decade, while cancer typically requires 15-20 years to develop. It seems likely that studies conducted in future years may find more consistent and higher cancer risks (Ahlbom 2004; Ahlbom 2009; Krewski 2001; Krewski 2007; Kundi 2009; Kundi 2004).
Strikingly, the field of research on the health effects of cell phone use has exhibited the signature pattern of a so-called “funding effect,” a biased outcome due to source of funding, observed in studies funded by tobacco companies or the manufacturers of industrial chemicals such as the endocrine disrupting plasticizer BPA (vom Saal 2005). In 2001, the U.S. Government Accountability Office voiced a strong concern about the reliability of results from industry-funded studies conducted without government oversight (GAO 2001). A recent systematic review of the source of funding and results of studies of health effects of cell phone use indicated that studies funded by the cell phone industry were ten times more likely to report no adverse effects compared to studies funded by public agencies or charities (Huss 2007; Huss 2008). Thus, some of the heterogeneity in the earlier literature could be related to the source of funding, whereby research sponsors could influence the design of the study, the nature of the exposure, and the type of outcome assessed.
Cell phones and health effects other than cancer
New lines of research are examining central nervous system diseases other than brain tumors in relation to cell phone use:
A recent Danish study noted an increased risk for neurological symptoms such as migraine and vertigo for cell phone users (Schuz 2009);
Scientists have found an increased risk for Alzheimer disease associated with electromagnetic radiation (Huss 2009);
A study from the University of California, Los Angeles found a correlation between prenatal exposure to cell phone radiation and behavioral problems in children (Divan 2008).
Six studies from the U.S., Australia, Japan and Europe reported that exposure to cell phone radiation has an adverse effect on sperm counts, motility and vitality (Agarwal 2009; De Iuliis 2009; Erogul 2006; Fejes 2005; Salama 2009; Yan 2007).
In animal studies, scientists have found that exposure during gestation to radiofrequency radiation like that emitted by cell phones is associated with decreased fetal growth, developmental abnormalities, and death of offspring (BioInitiative 2007; Heynick 2003). In occupational health studies for female physiotherapists, conducted in Sweden, Israel, and Finland, scientists found that workplace exposure to radiofrequency radiation during pregnancy is associated with low birth weight, congenital malformations, fetal death, and spontaneous abortions (Kallen 1982; Lerman 2001; Taskinen 1990).
The key question in the cell phone research field is how radiofrequency radiation like that from cell phones affects biological tissues and cells. Scientists have proposed and explored a number of possible mechanisms:
A number of studies examined the potential for genotoxicity of elecromagnetic fields (harm to genetic material in body cells that can lead to mutations and cancer) (BioInitiative 2007; Phillips 2009). While the evidence is not yet conclusive, one quarter of studies published on this issue found a genotoxic effect from low-level exposures (Vijayalaxmi 2008).
Scientists have reported that cell phone radiation affects levels of reactive oxygen species (ROS) inside the cell (Irmak 2002; Zmyslony 2004). In turn, higher ROS levels trigger intracellular signaling cascades that interrupt the smooth functioning of the cell. Changes in the activation status of molecules within these signaling cascades can lead to inflammation, heart disease, cancer and other chronic health conditions (Boutros 2008; Muslin 2008; Skaper 2007).
Cell phone radiation-induced reactive oxygen species may well be the causative agent that induces DNA damage, which is a precursor to cancer (Phillips 2009) and a potential mechanism of toxicity to sperm cells (De Iuliis 2009).
Radiofrequency radiation has been associated with a change in the activity of white blood cells (Aly 2008).
Exposure to cell phone radiation has been associated with cell death and activation of intracellular signaling molecules (Lee 2008). There is a vigorous debate in the literature regarding the types of conditions under which radiofrequency radiation would cause cell death (Guney 2007; Nikolova 2005; Palumbo 2008; Zhao 2007).
As described in a recent expert review, “In a living cell, many important processes occur by electron transfer across membrane structures in a well-organized manner, ions cross selective channels, proteins get activated and deactivated by cascades of precisely regulated enzymes” (Kundi 2009). These electronic processes would likely be affected by the electromagnetic fields, leading to altered cellular function, growth, and differentiation (Karinen 2008; Moisescu 2008; Zareen 2009). While none of these processes individually can be considered equivalent to the development of disease, all of them are associated with chronic adverse health effects and need to be considered in the assessment of radiofrequency radiation impact on biological organisms.