Occupation and risk for testicular cancer: a case-control study

5G mobile networks and health-a state-of-the-science review of the research into low-level RF fields above 6 GHz

The increased use of radiofrequency (RF) fields above 6 GHz, particularly for the 5 G mobile phone network, has given rise to public concern about any possible adverse effects to human health. Public exposure to RF fields from 5 G and other sources is below the human exposure limits specified by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). This state-of-the science review examined the research into the biological and health effects of RF fields above 6 GHz at exposure levels below the ICNIRP occupational limits. The review included 107 experimental studies that investigated various bioeffects including genotoxicity, cell proliferation, gene expression, cell signalling, membrane function and other effects. Reported bioeffects were generally not independently replicated and the majority of the studies employed low quality methods of exposure assessment and control. Effects due to heating from high RF energy deposition cannot be excluded from many of the results. The review also included 31 epidemiological studies that investigated exposure to radar, which uses RF fields above 6 GHz similar to 5 G. The epidemiological studies showed little evidence of health effects including cancer at different sites, effects on reproduction and other diseases. This review showed no confirmed evidence that low-level RF fields above 6 GHz such as those used by the 5 G network are hazardous to human health. Future experimental studies should improve the experimental design with particular attention to dosimetry and temperature control. Future epidemiological studies should continue to monitor long-term health effects in the population related to wireless telecommunications.

Etiology and early pathogenesis of malignant testicular germ cell tumors: towards possibilities for preinvasive diagnosis

Malignant testicular germ cell tumors (TGCT) are the most frequent cancers in Caucasian males (20-40 years) with an 70% increasing incidence the last 20 years, probably due to combined action of (epi)genetic and (micro)environmental factors. It is expected that TGCT have carcinoma in situ(CIS) as their common precursor, originating from an embryonic germ cell blocked in its maturation process. The overall cure rate of TGCT is more than 90%, however, men surviving TGCT can present long-term side effects of systemic cancer treatment. In contrast, men diagnosed and treated for CIS only continue to live without these long-term side effects. Therefore, early detection of CIS has great health benefits, which will require an informative screening method. This review described the etiology and early pathogenesis of TGCT, as well as the possibilities of early detection and future potential of screening men at risk for TGCT. For screening, a well-defined risk profile based on both genetic and environmental risk factors is needed. Since 2009, several genome wide association studies (GWAS) have been published, reporting on single-nucleotide polymorphisms (SNPs) with significant associations in or near the genes KITLG, SPRY4, BAK1, DMRT1, TERT, ATF7IP, HPGDS, MAD1L1, RFWD3, TEX14, and PPM1E, likely to be related to TGCT development. Prenatal, perinatal, and postnatal environmental factors also influence the onset of CIS. A noninvasive early detection method for CIS would be highly beneficial in a clinical setting, for which specific miRNA detection in semen seems to be very promising. Further research is needed to develop a well-defined TGCT risk profile, based on gene-environment interactions, combined with noninvasive detection method for CIS.

Occupational and environmental exposures associated with testicular germ cell tumours: systematic review of prenatal and life-long exposures

Background

Testicular germ cell tumours (TGCT) are the most common cancers in men aged between 15 and 44 years and the incidence has increased steeply over the past 30 years. The rapid increase in the incidence, the spatial variation and the evolution of incidence in migrants suggest that environmental risk factors play a role in TGCT aetiology. The purpose of our review is to summarise the current state of knowledge on occupational and environmental factors thought to be associated with TGCT.

Methods

A systematic literature search of PubMed. All selected articles were quality appraised by two independent researchers using the ‘Newcastle-Ottawa Quality Assessment Scale’.

Results

After exclusion of duplicate reports, 72 relevant articles were selected; 65 assessed exposure in adulthood, 7 assessed parental exposures and 2 assessed both. Associations with occupation was reported for agricultural workers, construction workers, firemen, policemen, military personnel, as well as workers in paper, plastic or metal industries. Electromagnetic fields, PCBs and pesticides were also suggested. However, results were inconsistent and studies showing positive associations tended to had lower quality ranking using the assessment scale (p=0.02).

Discussion

Current evidence does not allow concluding on existence of any clear association between TGCT and adulthood occupational or environmental exposure. The limitations of the studies may partly explain the inconsistencies observed. The lack of association with adulthood exposure is in line with current hypotheses supporting the prenatal origin of TGCT. Future research should focus on prenatal or early life exposure, as well as combined effect of prenatal and later life exposure. National and international collaborative studies should allow for more adequately powered epidemiological studies. More sophisticated methods for assessing exposure as well as evaluating gene–environment interactions will be necessary to establish clear conclusion.

A population-based case-control study on social factors and risk of testicular germ cell tumours

OBJECTIVES

Incidence rates for testicular cancer have risen over the last few decades. Findings of an association between the risk of testicular cancer and social factors are controversial. The association of testicular cancer and different indicators of social factors were examined in this study.

DESIGN

Case-control study.

SETTING

Population-based multicentre study in four German regions (city states Bremen and Hamburg, the Saarland region and the city of Essen).

PARTICIPANTS

The study included 797 control participants and 266 participants newly diagnosed with testicular cancer of which 167 cases were classified as seminoma and 99 as non-seminoma. The age of study participants ranged from 15 to 69 years.

METHODS

Social position was classified by educational attainment level, posteducational training, occupational sectors according to Erikson-Goldthorpe-Portocarrero (EGP) and the socioeconomic status (SES) on the basis of the International SocioEconomic Index of occupational status (ISEI). ORs and corresponding 95% CIs (95% CIs) were calculated for the whole study sample and for seminoma and non-seminoma separately.

RESULTS

Testicular cancer risk was modestly increased among participants with an apprenticeship (OR=1.7 (95% CI 1.0 to 2.8)) or a university degree (OR=1.6 (95% CI 0.9 to 2.8)) relative to those whose education was limited to school. Analysis of occupational sectors revealed an excess risk for farmers and farm-related occupations. No clear trend was observed for the analyses according to the ISEI-scale.

CONCLUSIONS

Social factors based on occupational measures were not a risk factor for testicular cancer in this study. The elevated risk in farmers and farm-related occupations warrants further research including analysis of occupational exposures.

Case-control study of male germ cell tumors nested in a cohort of car-manufacturing workers: Findings from the occupational history

BACKGROUND

To examine whether the previously observed excess risk of male germ cell cancer in a cohort of car-manufacturing workers can be attributed to occupational activities inside and/or outside the car industry.

METHODS

A nested case-control study among workers in six plants included 205 cases of germ cell cancer and 1,105 controls, individually matched by year of birth (±2 years). Job periods of the individual occupational histories were coded based on the International Standard Classification of Occupations (ISCO) and the industrial classification of economic activities (NACE). Odds ratios (ORs) and corresponding 95%-confidence intervals (CI) for ever-never and cumulative employment were calculated by conditional multivariate logistic regression adjusted for cryptorchidism.

RESULTS

Significantly increased risks were observed for machinery fitters and assemblers (A) (OR = 1.8, 95% CI 1.25-2.53) and "workers not elsewhere classified" (OR = 2.10, 95% CI 1.27-3.54), but no trend was observed for employment duration in either occupational group. Stratification of job group A by metal-cutting and non-cutting jobs yielded ORs of 1.87 (95% CI 1.31-2.67) and of 1.24 (95% CI 0.68-2.28), respectively. Among "plumbers, welders, sheet & structural metal workers" (adjusted OR 1.4, 95% CI 0.99-1.95) only "structural metal preparers and erectors" showed a substantially increased risk (OR = 2.30; 95% CI 1.27-4.27).

CONCLUSIONS

Our results do not fully explain the increased incidence of germ cell cancer in the cohort, but support previous findings showing increased risks among metal workers. These risks were most strongly pronounced in metal-cutting activities.

Testicular cancer risk associated with occupational radiation exposure: a systematic literature review

Testicular cancer is a rare disease, affecting mainly young men aged 15-49. There have been some recent reports that it might be associated with radiation exposure. We have systematically reviewed this topic. English-language articles published between 1990 and 2008 studying the relationship between occupational radiation exposure and testicular cancer were included. Risk of bias was assessed using a modified version of the EPHPP checklist. For ionising radiation we subdivided study populations into occupational groups. No pooled analysis was performed due to the heterogeneity of studies. Seven case-control and 30 cohort studies were included in the review. For radiation workers, one incidence study showed a significant increase and four showed no effect. Eight mortality studies did not indicate an effect while four showed a non-significant increase. Incidence among persons with military exposure was not increased in two studies and non-significantly increased in another two. Among aircrew studies, one showed no effect against five with slight increases. Medical exposure studies showed no increases. For EMF exposure, three studies showed no effect, two reported a significant and four a non-significant increase in incidence. Overall, there was very limited evidence for associations between occupational ionising radiation and testicular cancer, while there were some positive associations for EMF. Testicular cancer mortality is generally low and was not associated with radiation. New incidence studies are recommended to investigate the association between radiation exposure and testicular cancer where exposure is better specified and individually estimated.

Testicular cancer and hormonally active agents

Testicular cancer (TC) is a rare form of cancer, accounting for 1% of all new cancer cases in Canadian males. TC is the most common malignancy among young men, aged 25-34 yr old. Over previous decades, the incidence of TC has increased in many Western countries. Countries with a sufficiently long period of cancer registration, such as Denmark, document this trend back to the first half of the 20th century. The etiology of TC remains poorly understood. Most of the established risk factors are likely related to in utero events, including some factors that are purported to be surrogate measures for exposure to endogenous estrogens. The correlation of TC with other testicular abnormalities and with pregnancy factors led to the proposal that these conditions are a constellation of sequelae of impairment of testicular development called testis dysgenesis syndrome. There is some limited evidence suggesting that exposure to pharmacological estrogens may contribute to some cases of TC. There is currently no compelling evidence that exposure to environmental estrogenic or other hormonally active substances is contributing to the rise in TC incidence observed in Western nations over the last several decades; however, this question has not been extensively studied. The (1) rarity of this condition in the population, (2) long lag time between the presumed sensitive period during fetal development and clinical appearance of the condition, and (3) lack of a good animal model to study the progression of the disease have greatly hindered the understanding of environmental influences on TC risk.

Fielding a current idea: exploring the public health impact of electromagnetic radiation

Several publications in the scientific literature have raised concern about the individual and public health impact of adverse non-ionizing radiation (a-NIR) from electromagnetic field (EMF) exposure emanating from certain power, electrical and wireless devices commonly found in the home, workplace, school and community. Despite the many challenges in establishing irrefutable scientific proof of harm and the various gaps in elucidating the precise mechanisms of harm, epidemiological analyses continue to suggest considerable potential for injury and affliction as a result of a-NIR exposure. As environmental health has not been emphasized in medical education, some clinicians are not fully aware of possible EMF-related health problems and, as a result, manifestations of a-NIR may remain misdiagnosed and ineffectually managed. It is important for physicians and public health officials to be aware of the fundamental science and clinical implications of EMF exposure. A review of the scientific literature relating to the link between electromagnetic radiation and human health, several public health recommendations, and four case histories are presented for consideration.

Endocrine-disrupting chemicals and testicular cancer: a case-control study

Environmental factors appear to be important in the etiology of testicular cancer. In this study, the authors identified some risk factors for testicular cancer, paying particular attention to prenatal and early life exposure to endocrine-disrupting chemicals (EDCs). Using a questionnaire, the authors obtained information on male participants' environmental and occupational exposures during adolescence and adulthood. A multivariate logistic regression analysis of 103 cases and 215 controls showed an association between seminoma and nonseminoma and hobby activities that potentially involved the use of EDCs (eg, paints, glues, or solvents). Rural residence during adolescence was associated with all histological types of testicular cancer and with seminoma. No association was found with occupational exposures of the subjects. This study's findings also confirm previously identified risk factors, such as history of cryptorchidism and undescended testicle, high educational level, and low birth weight, and it gives some support to the hypothesis of a possible association between EDC exposures and testicular cancer.

Epidemiology of testicular cancer: An overview

Testicular cancer is a rare disease, accounting for 1.1% of all malignant neoplasms in Canadian males. Despite the low overall incidence of testicular cancer, it is the most common malignancy among young men. The incidence rate of testicular cancer has been increasing since the middle of the 20th century in many western countries. However, the etiology of testicular cancer is not well understood. A search of the peer-reviewed literature was conducted to identify important articles for review and inclusion in this overview of the epidemiology of testicular cancer. Most of the established risk factors are related to early life events, including cryptorchidism, carcinoma in situ and in utero exposure to estrogens. Occupational, lifestyle, socioeconomic and other risk factors have demonstrated mixed associations with testicular cancer. Although there are few established risk factors for testicular cancer, some appear to be related to hormonal balance at various life stages. Lifestyle and occupational exposures occurring later in life may play a role in promoting the disease, although they are not likely involved in cancer initiation. In addition to summarizing the current epidemiologic evidence on risk factors for testicular cancer, we suggest future research directions that may elucidate the etiology of testicular cancer.

Residential exposure to overhead high-voltage lines and the risk of testicular cancer: results of a population-based case-control study in Hamburg (Germany)

BACKGROUND

In a population-based case-control study we examined the association between residential exposure to overhead high-voltage lines and testicular cancer.

METHODS

We recorded the residential biography of cases with testicular cancer identified by the Hamburg Cancer Registry and of controls that were randomly selected from the mandatory registry of residents in Hamburg. The study included 145 incident cases between 15 and 69 years of age, diagnosed between 1995 and 1997, and 313 controls, matched for age in 5-year strata. In model A, exposure was defined by distance (ever vs never). Model B took into account residence time and the inverse distance from the nearest high-voltage line. It distinguished between low and high exposure, the never exposed persons serving as a reference group. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated by unconditional logistic regression. For men below the age of 40 years and men aged 40 years and over separate analyses were carried out.

RESULTS

Within a corridor of 100 m the prevalence of exposure to high-voltage lines in Hamburg was 6.9% in cases and 5.8% in controls (OR=1.3; 95% CI=0.56-2.80). In the more complex model B we found an OR of 1.2 (95% CI=0.60-2.47) for low exposure and 1.7 (95% CI=0.91-3.32) for high exposure. Younger men show slightly increased risks in both models.

CONCLUSIONS

In all, residential exposure to high-voltage lines did not seem to be a major risk factor for testicular cancer in our study. Yet, the fact that risks for men below the age of 40 years were slightly increased in both exposure models deserves further attention.

Epidemiology of health effects of radiofrequency exposure

We have undertaken a comprehensive review of epidemiologic studies about the effects of radiofrequency fields (RFs) on human health in order to summarize the current state of knowledge, explain the methodologic issues that are involved, and aid in the planning of future studies. There have been a large number of occupational studies over several decades, particularly on cancer, cardiovascular disease, adverse reproductive outcome, and cataract, in relation to RF exposure. More recently, there have been studies of residential exposure, mainly from radio and television transmitters, and especially focusing on leukemia. There have also been studies of mobile telephone users, particularly on brain tumors and less often on other cancers and on symptoms. Results of these studies to date give no consistent or convincing evidence of a causal relation between RF exposure and any adverse health effect. On the other hand, the studies have too many deficiencies to rule out an association. A key concern across all studies is the quality of assessment of RF exposure. Despite the ubiquity of new technologies using RFs, little is known about population exposure from RF sources and even less about the relative importance of different sources. Other cautions are that mobile phone studies to date have been able to address only relatively short lag periods, that almost no data are available on the consequences of childhood exposure, and that published data largely concentrate on a small number of outcomes, especially brain tumor and leukemia.

Mobile telephones and cancer--a review of epidemiological evidence

There is considerable public concern about possible long-term adverse health effects of mobile phones. While there is scientific controversy about long-term health effects of high-frequency electromagnetic fields lasting for at least 50 yr, the rise and success of mobile telecommunication made it necessary to investigate the problem more comprehensively and assess the possible risk cautiously because never before in history has a substantial proportion of the population been exposed to microwaves in the near field and at comparably high levels. Because the mostly localized exposure target region is the head, most epidemiological studies focus on brain tumors. Overall nine epidemiological studies have been published, four from the United States, two from Sweden, and one each from Denmark, Finland, and Germany. Seven studies were mainly on brain tumors, with one investigating in addition to brain tumors salivary gland cancer and another cancer of the hematopoietic and lymphatic tissues, and one examining intraocular melanoma. All studies have some methodological deficiencies: (1) too short duration of mobile phone use to be helpful in risk assessment, (2) exposure was not rigorously determined, and (3) there is a possibility of recall and response error in some studies. Nevertheless, all studies approaching reasonable latencies found an increased cancer risk associated with mobile phone use. Estimates of relative risk in these studies vary between 1.3 and 4.6 with highest overall risk for acoustic neuroma (3.5) and uveal melanoma (4.2), and there is evidence for enhanced cancer risk with increasing latency and duration of mobile phone use.

Clinical epidemiology of testicular germ cell tumors

Clinical epidemiology is sometimes called the basic science of clinical medicine. In terms of the pathogenesis of testicular germ cell tumors (GCTs), clinical epidemiology analyzes suspected risk factors. The present review highlights the risk factors established so far and briefly summarizes those factors currently under investigation. In analogy to the methods of evidence based medicine, this review attributes levels of evidence to each of the putative risk factors. Level I represents highest quality of evidence while level V denotes the lowest level. So far, undescended testis (UDT), contralateral testicular GCT and familial testis cancer are established risk factors attaining high levels of evidence (levels I-III a). In a meta-analysis of 21 studies exploring the association of UDT with GCT risk, an over-all relative risk (RR) of 4.8 (95% confidence interval 4.0-5.7) was found. Contralateral testicular GCT involves a roughly 25-fold increased RR of GCT, while familial testis cancer constitutes a RR of 3-10. Infertility, testicular atrophy, and twin-ship represent risk factors with lesser levels of evidence (level III a). There is also some evidence for HIV infection being a predisposing factor for GCT (level IV a). Scrotal trauma is probably not associated with GCT risk. The estrogen excess theory implies high estrogen levels during the first trimester of pregnancy. As a consequence, primordial germ cells lose track of the normal developmental line and transform into premalignant cells that later become testicular intraepithelial neoplasia (TIN), the precursor of full-blown testicular GCT. Surrogate parameters for high gestational estrogen levels are investigated in case control studies. Such factors are maternal age >30 years, first-born, low birth weight, maternal breast cancer, high sex-ratio of siblings. So far, the sum of evidence is promising but still conflicting (especially for level III b). Another novel theory is the childhood nutrition hypothesis. This concept postulates a modulating or "catalyzing" effect by high dietary intake during childhood on the pathogenesis of testicular GCT. A surrogate parameter of early childhood nutrition is adult height. So far, 12 controlled studies have looked to the possible association of attained height and GCT risk of which six demonstrated a significant association. Thus, the sum of evidence corresponds to level III b. This concept is appealing because it would explain several hitherto unexplained epidemiological features of GCT.

Epidemiological studies of radio frequency exposures and human cancer

Epidemiological studies of radio frequency (RF) exposures and human cancers include studies of military and civilian occupational groups, people who live near television and radio transmitters, and users of mobile phones. Many types of cancer have been assessed, with particular attention given to leukemia and brain tumors. The epidemiological results fall short of the strength and consistency of evidence that is required to come to a conclusion that RF emissions are a cause of human cancer. Although the epidemiological evidence in total suggests no increased risk of cancer, the results cannot be unequivocally interpreted in terms of cause and effect. The results are inconsistent, and most studies are limited by lack of detail on actual exposures, short follow-up periods, and the limited ability to deal with other relevant factors. In some studies, there may be substantial biases in the data used. For these same reasons, the studies are unable to confidently exclude any possibility of an increased risk of cancer. Further research to clarify the situation is justified. Priorities include further studies of leukemia in both adults and children, and of cranial tumors in relationship to mobile phone use.

Radio frequency electromagnetic fields: Cancer, mutagenesis, and genotoxicity

We present critiques of epidemiologic studies and experimental investigations, published mostly in peer-reviewed journals, on cancer and related effects from exposure to nonionizing electromagnetic fields in the nominal frequency range of 3 kHz to 300 GHz of interest to Subcommittee 4 (SC4) of the International Committee on Electromagnetic Safety (ICES). The major topics discussed are presented under the headings Epidemiologic and Other Findings on Human Exposure, Mammals Exposed In Vivo, Mammalian Live Tissues and Cell Preparations Exposed In Vitro, and Mutagenesis and Genotoxicity in Microorganisms and Fruit Flies. Under each major topic, we present minireviews of papers on various specific endpoints investigated. The section on Epidemiologic and Other Findings on Human Exposure is divided into two subsections, the first on possible carcinogenic effects of exposure from emitters not in physical contact with the populations studied, for example, transmitting antennas and other devices. Discussed in the second subsection are studies of postulated carcinogenic effects from use of mobile phones, with prominence given to brain tumors from use of cellular and cordless telephones in direct physical contact with an ear of each subject. In both subsections, some investigations yielded positive findings, others had negative findings, including papers directed toward experimentally verifying positive findings, and both were reported in a few instances. Further research on various important aspects may resolve such differences. Overall, however, the preponderance of published epidemiologic and experimental findings do not support the supposition that in vivo or in vitro exposures to such fields are carcinogenic.

Testicular cancer among Swedish pulp and paper workers

BACKGROUND

The incidence of testicular cancer has increased in recent decades. The aims of the present study were to elucidate whether Swedish paper and pulp mill workers had an increased incidence of testicular cancer, and to investigate whether certain occupational groups within the pulp and paper mill workforce were at increased risk.

METHODS

The study was based on the Swedish Cancer Environment Register, which links the incidence of cancer for the period 1971-1990 with 1960 and 1970 National Census data on specific industries and occupations for all employed subjects in Sweden.

RESULTS

Among maintenance workers employed both in 1960 and in 1970 in paper mills there was an increased risk for testicular cancer (standardized incidence ratio (SIR) 7.4, 95% confidence intervals (CI) 1.5-22), especially for seminomas (SIR 10.1, 95% CI 2.1-29). Maintenance workers were also at increased risk when analyzing workers employed in 1960, 1970, or both years.

CONCLUSIONS

This study indicates an increased risk for testicular cancer, especially seminomas, among maintenance workers, but not among process workers, in Swedish paper mills.

Incidence of testicular cancer and occupation among Swedish men gainfully employed in 1970

PURPOSE

To estimate occupation-specific risk of seminomas and nonseminoma subtypes of testicular cancer among Swedish men gainfully employed in 1970 over the period 1971-1989.

METHODS

Age-period standardized incidence ratios were computed in a dataset linking cancer diagnoses from the Swedish national cancer register to occupational and demographical data obtained in the census in 1970. Log-linear Poisson models were fitted, allowing for geographical area and town size. Taking occupational sector as a proxy for socioeconomic status, occupational risks were recalculated using intra-sector analyses, where the reference group comprised other occupations in the same sector only. Risk estimators per occupation were also computed for men reporting the same occupation in 1960 and 1970, a more specifically exposed group.

RESULTS

Seminomas and nonseminomas showed a substantial geographical variation. The association between germ-cell testicular tumors and high socioeconomic groups was found mainly for nonseminomas. Positive associations with particular occupations were more evident for seminomas, for which railway stationmasters, metal annealers and temperers, precision toolmakers, watchmakers, construction smiths, and typographers and lithographers exhibited a risk excess. Concrete and construction worker was the only occupation consistently associated with nonseminomas.

CONCLUSIONS

Among the many occupations studied, our results corroborate the previously reported increased risk among metal workers, specifically related with seminomatous tumors in this study. Our results confirm the geographical and socioeconomical differences in the incidence of testicular tumors. These factors should be accounted for in occupational studies. The different pattern of occupations related with seminomas and nonseminomas support the need to study these tumors separately.

Molecular cloning of a novel human acid phosphatase gene (ACPT) that is highly expressed in the testis

Acid phosphatases are enzymes capable of hydrolyzing orthophosphoric acid esters in an acid medium. Prostatic acid phosphatase has served as a tumor marker for metastatic prostate cancer for many years. We have cloned a new human acid phosphatase gene (named testicular acid phosphatase, ACPT), which is expressed mainly in testis and to a lower extent in the prostate, trachea, and other tissues. This gene maps to chromosome 19q13.4, in an area that harbors many cancer-related genes. The testicular acid phosphatase gene is composed of 11 exons, and the protein is predicted to have a luminal domain, a transmembrane domain, and a cytoplasmic domain. The N-terminal end of the protein encodes a signal peptide. The protein has approximately 50% homology with both the prostatic and the lysosomal acid phosphatases, and the position of the cysteine residues, the N-glycosylation sites, and the histidine catalytic site are conserved among the three proteins. The testicular acid phosphatase gene is up-regulated by androgens and is down-regulated by estrogens in the prostate cancer cell line LNCaP. Our preliminary results indicate that this gene exhibits a lower level of expression in testicular cancer tissues than in their normal counterparts.

Cellular telephones and cancer--a nationwide cohort study in Denmark

BACKGROUND

Use of cellular telephones is increasing exponentially and has become part of everyday life. Concerns about possible carcinogenic effects of radiofrequency signals have been raised, although they are based on limited scientific evidence.

METHODS

A retrospective cohort study of cancer incidence was conducted in Denmark of all users of cellular telephones during the period from 1982 through 1995. Subscriber lists from the two Danish operating companies identified 420 095 cellular telephone users. Cancer incidence was determined by linkage with the Danish Cancer Registry. All statistical tests are two-sided.

RESULTS

Overall, 3391 cancers were observed with 3825 expected, yielding a significantly decreased standardized incidence ratio (SIR) of 0.89 (95% confidence interval [CI] = 0.86 to 0.92). A substantial proportion of this decreased risk was attributed to deficits of lung cancer and other smoking-related cancers. No excesses were observed for cancers of the brain or nervous system (SIR = 0.95; 95% CI = 0.81 to 1.12) or of the salivary gland (SIR = 0.72; 95% CI = 0.29 to 1.49) or for leukemia (SIR = 0.97; 95% CI = 0.78-1.21), cancers of a priori interest. Risk for these cancers also did not vary by duration of cellular telephone use, time since first subscription, age at first subscription, or type of cellular telephone (analogue or digital). Analysis of brain and nervous system tumors showed no statistically significant SIRs for any subtype or anatomic location.

CONCLUSIONS

The results of this investigation, the first nationwide cancer incidence study of cellular phone users, do not support the hypothesis of an association between use of these telephones and tumors of the brain or salivary gland, leukemia, or other cancers.

Ets1 oncogene induction by ELF-modulated 50 MHz radiofrequency electromagnetic field

We have analyzed gene expression in hemopoietic and testicular cell types after their exposure to 50 MHz radiofrequency (RF) non-ionizing radiation modulated (80%) with a 16 Hz frequency. The exposure system generates a 0.2 microT magnetic field parallel to the ground and a 60 V/m electric field orthogonal to the earth's magnetic field. Exposure conditions were selected so as to interfere with the calcium ion flow. Under these electromagnetic field (EMF) conditions, we observed an overexpression of the ets1 mRNA in Jurkat T-lymphoblastoid and Leydig TM3 cell lines. This effect was observed only in the presence of the 16 Hz modulation, corresponding to the resonance frequency for calcium ion with a DC magnetic field of 45.7 microT. We have also identified a putative candidate gene repressed after EMF exposure. The experimental model described in this paper may contribute to the understanding of the biological mechanisms involved in EMF effects.

Risk factors for testicular germ cell tumours by histological tumour type. United Kingdom Testicular Cancer Study Group

There are two main histological groups of testicular germ cell tumours, which may have different risk factors. Some authors have analysed potential risk factors by histological group but few consistent differences have been identified. In this paper we examine risk factors for pure seminoma and other tumours using data from the United Kingdom case control study of testicular cancer. Seven hundred and ninety-four cases were included in the study, each with a matched control; 400 cases had pure seminoma tumours, and 394 had other testicular tumours. The risk of seminoma associated with undescended testis was slightly higher than that for other tumours (odds ratio of 5.3 compared with 3.0). When split at the median age at diagnosis, this difference was greater in men aged 32 and over (odds ratio of 11.9 compared with 5.1) than in the younger men (3.0 compared with 2.5). Risks associated with testicular or groin injuries were higher in the non-seminoma group, as was the risk for a history of sexually transmitted disease. The protective effect of a late puberty was more marked for tumours of other histologies. Some differences were also detected for participation in sports. Whilst some of the differences detected may have arisen by chance, the stronger association between undescended testis and pure seminoma has been identified by a number of other studies and may reflect a genuine difference in aetiology.

A critical review of epidemiologic studies of radiofrequency exposure and human cancers

This paper reviews studies that have assessed associations between likely exposure to radiofrequency (RF) transmissions and various types of human cancer. These studies include three cluster investigations and five studies relating to general populations; all of these studies consider place of residence at the time of cancer diagnosis in regard to proximity to radio or television transmitters. There are also five relevant occupational cohort studies and several case-control studies of particular types of cancer. These studies assessed a large number of possible associations. Several positive associations suggesting an increased risk of some types of cancer in those who may have had greater exposure to RF emissions have been reported. However, the results are inconsistent: there is no type of cancer that has been consistently associated with RF exposures. The epidemiologic evidence falls short of the strength and consistency of evidence that is required to come to a reasonable conclusion that RF emissions are a likely cause of one or more types of human cancer. The evidence is weak in regard to its inconsistency, the design of the studies, the lack of detail on actual exposures, and the limitations of the studies in their ability to deal with other likely relevant factors. In some studies there may be biases in the data used

Occupational exposure to polyvinyl chloride as a risk factor for testicular cancer evaluated in a case-control study

Occupational exposures were assessed in a case-control study on testicular cancer using self-administered questionnaires. In total, answers were obtained for 148 (91%) cases and 315 (87%) controls. Of the cases, 101 had seminoma and 47 had embryonal testicular cancer. An increased odds ratio (OR) was found for exposure to polyvinyl chloride (PVC) yielding an OR of 6.6 (95% confidence interval, 1.4-32). The risk increased further if cases with self-reported cryptorchidism or orchitis were excluded. Six of the 7 exposed cases had seminoma. Exposure to other types of plastics did not significantly increase the risk of testicular cancer.

Occupation and risk of germ cell testicular cancer by histologic type in Ontario

Incidence of both major histologic subgroups of germ cell testicular cancer, seminoma and nonseminoma, is increasing, but the etiology is largely unknown. Occupational clusters have been observed. In a case-control study in Ontario with 495 incident cases and 974 population control subjects, jobs and industries were coded and analyzed. There is little evidence of occupational risk for all cases or for seminoma. Significantly increased risk of nonseminoma was associated with: miners (odds ratio [OR] = 12.39; 95% confidence interval [CI], 2.22 to 69.27), food and beverage processors (OR = 3.20; 95% CI, 1.39 to 7.35), utilities employees (OR = 3.15; 95% CI, 1.15 to 8.61), and other service workers (OR = 1.05; 95% CI, 1.05 to 4.56). Leather-industry employees had elevated risk of nonseminoma (OR = 4.60; 95% CI, 0.75 to 28.28) consistent with a leather tannery cluster. Increased risk of nonseminoma among some workers can be explained if an additional event is required for converting seminoma to nonseminoma.

Risks of testicular cancer and cryptorchidism in relation to socio-economic status and related factors: case-control studies in Denmark

To explore risk factors for testicular cancer and cryptorchidism, 2 parallel case-control studies were conducted in Denmark. The testicular-cancer study was population-based and included 514 cases and 720 controls. The cryptorchidism study included 387 cases and 416 controls and was based on 2 hospital series of men treated for cryptorchidism and a control group sampled among residents in the Copenhagen area. The 2037 men were interviewed by telephone, and self-administered questionnaires were sent to their mothers. A strong association was seen between low social class and cryptorchidism, with sons of unskilled workers having a 3-fold higher risk of cryptorchidism than sons of self-employed men. Testicular cancer was only moderately associated with high-social-class indicators, and only with such indicators pertaining to the mother. Both testicular cancer and cryptorchidism tended to occur more frequently in first-born men and in sons of older women but these associations were not statistically significant. Late puberty was associated with reduced risk of testicular cancer. The effect of age at puberty may be due both to advanced age at diagnosis and to the existence of common determinants of age at puberty and testicular cancer. Men who had been treated for cryptorchidism entered puberty later than other men, possibly because of impaired hormonal function of the testes. There was no indication of increased risk of testicular cancer or cryptorchidism in sons of mothers who smoked around the time of conception or during the pregnancy.

Continuing increase in incidence of germ-cell testis cancer in young adults: experience from Connecticut, USA, 1935-1992

The current study is designed to examine long-term trends by histologic types of testis cancer in Connecticut. A regression model was used to identify age, period, or cohort as determinants of the time-trend on histologic types of testis cancer. The results from this descriptive epidemiologic study show that the overall age-adjusted incidence rate of testis cancer has increased 3.5-fold in Connecticut during the past nearly 60 years of cancer registration. The rates for seminoma and non-seminoma have been increasing since the mid-1950s and increase in a similar manner for those aged 15 to 49. The largest increase was observed in the age groups 20 to 44 for seminoma and 15 to 34 for non-seminoma. The observed increase was limited to whites. The results from age-period-cohort modeling suggest that the observed increase in seminoma before 1950s could be largely attributable to a period effect, while the increase for cohorts born after about 1910 both for seminoma and for non-seminoma are mainly explained by a strong birth-cohort effect. Therefore, the observed increase in germ-cell testis cancer in this population is likely to continue in the coming years. Thus far, the proposed hypotheses, such as exposure to DES in utero, earlier lifetime exposure to viruses, trauma or unusual amounts of heat to the testis, cannot adequately explain the observed incidence patterns of testis cancer. Analytical epidemiologic studies with large sample size are urgently needed to examine the risk factors responsible for the increase.

High frequency of metalworkers among patients with seminomatous tumors of the testis: a case-control study

Occupational analyses were conducted between 1971 and 1978 comparing 165 cases of testicular cancer in the Hannover region of Germany with 187 controls without neoplastic diseases admitted to the Hannover University Medical School during the same period. The results showed a significantly higher risk of metal workers developing seminomas and mixed seminomatous tumors compared to the controls (odds ratio 2.05; 1.17-3.58). There was a lack of risk for the nonseminomatous tumors as a whole group, and cases with a history of metal work may have a decreased risk for embryonal carcinomas. No definite single noxious substance responsible for the development of testicular tumors could be detected. In view of the results in animal experiments, cadmium and zinc are especially considered in the discussion.

Social, behavioural and medical factors in the aetiology of testicular cancer: results from the UK study. UK Testicular Cancer Study Group

Although many risk factors have been proposed for the aetiology of testicular cancer, only a history of cryptorchidism is well established. All risk factors previously suggested have been explored in this study. This population-based case-control study was carried out in nine health regions in England and Wales and included 794 men, aged 15-49 years, diagnosed with a testicular germ cell tumour between 1 January 1984 and 30 September 1986, each with an individually age-matched control. Cases and controls were interviewed and data were abstracted from their general practitioner notes. Participation rates for cases and controls were 92.0% and 83.1% respectively. Where possible the mother of each interviewed man was sent a postal questionnaire for self-completion. Testicular trauma at least 2 years prior to diagnosis was associated with an odds ratio (OR) of 2.00 [95% confidence interval (CI) 1.54-2.61]. Ever having had a sexually transmitted disease was also associated with an increased risk (OR = 2.22, 95% CI 1.46-3.39). There was little evidence of an association with cigarette smoking. Sporting activity had a protective effect. Detailed exploration of testicular temperature (wearing of tight underpants, jeans or trousers, hot baths and central heating) failed to reveal any relationship with risk of testicular cancer. There were no clear occupational associations.