Estimating magnetic fields of homes near transmission lines in the California Power Line Study

Pesticides as a potential independent childhood leukemia risk factor and as a potential confounder for electromagnetic fields exposure

BACKGROUND

Both pesticides and high magnetic fields are suspected to be childhood leukemia risk factors. Pesticides are utilized at commercial plant nurseries, which sometimes occupy the areas underneath high-voltage powerlines.

OBJECTIVES

To evaluate whether potential pesticide exposures (intended use, chemical class, active ingredient) utilized at plant nurseries act as an independent childhood leukemia risk factor or as a confounder for proximity to, or magnetic fields exposure from, high-voltage powerlines.

METHODS

We conducted a state-wide records-based case-control study for California with 5788 childhood leukemia cases and 5788 controls that examined specific pesticide use, magnetic field exposures and distances to both powerlines and plant nurseries. Exposure assessment incorporated geographic information systems, aerial satellite images, and other historical information.

RESULTS

Childhood leukemia risk was potentially elevated for several active pesticide ingredients: permethrin (odds ratio (OR) 1.49, 95% confidence interval (CI) (0.83-2.67), chlorpyrifos (OR 1.29, 95% CI 0.89-1.87), dimethoate (OR 1.79, 95% CI 0.85-3.76), mancozeb (OR 1.41, 95% CI 0.85-2.33), oxyfluorfen (OR 1.41, 95% CI 0.75-2.66), oryzalin (OR 1.60, 95% CI 0.97-2.63), and pendimethalin (OR 1.82, 95% CI 0.81-2.25). Rodenticide (OR 1.42, 95% CI 0.78-2.56) and molluscicide (OR 1.22, 95% CI 0.82-1.81) exposure also presented potentially elevated childhood leukemia risks. Childhood leukemia associations with calculated fields or powerline proximity did not materially change after adjusting for pesticide exposure. Childhood leukemia risks with powerline proximity remained similar when pesticide exposures were excluded.

DISCUSSION

Pesticide exposure may be an independent childhood leukemia risk factor. Childhood leukemia risks for powerline proximity and magnetic fields exposure were not explained by pesticide exposure.

Estimation of the general population and children under five years of age in France exposed to magnetic field from high or very high voltage power line using geographic information system and extrapolated field data

BACKGROUND

The effects of extremely low-frequency magnetic fields, especially their long-term health effects, including childhood leukaemia, remain elusive. The International Agency for Research on Cancer has classified the exposure to magnetic fields >0.4 μT as 'possibly carcinogenic to humans (group 2 B)' for childhood leukaemia. However, the number of exposed individuals, particularly children, remains poorly documented in international literature. The objective of this study was to estimate the number of individuals living near a high or very high voltage line in France (≥63 kV), among the general population and children under the age of five years.

METHODS

The estimate considered different exposure scenarios depending on the line voltage and the distance of the housing from it, and whether the line is overhead or underground. The exposure scenarios were obtained using a multilevel linear model created from a measurement database published by "Réseau de transport d'électricité", the operator of the French electricity transmission network.

RESULTS

Between 0.11% (n = 67,893) and 1.01% (n = 647,569) of the French population and between 0.10% (n = 4712) and 1.03% (n = 46,950) of children under five years of age were estimated to be living in an area potentially exposed to a magnetic field, depending on the exposure scenario (>0.4 μT and >0.1 μT, respectively).

CONCLUSIONS

By making it possible to estimate the total number of residents, schools, and health institutions near high-voltage power lines, the proposed methodology can help identify potential co-exposures near high-voltage power lines, which are regularly cited as a possible explanation for contradictory results from epidemiological studies.

Estimating exposure to extremely low frequency magnetic fields near high-voltage power lines and assessment of possible increased cancer risk among Slovenian children and adolescents

BACKGROUND

Some previous research showed that average daily exposure to extremely low frequency (ELF) magnetic fields (MF) of more than 0.3 or 0.4 μT could potentially increase risk of childhood leukaemia.

MATERIALS AND METHODS

To allow calculations of ELF MF around high voltage (HV) power lines (PL) for the whole Slovenia, a new three-dimensional method including precision terrain elevation data was developed to calculate the long-term average ELF MF. Data on population of Slovenian children and adolescents and on cancer patients with leukaemia's aged 0-19 years, brain tumours at age 0-29, and cancer in general at age 0-14 for a 12-year period 2005-2016 was obtained from the Slovenian Cancer Registry.

RESULTS

According to the large-scale calculation for the whole country, only 0.5% of children and adolescents under the age of 19 in Slovenia lived in an area near HV PL with ELF MF density greater than 0.1 μT. The risk of cancer for children and adolescents living in areas with higher ELF MF was not significantly different from the risk of their peers.

CONCLUSIONS

The new method enables relatively fast calculation of the value of low-frequency magnetic fields for arbitrary loads of the power distribution network, as the value of each source for arbitrary load is calculated by scaling the value for nominal load, which also enables significantly faster adjustment of calculated estimates in the power distribution network.

Commercial outdoor plant nurseries as a confounder for electromagnetic fields and childhood leukemia risk

BACKGROUND

Close residential proximity to powerlines and high magnetic fields exposure may be associated with elevated childhood leukemia risks as reported by prior studies and pooled analyses. Magnetic fields exposure from high-voltage powerlines is associated with proximity to these powerlines and consequently with any factor varying with distance. Areas underneath powerlines in California may be sites for commercial plant nurseries that can use pesticides, a potential childhood leukemia risk factor.

OBJECTIVES

Assess if potential pesticide exposure from commercial plant nurseries is a confounder or interacts with proximity or magnetic fields exposure from high-voltage powerlines to increase childhood leukemia risk.

METHODS

A comprehensive childhood leukemia record-based case-control study with 5788 cases and 5788 controls (born and diagnosed in California, 1986-2008) was conducted. Pesticide, powerline, and magnetic field exposure assessment utilized models that incorporated geographical information systems, aerial satellite images, site visits and other historical information.

RESULTS

The relationship for calculated fields with childhood leukemia (odds ratio (OR) 1.51, 95% confidence interval (CI) 0.70-3.23) slightly attenuated when controlling for nursery proximity (OR 1.43, 95% CI 0.65-3.16) or restricting analysis to subjects living far (>300 m) from nurseries (OR 1.43, 95% CI 0.79-2.60). A similar association pattern was observed between distance to high-voltage powerlines and childhood leukemia. The association between nursery proximity and childhood leukemia was unchanged or only slightly attenuated when controlling for calculated fields or powerline distance; ORs remained above 2 when excluding subjects with high calculated fields or close powerline proximity (OR 2.16, 95% CI 0.82-5.67 and OR 2.15, 95% CI 0.82-5.64, respectively). The observed relationships were robust to different time periods, reference categories, and cut points.

DISCUSSION

Close residential proximity to nurseries is suggested as an independent childhood leukemia risk factor. Our results do not support plant nurseries as an explanation for observed childhood leukemia risks for powerline proximity and magnetic fields exposure, although small numbers of subjects concurrently exposed to high magnetic fields, close powerline proximity and plant nurseries limited our ability to fully assess potential confounding.

Magnetic Fields and Cancer: Epidemiology, Cellular Biology, and Theranostics

Humans are exposed to a complex mix of man-made electric and magnetic fields (MFs) at many different frequencies, at home and at work. Epidemiological studies indicate that there is a positive relationship between residential/domestic and occupational exposure to extremely low frequency electromagnetic fields and some types of cancer, although some other studies indicate no relationship. In this review, after an introduction on the MF definition and a description of natural/anthropogenic sources, the epidemiology of residential/domestic and occupational exposure to MFs and cancer is reviewed, with reference to leukemia, brain, and breast cancer. The in vivo and in vitro effects of MFs on cancer are reviewed considering both human and animal cells, with particular reference to the involvement of reactive oxygen species (ROS). MF application on cancer diagnostic and therapy (theranostic) are also reviewed by describing the use of different magnetic resonance imaging (MRI) applications for the detection of several cancers. Finally, the use of magnetic nanoparticles is described in terms of treatment of cancer by nanomedical applications for the precise delivery of anticancer drugs, nanosurgery by magnetomechanic methods, and selective killing of cancer cells by magnetic hyperthermia. The supplementary tables provide quantitative data and methodologies in epidemiological and cell biology studies. Although scientists do not generally agree that there is a cause-effect relationship between exposure to MF and cancer, MFs might not be the direct cause of cancer but may contribute to produce ROS and generate oxidative stress, which could trigger or enhance the expression of oncogenes.

3D GIS for surface modelling of magnetic fields generated by overhead power lines and their validation in a complex urban area

Residential exposure to magnetic fields generated by overhead high-voltage power lines, continues to be a matter of social concern and, for the scientific community, a challenge to model this exposure accurately enough to reliably detect even small effects in large populations complexes. In any expression of the magnetic field intensity, the source-receiver distance is a determining variable, especially in an environment closer to the electrical installation and critical with the existence of significant unevenness in the terrain. However, MF exposure studies adopt, due to their complexity, simplifications of reality where even sometimes the terrain relief and the buckling of the line are not considered. The application of 3D techniques with Geographic Information Systems (GIS) allows us to address this problem. This article presents a model for generating magnetic field intensity surfaces from high-precision terrain elevation data. The series expansion of the Biot-Savart law to an infinite rectilinear conductor with variable height according to the catenary described by the cables using ArcGIS software is applied to calculate the magnetic field. For the validation, 69 control points (1035 field measurements) were used in a free urban area and another 28 points (420 field measurements) in a built-up urban area with complex relief. Good estimates were obtained, although with differences in both areas. With MAPE 9.65% and 19.51%, R2 = 0.922 and 0.949, RMSE = 0.154 and 0.094 μT, respectively. Furthermore, 86% of the points were correctly classified according to usual exposure percentiles. However, the use of a 5 m resolution digital terrain model to obtain high-precision elevation data was an indispensable condition for the good performance of our model. The result as a continuous surface of magnetic field values at the real elevation of the ground can contribute significantly to the development of new environmental and public health studies.

Relationship between distance to overhead power lines and calculated fields in two studies

There is some evidence that both distance from transmission lines and measured or calculated magnetic fields are associated with childhood leukemia. Because distance is a key component when calculating the magnetic field generated by power lines, distance from lines and calculated fields based on lines tend to be highly correlated. Socioeconomic status (SES) and dwelling type are also associated with magnetic field exposure. We used exposure data from two large studies of childhood leukemia and other cancers, in the US and the UK, to describe a relationship between distance and magnetic fields across the population within 100 meters (m) of power lines as a whole and evaluate potential modifiers such as SES and type of dwelling. There were 387 subjects living within 100 m of an overhead power line. There was no significant difference in mean calculated fields or distance to 200+ kV lines within 100 m by study. Within the range where the power-line field is expected to be significant compared to other sources, which we take as 100 m, distance to high-voltage lines predicted magnetic field (MF) variation in both studies better than other functions of distance tested in both linear and logistic regression. There were no differences between high and low SES or dwelling types (single-family home versus other). In conclusion, we found that calculated fields do appear to diminish linearly with increasing distance from overhead power lines, up to 100 m, particularly those 200+ kV and above. These results are stronger in the UK study. Within 100 m, distance to high-voltage lines continues to be highly correlated with calculated MFs and each can be a proxy for the other.

The role of dwelling type when estimating the effect of magnetic fields on childhood leukemia in the California Power Line Study (CAPS)

PURPOSE

The type of dwelling where a child lives is an important factor when considering residential exposure to environmental agents. In this paper, we explore its role when estimating the potential effects of magnetic fields (MF) on leukemia using data from the California Power Line Study (CAPS). In this context, dwelling type could be a risk factor, a proxy for other risk factors, a cause of MF exposure, a confounder, an effect-measure modifier, or some combination.

METHODS

We obtained information on type of dwelling at birth on over 2,000 subjects. Using multivariable-adjusted logistic regression, we assessed whether dwelling type was a risk factor for childhood leukemia, which covariates and MF exposures were associated with dwelling type, and whether dwelling type was a potential confounder or an effect-measure modifier in the MF-leukemia relationship under the assumption of no-uncontrolled confounding.

RESULTS

A majority of children lived in single-family homes or duplexes (70%). Dwelling type was associated with race/ethnicity and socioeconomic status but not with childhood leukemia risk, after other adjustments, and did not alter the MF-leukemia relationship upon adjustment as a potential confounder. Stratification revealed potential effect-measure modification by dwelling type on the multiplicative scale.

CONCLUSION

Dwelling type does not appear to play a significant role in the MF-leukemia relationship in the CAPS dataset as a leukemia risk factor or confounder. Future research should explore the role of dwelling as an effect-measure modifier of the MF-leukemia association.

The sensitivity of reported effects of EMF on childhood leukemia to uncontrolled confounding by residential mobility: a hybrid simulation study and an empirical analysis using CAPS data

PURPOSE

Residential mobility is considered as a potential source of confounding in studies assessing environmental exposures, including in studies of electromagnetic field (EMF) exposures and childhood leukemia.

METHODS

We present a hybrid simulation study where we simulate a synthetic dataset based on an existing study and use it to assess the sensitivity of EMF-leukemia associations to different scenarios of uncontrolled confounding by mobility under two major hypotheses of the infectious etiology of childhood leukemia. We then used the findings to conduct sensitivity analysis and empirically offset the potential bias due to unmeasured mobility in the California Power Line Study dataset.

RESULTS

As expected, the stronger the assumed relationship between mobility and exposure and outcome, the greater the potential bias. However, no scenario created a bias strong enough to completely explain away previously observed associations.

CONCLUSIONS

We conclude that uncontrolled confounding by residential mobility had some impact on the estimated effect of EMF exposures on childhood leukemia, but that it was unlikely to be the primary explanation behind previously observed largely consistent, but unexplained associations.

Childhood leukemia risk in the California Power Line Study: Magnetic fields versus distance from power lines

Pooled analyses have suggested a small increased risk of childhood leukemia associated with distance and with exposure to high magnetic fields from power transmission lines. Because magnetic fields are correlated with distance from lines, the question of whether the risk is due to magnetic fields exposure or to some other factor associated with distance from lines is unresolved. We used data from a large records-based case-control study to examine several research questions formulated to disentangle the relationships among magnetic fields, distance from high voltage lines, and childhood leukemia risk. In models examining an interaction between distance and magnetic fields exposure, we found that neither close proximity to high voltage lines alone nor exposure to high calculated fields alone were associated with childhood leukemia risk. Rather, elevated risk was confined to the group that was both very close to high voltage lines (<50 m) and had high calculated fields (≥0.4 μT) (odds ratio 4.06, 95% CI 1.16, 14.3). Further, high calculated fields (≥0.4 μT) that were due solely to lower voltage lines (<200 kV) were not associated with elevated risk; rather, risk was confined to high fields attributable to high voltage lines. Whilst other explanations are possible, our findings argue against magnetic fields as a sole explanation for the association between distance and childhood leukemia and in favor of some other explanation linked to characteristics of power lines.

Residential mobility and childhood leukemia

AIMS

Studies of environmental exposures and childhood leukemia studies do not usually account for residential mobility. Yet, in addition to being a potential risk factor, mobility can induce selection bias, confounding, or measurement error in such studies. Using data collected for California Powerline Study (CAPS), we attempt to disentangle the effect of mobility.

METHODS

We analyzed data from a population-based case-control study of childhood leukemia using cases who were born in California and diagnosed between 1988 and 2008 and birth certificate controls. We used stratified logistic regression, case-only analysis, and propensity-score adjustments to assess predictors of residential mobility between birth and diagnosis, and account for potential confounding due to residential mobility.

RESULTS

Children who moved tended to be older, lived in housing other than single-family homes, had younger mothers and fewer siblings, and were of lower socioeconomic status. Odds ratios for leukemia among non-movers living <50 meters (m) from a 200+ kilovolt line (OR: 1.62; 95% CI: 0.72-3.65) and for calculated fields ≥ 0.4 microTesla (OR: 1.71; 95% CI: 0.65-4.52) were slightly higher than previously reported overall results. Adjustments for propensity scores based on all variables predictive of mobility, including dwelling type, increased odds ratios for leukemia to 2.61 (95% CI: 1.76-3.86) for living < 50 m from a 200 + kilovolt line and to 1.98 (1.11-3.52) for calculated fields. Individual or propensity-score adjustments for all variables, except dwelling type, did not materially change the estimates of power line exposures on childhood leukemia.

CONCLUSION

The residential mobility of childhood leukemia cases varied by several sociodemographic characteristics, but not by the distance to the nearest power line or calculated magnetic fields. Mobility appears to be an unlikely explanation for the associations observed between power lines exposure and childhood leukemia.

Proximity to overhead power lines and childhood leukaemia: an international pooled analysis

BACKGROUND

Although studies have consistently found an association between childhood leukaemia risk and magnetic fields, the associations between childhood leukaemia and distance to overhead power lines have been inconsistent. We pooled data from multiple studies to assess the association with distance and evaluate whether it is due to magnetic fields or other factors associated with distance from lines.

METHODS

We present a pooled analysis combining individual-level data (29,049 cases and 68,231 controls) from 11 record-based studies.

RESULTS

There was no material association between childhood leukaemia and distance to nearest overhead power line of any voltage. Among children living < 50 m from 200 + kV power lines, the adjusted odds ratio for childhood leukaemia was 1.33 (95% CI: 0.92-1.93). The odds ratio was higher among children diagnosed before age 5 years. There was no association with calculated magnetic fields. Odds ratios remained unchanged with adjustment for potential confounders.

CONCLUSIONS

In this first comprehensive pooled analysis of childhood leukaemia and distance to power lines, we found a small and imprecise risk for residences < 50 m of 200 + kV lines that was not explained by high magnetic fields. Reasons for the increased risk, found in this and many other studies, remains to be elucidated.

24-h personal monitoring of exposure to Power Frequency Magnetic Fields in adolescents - Results of a National Survey

OBJECTIVES

The aim of this exposure assessment study was to gain information about the exposure levels of adolescents in Israel to power frequency (50Hz) magnetic fields (MF) through personal monitoring, and to provide reliable data for national policy development.

METHODS

84 adolescents, 6-10th grade students, carried an EMDEX II meter attached to their body for 24h. The meter recorded the MF every 1.5s. The students documented their activities and microenvironments, such as apartment (awake or asleep), school, transportation, open public areas and other indoor environments.

RESULTS

The geometric mean (GM) of the daily time weighted average (TWA) of all the participants was 0.059 μT (STD = 1.83). This result is similar to those of personal exposure surveys conducted in the UK (GM 0.042-0.054μT), but lower than levels found in the US (GM 0.089 - 0.134μT). The arithmetic mean was 0.073μT, 23% higher than the GM. Fields were lowest at school (GM 0.033μT), and average outdoor exposures were higher than indoor ones. 3.6% of the participants were exposed to daily TWA above 0.2μT. The typical time spent above 0.2μT ranged from few minutes to few hours. The time spent above 0.4μT and 1μT were much shorter, around 1-15min and from few seconds to 2min, respectively. Momentary peaks ever recorded were in the range of 0.35-23.6μT CONCLUSIONS: Exposure of adolescents in Israel is similar to data reported in other countries, being below 0.1μT for the vast majority, with very few average exposures above 0.2μT. Analysis of the different microenvironments allows for a cost-effective and equitable policy development.

Residential magnetic fields exposure and childhood leukemia: a population-based case-control study in California

PURPOSE

Studies have reported an increased risk of childhood leukemia associated with exposure to magnetic fields. We conducted a large records-based case-control study of childhood leukemia risk and exposure to magnetic fields from power lines in California.

METHODS

The study included 5,788 childhood leukemia cases (born in and diagnosed in California 1986-2008) matched to population-based controls on age and sex. We calculated magnetic fields at birth addresses using geographic information systems, aerial imagery, historical information on load and phasing, and site visits.

RESULTS

Based on unconditional logistic regression controlling for age, sex, race/ethnicity, and socioeconomic status using subjects geocoded to a basic standard of accuracy, we report a slight risk deficit in two intermediate exposure groups and a small excess risk in the highest exposure group (odds ratio of 1.50 (95% confidence interval [0.70, 3.23])). Subgroup and sensitivity analyses as well as matched analyses gave similar results. All estimates had wide confidence intervals.

CONCLUSION

Our large, statewide, record-based case-control study of childhood leukemia in California does not in itself provide clear evidence of risk associated with greater exposure to magnetic fields from power lines, but could be viewed as consistent with previous findings of increased risk.

Exposure Modelling of Extremely Low-Frequency Magnetic Fields from Overhead Power Lines and Its Validation by Measurements

A three-dimensional model for calculating long term exposure to extremely low-frequency magnetic fields from high-voltage overhead power lines is presented, as well as its validation by measurements. For the validation, the model was applied to two different high-voltage overhead power lines in Iffwil and Wiler (Switzerland). In order to capture the daily and seasonal variations, each measurement was taken for 48 h and the measurements were carried out six times at each site, at intervals of approximately two months, between January and December 2015. During each measurement, a lateral transect of the magnetic flux density was determined in the middle of a span from nine measurement points in the range of ±80 m. The technical data of both the lines as well as the load flow data during the measurement periods were provided by the grid operators. These data were used to calculate 48 h averages of the absolute value of the magnetic flux density and compared with modelled values. The highest 48 h average was 1.66 µT (centre of the line in Iffwil); the lowest 48 h average was 22 nT (80 m distance from the centre line in Iffwil). On average, the magnetic flux density was overestimated by 2% (standard deviation: 9%) in Iffwil and underestimated by 1% (8%) in Wiler. Sensitivity analyses showed that the uncertainty is mainly driven by errors in the coordinates and height data. In particular, for predictions near the centre of the line, an accurate digital terrain model is critical.