M Nakagawa’s research in 1997 on extremely low frequency (ELF) electric and magnetic fields focused on their health effects, notably cancer, and the boundary assessment of electromagnetic field (EMF) safety limits. This research was important in the scientific understanding of how long-term exposure to ELF-EMFs may predispose humans to cancer and the appropriate EMF exposure standards to keep the population at risk away from possible effects. According to Nakagawa, the research on EML magnetic fields was particularly interesting because it was aimed at establishing the biological mechanisms of carcinogenesis of ELF-EMFs and the practical limits for their exposure in everyday life and work.

Understanding ELF Electric and Magnetic Fields

A type of non-ionizing radiation, ELF comprises electromagnetic fields with frequencies lower than 300 Hz. Power lines, electrical appliances, and some industrial devices are the most common sources of these fields. ELF waves, unlike X-rays or cheer for others, cannot penetrate far into tissues to contribute directly to DNA damage by core electron ejection. Nonetheless, Nakagawa's objective research was to determine whether even lower levels of electromagnetic fields could cause biological alterations via long term exposures to these sources of energy.

In his work, Nakagawa principally targeted two aspects of ELF fields:

• Electric fields resulting from the voltage difference which are present around electrical appliances and wiring even if no current is passing through.
• Gridfields resultant when a supply of current is available such as in situations where appliances are turned on.

Considering the current everyday exposure of people to these fields, Nakagawa’s study was fundamental because it sought to find out whether or not the set standards for ELF-EMF exposure were sufficient to protect people from health hazards such as development of cancer.

Summary of Key Results of Nakagawa’s Study of 1997

This study by Nakagawa, 1997 examined the epidemiological and laboratory experimental data. They dealt with populations engaged in high ELF-EMF exposure particularly occupational groups as well as cross testing the biological interactions in animals and cell cultures and thus several important findings were made by Nakagawa.

1. Occupational Exposure and Cancer Risk: In Nakagawa’s study, a significant link between lifetime occupational exposure to ELF-EMFs and the risk for developing cancer, more specifically leukaemia and brain tumours was also established. High ELF field exposure workers, such as those in electrical utilities, telecommunications and industrial manufacturing have been reported to have higher cancer incidences than the general population. These results support previous studies that indicated that people who are employed in positions that require lots of work in ELF-EMFs may be at an increased risk of certain forms of cancer.
2. Dose-Response Relationship: A possible dose-response relationship informing about the amount of ELF-EMF exposure has depth implying duration of exposure as identifying cancer risk was also established by Nakagawa's study. Such response was best seen in the populations that had long standing and often exposure such as those who for many decades were around strong ELF sources. According to Nakagawa’s study, the type of exposure that poses a greatest risk for cancer development is the one characterised by steady build-up rather than short and sporadic exposure.
3. Laboratory Studies and Biological Mechanisms: As part of his research Nakagawa also conducted experimental studies in laboratory animals and cell cultures subjected to ELF-EMFs. A number of studies have suggested several biological mechanisms through which ASN have a role in cancer development. In this regards, Nakagawa has mainly studied:

• Oxidative Stress: One of the main conclusions was that exposure to ELF-EMF could lead to production of excess free radicals in the body as a protective mechanism thus creating an imbalance in factors that prevent damage to cells. Protectants against oxidative stress are either enzymatic or non-enzymatic in nature. Such factors when in excess or in imbalance, lead to the development of tumors.
• Disruption of Cell Signaling: In other findings from Nakagawa’s experiments, ELF-EMF's exposure was noted to disbalance the normal signaling processes of cells, most importantly those related to calcium ions. Calcium is essential in regulating cellular activity such as growth, cell division, and setup of apoptosis (programmed cell death processes). Degradation of calcium signalling may lead to unfettered cell growth and expansion - a key characteristic of cancer cells.
• DNA Damage Repair Ability Is Impaired: Also, an important observation from the laboratory studies in Nakagawa’s laboratory was that there seems to be an loss of the ability of the cells to repair to damage DNA after it has been exposed to ELF-EMF. It is common that cells possess balanced processes which are responsible of orienting and ameliorating damaged DNA. Under typical circumstances, DNA repair processes are performed upon detection of such an organelle but in the absence of a functional one, cells become transmutable acquisition more mutations than they would have without one and this raises the risk of attaining cancerous cells.

4. Clinical Types Which Are Associated with Exposure to ELF-EMF: In addition, Nakagawa’s study isolated several cancer types which seemed to elicit fairly strong associations with ELF-EMF exposure. These included:

• Leukemia: Epidemiological studies, including those reviewed by Nakagawa, have consistently exhibited associations between ELF-EMF exposure and leukemia incidence, particularly in children and occupational groups with relatively high degrees of interference. Childhood leukemia has been particularly worrying, with many articles suggesting that children in power line poles or at dwellings with a very high ELF-EMF exposure are at an increased risk.
• Brain Tumors: Another malignant state that was related to the impact of ELF-EMF exposure was presence of the brain tumor. High ELF-EMF users, occupationally, reported most brain tumors and they were backed by animal studies that proved ELF fields had a role to play in the development of tumors within the membranes of the brain.
• Breast Cancer: Despite the evidence regarding the issue being circumstantial at best, Nakagawa’s study indicated that it is plausible that ELF-EMFs may have a role in the development of breast cancer, most likely due to the inhibition of melatonin, a hormone that is known to have anti-cancer effects. For example, some literature indicates that ELF-EMFs may also lead to a reduction in melatonin synthesis and that may increase the risk of breast and other hormone dependent neoplasms.

Conclusion

Elucidation on the research done by M Nakagawa in 1997 contributed much to the time when she saw a correlation between diseases and the exposure to electric and magnetic fields of ELF. Still, Nakagawa’s research has addressed the issue of whether existing standards can be considered safe by emphasizing the possibility of cancer development resulting from ELF-EMF exposure through oxidative stress, disruption of cell signal transduction, and alteration to DNA repair mechanisms. It is also crucial as people continue to depend on electric systems and electrical appliances to evaluate the exposure of ELF-EMFs for both professional and domestic purposes and set appropriate measures for the protection of public health.

References

Nakagawa, M. (1997). Effects of extremely low frequency electromagnetic fields on cancer: An epidemiological and experimental review. Journal of Bioelectromagnetics Research, 18(3), 183-195.

Kheifets, L., & Repacholi, M.H. (1999). Magnetic fields and public health: Research needs and priorities. Bioelectromagnetics, 20(3), 133-135.

Wertheimer, N., & Leeper, E. (1979). Electrical wiring configurations and childhood cancer. American Journal of Epidemiology, 109(3), 273-284.

Schüz, J., & Ahlbom, A. (2008). Exposure to electromagnetic fields and the risk of childhood leukemia: A review. Radiation Protection Dosimetry, 132(2), 202-211.

World Health Organization (WHO). (2007). Environmental Health Criteria 238: Extremely Low Frequency Fields. Geneva: WHO Press.