Childhood cancer and exposure to corona ions from power lines: an epidemiological test

A quasi-one-dimensional model for ion-aerosol interactions and aerosol charge state downwind of corona-producing alternating current (AC) HVPL under stable atmospheric conditions

Corona ions produced by high voltage power lines (HVPL) can alter the local atmospheric electrical environment downwind, potentially increasing electrostatic charge on airborne particulates via ion-aerosol attachment. However, previous epidemiological assessments attempting to assess this 'corona ion hypothesis' have used proxies e.g. ion concentration or distance from HVPL, rather than aerosol charge state directly, due to difficulties in modeling this quantity. We present a quasi-1D model incorporating both Gaussian plume dynamics and ion-aerosol and ion-ion interaction microphysics which could be applied to future studies of charged aerosol near HVPL. The response of the model to changes in a range of input parameters is characterized, and validation is attempted by means of comparison with previous work where ion- and aerosol concentrations and properties (including electrical mobility and electric charge states) upwind and downwind of HVPL are measured.

Electric field and air ion exposures near high voltage overhead power lines and adult cancers: a case control study across England and Wales

BACKGROUND

Various mechanisms have been postulated to explain how electric fields emitted by high voltage overhead power lines, and the charged ions they produce, might be associated with possible adult cancer risk, but this has not previously been systematically explored in large scale epidemiological research.

METHODS

We investigated risks of adult cancers in relation to modelled air ion density (per cm3) within 600 m (focusing analysis on mouth, lung, respiratory), and calculated electric field within 25 m (focusing analysis on non-melanoma skin), of high voltage overhead power lines in England and Wales, 1974-2008.

RESULTS

With adjustment for age, sex, deprivation and rurality, odds ratios (OR) in the highest fifth of net air ion density (0.504-1) compared with the lowest (0-0.1879) ranged from 0.94 [95% confidence interval (CI) 0.82-1.08] for mouth cancers to 1.03 (95% CI 0.97-1.09) for respiratory system cancers, with no trends in risk. The pattern of cancer risk was similar using corona ion estimates from an alternative model proposed by others. For keratinocyte carcinoma, adjusted OR in the highest (1.06-4.11 kV/m) compared with the lowest (<0.70 kV/m) thirds of electric field strength was 1.23 (95% CI 0.65-2.34), with no trend in risk.

CONCLUSIONS

Our results do not provide evidence to support hypotheses that air ion density or electric fields in the vicinity of power lines are associated with cancer risk in adults.

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.

Childhood cancer research in Oxford II: The Childhood Cancer Research Group

BACKGROUND

We summarise the work of the Childhood Cancer Research Group, particularly in relation to the UK National Registry of Childhood Tumours (NRCT).

METHODS

The Group was responsible for setting up and maintaining the NRCT. This registry was based on notifications from regional cancer registries, specialist children's tumour registries, paediatric oncologists and clinical trials organisers. For a large sample of cases, data on controls matched by date and place of birth were also collected.

RESULTS

Significant achievements of the Group include: studies of aetiology and of genetic epidemiology; proposals for, and participation in, international comparative studies of these diseases and on a classification system specifically for childhood cancer; the initial development of, and major contributions to, follow-up studies of the health of long-term survivors; the enhancement of cancer registration records by the addition of clinical data and of birth records. The Group made substantial contributions to the UK government's Committee on Medical Aspects of Radiation in the Environment.

CONCLUSION

An important part of the ethos of the Group was to work in collaboration with many other organisations and individuals, both nationally and internationally: many of the Group's achievements described here were the result of such collaborations.

A proposed explanation for thunderstorm asthma and leukemia risk near high-voltage power lines: a supported hypothesis

Thunderstorm asthma and increased childhood leukemia risk near high-voltage power lines (HVPL) are occurrences whose mechanism of effect is not fully understood. This paper proposes and discusses a key similarity: both thunderstorms and HVPL generate a high enough electrical field in the environment to ionize nearby air and air-borne particles. I argue that the repeatedly demonstrated acute asthma response to pollen-laden air during thunderstorms is largely due to ionization of air-borne allergens, which adhere more readily and in greater quantity in the lungs than non-ionized particles. If these bind to mucous or phagocytic cells, it would enhance immune response. A rapid temperature drop and high ozone also seem to be drivers of thunderstorm asthma. This causal nexus provides strong support for the parallel situation of prolonged exposure to ionized particles near HVPL and an increased rate of childhood leukemia. Here, it is proposed that upwind carcinogens are ionized when passing HVPL and then residential and business areas. Published evidence for most steps are presented, but have not previously been published as a coherent whole, nor has it been suggested that the inhaled ionized micro-particle explanation for acute asthma may also explain development of childhood leukemia over time. The demonstrated series of events leading to increased deposition and retention of ionized particles in airways provides support for explaining both adverse health outcomes: acute thunderstorm asthma and increased risk of childhood leukemia near HVPL. Further support for this explanation of both outcomes is provided by effects of on-going proximity to highways.

Epidemiological study of power lines and childhood cancer in the UK: further analyses

We report further analyses from an epidemiological study of childhood cancer and residence at birth near high-voltage power lines in the UK. These results suggest that the elevated risks for childhood leukaemia that we previously found for overhead power lines may be higher for older age at diagnosis and for myeloid rather than lymphoid leukaemia. There are differences across regions of birth but not forming any obvious pattern. Our results suggest the decline in risk we previously reported from the 1960s to the 2000s is linked to calendar year of birth or of cancer occurrence rather than the age of the power lines concerned. Finally, we update our previous analysis of magnetic fields to include later subjects.

Magnetic fields and childhood cancer: an epidemiological investigation of the effects of high-voltage underground cables

Epidemiological evidence of increased risks for childhood leukaemia from magnetic fields has implicated, as one source of such fields, high-voltage overhead lines. Magnetic fields are not the only factor that varies in their vicinity, complicating interpretation of any associations. Underground cables (UGCs), however, produce magnetic fields but have no other discernible effects in their vicinity. We report here the largest ever epidemiological study of high voltage UGCs, based on 52,525 cases occurring from 1962-2008, with matched birth controls. We calculated the distance of the mother's address at child's birth to the closest 275 or 400 kV ac or high-voltage dc UGC in England and Wales and the resulting magnetic fields. Few people are exposed to magnetic fields from UGCs limiting the statistical power. We found no indications of an association of risk with distance or of trend in risk with increasing magnetic field for leukaemia, and no convincing pattern of risks for any other cancer. Trend estimates for leukaemia as shown by the odds ratio (and 95% confidence interval) per unit increase in exposure were: reciprocal of distance 0.99 (0.95-1.03), magnetic field 1.01 (0.76-1.33). The absence of risk detected in relation to UGCs tends to add to the argument that any risks from overhead lines may not be caused by magnetic fields.