The overall objectives of the Environment and Lifestyle Epidemiology Branch (ENV) are to investigate environmental, lifestyle, occupational, and radiation-related causes of cancer in human populations. ENV investigates these exogenous factors with the aims of contributing to primary prevention of cancer, increasing the understanding of biological mechanisms of carcinogenesis, and assessing the impact of environmental factors in the prognosis and course of disease and how best to implement protection. These objectives are achieved through collaborative international epidemiological studies using a multidisciplinary approach, or through the initiation of individual analytical epidemiological studies. ENV also coordinates international consortia of epidemiological studies.
With studies related to environmental, lifestyle, occupational, or radiation-related exposures, the scope of ENV is broad.
The main areas of environmental, occupational, and lifestyle-related research include pesticides and cancer (in particular, testicular cancer, breast cancer, and haematological malignancies), occupational carcinogens and lung cancer, asbestos and cancer, lifestyle-related and environmental risk factors for oesophageal cancer, lifestyle-related occurrence and survival of breast cancer in Africa, and risk factors for childhood leukaemia. Related to exposure to ionizing radiation, ENV has projects to study the effects of protracted low doses of external ionizing radiation from medical diagnostic examinations and from occupational activities, and studies of populations exposed to Chernobyl fallout and to radiation contamination in the Southern Urals and in the territories adjacent to the former Semipalatinsk nuclear weapons test site in Kazakhstan. With regard to non-ionizing radiation, research continues on possible cancer risks related to mobile phone use.
Some agents within this scope of environmental, lifestyle, occupational, and radiation-related exposures have already been identified as major causes of cancer, for instance smoking and ultraviolet radiation, but further characterization of their associated risks is still needed. For example, ionizing radiation is a well-established carcinogen, although considerable uncertainties and divergent views remain about cancer risks at low doses.
For environmental pollutants and occupational exposures, the attributable fraction of the total cancer burden is difficult to estimate but is expected to be smaller than that from some behavioural factors or certain infections. Nevertheless, environmental or occupational risk factors are often modifiable by reducing or eliminating exposure, for instance through safety standards or technology, or the banning of chemicals. If the agents have been scientifically established as carcinogens and the political will for action exists, interventions targeted at reducing or eliminating exposure to these agents may affect a large proportion of the realistically modifiable cancer burden. For some cancers with few known risk factors, the contribution from environmental factors might be larger than currently estimated; candidates include testicular cancer and oesophageal cancer, for which the role of environmental factors is suggested by the descriptive epidemiology of geographical variation and/or by migrant studies. In addition, breast cancer, brain tumours, or cancers in childhood may have a significant contribution from the environment.
Challenges in identifying environmental and occupational risk factors are often shortcomings in the characterization of exposure. Further challenges arise in designing studies with sufficient heterogeneity in exposure distributions for ubiquitous environmental exposures, while at the same time contrasting comparable population groups in terms of other potential confounding factors. However, exposure assessment in occupational epidemiology has recently improved with the conversion of measurements at workplaces into more general exposure metrics applicable in large-scale epidemiological studies; such improvements are also necessary for environmental exposures, and advances are expected for future studies with the use of biomarkers, exposure modelling, and better accessibility of secondary data sources.