Electromagnetic fields and male breast cancer

Male Breast Cancer

Male breast cancer (MBC) is a rare disease, accounting for less than 1% of all breast cancer diagnoses worldwide. Although breast carcinomas share certain characteristics in both genders, there are notable differences. Most studies on men with breast cancer are very small. Thus, most data on male breast cancer are derived from studies on females. However, when a number of these small studies are grouped together, we can learn more from them. This review emphasizes the incidence, etiology, clinical features, diagnosis, treatment, pathology, survival, and prognostic factors related to MBC.

Male breast cancer: risk factors, biology, diagnosis, treatment, and survivorship

BACKGROUND

The causes, optimal treatments, and medical/psychosocial sequelae of breast cancer in men are poorly understood.

DESIGN

A systematic review of the English language literature was conducted to identify studies relevant to male breast cancer between 1987 and 2012 and including at least 20 patients. Searches were carried out on PubMed using the title terms 'male breast cancer' or 'male breast carcinoma'.

RESULTS

Relevant published data regarding risk factors, biological characteristics, presentation and prognosis, appropriate evaluation and treatment, and survivorship issues in male breast cancer patients are presented. BRCA2 mutations, age, conditions that alter the estrogen/androgen ratio, and radiation are proven risk factors. Disease biology is distinct in men, but diagnostic approaches and treatments for men are generally extrapolated from those in women due to inadequate research in men. Survivorship issues in men may include sexual and hormonal side-effects of endocrine therapies as well as unique psychosocial impacts of the disease.

CONCLUSION

Further research is needed to address gaps in knowledge pertaining to care of male breast cancer patients and survivors.

Occupation and occupational exposure to endocrine disrupting chemicals in male breast cancer: a case-control study in Europe

OBJECTIVES

Male breast cancer is a rare disease of largely unknown aetiology. In addition to genetic and hormone-related risk factors, a large number of environmental chemicals are suspected of playing a role in breast cancer. The identification of occupations or occupational exposures associated with an increased incidence of breast cancer in men may help to identify mammary carcinogens in the environment.

METHODS

Occupational risk factors for male breast cancer were investigated in a multi-centre case-control study conducted in eight European countries which included 104 cases and 1901 controls. Lifetime work history was obtained during in-person interviews. Occupational exposures to endocrine disrupting chemicals (alkylphenolic compounds, phthalates, polychlorinated biphenyls and dioxins) were assessed on a case-by-case basis using expert judgement.

RESULTS

Male breast cancer incidence was particularly increased in motor vehicle mechanics (OR 2.1, 95% CI 1.0 to 4.4) with a dose-effect relationship with duration of employment. It was also increased in paper makers and painters, forestry and logging workers, health and social workers, and furniture manufacture workers. The OR for exposure to alkylphenolic compounds above the median was 3.8 (95% CI 1.5 to 9.5). This association persisted after adjustment for occupational exposures to other environmental oestrogens.

CONCLUSION

These findings suggest that some environmental chemicals are possible mammary carcinogens. Petrol, organic petroleum solvents or polycyclic aromatic hydrocarbons are suspect because of the consistent elevated risk of male breast cancer observed in motor vehicle mechanics. Endocrine disruptors such as alkylphenolic compounds may play a role in breast cancer.

The significance of nipple discharge of the male breast

Although male breast cancer typically presents as a palpable mass, failure to recognize the significance of other symptoms may lead to a delay in diagnosis. Here we present our experience with male patients presenting with a chief complaint of nipple discharge (ND). Using the ICD-9 code for "breast symptoms," we identified 2,319 patients without a current cancer diagnosis who presented to Memorial Sloan-Kettering Cancer Center for evaluation; 24 (1%) patients were male (1995-2005). Data were collected by retrospective review. Among 24 male patients presenting for evaluation, 14 (58%) presented with a chief complaint of ND, while the remaining 10 (42%) presented for evaluation of a palpable mass in the absence of ND. Among 14 patients presenting with ND, subsequent clinical breast examination identified a breast mass +/- nipple changes in 7 of 14 patients. In total, 8 of 14 (57%) patients had an underlying malignancy; two of seven patients with ND alone had DCIS (median interval from onset of ND to presentation 3 weeks, range 2-4 weeks), and six of seven patients with ND and a palpable mass had invasive disease (median interval between onset of ND and presentation 16 weeks, range 2-52). The remaining 10/24 patients presented with a painless palpable mass of whom 8 (80%) were found to have underlying invasive disease (median interval between onset of mass, and presentation was 4 weeks, range 2-20 weeks). All patients with invasive disease were node-positive. At 23.7 months median follow-up (range, 7.7-88.3 months), 14 of 16 cancer patients remain free of disease and two have died as a direct result of metastatic disease. The incidence of cancer among males presenting with ND was 57%. In the absence of additional clinical findings, ND may be a herald for early, non-invasive disease. Increased awareness of subtle features of malignancy may represent a window of opportunity for early diagnosis and improved outcomes for male breast cancer patients.

[Male breast cancer: a review of 52 cases collected at the Institute Bergonié (Bordeaux, France) from 1980 to 2004]

OBJECTIVES

To analyze the characteristics and to establish prognosis factors for 52 men suffering from breast cancer from 1980 to 2004.

PATIENTS AND METHODS

Men treated for breast cancer (invasive or in situ). A retrospective study analyzed clinical and histological characteristics, and treatment procedures. The probability of survival or recurrence was calculated using the Kaplan-Meier method. Prognostic factors were studied using the Log Rank test.

RESULTS

The mean age of our patients was 63.5 years old. In 73.1% of cases, subaerolar tumors were the initial symptoms, the average size was 30.31 mm. Among patients, 17 (32.7%) had T1, 19 (36.5%) T2, two (3.8%) T3 and 14 (26.9%) T4. The most represented histological type was the infiltrative ductal carcinoma (84.6%). The spread rate to axillary lymph nodes was 63.6%. The hormone dependency of these tumors was proven in 84.6% of cases. Overall survival rate were about 69% at five years and 32% at 10 years. The spread to lymph node and to derm, the clinical stage were significant factors influencing disease free survival. None of these factors had any significance regarding overall survival.

DISCUSSION AND CONCLUSION

Male breast cancer is a rare disease (about 1% of breast cancer) with a poor prognosis (32% 10 years disease free survival). An early diagnosis and better knowledge of the disease would certainly lead to improvement of prognosis.

Male breast cancer

Occurrence of male breast cancer, a rare disease, peaks at age 71 years. Familial cases usually have BRCA2 rather than BRCA1 mutations. Occupational risks include high temperature environments and exhaust fumes, but electromagnetic fields have not been implicated. Hyperoestrogenisation resulting from Klinefelter's, gonadal dysfunction, obesity, or excess alcohol, all increase risk as does exposure to radiation, whereas gynaecomastia does not. Presentation is usually a lump or nipple inversion, but is often late, with more than 40% of individuals having stage III or IV disease. Most tumours are ductal and 10% are ductal carcinoma in situ. Surgery is usually mastectomy with axillary clearance or sentinel node biopsy. Indications for radiotherapy, by stage, are similar to female breast cancer. Because 90% of tumours are oestrogen-receptor-positive, tamoxifen is standard adjuvant therapy, but some individuals could also benefit from chemotherapy. Hormonal therapy is the main treatment for metastatic disease, but chemotherapy can also provide palliation. National initiatives are increasingly needed to improve information and support for male breast cancer patients.

The Effect of Environment on Breast Cancer Risk

Environmental factors are believed to explain a large proportion of breast cancer incidence. Known risk factors for breast cancer, which are related to the reproductive life of women, and other factors, such as inheritance and socioeconomic status, explain only about half of the breast cancer cases in the US. Ionizing radiation is a well established environmental risk factor for breast cancer. Chemicals that induce mammary cancer in rodents have served as leads for studies in humans, but occupational and environmental exposure to these chemicals have for the most part lacked association with breast cancer risk. However, there is recent evidence in rats that cadmium at very low doses acts as an estrogen mimic, indicating a need to investigate the effects of metals on breast cancer risk. Studies suggest that circadian rhythm disruption is linked with breast cancer, but too few studies have been done to be conclusive. Over the years, cigarette smoking as a risk factor for breast cancer has remained controversial. However, recent research has found passive smoke exposure to be associated with increased breast cancer risk, which is hypothesized to be accounted for on the basis of an antiestrogenic effect of smoking. Solar radiation has been noted to be associated with reduced breast cancer, supporting the hypothesis that vitamin D plays a protective role in reducing this risk. Although, most of the environmental factors discussed in this review have not been convincingly found to influence breast cancer risk, research suggests that environmental exposure in combination with genetic pre-disposition, age at exposure, and hormonal milieu have a cumulative effect on breast cancer risk.

Follow-up of radio and telegraph operators with exposure to electromagnetic fields and risk of breast cancer

It is still unclear whether exposure to electromagnetic fields (EMF) is associated with breast cancer. To further investigate the issue, we followed-up a cohort of Norwegian female radio and telegraph operators in the period 1 January 1961 to 31 May 2002, with 99 breast cancer cases. The standardized incidence ratio (SIR) for breast cancer was 1.30 (95% confidence intervals (CI) 1.05-1.58), compared with the total Norwegian female population. In a subsequent nested case-control study, exposure to radio frequency (405 kHz-25 MHz) and extremely low-frequency (50 Hz) fields due to stay in the radio room during day and night was cumulated by years of employment and workload according to ship type. The exposure was assessed in two age groups (<50, 50+) with regard to risk of breast cancer. The odds ratios in the group with the highest cumulative exposure were 1.78 (95% CI 0.59-5.41) and 2.37 (95% CI 0.88-6.36) in the younger and the older women, respectively. P-value for trend was 0.03 in both age groups. The results of the oestrogen receptor status analysis by exposure to EMF showed an increased risk of oestrogen receptor-positive breast cancer in the younger women, while the older age group had an elevated risk of oestrogen receptor-negative breast cancer. Thus, the present study contributes to the hypothesis of an association between occupational exposure to EMF and increased risk of breast cancer.

Environmental risk factors for breast cancer among African-American women

There are few unequivocably established environmental carcinogens for breast cancer in women. Nevertheless, environmental factors are believed to explain much of the international variation in breast cancer risk and possibly differences among racial/ethnic groups. Along with lifestyle, some adverse exposures may be higher in minority racial/ethnic groups and in underserved populations that experience higher ambient contamination. Associations have been found between environmental agents and breast cancer in subgroups of women who can be identified by common susceptibility traits as well as by timing of exposures at certain milestones of reproductive life. Susceptibility can be defined by social, environmental, and genetic modalities-factors that may predominate in certain racial/ethnic groups but that also transcend racial/ethnic boundaries. For example, genes involved in transcription and estrogen metabolism have rapid variants that are more prevalent among African-Americans, yet risk accompanying metabolic changes from these genes will prevail in all racial/ethnic groups. Lack of reliable exposure assessment remains a principal obstacle to elucidating the role of environmental exposures in breast cancer. Resources must be identified and consolidated that will enable scientists to improve exposure assessment and to assemble studies of sufficient size to address questions regarding exposure, susceptibility, and vulnerability factors in breast cancer. Breast cancer studies should be expanded to examine combinations of chemicals as well as competing or complementary exposures such as endogenous hormones, dietary intake, and behavioral factors.

Epidemiology and aetiological factors of male breast cancer: a ten years retrospective study in eastern Turkey

The aim of this study was to assess the epidemiological and aetiological factors of male breast carcinoma in eastern Turkey. For this purpose we evaluated breast carcinoma patients admitted to our regional hospital from 1990 to 2000. A total of 196 patients were admitted during that time, 11 of whom were male (5%). The average age at presentation was 60.7 +/- 7.5. Infiltrating ductal carcinoma was the most frequent histopathological type; lobular carcinoma was detected in only one of our cases. Right-sided male breast carcinoma was seen in 7 of 11 cases, left-sided in four cases. We detected gynaecomastia in two patients. Other factors were excessive alcohol consumption for 35 years in one patient, family history in one patient and exposure to electromagnetic fields (EMFs) and light at night in four patients. We demonstrated no risk factor in the other three cases. Of the patients in our study, the youngest was 45 years old--the patient with post-pubertal gynaecomastia. The overall rate of male breast carcinoma seen among people who had worked for the Turkish Institution of Electricity in eastern Turkey was 0.3%. In our study we demonstrated a close relation between exposure to EMFs and light at night and male breast carcinoma in eastern Turkey. We also supposed that not only exposure to EMFs but also the duration of the exposure could affect the risk of development of male breast carcinoma.

Breast cancer and electromagnetic fields--a review

PURPOSE

Several statements have been issued to the effect that no consistent, significant link has been demonstrated between cancer and electromagnetic fields (EMF). However, there continues to be much interest in a possible association with breast cancer, in part because breast cancer risk is substantially higher in industrialized countries than in other areas, and electric power generation and consumption is one of the hallmarks of industrialized societies. In 1987, Stevens proposed a biological mechanism whereby two products of electric power generation, EMF and light at night, might contribute to mammary carcinogenesis through inhibition of melatonin.

METHODS

We conducted a comprehensive review of the epidemiologic literature and hypothesized mechanisms pertaining to EMF exposure and the risk of breast cancer, in order to assess whether or not there was evidence to suggest a link between EMF and breast cancer.

RESULTS

Some occupational epidemiological studies have demonstrated an increased incidence of breast cancer among mainly male electrical workers. It has been difficult to study women, as few are employed in these types of occupations. In all, there have been eleven occupational studies related to breast cancer in women, and statistically significant risk ratios have been observed: 1.98 for pre-menopausal women in occupations with high EMF exposure in one study, 2.17 in all women who worked as telephone installers, repairers, and line workers in another study, and 1.65 for system analysts/ programmers, 1.40 for telegraph and radio operators, and 1.27 for telephone operators in a third study. However, six of the studies did not find any significant effects and two found effects only in subgroups. The results of the eight studies of residential exposure and four electric blanket studies have been inconsistent, with most not demonstrating any significant association. However, this might be attributed, at least to some extent, to difficulties in assessing residential exposure in these studies, as well as other methodological considerations.

CONCLUSIONS

The biologic plausibility of an association between EMF and breast cancer, coupled with suggestive data from occupational studies and unexplained high incidence rates of breast cancer, suggests that further investigation of this possible association is warranted.

Occupational and residential magnetic field exposure and breast cancer in females

The purpose of this study was to evaluate the effect of occupational magnetic field exposure on breast cancer in females and to combine residential and occupational magnetic field exposure to reduce misclassification. The study was conducted as a case-control study within a population living within 300 meters of transmission lines in Sweden. We identified cases of breast cancer in females from the national cancer registry, and we selected one matched control per case at random. Residential exposure was estimated through calculations of the magnetic fields generated by power lines. We obtained information about occupation from censuses, and the occupations were linked to a job-exposure matrix that was based on magnetic field measurements. For occupational exposure to magnetic fields over 0.25 microT closest in time before diagnosis, the estimated relative risk was 1.0 [96% confidence interval (CI) = 0.6-1.7]. Women below age 50 years at diagnosis had a relative risk of 1.5 (95% CI = 0.6-3.5). For women below 50 years of age who had estrogen receptor-positive breast cancer, there was a relative risk of 3.2 (95% CI = 0.5-18.9). The results for residential and occupational exposures combined showed similar results.

Incidence of breast cancer in a Norwegian cohort of women with potential workplace exposure to 50 Hz magnetic fields

BACKGROUND

The risk of breast cancer was investigated in a large dynamic population-based cohort of all 1.1 million economically active women in Norway with potential exposure to 50 Hz magnetic fields at the censuses of 1960, 1970, and 1980.

METHODS

The follow-up period for the cohort was 1961-1992. For each woman, date of birth and census information on occupation and socioeconomic status were ascertained. These data were linked to the breast cancer morbidity information in the Cancer Registry of Norway. Exposure to magnetic fields was assessed a priori using two different approaches. In the first approach, hours per week in a potential magnetic field above background level (0.1 microT) were classified by an expert panel. In the second approach, measured magnetic fields from a separate study of men at work were allocated to the women's census job titles. In both approaches, exposure was cumulated over the years of employment (work hours and microT-years, respectively).

RESULTS

The Poisson regression analysis showed a risk ratio (RR) of 1.14 (95% confidence interval (CI) = 1.10-1.19) in the highest exposure category compared to the lowest when using the first approach, and the corresponding RR was 1.08 (95% CI = 1.01-1.16) when using the second approach. For women younger than 50 years, RR was 1.20 (95% CI = 1.11-1.29) and 1.12 (95% CI = 0.98-1.28), respectively.

CONCLUSIONS

The results give some support to the hypothesis that exposure to 50 Hz magnetic fields may increase the risk of breast cancer. However, since no direct information on exposure was available, no firm conclusions can be drawn.

High-risk occupations for breast cancer in the Swedish female working population

OBJECTIVES

The purpose of this study was to estimate, for the period 1971 through 1989, occupation-specific risks of breast cancer among Swedish women employed in 1970.

METHODS

Age-period standardized incidence ratios were computed. Log-linear Poisson models were fitted, with geographical area and town size taken into account. Risks were further adjusted for major occupational group, used as a proxy for socioeconomic status. Risk estimators were also calculated for women reporting the same occupation in 1960 and 1970.

RESULTS

Most elevated risks among professionals, managers, and clerks were reduced when intragroup comparisons were carried out, indicating the confounding effect of socioeconomic status. Excess risks were found for pharmacists, teachers of theoretical subjects, schoolmasters, systems analysts and programmers, telephone operators, telegraph and radio operators, metal platers and coaters, and hairdressers and beauticians, as well as for women working in 1960 and 1970 as physicians, religious workers, social workers, bank tellers, cost accountants, and telephonists.

CONCLUSIONS

While the high risks observed among professional, administrative, and clerical workers might be related to lower birth rates and increased case detection, excess risks found for telephone workers and for hairdressers and beauticians deserve further attention.

Exposure to power frequency magnetic fields and risk of breast cancer in the Upper Cape Cod Cancer Incidence Study

Investigators used a population-based case-control study to evaluate the relationship between breast cancer risk and exposure to 60-Hz magnetic fields from various sources. There was no increase in breast cancer risk associated with (a) holding a job with high (odds ratio [OR] = 1.2; 95% confidence interval [CI] = 0.4, 3.4) or medium (OR = 0.9; 95% CI = 0.5, 1.7) exposure to magnetic fields; (b) living in a home heated electrically (OR = 1.0; 95% CI = 0.7, 1.4); or (c) sleeping with an electric blanket (OR = 1.0; 95% CI = 0.7, 1.4). There was a nonsignificant 50% increase in risk for subjects who lived within 152 m (500 ft) of an electricity transmission line or substation (OR = 1.5; 95% CI = 0.6, 3.3). Although limited by small numbers and exposure misclassification, the data in this study did not support the hypothesis that exposure to 60-Hz magnetic fields increases the risk of breast cancer in women.

Case-control study of occupational exposures and male breast cancer

OBJECTIVE

To investigate whether risk of male breast cancer is associated with workplace exposures.

METHODS

A case-control study of 178 cases of male breast cancer and 1041 controls was carried out with data from the United States national mortality follow-back survey, which collected questionnaire information from proxy respondents of a 1% sample of all 1986 United States deaths among subjects aged 25-74 years. Occupational exposure to electromagnetic fields, high temperatures, polycyclic aromatic hydrocarbons (PAHs), herbicides, other pesticides, and organic solvents was assessed by applying job-exposure matrices, based on the 1980 United States census occupation and industry codes, to the longest job held by study subjects as reported by the informants. A socioeconomic status index was created by combining information on annual family income, education, assets, and occupation to assess the association of socioeconomic status with male breast cancer. Relative risks were derived from logistic regression modelling, which included age, socioeconomic status, marital status, and body mass index, as well as occupational exposures.

RESULTS

Risk for male breast cancer increased significantly with increasing socioeconomic status index (test for trend: p < 0.01), but the risks associated with individual socioeconomic status variables were smaller and the trends were not significant. A significant increase in risk of male breast cancer was associated with employment in blast furnaces, steel works, and rolling mills (odds ratio (OR) 3.4; 95% confidence interval (95% CI) 1.1 to 10.1, based on six cases), and motor vehicle manufacturing (OR 3.1; 95% CI 1.2 to 8.2, based on seven cases). However, exposures to electromagnetic fields, high temperature, PAHs, herbicides, other pesticides, and organic solvents were not associated with risk of male breast cancer.

CONCLUSIONS

The role of workplace exposures in increasing risk of breast cancer among men employed in motor vehicle manufacturing and in blast furnaces, steel works, and rolling mills deserves further investigation. The finding on socioeconomic status suggests that, as well as reproductive factors, other lifestyle factors such as diet that may be related to high socioeconomic status in men should be investigated further.

Cancer in electrical workers: an analysis of cancer registrations in England, 1981-87

Associations between work in the electrical and electronic industry and cancer incidence were assessed using data for 371 890 cancers registered in England between 1981 and 1987, of which 7981 were in electrical workers. Proportional registration ratios (PRRs) were calculated, both with and without the commonest cancers, with adjustment for age, social class, cancer registry of origin and sex. Of four cancers previously linked with work in the electrical and electronic industry (leukaemia, brain, breast and melanoma), only two were significantly raised: leukaemia (PRR=124, 95% CI=109-142, based on 217 cases) and malignant brain cancer (PRR=118, 95% CI=103-136, based on 204 cases). A significantly increased risk was also observed for pleural cancer (PRR=201, 95% CI=167-241, based on 115 cases). The histology of almost 90% of pleural cancers was coded as mesothelioma, confirming the previously observed association between pleural cancer and exposure to asbestos in electrical workers. The extent to which workplace exposures to extremely low frequency electromagnetic fields explains the excesses seen here for leukaemia and brain cancer requires further study.

Incidence of breast cancer in Norwegian female radio and telegraph operators

Exposure to electromagnetic fields may cause breast cancer in women if it increases susceptibility to sex-hormone-related cancer by diminishing the pineal gland's production of melatonin. We have studied breast cancer incidence in female radio and telegraph operators with potential exposure to light at night, radio frequency (405 kHz-25 MHz), and, to some extent, extremely low frequency fields (50 Hz). We linked the Norwegian Telecom cohort of female radio and telegraph operators working at sea to the Cancer Registry of Norway to study incident cases of breast cancer. The cohort consisted of 2,619 women who were certified to work as radio and telegraph operators between 1920 and 1980. Cancer incidence was analyzed on the basis of the standardized incidence ratio (SIR), with the Norwegian female population as the comparison group. The incidence of all cancers was close to unity (SIR = 1.2). An excess risk was seen for breast cancer (SIR = 1.5). Analysis of a nested case-control study within the cohort showed an association between breast cancer in women aged 50+ years and shift work. In a model with adjustment for age, calendar year, and year of first birth, the rate ratio for breast cancer associated with being a radio and telegraph operator--in comparison with all Norwegian women born 1935 or later--analyzed with Poisson regression, was 1.5 after adjustment for fertility factors. These results support a possible association between work as a radio and telegraph operator and breast cancer. Future epidemiologic studies on breast cancer in women aged 50 and over, should address possible disturbances of chronobiological parameters by environmental factors.

Melatonin suppression by static and extremely low frequency electromagnetic fields: relationship to the reported increased incidence of cancer

An increased cancer incidence has been reported in individuals living and/or working in an environment in which they are exposed to higher than normal artificial electromagnetic fields. One of the most uniform changes associated with the exposure of animals to either pulsed static geomagnetic fields or to sinusoidal extremely low frequency magnetic fields has been a reduction in high night-time levels of melatonin. Melatonin is a hormone produced especially at night in the pineal gland, a pea-sized organ near the center of the human brain. The high nocturnal production of melatonin leads to elevated blood melatonin levels at night as well. The exposure of humans or animals to light (visible electromagnetic radiation) at night rapidly depresses pineal melatonin production and blood melatonin levels. Likewise, the exposure of animals to various pulsed static and extremely low frequency magnetic fields also reduces melatonin levels. Melatonin is a potent oncostatic agent and it prevents both the initiation and promotion of cancer. Reduction of melatonin, at night, by any means, increases cells' vulnerability to alteration by carcinogenic agents. Thus, if in fact artificial electromagnetic field exposure increases the incidence of cancer in humans, a plausible mechanism could involve a reduction in melatonin which is the consequence of such exposures.

Incidence of cancer in persons with occupational exposure to electromagnetic fields in Denmark

Several studies suggest that work in electrical occupations is associated with an increased risk of cancer, mainly leukaemia and brain tumours. These studies may, however, not be representative if there is a publication bias where mainly positive results are reported. To study an unselected population the incidence of cancer was followed up over a 17 year period (1970-87) in a cohort of 2.8 million Danes aged 20-64 years in 1970. Each person was classified by his or her industry and occupation in 1970. Before tabulation of the data on incidence of cancer, each industry-occupation group was coded for potential exposure to magnetic fields above the threshold 0.3 microT. Some 154,000 men were considered intermittently exposed and 18,000 continuously exposed. The numbers for women were 79,000 and 4000 respectively. Intermittent exposure was not associated with an increased risk of leukaemia, brain tumours, or melanoma. Men with continuous exposure, however, had an excess risk of leukaemia (observed (obs) 39, expected (exp) 23.80, obs/exp 1.64, 95% CI 1.20-2.24) with equal contributions from acute and other leukaemias. These men had no excess risk of brain tumours or melanoma. A risk for breast cancer was suggested in exposed men but not in women. The risk for leukaemia in continuously exposed men was mainly in electricians in installation works and iron foundry workers. Besides electromagnetic fields other exposures should be considered as possible aetiological agents.

ELF magnetic fields, breast cancer, and melatonin: 60 Hz fields block melatonin's oncostatic action on ER+ breast cancer cell proliferation

In this study we investigated whether a 60 Hz magnetic field can act at the cellular level to influence the growth of human estrogen-dependent breast cancer cells. Our experimental design assessed cell proliferation of a human breast cancer cell line, MCF-7, in the absence or the presence of melatonin which inhibits growth at a physiological concentration of 10(-9) M. In three experiments, continuous exposure to average sinusoidal 60 Hz magnetic fields of 1.90 +/- 0.01, 2.40 +/- 0.70, and 2.53 +/- 0.50 mG, or simultaneous exposure in matched incubators to average 60 Hz magnetic fields of 10.4 +/- 2.12, 11.95 +/- 2.73, and 11.95 +/- 3.28 mG, respectively, had no effect on cell proliferation in the absence of melatonin. When MCF-7 cells were cultured in the presence of 10(-9) M melatonin, an 18% inhibition of growth was observed for cells in a 2.40 +/- 0.70 mG field. This effect was blocked by a 60 Hz magnetic field of 11.95 +/- 2.75 mG. In a second experiment, a 27% inhibition of MCF-7 cell growth was observed for cells in a 2.53 +/- 0.50 mG magnetic field, and this was blocked by a 60 Hz magnetic field of 11.95 +/- 3.28 mG. These results provide the first evidence that ELF frequency magnetic fields can act at the cellular levels to enhance breast cancer cell proliferation by blocking melatonin's natural oncostatic action. In addition, there appears to be a dose threshold between 2 and 12 mG. The mechanism(s) of action is unknown and may involve modulation of signal transduction events associated with melatonin's regulation of cell growth.

Review article: epidemiology of male breast cancer. A meta-analysis of published case-control studies and discussion of selected aetiological factors

Male breast cancer is a rare tumour in all parts of the world. About 1% of all breast cancers occur in men, but the male/female ratio is higher among black than among white populations. This effect can be seen in US cancer registries and even more markedly in African data. A positive correlation exists on a population scale between male breast cancer and prostate cancer. Seven case-control studies of male breast cancer are available, and a pooled analysis was conducted of the most commonly suspected risk factors. Male breast cancer appears to be associated with marital status: Mantel-Haenszel exposure odds ratio (EOR) for never married = 1.6; 95% confidence limits (CL) = 1.1, 2.3, religion (EOR for being Jewish = 2.1; 95% CL = 1.4, 3.2), previous breast pathology (EOR for positive history of benign breast disease = 2.7; 95% CL = 1.7, 4.2), gynaecomastia (EOR for positive history = 6.2, 95% CL = 3.4, 11.4), previous testicular pathology (EOR for positive history = 2.2; 95% CL = 1.5, 3.3), previous liver diseases (EOR for positive history = 1.6; 95% CL = 1.0, 2.4) and family history of breast cancer (EOR for first-degree relative with breast cancer = 2.5; 95% CL = 1.7, 3.7). No association is found with smoking history. Other potential risk factors such as reproductive history, education, occupation, anthropometric variables, association with various diseases, and specific exposures such as drug use, were not systematically evaluated in all studies and provide sometimes contradictory results, possibly due to small numbers of exposed subjects. Overall, the analytical epidemiology of male breast cancer presents similarities with the epidemiology of female breast cancer, with a potential role of factors related to hormonal status, relative hyperoestrogeny in men being potentially linked to increased risk of disease. Genetics may also play a role, with high risk linked to a familial history of breast cancer, and with a major risk in patients with Klinefelter's syndrome.

Breast cancer and electric power

Breast cancer is a leading cause of death among women in industrialized societies. It is far less common in less industrialized nations and the reason for this difference is unclear. One possibility is the distribution and use of electricity which results in two new exposures in the human environment: light-at-night and electromagnetic fields. These can reduce nocturnal melatonin production. Melatonin, in turn, has a protective effect on breast cancer in experimental animals.

Electromagnetic fields and male breast cancer

The aetiology of male breast cancer is still considered to be rather unclear. Epidemiological studies have recently shown an excess risk of male breast cancer in "electrical workers" with potential exposure to electromagnetic (EM) fields. Interest on the possible association between pineal function and breast cancer has come into focus. The pineal hormone melatonin has been shown to reduce the incidence of experimentally-induced breast cancer in rats, the hormone is oncostatic and cytotoxic to breast, ovarian, and bladder cancer cell lines in vitro. Treatment of cancer patients with orally administered melatonin has been tried. Pineal function in humans is suppressed by light-at-night (LAN). Animal studies have shown that exposure to 60-Hz electric fields may also suppress the nocturnal rise in pineal melatonin production in adult rats. Breast cancer is the leading cause of cancer death among women in industrialised world. No good explanation has so far been provided for the increased incidence of this site during the last decades, although changes in fertility factors have had some effect. If new epidemiological and experimental data give support to the hypothesis that exposure to LAN and EM fields may increase breast cancer risk, this may have regulatory and political consequences for future use of electric power.

Analysis of chromosomal aberrations, sister chromatid exchanges and micronuclei among power linesmen with long-term exposure to 50-Hz electromagnetic fields

Chromosomal aberrations, sister chromatid exchanges (SCEs), replication indices and micronuclei in peripheral blood lymphocytes were analysed among 27 nonsmoking power linesmen with considerable long-term exposure to 50-Hz electromagnetic (EM) fields, and among 27 nonsmoking telephone linesmen serving as a reference group, pairwise matched with the exposed workers for age and geographical region. Blood samples from the two groups were collected, cultured and analysed in parallel. No differences between the groups were observed on analysis of SCEs, replication indices or micronuclei. However, the mean rate of lymphocytes with chromatid-type breaks was higher among the power linesmen (0.96% gaps excluded, 1.41% gaps included) than among the reference group (0.44% and 0.70%, respectively). The excess of aberrant cells was concentrated among those power linesmen who had worked earlier in their life. Although the interpretation is somewhat complicated by the confounding effect of previous smoking, these results suggest that exposure to 50-Hz EM fields is associated with a slight increase in chromatid breaks.

Alternative functional relationships between ELF field exposure and possible health effects: report on an expert workshop

If exposure to 60 Hz fields poses risks to public health, the relationship between exposure and risk may involve something other than the product of field strength and time. Such alternative possible relations, or "effects functions," are of great interest to epidemiologists, engineers, risk analysts, and regulators. A structured survey and workshop were used to explore whether leading researchers in bioelectromagnetics share similar views about alternative possible effects functions. Substantial agreement was found about several effects functions in a few specific contexts such as calcium-ion efflux and cell signalling, and biosynthesis pathways. No significant agreement emerged in many other contexts. No effects function possibilities were ruled out. Further effort of this sort was judged unlikely to yield greater consensus until more complete scientific understanding becomes available. However, a series of structured workshops on research planning and priority setting were judged to hold great potential for useful results.