Work, Environment and Cancer

Head of Group, Ole Raaschou-Nielsen

The environment is affected by new chemical substances and other man-made exposures introduced concurrently with the industrial and technological evolution. This is often done without knowledge of possible long-term effects on humans. In addition, naturally occurring environmental exposures, such as sunlight and radon, may be human carcinogens. A new avenue in environment and cancer research is investigation of the impact of ill-timed exposure to artificial light, especially at night.

Environmental Causes for Cancer

We seek to identify environmental causes for cancer by utilising epidemiological methods for the analysis. In particular, we focus on the harmful effects of air pollution and certain naturally occurring bioactive substances, such as radon and arsenic.

We work on qualifying and validating methods for determining the environmental exposure of human beings, since determination of exposure at the individual level is a critical issue within environmental epidemiology. Individual sensitivity towards environmental exposures might differ due to genetic differences, which is also addressed in our research.

Studying the Work Environment

Most chemical carcinogenic exposures known today have been historically documented through examinations of exposures in the work environment. Exposure to chemicals in the work environment still exists; including chemicals found to be carcinogenic in animal experiments and, therefore, suspected of being carcinogenic to humans, too, and chemicals that have yet to be examined for carcinogenic effects on humans.

Many of the same exposures occur in the external environment but typically at lower concentrations. It can, therefore, be an advantage to examine whether chemical exposures in the work environment increases the risk of cancer and then subsequently examine whether there is a risk for the larger number of people who are exposed in the external environment.

Current Projects, Environment and Cancer

Our projects on environment and cancer can be categorized in 5 headings:

• Air pollution is investigated with respect to risk of different types of cancer and other diseases. We implement various cohort studies, among others Diet, Cancer and Health and the Danish National Birth Cohort, as well as population based case-control studies. We also participate in large, European collaborations. See e.g.
  http://www.escapeproject.eu/
• Chemical substances, magnetic fields and radiation are investigated with respect to cancer in a number of studies, including indoor radon, fluorinated compounds (PFOA, PFOS), cadmium, and extremely low-frequency magnetic fields from electrical installations
• Lifestyle is investigated in among others a study of antioxidants and colorectal cancer
• Geographical studies investigating whether cancer cluster in time and space, forming the basis for new hypotheses on environmental causes. We are studying testicular cancer, non-Hodgkin's lymphoma, and breast cancer using new cluster methods that take advantage of the unique Danish registry data on residential history
• Interaction between genes and environment is investigated among others in a study of arsenic in drinking water and polymorphisms in genes involved in DNA repair, and a study of polymorphisms and enzymatic activity in catalase and gluthion reductase and the risk of colorectal cancer

Current Projects on Work and Cancer

Our projects on work and cancer can be categorised under 3 headings:

• Night work, disturbance of circadian rhythms, and risk of cancer. In 2007, the International Agency for Research on Cancer under the WHO classified "shift work that involves circadian disruption is probably carcinogenic to humans". Still, a number of unresolved questions relating to this remains, e.g. which types of cancer in addition to breast cancer are associated with night work, is there a lower limit with respect to the duration of the night work that does not increase the risk of cancer, are some types of night work less dangerous than others, and whether persons with evening preference have higher tolerance of night work than persons with morning preference
• Exposure to chemicals at the workplace that are carcinogenic to experimental animals with limited or non-existent documentation of the effect on humans, e.g. certain organic solvents, formaldehyde, or welding fume
• Monitoring cancer risks associated to occupation. We take advantage of the unique situation in Denmark, where we have nationwide registries with individual information on employment etc. that can be linked to information on cancer. We have thus established a database with information on all approximately 700,000 employees who have been diagnosed with cancer in the period 1970-2007, including their employment history. Based on this, it is possible to assess which types of job entail the highest and lowest risk and where the risks are increasing or decreasing over time. A new aspect of this work is studies of parental occupation related to cancer in childhood