Identifying sources of electromagnetic field for a naval ship and the risk effects on the human body.

Samoilescu, Gheorghe ; Sotir, Alexandru ; Grozeanu, Silvestru 等

Abstract: The paper focuses on the main sources of electromagnetic field in the case of a naval ship, their pollution and the risk effects upon the environment. The choice for the environmental study is a naval ship, due to the special conditions in which people are working and living for a period of maximum 8 months per year. This limited space is habitat with many different and poorly studied characteristics. Onboard a naval ship there is a variety of electromagnetic sources which cover a wide range of frequencies from zero to 20 GHz. All these represent sources of electromagnetic changes transmitted through conduction and through the field. These changes can influence the proper functioning of the board equipments and the life of the crew.

Keywords: risk, electromagnetic disturbance, electric conductibility, electromagnetic field.

1. INTRODUCTION

The risk may be defined by means of alternate ways [1, 3]. As far as the risk estimate is concerned, we may distinguish among the following categories: a). Identifying risk factors resides in establishing the nature of the potential negative aspects; b). The estimate of the doses--effect ratio establishes the quantity ratio between the danger and the estimated adverse effect and the influence doses. c). The estimate of exposure determines exposure or, if possible, the doses administered to a certain target organ from the body of one of the persons exposed to a certain pathogenic aggression d). Risk characterization determines the action of harmful factors, taking into account the real terms of aggression. We make a distinction between the exposure and the dose.

This restricted space represents a less studied habitat, with many various characteristics (they are people living and unfolding their activity for a long period of time). Onboard a naval ship there is a great variety of electromagnetic sources which cover a large range of frequencies between 0 and 20 GHz consisting of: synchronous generators, electric engines, converters, radio communication systems, radiolocation, telecommunication, radiotelephones, and calculator networks. All these represent sources of electromagnetic perturbations transmitted both by conduction as well as by field. The perturbations may influence the good functioning of the equipment onboard as well as the life of the crew producing major pollution. [3, 4, 5].

2. EXPERIMENTAL PART

The data obtained hereby have been compared to the already known data in the field, establishing a number of 22 "points" for which these norms have been exceeded. As to the resulting situation some protection measures of the personnel must be taken such as protection suits, shields, protection screens, protection curtains. The measurements meant to determine the density of the power flux of the electromagnetic field onboard the ship have been performed in 2006. When performing the measurements we have used the complex measurement system Narda, 8718 model, USA, with sounding lines within 300kHz--50 GHz. On the basis of the data obtained by measurements we have drawn the electromagnetic chart of the ship.

3. RESULTS AND DISCUSSIONS

First of all, we have established the 22 points of the ship where we have deemed proper to make measurements, these points being situated on decks, in areas where the ship personnel is directly exposed to the radiation fields. With a view to checking the stability of the measurements, we have performed repeated measurements, over a day, or day by day, in the main measurement points, noticing identical or very close values of the density of electromagnetic power [1, 6, 7, 8] radiated in the same source context. As a result of measurements it results that:

a). the values obtained in the same point, in two days, between the same hours (8-16), and in the same perturbing context, with the same operating sources respectively, have a very slight variation among themselves: 13.1 [mu] W/[cm.sup.2] as compared to 12.5 [mu] W/[cm.sup.2]

b). the measured values in the two days are at the same size order.

Taking into account the average values measured during a 8-hour span and comparing them to the limited provided by the General Norms of Labour Protection, Annex 48/1996, edited by the Labour and Protection Ministry [11, 12], we noticed that in the 22 measurement selected points on the naval ship under study, the maximum level is over seeded, by 12.5 [mu] W/[cm.sup.2] /8 hours, or is very close to this level.

The exposure of human body to electromagnetic fields. In this section we shall make a distinction between the exposure with cumulative biochemical effects (long-term) and the exposure with acute (immediate) biochemical effects. [6, 7, 9, 10, 13, 14].

a). the exposure with cumulative biochemical effects is characterized by: 1). The preponderant action of very weak magnetic fields, of (0,1 / 0,2) [mu] T order, existing in domestic environments, as well as in occupational environments; 2). Quasi-permanent nature, which triggers the name of background field equivalent to the average exposure of a human being (domestic exposure); 3). Possible biochemical actions, which, during a long span of time, may lead to genetic alterations. The significant specific parameter in the case of cumulative biochemical effects is the magnetic field dose accumulated by the human being over a long period of time, like tens of years. The domestic dose corresponds to an average exposure of 0,13 [mu] T, which, in the case of an average individual, who is not supplementary exposed during work hours, leads to an annual value of 0,13 [mu]T x 8760 hours/year = 1,14 x 103 [mu]T. h/year= 1140 mT.h/year.

b). Exposures with biochemical acute effects is characterized by :1). Temporary action of some magnetic fields with exceed values of a couple of mT order, specific fields for some occupational environments (for instance, the vicinity of some electric ovens with induction); 2). Acute biochemical effects appear together with the surpassing of a critical value of the magnetic field intensity and disappear at the same time with the field disappearance; 3). Establishing limitations for the instantaneous action, which, unless surpassed, ensure the avoidance of acute biochemical effects. The limitations have been set by the World Health Organization and the International Board for Protection against Non-ionized Radiation (ICNIRP); 4). The existence of a monotonously rising dependence between the intensity of the magnetic field, which exposure is occurring at, and its biochemical effects. In table 2 we have presented an estimate of the exposure time in magnetic field, for various working positions in the engine room and the doses of accumulated exposure over a year are of 14 mT.h/year.

On the basis of the exposure doses we have been able to calculate the risk factors. The total annual doses is:

* For a person working in the engine room with electric equipment: Dt=[D.sub.0] +[D.sub.d] = 13520 +(8760 - 1600) 0,13+ 14450 nT.h/year = 14 mT.h/year. Therefore, the dosis is of 13 times greater, as compared to a person who is not occupationally exposed (1,14 mT/h/year).

* For a person working in telecommunication and transmission stations: Dt=[D.sub.0] +[D.sub.d] = 55630 +(8760 - 1600) 0,13 =55560 [mu]T.h/year =56 mT.h/year. Therefore, the doses is 50 times greater, than in the case of a not occupationally- exposed person.

The total annual doses is practically determined, only by activities deployed in the close vicinity of the central command point and is accumulated during time intervals, which, if summed up, represent the following percentages out of the whole occupational duration: 43 % in the case of stations and 34% in the case of electric generators.

For cummulative exposures in magnetic field of 3,1 [mu]T we have determined the relative risk factors RR = 2,41 for acute leukemia (non lymphocytic leukemia ANLL) and RR = 3,15 for myeloid acute leukemia (acute myeloidleukemia AML). For cummulative exposures in magnetic field of 2 [mu]T we have determined the relative risk factors: RR = 2,36 for ANLL and RR= 2,25 for AML. We have noticed an incerased frequency, towards the persons working in other occupational environments, of brain cancer, in the case of people working in electroenergetic installations. The risk factor in the case of brain cancer is RR = 1,64, for inductions of (0,2 -0,3) [mu]T. For other various locations of cancer (skin melanome, prostatis, lungs) the relative risk factor, determined for these workers, is RR = 0,96, for exposure to inductions of (0,2 -0,3) [mu]T, RR = 1,51 respectively, for exposure to fields greater than 0,3 [mu]T.

4. CONCLUSIONS

As a result, assigning the personnel in the 22 points may lead, in time, to a degradation of the health status, with negative effects on the board activities. One of the decks most affected by radiations is the main deck, where the watch is deployed involving every member of the crew.

1. we suggest that the personnel working in the engine rooms and with low frequency manning gear (like asynchronous electric engine, eletric transformers, electric distribution pannels, electric converters), be protected by means of costumes and protection shields, together with measures to ensure the anti-perturbant protection of the electronic equipment.

2. As a result of research done, we have drawn an electromagnetic chart of the ship, with an accurate location for the increased density areas of the field, namely the energy, in various operating modes of the ship.

3. We have established the relative risk factors correlated with various diseases.

5. REFERENCES

Calota S.V., Deliu N., Licurici M., Ferastraeru C., Contulescu A., (1998) Study regarding the professional exposure to non-ionized radiation of high frequency and the risk for health, Public Health Institute, Bucharest.

Gary C., (1993) Les effects biologiques des champs magnetiques. Que peut dire l'electricien a ce suget?, in Energy Magazine, 41, nr. 2-B.

Ianoz M., (2003) Biological land Health Effects of Electromagnetic Fields, Conference, University of Polytechnics, Bucharest, Faculty of Energy, Research center TICEM, march

King P.W.R., (1998) Fields and Currents in the Organs of the Human Body when Exposed to power Lines and VLF Transmitters, IEEE Transactions on Biomedical Engineering, vol.45, nr. 4.

Mocanu C. I., (1981) Theory of electromagnetic field, Didactics si Pedagogical Printing House, Bucharest

Nair I., (1993) Biological Effects of Electric and Magnetic Fields: What do we know?, Department of Engineering and Public Policy, Carnegie Mellon University (not presented at Stockholm Conference of EMC)

Nicolaescu V.S. and partners, (2004) The risk generated by electromagnetic fields produced by cellular mobile telecommunication appliances, Project of development-research INF 68, program INFOSOC, INSCC ICMET Craiova-UMF Carol Davila- University of Craiova

Nicolau E., (1989) Radiation and propagation of electromagnetic waves, Romanian Academy Publishing House, SRR, Bucharest.

Radu S., (1995) Introduction to electromagnetic compatibility, vol. 1, Screening of electronic devices Gheorghe Asachi Publishing House, Iasi, Romania

Samoilescu Gh. and partners.., (2004-2006) Means of complex protection for electromagnetic interference - CERES Grant

Sotir A., (2005) Perturbing electromagnetic interferences. Theoretical bases. Military Publishing House, Bucharest

Zamfirescu M., Sajin I., Rusu I., Sajin M., Kovacs E., (2000) Biochemical effects of electromagnetic radiation of radio frequency and microwaves, Medical Publishing House, Bucharest

*** Human exposure to electric and magnetic fields of industrial frequency, (1994) Project of Romanian Standard: SR EN 50166-1, IRS, Bucharest (in conformity with the standard EN 50166-1/1994)

***Human exposure to electromagnetic fields from the frequency range 10 kHz-300 GHz, Standard: EN 50166-2/1994 IRS, Bucharest

Table 2 Doses of accumulated exposure over a year for the
boarding personnel in the engine room

 Working position

 In on deck
 contact at a (15-20)m related
 (L<1m) distance (5-6)m activities Total

stations 20 300 370 700 1600
duration/
h/year

stations 3100 9440 890 90 13520
duration
[mu]T/year

working 12 244 294 1050 1600
points
duration/
h/year

working 8550 30620 16320 140 55630
points
duration
[mu]T/year