The authors have declared that no competing interests exist.
Conceived and designed the experiments: MFF NO. Performed the experiments: IC. Analyzed the data: IC. Contributed reagents/materials/analysis tools: MIN NO MFF. Contributed to the writing of the manuscript: IC MFF. In charge of field activities (recruitment of children in follow-ups, questionnaire and data basis): CDA OOH RPL RR FAC NO MIN.
To characterize the exposure to electric fields and magnetic fields of non-ionizing radiation in the electromagnetic spectrum (15 Hz to 100 kHz) in the dwellings of children from the Spanish Environment and Childhood-“INMA” population-based birth cohort.
The study sample was drawn from the INMA-Granada cohort. Out of 300 boys participating in the 9–10 year follow-up, 123 families agreed to the exposure assessment at home and completed a specific
Survey data showed a low exposure in the children's homes according to reference levels of the International Commission on Non-Ionizing Radiation Protection but with large differences among homes in mean and maximum values. Daytime electrostatic and magnetic fields were below the quantification limit in 78.6% (92 dwellings) and 92.3% (108 dwellings) of houses, with an arithmetic mean value (± standard deviation) of 7.31±9.32 V/m and 162.30±91.16 nT, respectively. Mean magnetic field values were 1.6 lower during the night than the day. Nocturnal electrostatic values were not measured. Exposure levels were influenced by the area of residence (higher values in urban/semi-urban
Given the greater sensitivity to extremely low-frequency electromagnetic fields of children and following the precautionary principle, preventive measures are warranted to reduce their exposure.
Human exposure to electromagnetic fields from non-ionizing radiation (EMF-NIR) has increased over recent decades, raising concerns about possible adverse health effects, although these remain controversial
ELF electromagnetic fields were recently classified as possibly carcinogenic (2B group) by the International Agency for Research on Cancer (IARC), based on epidemiological studies of childhood leukemia
Exposure to electric and magnetic fields in the home is influenced by various factors, including the use of electrical appliances, amount of electrical current flowing through the earth in the electrical distribution board, power consumption in the neighborhood, and distance between dwellings and from the power distribution system, among others. The field strength is significantly reduced with greater distance from the source.
The walls and roofs of houses can reduce the exposure to electrical fields from external equipment (e.g., power lines)
The strength of magnetic field in a dwelling, which is determined by the use of energy by neighbors as well as by the occupants, varies according to the time of day and season of the year. Thus, magnetic fields are generally at maximum values between 6 pm and 8 pm and at minimal values during the night, and there are also seasonal variations
All electrical equipment produces an electric field and a magnetic field when in use. Electrical energy in the home is low-voltage, generating an electric field of only a few volts per meter. However, it has been reported that long-term exposure to these levels in buildings that are well-equipped with wireless devices but have inadequate ventilation and inappropriate construction materials may be responsible for the so-called “sick building syndrome”, associated with semi-circular lipoatrophy and other conditions
Increasing concerns about the possibility of adverse effects of exposure have led to investigations designed to improve methods for measuring exposure to electromagnetic fields from non-ionizing radiation (EMF-NIR) in the ranges of extremely low and low frequency electric [(ELF-LF)-EF] and magnetic [(ELF-LF)-MF] fields, and several studies have characterized this exposure in recent years
It has been documented that children may be especially susceptible to exposure to EMF-NIR
The objective of this study was to characterize the exposure to electric and magnetic fields of NIR in the 15 Hz to 100 kHz frequency range in the homes of children from the Spanish Environment and Childhood-“INMA” birth cohort.
The study sample was drawn from the INMA network, a population-based cohort study in different regions of Spain (Ribera d'Ebre, Menorca, Granada, Valencia, Sabadell, Asturias, and Gipuzkoa) that focuses on prenatal environmental exposures in relation to growth, development, and health from early fetal life through childhood. The INMA study protocol includes medical follow-ups of the children from birth through childhood as well as epidemiological questionnaires and biological sample collections
From October 2000 through July 2002, 700 eligible mother–son pairs registered at the San Cecilio University Hospital of Granada (province in Southern Spain) were recruited at delivery, establishing the INMA-Granada cohort. The inclusion and exclusion criteria were published elsewhere
We obtained written informed consent from the parents (mother or father) on behalf of children enrolled in your study. The 300 families registered in the follow-up signed the informed consent form, which included completion of ad hoc questionnaires. Two hundred-fifty out of three hundred families signed an additional informed consent to the performance of EMF-NIR measurements at home, but at the moment of the appointment became due, 127 families reneged on their decision. The study followed the guidelines laid down in the Declaration of Helsinki and was approved by the Ethics Committee of San Cecilio University Hospital, Granada, Spain.
The setting of the INMA-Granada study is the health district of the San Cecilio University Hospital, an area of 4000 km2 with a total population of 512,000 inhabitants, including part of the city of Granada (236,000 inhabitants) and 50 towns and villages. Three areas of residence are differentiated: a) urban areas, corresponding to the city of Granada and towns with more than 20,000 inhabitants in the surrounding metropolitan area, b) semi-urban areas, towns with 10,000–20,000 inhabitants in the surrounding metropolitan area, and c) rural areas: small villages with less than 10,000 inhabitants. In the present study sample, 9.8% of households were in rural areas, 45.5% in semi-urban areas, and 44.7% in urban areas.
General characteristics of the households were as follows: 15.5% of families lived in detached houses, 45.5% in semi-detached houses, and 39% in apartments. The median age of the buildings was 15 yrs (range, 1.5 yrs to 62 yrs). The mean and median time of families in their current dwelling was 11 years (range, 0.16 to 28.0 yrs). Two rooms of the house were selected for ELF-LF measurements: the living room and the child's bedroom. Half of bedrooms (54.2%) were on the 3rd floor, 44.4% on the 2nd, and the remainder on the 1st floor. The living room was on the 2nd floor in 83.3% of the dwellings.
The main sources of exposure to ELF-LF radiation in the living rooms and bedrooms were televisions, computers, music/DVD devices, electric braziers/radiators, heaters, air conditioning units, and energy-saving light bulbs. The largest proportions of electric-electronic devices were televisions (34%) and computers (32%), which were most frequently in the living room. Some type of energy-saving system (e.g., cold cathode fluorescent lamps) was used in the living room by 24.4% of families and in both rooms by 43.1%.
The EMF-NIR is composed of two separate components: electric and magnetic fields. ELF-LF fields are associated with all aspects of the production, transmission, consumption, and transformation of electricity
Measurements were carried out for indoor sources using a Taoma base unit (Tecnocervizi, Rome, Italy), a broadband device with electric field and magnetic field isotropic probes with measurement ranges from 10 V/m to 100 kV/m and from 100 nT to 10 mT in the 15 Hz to 100 kHz frequency range. Quantification limits for electric [(ELF-LF)-EF] and magnetic [(ELF-LF)-MF] fields were 10 V/m and 100 nT (for the sum of all frequencies), respectively. These quantification limits are well below the most cautious guideline levels and therefore adequate for the purpose of the study; although some medical associations consider these limits to be too high for certain health problems associated with “electrosmog”
Long-term [(ELF-LF)-EF] and [(ELF-LF)-MF] measurements were performed every 240 s in the living room and child's bedroom, the areas at home where the children spent most time. The measurement procedure began with an initial exploration of the area of interest in order to identify punctual sources and to minimize perturbations caused by the proximity of the operator to the probe. Broadband measurements were then taken of electric and magnetic fields. The I-BOX and probes were placed on a non-metallic surface (desk/table in the center of the living rooms, and at the bed-side table [top end of the bed] in bedrooms) at an average height of 79 cm above the floor (based on the children's height at head and chest level). All devices in the household remained in their usual state during recordings, and there were no changes in the habitual internal sources. In a pilot study of 10 homes, the exposure was characterized on three different days. However, because virtually no difference was observed among the measurements on the different days, it was decided to perform the measurements on one day alone in the main study. In order to characterize everyday life exposure to all sources, measurements were made over a total of 17 h/day (between 3 pm and 10 pm in the living room and between 10 pm and 8 am in the bedroom) during a typical working day between October and June during the two-year study period.
An
Descriptive analysis of measurements was performed, computing arithmetic means and standard deviations (SDs), median values, 5% trimmed mean values (after omitting lowest and highest 5% of measurements), and 25th and 75th percentiles. Comparison between variables was performed using the non-parametric Kruskal-Wallis test (χ2) and the Mann-Whitney U test. P≤0.05 was considered significant.
All measurements were performed by a single operator (I.C.). Excel 2010 and SPSS version 18 (IBM, Chicago, IL) were used for the data analyses.
Field | AM±SD | GM±SDG | Median | 5% TM | p25 | p75 |
Day 3pm–10pm | 7.31±9.32 | 2.54±9.30 | 3.68 | 6.08 | 1.84 | 8.58 |
Maximum | 16.74±20.51 | 9.17 | 13.97 | 5.15 | 21.03 | |
Minimum | 2.78±4.91 | 1.25 | 2.01 | 0.01 | 2.17 | |
Day (3pm–10pm) | 162.30±91.16 | 142.53±1719 | 134.20 | 152.70 | 120.00 | 188.3 |
Maximum | 1177.39±2375.34 | 685.00 | 859.70 | 445.50 | 1245.0 | |
Minimum | 42.23±22.22 | 49.00 | 42.42 | 36.00 | 56.00 | |
Night (10pm–8am) | 103.00±30.66 | 99.70 | 100.50 | 91.80 | 108.30 | |
Maximum | 476.00±2278.57 | 149.00 | 169.3 | 141.50 | 162.00 | |
Minimum | 44.25±21.03 | 43.00 | 44.30 | 33.00 | 57.50 | |
Day-night (3pm–8am) | 128.20±43.70 | 116.40 | 124.60 | 105.30 | 140.60 | |
Maximum | 1217.35±2280.36 | 788.00 | 907.67 | 461.50 | 1365.0 | |
Minimum | 37.83±21.51 | 42.00 | 37.54 | 26.50 | 52.50 |
nT: nanoTeslas; V/m: Volts/meter; AM: Arithmetical Mean; SD: Standard Deviation; GM: Geometrical Mean; SDG: Standard Deviation Geometrical; TM: Trimmed mean; p: percentile.
ELF-LF exposure levels were below the quantification limit of the probe (10 V/m) in 92 dwellings (78.6%). The arithmetic mean ±SD (ELF-LF)-EF value in the 117 dwellings was 7.31±9.32 V/m (above this mean value in 29.06% of dwellings), and the geometric mean was 2.54±9.30 V/m. The mean maximum value was 16.74±20.51 V/m and mean minimum value was 2.78±4.91 V/m; 25% of measurements were below 1.84 V/m or above 8.58 V/m (
The arithmetic mean ±SD (ELF-LF)-MF value for the 117 dwellings was 162.30±91.16 nT (above this mean value in 38.46% of dwellings) and the geometric mean value was 142.53±1719 nT. The mean maximum value was 1177.39±2375.34 nT and the mean minimum value was 42.23±22.22 nT; 25% of the measurements were below 120 nT or above 188.30 nT (
Nocturnal measurements were only performed for magnetic field values. The arithmetic mean was 103.00±30.66 nT, i.e., 1.6-fold lower than daytime values, with 92% of measurements above the mean value and a geometric mean of 92.11±26.02 nT. The median value was 134.20 nT in the daytime and 99.70 nT at night. Median minimum values were similar between daytime and nocturnal measurements (
EF (V/m) Day: 3 pm–10 pm | MF (nT) Day: 3 pm–10 pm | MF (nT) Night: 10 pm–8 am | ||||||||||||||||
n | mean | sd | p25 | p75 | p | n | mean | sd | p25 | p75 | p | n | mean | sd | p25 | p75 | p | |
Rural | 12 | 3.83 | 6.24 | 1.43 | 2.88 | 12 | 136.00 | 65.13 | 105.00 | 178.10 | 10 | 100.90 | 42.23 | 80.30 | 98.65 | |||
Urban/semi-urban | 105 | 7.71 | 9.55 | 1.89 | 9.27 | 104 | 165.60 | 93.83 | 121.90 | 188.70 | 59 | 103.30 | 28.72 | 93.60 | 108.60 | |||
0.189 | ||||||||||||||||||
Semi-detached/Attached | 71 | 6.26 | 9.26 | 1.62 | 5.38 | 70 | 156.80 | 89.97 | 116.70 | 186.40 | 36 | 99.80 | 325.6 | 86.30 | 102.70 | |||
Apartments | 46 | 8.95 | 9.27 | 2.77 | 13.68 | 46 | 171.30 | 94.10 | 125.10 | 189.60 | 33 | 106.50 | 28.53 | 96.40 | 116.00 | |||
0.072 | 0.841 | |||||||||||||||||
<15 yrs | 48 | 6.48 | 9.71 | 1.65 | 7.37 | 49 | 172.60 | 85.00 | 123.90 | 190.10 | 28 | 106.90 | 31.60 | 93.50 | 108.20 | |||
≥15 yrs | 55 | 8.20 | 9.50 | 2.13 | 10.11 | 53 | 145.60 | 82.54 | 115.50 | 160.40 | 32 | 104.00 | 32.94 | 88.20 | 108.60 | |||
0.732 | 0.876 | 0.00 | 0.930 | |||||||||||||||
<9 yrs | 36 | 7.25 | 10.60 | 1.84 | 7.37 | 35 | 171.80 | 108.72 | 121.80 | 190.00 | 24 | 104.20 | 26.53 | 93.50 | 107.40 | |||
≥9 yrs | 81 | 7.34 | 8.90 | 1.80 | 8.97 | 81 | 158.60 | 83.42 | 118.30 | 188.30 | 45 | 102.30 | 32.92 | 89.60 | 108.30 | |||
0.081 | 0.843 | |||||||||||||||||
<3a | 92 | 6.58 | 8.71 | 1.77 | 7.78 | 91 | 159.40 | 80.29 | 118.70 | 190.00 | 50 | 100.80 | 28.35 | 89.90 | 107.10 | |||
≥ 3a | 25 | 10.01 | 11.06 | 2.25 | 14.16 | 25 | 174.20 | 125.54 | 123.60 | 184.10 | 19 | 108.80 | 36.24 | 99.70 | 112.30 | |||
0.487 | ||||||||||||||||||
≤1 h | 26 | 6.15 | 9.31 | 1.71 | 8.66 | 26 | 175.00 | 61.10 | 126.2 | 222.9 | ||||||||
>1 h | 90 | 7.59 | 9.38 | 1.89 | 8.13 | 90 | 158.4 | 98.55 | 118.0 | 188.0 | ||||||||
0.774 | 0.802 | |||||||||||||||||
≤1 h | 105 | 7.14 | 9.39 | 1.81 | 7.89 | 105 | 164.50 | 93.83 | 120.20 | 189.10 | ||||||||
>1 h | 11 | 8.52 | 9.23 | 1.86 | 19.42 | 10 | 136.7 | 59.53 | 101.60 | 185.8 | ||||||||
0.532 | 0.395 | |||||||||||||||||
No | 78 | 7.48 | 9.48 | 2.28 | 7.73 | 78 | 163.10 | 86.66 | 118.20 | 119.10 | ||||||||
Yes | 39 | 6.99 | 9.10 | 1.65 | 10.11 | 39 | 160.7 | 100.72 | 121.10 | 157.30 | ||||||||
0.967 | 0.608 | 0.348 | ||||||||||||||||
No | 65 | 6.80 | 8.31 | 1.81 | 8.58 | 64 | 155.10 | 71.69 | 121.30 | 175.10 | 61 | 103.70 | 31.81 | 93.50 | 108.3 | |||
Yes | 51 | 8.08 | 10.57 | 1.88 | 11.57 | 52 | 170.00 | 111.16 | 118.70 | 193.10 | 7 | 98.70 | 22.03 | 84.7 | 113.2 | |||
0.409 | 0.394 | 0.089 | ||||||||||||||||
No | 46 | 7.40 | 8.80 | 1.98 | 10.53 | 44 | 144.10 | 57.32 | 119.10 | 183.40 | 54 | 102.40 | 34.12 | 89.90 | 107.50 | |||
Yes | 71 | 7.26 | 9.70 | 1.75 | 7.84 | 73 | 173.30 | 105.35 | 120.00 | 191.50 | 15 | 105.10 | 12.39 | 9.97 | 112.30 | |||
0.666 | 0.634 | |||||||||||||||||
No | 40 | 6.36 | 6.78 | 2.43 | 7.83 | 35 | 138.00 | 79.64 | 115.70 | 156.50 | 28 | 100.90 | 28.99 | 90.80 | 107.90 | |||
Yes | 77 | 7.81 | 10.40 | 1.75 | 9.88 | 82 | 172.70 | 94.19 | 122.5 | 194.80 | 41 | 104.40 | 32.03 | 92.30 | 108.70 | |||
0.852 | 0.099 | |||||||||||||||||
Spring-Summer | 66 | 6.98 | 8.73 | 1.98 | 7.87 | 65 | 150.60 | 79.57 | 116.60 | 174.10 | 42 | 101.90 | 37.36 | 86,20 | 108.60 | |||
Autumn-Winter | 51 | 7.74 | 10.10 | 1.75 | 9.25 | 51 | 177.80 | 103.59 | 125.30 | 201.00 | 27 | 104.70 | 15.88 | 100,60 | 108.10 |
Air-con: Air-conditioning; mean: arithmetical mean; SD: standard deviation; p25: Percentile 25; p75; Percentile 75; MF: Magnetic field or magnetic induction; EF: electric field; nT: nanoTeslas; V/m: Volts/meter.
Daytime (ELF-LF)-MF values were significantly higher (p = 0.025) in younger
Daytime (ELF-LF)-MF values were significantly higher in the spring/summer than in the autumn/winter (p = 0.036). A similar but non-significant tendency was observed for daytime (ELF-LF)-EF and nocturnal (ELF-LF)-MF exposure levels.
In this study, we characterized the exposure of children to EFs and MFs of NIR by performing long-term (daytime and nocturnal) measurements in the electromagnetic spectrum (15 Hz to 100 kHz) in the dwellings of children belonging to the INMA-Granada birth cohort. The EF and MF values found were very low, below International Commission on Non-Ionizing Radiation Protection (ICNIRP) guideline levels
As far as we know, the present study is the first to measured children's exposure to long-term (ELF-LF)-EF and (ELF-LF)-MF within their homes throughout lengthy daytime and nocturnal periods. Various approaches have been used to assess exposure to electromagnetic fields, including spot or long-term measurements, personal exposimetry/dosimeters, and the characterization of exposure based on activities and sources
(ELF-LF)-EF levels were generally below the quantification limit of the probe (10 V/m). Overall exposure (ELF-LF)-EF values were lower than residential values reported in Austria
(ELF-LF)-MF values were above 100 nT in 92.31% of daytime measurements, 63.77% of nocturnal measurements, and 86.96% of overall measurements. Mean residential ELF-MF levels have been reported to range between 25 nT and 70 nT in Europe and between 55 nT and 110 nT in the USA
We distinguished between daytime (3 pm–10 pm) and nocturnal (10 pm–8 am) exposure measured in the living room and child's bedroom, finding that mean (ELF-LF)-MF values were 1.64-fold higher during the day (169 nT) than at night (103 nT). Various authors have reported higher day-time than nocturnal measurements
Mean ELF-LF measurements were higher in dwellings in urban or semi-urban
Lower values were recorded in spring-summer than in autumn-winter, likely attributable to the greater use of electric heating and/or storage heaters during the colder months. Straume et al. also found differences in mean ELF-MF measurements between the summer (30 nT) and winter (70–80 nT) in public outdoor spaces in Norway
Relationships between ELF-LF levels and specific sources (televisions, computers, heaters, etc.) were not consistent in our study, although a stronger association was observed when multiple domestic electrical and electronic devices were considered together (data not shown).
Study limitations include the relatively small sample size, the lack of data on individual exposure, and the fact that only 21.36% of electric measurements were within the range of the instrument. Moreover, the statistical power of the study was reduced by the application of non-parametric tests, although significance was reached (p<0.05). A study strength is that a single researcher was responsible for measuring levels in all dwellings and for gathering and analyzing all data. In addition, real measurements were analyzed, rather than estimates. The fact that the sample was drawn from an ongoing birth cohort also opens up the possibility of comparing exposure data with future health outcomes.
Various epidemiological studies have estimated that the risk of leukemia is two-fold higher in children who are exposed at home to ELF-MF levels above 300-400 nT
This study applied a detailed and accurate measurement protocol to characterize the indoor exposure of children to ELF-LF electric and magnetic fields at home. Residential exposure levels were below ICNIRP reference levels, but there was a wide variability in mean and maximum values, with 9.4% of the children receiving daytime exposure of >300 nT. There is a need for further studies of long-term exposure and for detailed research on its relationship with health outcomes.
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The authors are grateful to all participating “INMA families” for their cooperation and thank Richard Davies for editorial assistance.