International Journal of Cancer and Clinical Research Microwave/Radiofrequency (MW/RF) Radiation Exposure and Cancer Risk: A Meta-analysis of Time-related Trends in the Accumulated Empirical Evidence

Iris Atzmon firstname.lastname@example.com
School of Public Health
University of Haifa
Israel

Boris Portnov
Department of Natural Resources & Environmental Management
Faculty of Management
University of Haifa
Israel

Shai Linn
School of Public Health
University of Haifa
Israel

Unit of Clinical Epidemiology
Rambam Medical Center
HaifaIsrael

Elihu D Richter
Unit of Occupational and Environmental Medicine
School of Public Health
Hebrew University of Jerusalem
Hadassah Medical Center
Israel

University of Haifa
6536HaifaP.O boxIsrael

International Journal of Cancer and Clinical Research Microwave/Radiofrequency (MW/RF) Radiation Exposure and Cancer Risk: A Meta-analysis of Time-related Trends in the Accumulated Empirical Evidence
Received: October 21, 2015: Accepted: January 25, 2016: Published: January 27, 2016Research Article: Open Access C l i n M e d International Library Citation: Atzmon I, Portnov B, Linn S, Richter ED (2016) Microwave/Radiofrequency (MW/ RF) Radiation Exposure and Cancer Risk: A Meta-analysis of Time-related Trends in the Accumulated Empirical Evidence. Int J Cancer Clin Res 3:039 Atzmon et al. Int J Cancer Clin Res 2016, 3:039 Volume 3 | Issue 1 *Corresponding author:
Background: Scientific debate regarding health effects from MW/ RF radiation has increased considerably in recent years. In the early 1980's much of the evidence concerning the health effects of MW/RF radiation came from occupational studies, however, in the 1990's and the 2000's, environmental studies became more dominant. This resulted from an increase in public awareness about exposure to MW/RF radiation. It remains unclear, however, whether scientific evidence gathered so far supports a general expectation that estimated cancer risks attributed to MW/RF radiation, will increase over time in conjunction with rapid proliferation of MW/RF technology. This study attempts to answer this question.Study goal:The study follows time-related changes in the body of scientific evidence associating cancer risk with MW/RF radiation.Methods: 57 studies, published over 30 years (between 1982  and 2012), and addressing the association between exposure to MW/RF radiation and cancer risk, were analyzed using time-trend analysis tools.Results: No significant 'upward' trend was uncovered in the association between MW/RF radiation and cancer, during comparison of earlier and more recent studies.Conclusions: Early occupational studies found higher associations of risk, compared to later environmental studies which detected relatively lower risks, possibly due to differences in exposure settings. It is difficult to draw conclusions whether this fact alone led the lack of 'upward' time-related trends, in the degree of a link between MW/RF radiation and cancer, and further studies are needed.

Introduction

Public exposure to microwave/radiofrequency (MW/RF) radiation has been increasing rapidly since the development and proliferation of wireless technologies [1][2][3][4][5][6], resulting in widespread health concerns [7][8][9][10][11][12][13]. According to International Telecommunication Union's estimates (Figure 1), in 2001 there were 962 million cellular phone users across the globe, in 2010 5,290 million and in 2015 7,085 million. In addition to environmental exposure, occupational exposure to MW/RF radiation has also increased, due to a widespread use of wireless technology in hospitals, clinics, medical laboratories and implanted medical devices [14].

The proliferation of MW/RF radiation has been a health concern for years [7][8][9][10][11][12][13]. Thus, in an early study by Milham [15], television and radio repairmen had an increased risk of leukemia mortality. This was also revealed by Pearce [16] in TV and radio repairmen. Increased risk of leukemia morbidity was likewise detected in an early study by Coleman [17], who investigated radio and telegraph operators, and by Calle [18] and Mcdowall [19], who studied leukemia mortality in radio and telegraph operators. Milham [20,21], who investigated several occupational groups exposed to electromagnetic fields, also found increased risk for acute leukemia mortality, mortality from myeloid leukemia and all leukemia in male members of the American Radio Relay League, residing in Washington and California. In two early studies, Milham [22,23] revealed significant increased mortality from lymphatic cancers, including multiple myeloma and non-Hodgkin's lymphoma among amateur radio operators and lymphatic and hematopoietic cancers among the technician class of amateur radio operators.

Association indices

We considered all types of association ratios. The most common measures of risks in studies were OR, RR followed by SMR. Odds Ratio (OR) represents the odds of a disease in the exposed vs. the odds in the non-exposed. Odds ratio is most commonly used in case control studies. PMR gives results similar to SMR (personal [32], Elliot [33] and Chung Yi [13]. Thus, Hocking [7] found a statistically significant association between residential proximity to television towers and a decrease in survival rates among children with leukemia in North Sydney, Australia. In 2004, two further studies found increased cancer risk among neighborhoods located close to cellular towers [9,10]. In yet another study published in 2004, Park [8] found higher rates of leukemia mortality among young adults aged less than 30 years residing in urban areas surrounded by AM radio broadcasting towers.

In a study published three years later, Ha [11] found an increased risk of lymphocytic leukemia among children residing in areas surrounded by AM radio transmitters whilst in Belo Horizonte, Brazil, Dode [12] found higher mortality among residents whose homes were located within a radius of 500 meters from base stations, when compared with the average mortality rate of the city as a whole.

Despite the emerging body of scientific evidence regarding a MW/RF-cancer association, to the best of our knowledge, there have been no attempts to analyze time-related trends of the strength of MW/RF-cancer risk association between earlier and more recent studies. To the best of our knowledge, the present study is the first one that attempts to look into the time related changes in the detected strength of the relationship between MW/RF radiation and cancer in both occupational and environmental settings.

Study Methods

Data sources

We analyzed peer-reviewed papers published between 1982 and 2012 dealing with MW/RF radiation associated with cancer. A total of 57 papers, retrieved using the Google Scholar search engine were reviewed. Out of the 57 studies collected, 4 studies were excluded because they did not contain epidemiologic analysis [34,35] reported a very high result that masked other studies' results on the graph (there was one underlying cause of death due to leukemia compared with 0.2 expected (standard mortality ratio [SMR] = 437, 95% confidence interval [CI] = 11-2433), and two multiple listed causes of death due to leukemia compared with 0.3 expected (SMR = 775, 95% CI = 94-2801)] [36] or used a case series method with no epidemiological ratios and/or probability values [37].  1 to make the level of association visually clear. Studies were ordered by years in order to take into consideration the possibility of trends in years. In order to not lose data, we included several results of the same study, in these cases the name of the author appears more than once on the same graph.

In order to determine whether the results were statistically significant, time trend-analysis was performed, using WinPepi software (WinPepi © J.H Abramson version 11.47) [42], to examine the relationship between date and the reported strength of association related to radiation exposure. The WinPepi © computers programs for epidemiologists were designed as learning or teaching aids for use in practice and research in the health field. WinPepi © is the Windows version of the DOS-based PEPI (an acronym for Programs for EPI demiologists) package, which grew from a set of programs for programmable pocket calculations published in 1983 [42].

Results

The results of the analysis are shown in table 1 and figure 2, figure  3, figure 4, figure 5, figure 6 and figure 7. The results are presented according to the measure Kendall's tau. Kendall's tau is a nonparametric measure of correlation between two ranked variables. It is the difference between the probability that the observed data are in communication with Dr. Sam Milham, Decoufle [38]) while for a rare disease like cancer, RR is approximately equal to the OR [39]. SIR (Standardized Incidence Ratio) is the relationship between the rate of specific disease in the chosen population, and the rate of the same disease in the general population, standardized for age, gender and other relevant parameters or, when death is the outcome, SMR (standardized mortality ratio) [40,41].

Analytical methods

The analysis was performed in several steps. First we ordered all studies collected by the year of publication, and examined changes in the strength of association over time between exposure to MW/RF radiation and cancer. We performed the analysis by graphing timerelated trends of association separately for several types of malignancies. We entered data of associations found in the studies into Excel program files. Studies were ordered on X axis, independent variable, by year of publication. The dependent variable, Y axis, represents the strength of association. Logarithmic transformations were used in order to increase the resolution over the different associations, and to identify the line of For leukemia morbidity in adults (Figure 6), morbidity in children and mortality in adults, stable trends were detected. the same order versus the probability that the observed data are not in the same order.

There was a suggestion of some upward trends, but not at levels of significance for melanoma morbidity (    For several cancer types, early occupational studies had higher measures of association vs. later environmental studies. For example, on the graph of lymphoma morbidity (Figure 7), an early occupational study [43] found for non-hodgkin's lymphoma observed/expected ratios (OER) = 5.82 (95% CI 2. 11, 9.74) The OER were calculated using the non-exposed group as reference. Thus corresponding to the odds ratio. For breast cancer morbidity, an early occupational study [44], found an elevated measure of association for communication and broadcasting men workers OR=2.9 OR represents the odds of a disease in the exposed vs. the odds in the non-exposed. On the graph of testicular cancer (morbidity), two early occupational studies [45,46] found highly significant associations. On the graph of all cancer sites mortality, one early occupational study [47] found especially high correlation (crude death rate per 1000 = 7.23, 95% CI 1.2788, 40.8775; CI calculated by WinPepi © program) for one category of exposure. In this study on 40,000 of the US Naval personnel, the authors concluded that no adverse effects were detected that could be attributed to potential microwave radiation exposures. However, the study was re-analyzed by Goldsmith [47], who found that death rates for the group with the highest exposure, aviation electronics technicians (AT), were significantly higher than those for the remaining men for all deaths, disease-related death, deaths from malignancy and death from malignancy of the lymphatic and hematopoietic systems. Although this group had a higher mean age at the beginning of the study (23.4) than the average of the whole group (21.3), this mean age was younger than the average for aviation electrician's mates AE (24.7), a category that showed no increase in deaths from any malignancy or from other diseases. According to Goldsmith [47], when the authors adjusted for age, they combined the AT group with the fire control technicians (FT) group, which had a low malignancy rate. These two groups were about the same size and had 10 and 1 cases of lymphatic or hematological malignancies, respectively [47]. When earlier occupational studies with higher correlations were removed to test if the trend was influenced by the type of studies (occupational vs. environmental), they were found to have had visual influence (the trend became upwards when removed) but not statistically significant, therefore no conclusions can be drawn. Complete separation between environmental and occupational studies in analysis did not change the results.

Discussion

We could not detect any significant upward time-related trend in the strength of association between RF/MW radiation and cancer. Higher strength of association found in occupational studies vs. lower strength of association found in later published environmental studies, influenced visual trends of the graphs.

The differences between the strengths of associations in occupational vs. environmental studies may be related to the difference in exposure conditions in occupational vs. environmental studies. Occupational settings tend to have higher exposures and closer to the source of radiation vs. environmental settings with lower ambient exposures, greater distances from the source of exposure, taking into account that the intensity is falling quickly with increasing distance. However, many biological effects are reported at the low levels from environmental exposure [3,48].

Both environmental and occupational studies have limitations, due to confounders and exposure assessment deficits, misclassification of exposure or effect measured and the healthy worker effect bias that is specific to occupational studies. The healthy worker effect bias signifies the healthier health status of people who are able to work. In occupational studies, the mortality and morbidity rates within the workplace are lower than in the general population [49]. These factors may lead to an underestimation of risk. In environmental studies it is especially difficult to detect and control confounders or changes in exposure time. Misclassification of exposure is a recognized potential source of underestimation of risk and would provide an explanation for the negative findings. Also, latency of the effect might obscure associations. However, since both the decreasing and increasing trends were not statistically significant it is difficult to draw conclusions, and further studies may provide more answers.

Study Limitations

Our study has inherent limitations based on the limitation of individual studies, especially the limited information on exposure assessment and the lack of confounders on the individual level. Another limitation may be a short latency period and recent exposure to the wireless technologies.

Conclusion

Early occupational studies found higher associations of risk compared to later environmental studies which detected relatively lower risks, possibly due to lower and less homogeneous exposure settings in the latter group. It is difficult to draw conclusions whether this fact alone led the lack of 'upward' time-related trends, in the degree of a link between MW/RF radiation and cancer, and further studies are needed.

Figure 1 :
1Global mobile-cellular subscriptions, total and per 100 inhabitants, 2001-2015. Source: International Telecommunication Union Statistics http://www.itu.int/en/ITU-D/Statistics/Pages/default.aspx

Figure 2 :Figure 3 :
23Association between exposure to MW/RF and mortality from brain cancer. Association between exposure to MW/RF and brain cancer morbidity.* Occupational studies ISSN: 2378-3419 Atzmon et al. Int J Cancer Clin Res 2016, 3:039 in children (Figures 2-4) [R2= 0.926; Kendall's tau b=0.386 95%CI (-0.412-0.849) p> 0.05]; [R2=0.0822; Kendall's tau b=0.216 95%CI (-0.505-0.760) p>0.05]; [R2=0.1078; Kendall's tau b=0.400 95%CI (-0.596-0.911) p> 0.05], respectively.

Figure 5 )Figure 4 :
54[R2 = 0.2511; Kendall's tau b= 0.355 (95%CI -0.496-0.858; p>0.05]; all cancer sites morbidity [R2 = 0.0821; Kendall's tau b=0.053 (95%CI -0.576-0.642 p>0.05], brain cancer mortality, morbidity in adults and morbidity Brain cancer morbidity in children.

Figure 5 :
5Association between exposure to MW/RF and melanoma morbidity. * Occupational studies

Figure 6 :
6Association between exposure to MW/RF and adult leukemia morbidity.Generally a stable trend is seen over the years• Page 5 of 6 • ISSN: 2378-3419 Atzmon et al. Int J Cancer Clin Res 2016, 3:039

Figure 7 :
7Association between exposure to MW/RF and lymphoma morbidity.

McKenzie [28], Cooper [29], Michelozzi [30], Ha [31], Hocking [7], Park [8], Eger [9], Wolf [10], Ha [11], Merzenich Atzmon et al. Int J Cancer Clin Res 2016, 3:039ISSN: 2378-3419

Table 1 :
1Overall associations between RF exposure and different types of cancer.Type of Cancer
R 2
Kendall's tau b Significance

Kendall tau (P; CI)

Melanoma morbidity
0.2511 0.355
> 0.05 95%CI

(-0.496-0.858)

Brain tumors mortality
0.926
0.386
> 0.05 95%CI

(-0.412-0.849)

Brain tumors morbidity
0.0822 0.216
> 0.05 95%CI

(-0.505-0.760)

Brain cancer (morbidity) in
children

0.1078 0.400
> 0.05 95%CI

(-0.596-0.911)

Leukemia Mortality
0.002
-0.043
> 0.05 95%CI

(-0.598-0.540)

Childhood Leukemia
0.0128 -0.167
> 0.05 95%CI

(-0.734-0.538)

Adult Leukemia Morbidity
0.0005 -0.144
> 0.05 95%CI

(-0.696-0.515)

Lymphoma morbidity
0.0168 -0.122
> 0.05 95%CI

(-0.742-0.610)

Lymphoma mortality
0.009
0.160
> 0.05 95%CI

(-0.587-0.760)

Breast cancer morbidity
0.5517 -0.527
> 0.05 95%CI

(-0.942-0.527)

Testicular cancer morbidity 0.5057 -0.794
< 0.005 95%CI

( -0.983-0.227)

All cancer sites morbidity
0.0821 0.053
> 0.05 95%CI

(-0.576-0.642)

All cancer sites mortality
0.0168 0.333
> 0.05 95%CI

(-0.545-0.863)

AcknowledgementWe would like to thank Dr. Joe Abramson for reviewing the methodology with regard to WinPepi.
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How to Support Students in Selecting Graded Readers How to Support Students in Selecting Graded Readers

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83September 2017Publication date: September, 2017.To cite this article Barr, A., & Lyon, P. (2017). How to support students in selecting graded readers. To link to this article This article may be used for research, teaching and private study purposes. Please contact the authors for permission to re-print elsewhere. Scroll down for article 247extensive readingself-regulated readingautonomous readersself-access learning centerlearner autonomy
Learner autonomy, and giving students the ability to select their own learning materials as a way to encourage them to take charge of their own learning, is now a major focus in education(Ellis & Sinclair, 1989). However, students may not always feel confident making selections that were once made by their classroom teachers. The authors analyzed data from student surveys to determine possible factors that contribute to and influence students' graded reader selections. Results indicate that although some learners are able to make selections that meet their expectations, there are almost as many who are struggling to do so. In this report, the authors' aim is to offer suggestions as to how learners can be assisted to improve success in graded reader selection.

learners to select materials that they want to read at their own ability level and that is of interest to them, learners are able to also increase their reading confidence. However, Waring (2000) states that in order for reading fluency and confidence to develop, learners need to read at or below their comfort level. Since selecting material may prove to be a daunting task, Day and Bamford (2004) recommend that learners use books or magazines that have been specifically written for language learners at different ability levels. Graded readers are therefore a suitable choice for language learners. Thus, extensive reading is often referred to as graded reading (Waring, 2000).

According to the ERF (Extensive Reading Foundation), students are best at judging their own comfort zone with respect to their level (2011). In fact, in literature showing how graded readers have been implemented into university level reading/writing courses in Japan, studies have often focused on the need for learners to make autonomous choices (Cheetham, Elliot, Harper, & Sato, 2017;Harrold, 2013;O'Loughlin, 2012).

Harrold's (2013) study indicated that when students self-selected books, they tended to enjoy them more than the class sets that had previously been assigned by their classroom teachers. However, even after being given an orientation to graded readers, when given the power to choose, it remains unclear how learners make decisions when they selfselect books or how they make subsequent choices. This appears to be an important area to investigate.

Background

Several years ago, an extensive reading program was introduced into the English and International Communications Department curriculums at a private Japanese university to help students become more autonomous readers. After an orientation to graded readers in 2015, we (the authors -two teachers of the course) asked students in three freshman classes to choose their own graded readers. We limited the students' choices to graded readers for the following reason: editors and publishers control the vocabulary and grammar that readers will be exposed to, with higher frequency vocabulary and a close range of grammar at low levels and lower frequency words and more complex grammar at higher levels (Lake & Holster, 2014). The importance of selecting a level that students felt comfortable with was stressed to students in all three classes since it is unlikely that learners will develop into fluent readers with selections that are above their current ability level (Waring, 2000). Students in all three classes were required to self-select a new book at least every two weeks for a total of five books. Waring (2000) and Nation (2009) suggest that this is a good timeframe in order for students to receive enough exposure to sustained reading and repetition of language. To determine how students felt about the book selections that they were making, students were asked to complete pre-and post-reading questions.

How Students Viewed Graded Readers

Responses to the research questions (see Appendix) indicated that students enjoyed the books for several reasons: the books were interesting, easy to summarize, an enjoyable genre, an appropriate level, or funny, they had an unpredictable ending or touching scenes, or the students learned new information. Similarly, there were many reasons given for books that the students did not enjoy: the books were too difficult, too easy, dark, too long, too short, or not like the students had expected (or not like the movie), or had disturbing content, a predictable ending, or shallow content.

How Students Made Subsequent Material Choices

Whereas most responses indicated that many students were aware of factors to consider in making a selection that might better meet their expectations, some responses indicated that learners were unsure of how to improve their choices.

Examples of criteria that students indicated they would consider when making subsequent choices were choosing a higher or lower level, trying a new genre, choosing based on a friend/ learning advisor/ teacher recommendation, or making a selection based on a story that they were already familiar with or on a movie that they had seen. A unique idea employed by one student was to look for a popular book based on how many times it had been borrowed. This approach was taken after two disappointing previous decisions.

In this instance, the student liked the book and, more importantly, had found a suitable level.

Unfortunately, students did not always take their own advice and ignored the criteria they had specified for themselves when making their next selection. One student almost always commented that they would look at the blurb/cover for their next book selection. However, the student continued to base their choices on familiar stories, movies they had seen or on friend recommendations. This student's expectations were never really met; having finally decided to review the cover and read the blurb for the final book they chose, they found the book to be a good level. Unfortunately, they also commented that it was too short.

Another student indicated that for a subsequent selection they would choose a specific genre, but they instead chose a book based on a friend's recommendation. This student was ultimately dissatisfied with the level of the book. Surprisingly, it seemed that when students chose books that were recommended (either by a friend, classmate, teacher or learning advisor), results were mixed when it came to how the selection met their expectations. The books were either interesting and a good level match, or were too challenging. This indicates that choosing a book requires more consideration than just selecting one because it was recommended, once again showing the possibility that students are not necessarily aware of their personal interests and levels. These are clearly points that need to be highlighted to students.

Although students were given the option to stop reading and select a new book per cycle if they were not happy with their choices, few students took advantage of this.

Abandoning a book if it is either too difficult or not of interest is an important aspect of self-regulated learning (Lake & Holster, 2014). Since there was a question on the survey that related to this, and there were classroom reminders, it is unfortunate that students who were not making choices that met their expectations did not take advantage of this option more often. This is an option that could be further reinforced.

Developing an Awareness of How to Choose Materials

The results varied as to when students began making choices that consistently met their expectations. Students that were successful throughout the selection process often looked at the title, read the summary and made their selections based on genre. Students that were mostly successful with only a single unsuccessful choice midway through either quickly realized their dissatisfaction and chose a new book to read instead or were able to return to making successful selections with their next books. They often did this by returning to earlier criteria they had used, notably, reading the blurb and checking the level.

It should be noted that students who were able to make the transition from choices that did not meet their expectations to ones that did accomplished this by their third choice. For those learners who were only starting to make more successful choices toward the end of the semester, it was clear from their survey responses that it was only at this late point that they started looking at book features such as the blurb or level.

Although they had been through an orientation, some students did not take heed until this late stage.

Students that were inconsistent in meeting their expectations often struggled with choosing the appropriate level, mostly oscillating between being too challenging or too easy. Other reasons for choices not meeting expectations were that choices were 'not what they had expected (i.e. not like the movie), too predictable, or shallow'. Furthermore, students whose choices did not meet their expectations typically made their selections based on the title, the picture on the front cover and recommendations, but only occasionally read the blurb and/or considered the level. One exception was a student who consistently read the blurb and checked the level, but was still unable to make choices that met their expectations. The student's challenge was finding a genre in the graded readers that suited their interest.

Although some students were able to delve into multiple genres with success, it seemed that they were perhaps more aware of the level that was comfortable for them and the subjects that interested them. Unfortunately, for many of the learners who chose from multiple genres, it appeared that they were not considering levels; therefore, their feedback often indicated that the book they had chosen was an inappropriate level. This would indicate that students need more assistance/ reminders when determining the levels and genres that are most suitable for them.

Interventions for Helping Students to Make Effective Choices

We believe that it would be beneficial to review book elements (e.g. level, title, genre, the blurb) in class, if not prior to each and every book selection that students make, at least periodically. Furthermore, if students in classes that have undergone an orientation to selecting graded readers are struggling with making successful choices, it can only be assumed that students who have not had such an orientation might also struggle, perhaps more so. Consequently, it might be beneficial to have information available in the graded reader areas in SALCs and libraries that highlights important factors for selecting graded readers such as the genre, reading the blurb and reading the first page to check the level. Additional signs could be posted that clearly highlight the level of books, taking into consideration the differences often found between the different publishing houses, as well as signs reminding learners to ask SALC staff for advice when selecting a book. SALC staff could help learners think more carefully about what they need to consider when selecting a book. Another important role for SALC advisors, along with the classroom teachers, is to stress the importance of taking the time to review books, even if a particular book has been recommended or is famous/familiar.

Conclusion

Although students tend to prefer making reading choices when it comes to extensive reading, it is clear that selecting a book that matches one's expectations is not an easy task. Whilst some learners are able to immediately make successful selfselections, there are some learners who struggle and who are not as aware of their needs as a learner. It would benefit all learners making book selections to be able to refer to an easily accessible guide each and every time they make selections. Having one close at hand in the relevant section of the SALC or library would be useful. Learners clearly need added guidance and constant reinforcement on the path to becoming autonomous readers.

Notes on the contributors

Amber Barr is a Senior Lecturer at Kanda University of International Studies, Japan. Her main research interests are extensive reading and learner autonomy.

Phoebe Lyon is a Principal Lecturer for Curriculum and Assessment at Kanda University of International Studies, Japan. Her research interests include learner autonomy, materials development and assessment.

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