Glossary | ARPANSA

Absolute risk: A statistical measure used in epidemiological studies to describe the probability of a disease occurring under specific conditions. Absolute risk is calculated by the number of cases of a disease in a group divided by the total number of people in that group.
Acute effect: Biological or health effect with symptoms that develop rapidly, due to exposure to a substance or agent. These symptoms may or may not subside when the exposure stops.
Basic restriction: A mandatory limit on a particular electromagnetic field exposure (e.g. time-averaged exposure at a frequency of 2450 MHz). Protection against established adverse health effects requires that basic restrictions are not exceeded.
Benign (tumour): A tumour or growth that is not cancerous i.e. it does not spread to surrounding tissue or other parts of the body. (See also MedlinePlus definition)
Bias: Any systematic error in a study that that can lead to conclusions that are different from the truth.
Carcinogen: An agent (chemical, physical or biological) directly involved in the initiation or promotion of cancer. (See also Wikipedia definition)
Case: A person (or animal) in a study with a medical condition (or other outcome) of interest. (See case-control study)
Case-control study: A type of epidemiological study that compares subjects who have a disease or condition (the cases) with similar subjects who do not have the disease or condition (the controls). In a case-control study the medical and lifestyle histories of the subjects in each group are investigated to learn what factors may be associated with the disease or condition of interest. (See also the definition by the Geneva Foundation for Medical Education and Research)
Case report: Clinical evaluation and history of a patient. Case reports are useful when the disease is uncommon. (See also Wikipedia definition)
Causality: Broadly, causality is the relationship between a cause and the consequential effect. In biology and medicine cause is the exposure and effect is the resulting disease or condition. It is important to realise that even if an association is found between an exposure and a disease the connection cannot automatically be interpreted as causal. An association can, in addition to being causal, be due to chance, bias or confounding. (See also Wikipedia definition)
Chronic effect: Biological or health effect with symptoms that develop slowly, due to long and continuous exposure to a substance or agent e.g. cancer.

Cognition: Mental or thought processes including perception, memory, judgement, reasoning etc. (See also Wikipedia definition)
Cohort study: A type of epidemiological study in which a particular outcome, such as a medical condition, is compared according to a putative factor (a factor suspected to influence the chances of acquiring the medical condition) in a group of individuals who are linked in some way (the cohort). In a prospective cohort study the group of individuals is followed over time in order to determine how the putative factor affects rates of the outcome of interest. In a retrospective cohort study, the data is collected from past records of the cohort. (See also the definition by the Geneva Foundation for Medical Education and Research)
Confidence interval (CI): A range of values for a parameter of interest with a specified probability of including the true value of the parameter. Thus the confidence interval or CI is used to indicate the reliability of an estimate for the parameter of interest. The specified probability is called the confidence level, usually expressed as a percentage; thus one speaks of a "95% CI". Increasing the desired confidence level will widen the confidence interval. For example, a study found the average height of students in a 6th grade classroom to be (See also Wikipedia definition)
Confounder: An extraneous factor in a study which is related with both the probable cause and the outcome. A confounding factor may conceal an actual association or falsely demonstrate an apparent association between itself and the outcome where no real association between them exists. If confounding factors are not measured and considered, bias may result in the conclusion of the study. (See also Wikipedia definition)
Continuous wave (CW): Electromagnetic wave of constant amplitude and frequency.
Control: A sample or subject (animal/human) in which a parameter under investigation (cause or effect) is absent or is held constant, in order to provide a comparison. In an experimental study the experimental group is subjected to the factor under consideration, while the control group matches the experimental group in all aspects except that it is not subjected to the factor under investigation (see also Wikipedia). In an epidemiological case-control study the control is a subject without the disease or condition under investigation.

Crossover design: A research study design where the subjects receive a sequence of different exposures e.g. some subjects may receive the exposure, followed by sham whilst other subjects may receive sham first, followed by the exposure
Cross-sectional study: A type of epidemiological study that aims to describe the relationship between a disease or outcome and other factors of interest as they exist in a subset of a population at a particular point in time. Since both the outcome and the factors are measured at the same point in time these studies are not strong at showing causal relationships. (See also Wikipedia definition)
Disease cluster: A disease cluster is the occurrence of a greater than expected number of cases of a particular disease within a group of people in a geographic area over a period of time
Dose-response: The relationship between the amount of exposure (dose) to an agent and the resulting changes in the effect (response). (See also Wikipedia definition)
Dosimetry: The determination (by calculation or measurement) of energy absorption (or field strength) in matter and tissue resulting from exposure to a known amount of ionising or non-ionising radiation.
Double-blind experiment: An experimental procedure in which neither the subjects of the experiment nor the researchers know know the critical aspects of the experiment (e.g. who belongs to the control group or the experimental group). A double blind experiment is used to ensure impartiality, and avoid errors arising from bias. (See also Wikipedia definition)
Ecological study: A type of epidemiological study where data is analysed at the population or group level rather than the individual. They are inexpensive and easy to carry out, using routinely collected data, but they are prone to bias and confounding. (See also Wikipedia definition)
Electric field: Region around an electric charge in which an electric force is exerted on another charge. The strength of the electric field at a given point is defined as the force that would be exerted on a positive test charge placed at that point and is measured in units of volts per metre (V/m). (See also Wikipedia definition)

Electromagnetic field: A physical field produced by the combination of an electric field and a magnetic field. The electric field is produced by stationary electric charges, and the magnetic field by moving electric charges (currents). (See also Wikipedia definition)
Electromagnetic hypersensitivity: A medical condition (usually self-reported) characterised by a variety of non-specific symptoms, which afflicted individuals attribute to exposure to electromagnetic fields at levels below international standards. The World Health Organization (WHO) does not categorise electromagnetic hypersensitivity symptoms as part of any recognised syndrome. (See also the WHO fact sheet)

Excess relative risk: A statistical measure used in epidemiological studies to describe percentage change of an exposure causing a specific health outcome above the baseline risk.; For example, if a cohort study of radon exposure and lung cancer reported an excess relative risk of 0.16 per 100 Becquerel’s/m³ this would mean that there is an increased risk of 16% for the exposed population above the baseline risk.

Epidemiological study: Type of study investigating the pattern, frequency and causes of disease in populations (see also the World Health Organization for a definition of epidemiology). The most common types of epidemiological studies are case-control studies, cohort studies and cross-sectional studies.
Extremely low frequency: The frequency range occupying the lower part of the electromagnetic spectrum between 0 and 3000 Hz. The extremely low frequency range includes the power frequency of 50 Hz which in Australia is associated with the generation, distribution and use of electricity. (See also fact sheet on Extremely Low Frequency Electric and Magnetic Fields)
Far field: The region of an electromagnetic field sufficiently further away from the transmission source (e.g. mobile phone, communications antenna) that the field properties are more predictable where the measurement of one field property can be used to calculate others for exposure assessment. In addition, the decrease in field strength with distance away from the source within this region follows the inverse square law.
Genotoxicity: Harmful action on a cell's genetic material affecting its integrity. Genotoxic agents are known to be potentially carcinogenic (cancer causing), mutagenic (mutation causing) or teratogenic (birth defect-causing). (See also Wikipedia definition)
Hertz (Hz): The unit of measurement for frequency defined as the number of cycles per second. (See also Wikipedia definition)
Heterogeneity: Describes the differences in the properties of a dataset or between different datasets or different studies (e.g. in a meta-analysis). (See also Wikipedia definition)
Incidence: Measure of the risk of developing a disease or condition during a specified period of time. Usually given as the incidence rate which is the number of new cases per population at risk during the specified time period. For example, over the period 2001-2005 the cancer incidence rate for children aged 0-14 years in Australia was 14 per 100,000 (Source: Australian Institute of Health and Welfare) (See also Wikipedia definition)
In vitro study: Experimental study investigating biological properties on a subset of an organism’s constituent parts (e.g. organs, tissues, cells, biomolecules etc) and performed in a controlled environment such as in a test tube. Compared to in vivo studies in vitro studies are substantially faster, less expensive, and can be done with fewer ethical and safety concerns. However because the test conditions of an in vitro study may not correspond to the conditions inside of the organism, this may lead to results that do not represent the situation that arises in a living organism. (See also Wikipedia definition)

In vivo study: Experimental study investigating biological properties on a whole living organism. In vivo studies are far more expensive, and often more difficult, than in vitro studies. However they are better suited for observing the overall effects of an experiment on a living organism. (See also Wikipedia definition)
Ionising radiation: Radiation in the form of sub-atomic particles or electromagnetic waves that have enough energy so that during an interaction with an atom, tightly bound electrons can be removed from the atom’s orbit, causing the atom to become charged or ionised. This process can cause chemical changes by breaking chemical bonds which can in turn cause damage to living tissue. (See also fact sheet on Ionising and Non-ionising Radiation)
Latency period: The time elapsed between exposure to an agent and the clinical onset of a disease.
Magnetic field: Region where a force is produced by electric currents, which can be macroscopic currents in wires, or microscopic currents associated with electrons in atomic orbits (such as in magnetic materials). The strength of a magnetic field is defined as the force on moving charge and is measured in the common units of Tesla (T) or Gauss (G), where 1T=10000G. (See also Wikipedia definition)
Malignant (tumour): A tumour that can invade and destroy nearby tissue and spread (metastasize) to other parts of the body. (See also Wikipedia definition)
Median: One type of average value in a set of data values, found by arranging the values in ascending order and then selecting the middle value (See also Wikipedia definition)
Meta-analysis: A statistical analysis that combines the results of several studies that address a similar research topic. The advantage of a meta-analysis is that it combines all the research on the particular topic into one large study with many participants. The disadvantage is that the studies whose results are being combined may have different methodologies and experimental protocols (i.e. they are undertaken in a different way) and the results can become imprecise and difficult to interpret. (See also Wikipedia definition)
Microwave: Electromagnetic radiation within the radiofrequency range, from 300 MHz to 300 GHz
Misclassification: A type of bias in epidemiological studies arising from errors in the categorisation of either exposure or outcome in different study groups (e.g. categorising a subject as a smoker when he/she is not or categorising a subject as having lung cancer when he/she is healthy). (See also Wikipedia definition)
Morbidity: The presence of disease or medical condition. Morbidity rate is the number of new cases suffering from a particular disease or medical condition over the total population for a specific period of time.
Mortality: Incidence of death in a population. Mortality rate is the ratio of the number of deaths (in general, or due to a specific cause) in a population to the total number of that population, over a specific period of time, for example number of deaths per 100,000 individuals per year.
Near field: Near field – region of an electromagnetic field that is in close proximity to the transmission source (e.g. mobile phone, communications antenna). In this region, the behaviour of the field’s properties are unpredictable requiring separate measurement of electric and magnetic field components to make accurate assessments of exposure.

Nocebo effect: An adverse health effect resulting from psychological factors due to a person's belief that something is harmful.
Non-ionising radiation: Type of electromagnetic radiation that does not carry enough energy to ionise atoms i.e. to completely remove an electron from an atom’s orbit. On the electromagnetic spectrum non-ionising radiation ranges from extremely low frequency electric and magnetic fields, through the radiofrequency, microwave, and visible portions of the spectrum into the ultraviolet range. (See also fact sheet on Ionising and Non-ionising Radiation)
Non-response: Failure to obtain data from people selected in a survey or study who choose not to take part or are unobtainable for other reasons. Non-response can increase the potential for bias e.g. when respondents differ from non-respondents. (See also Wikipedia definition)
Odds ratio (OR): A statistical measure used in epidemiological studies to describe the strength of association between an exposure or factor and a particular disease or outcome. The odds ratio (OR) is a relative measure of risk, describing how likely someone who is exposed to the factor under study will develop the outcome as compared to someone who is not exposed. For example, a case-control study investigating smoking and lung cancer found an odds ratio of 17.4, i.e. the odds of smoking among the lung cancer patients was more than 17 times higher than the odds of smoking among the controls. (See also the British Medical Journal definition)
Placebo effect: A beneficial health effect resulting from psychological factors due to a person's belief that something is beneficial.
Pooled analysis: A statistical analysis similar to a meta-analysis where the results from a number of related studies (i.e. sharing a common protocol) are combined to provide an overall summary.
Population-based study: A type of study that includes participants from the entire population of a defined area. For example, a study investigating mobile phone use and brain tumours amongst residents of Melbourne.
Power density: The amount of power per unit volume expressed in units of Watts per square metre (W/m²)
Power frequency: Frequency at which electrical current is transmitted from a power plant to the end user. In Australia and most parts of the world the power frequency is 50 Hz, although in some countries including the United States it is 60 Hz. (See extremely low frequency)
Prevalence: The proportion of a population that is affected with a particular disease or condition at a given time. (See also Wikipedia definition)
Provocation study: Experimental human study where subjects are exposed to either an agent that is claimed to provoke a response, or to a sham agent that should provoke no response. (See also Wikipedia definition)
Radiofrequency: The frequency range occupying the part of the electromagnetic spectrum between 3 kHz and 300 GHz (3000 Hz to 300000000 Hz). Radiofrequency (RF) is mainly used for telecommunications purposes including television, AM/FM radio and mobile telephony. (See also the fact sheet Radiofrequency Radiation)

Randomised experiment: An experimental procedure where the experimental units (e.g. the exposure under study) are randomly allocated across different groups. For example, if a provocation study is investigating the effects of radiofrequency (RF) radiation then the volunteers in the study are either exposed to RF or sham using randomization
Recall bias: Type of bias that occurs in epidemiological studies when self-reported, historical information is inaccurate. For example, in a case-control study cases may over-report past exposure, especially if it is widely known to be associated with the disease under study.
Reference level: Alternative means of showing compliance with the mandatory limit (basic restriction) on a particular electromagnetic field exposure (e.g. radiofrequency radiation) which utilises quantities that are more practical to measure. Reference levels are conservatively formulated such that compliance with the reference levels ensures compliance with the basic restrictions.
Retrospective study: A study that looks backward in time, usually using medical records (retrospective cohort study) and interviews with patients who already know to have a disease (case-control study). Retrospective studies have the benefit of being cheaper and less time consuming however sources of error due to confounding and bias are more common in retrospective studies compared to prospective studies (e.g. prospective cohort).
Reverse causality: Reverse causality is when a study reports X causes Y, but in fact Y causes X. For instance, a study reporting that people who get brain freezes are more likely to eat ice cream is an example of reverse causality as we know eating ice cream is a cause of brain freezes.
Risk factor: A risk factor is any attribute, characteristic or exposure associated with an increased risk of disease or adverse health outcome. A risk factor may not necessarily be causal. See also Wikipedia definition.
Risk ratio: A statistical measure used in epidemiological studies to describe the risk of a disease or outcome relative to a particular exposure (Also called relative risk - Wikipedia). It is the ratio of the probability of an outcome occurring in a group exposed to a certain agent or factor versus a non-exposed group. For example, a cohort study investigating smoking and heart disease found a risk ratio of 5.2, i.e. smokers are five times more likely to develop heart disease compared to non-smokers.
Selection bias: Type of bias that occurs from the manner in which subjects are selected for a study. When the sample of subjects is not representative of the target population the results of the study may not be valid. For example in a case-control study of smoking and lung cancer, the association between the two will tend to be weaker if the controls are selected from a hospital population (because smoking is associated with many other diseases resulting in hospitalisation) than if controls are selected from the general population. (See also National Cancer Institute definition)
Sham exposure: The environmental conditions of exposed samples/subjects, but in absence of the exposure. Usually associated with controls.
Specific absorption rate: A measure of the rate at which electromagnetic energy is absorbed by the body when exposed to radiofrequency radiation. The specific absorption rate or SAR is defined as the power absorbed per unit mass of tissue and is measured in units of watts per kilogram (W/kg).
Static field: Electric or magnetic field that does not vary with time (i.e. it has a frequency of 0 Hertz).
Statistical power: The power of a statistical test is the probability that the test will reject the null hypothesis when the null hypothesis is actually false i.e. the likelihood that a study will detect an effect when there is an effect there to be detected. Statistical power is mainly affected by the size of the effect and the sample size of the sample used to detect it in the study. Bigger effects are easier to detect than smaller effects, while large sample sizes offer greater test sensitivity than small sample sizes. (See also Wikipedia definition).
Statistical significance: A statistical concept used to determine whether the outcome of an investigation is the result of a relationship between specific factors or due to chance. (See also Wikipedia definition).
Subjective symptoms: Health symptoms that are observed only by the patient and that cannot be objectively confirmed i.e. by measurement.
Systematic review: A literature review that follows specific objectives, materials and methods, and conducted according to a specific and reproducible methodology (systematic way), to answer a specific research question.