WP4: Exposure assessment
WP leader: Myron Maslanyj, DH-PHE
Development of an exposure gradient for RF and ELF
In the absence of clear and consistent data from laboratory or animal study, there is no definite idea of the most appropriate physical quantity to be related to possible health effects of electromagnetic fields radiated from mobile phones. However, it seems reasonable to quantify exposure in terms of the total energy delivered to the user’s body. This energy, in turn, depends on the time of use of the phone, and on the specific energy absorption rate (SAR), i.e., the energy delivered per second to the unit mass of tissue.
While the duration and frequency of use can be calculated from the questionnaires or from the data obtained from the network operators, the power actually absorbed in the body depends on several factors. Some of these factors are technical while others are related to the way the phone is used. The importance of these factors will be investigated, including the influence of power control and time channel occupancy on the effective power radiated as well as the position of the sources.
The main goal of the exposure assessment work package is to develop and implement one (or more) exposure index(es) for each subject in the case-control study based on these factors. The main tasks to be carried out in this work package are to: underpin the questionnaire developed in WP2; characterise exposure to radiofrequency fields (RF) from mobile phones in four different head models corresponding to different ages of children; measure exposure to extremely low frequency fields (ELF) from mobile phones in the same head models; assess ELF exposure from other sources in the environment (identified in developing the questionnaire); develop a generic spatial distribution representative of RF and ELF exposure in four head models known as the GridMaster head cartographies (GridMaster will be used by neuroradiologists to locate each case's tumour based on imaging); and deliver an "exposure gradient tool-kit," or a set of instructions, to the epidemiologists so they can calculate exposure values. This tool-kit will be based on information from the questionnaire and the GridMaster databases.
Exposure assessment for other occupational or environmental factors
In addition to electromagnetic fields, several environmental and occupational agents (including parental smoking and exposure to pesticides) have been suggested as being associated with brain tumours among children and adults. However, little is known about specific risk factors for brain tumours in adolescents, which fall in between the two age groups that have been studied most extensively. With this in mind, the questionnaires include detailed information on parental and personal occupational history, residential history, and school attendance history. Residential and school histories will be linked with GIS databases on environmental exposures, where available. Parental and personal occupational exposures will be estimated by linking reported jobs with existing job–exposure matrices.