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Skip to 0 minutes and 15 secondsThis week, we'll learn more about how environmental and lifestyle factors can affect our cancer incidence. There are a wide range of factors that can influence our risk of developing cancer during our lifetimes. When we're discussing factors related to cancer incidence, a carcinogen is defined as an agent that contributes to tumour formation. A mutagen is an agent that induces a DNA mutation. Generally speaking, most mutagens are likely to also be carcinogens. However, some carcinogens promote cancer without directly damaging DNA so it's important to remember the distinction between these two terms. The first category of risk factors that we'll consider in relation to cancer incidence is infection.

Skip to 1 minute and 3 secondsIn the UK, for example, infection with the human papillomavirus is found in almost all cervical cancers. The development of vaccines against HPV has given hope that rates of cervical cancer can be reduced. Viruses are not the only infectious agent to be linked to cancer incidence. Infection with the bacterium Heliobacter pylori is linked to stomach cancer. An infection with parasites such as the blood fluke Schistosoma haematobium is linked to bladder cancer. The second category of risk factors that we'll consider in relation to cancer incidence is radiation. This could be ultraviolet radiation from the sun or from sun beds or ionising radiation from natural or man-made sources.

Skip to 1 minute and 51 secondsExposure to ultraviolet radiation has been linked to skin cancer incidence and inhalation of radon has been linked to lung cancer. The third category of risk factors we'll consider is occupational exposure to carcinogens. These can range from asbestos to benzene, formaldehyde, and arsenic. The fourth category of risk factors are related to our lifestyle and we'll look at how these can influence our risk of cancer. The primary factor that we will consider is tobacco. In the UK, it is estimated that approximately 85% of lung cancer cases in men and 80% of lung cancer cases in women can be attributed to tobacco. Other factors that we will consider in this category are alcohol consumption, diet, physical activity, and body weight.

Skip to 2 minutes and 42 secondsThe final category of risk factors that we'll consider are hormonal factors in relation to cancer incidence in women. Studies have investigated the long-term effects of the intake of exogenous female sex hormones, such as oral contraceptives or hormone replacement therapy on cancer risk. We'll look at how these hormones can increase and decrease the risk of certain types of cancer. We'll also consider how breastfeeding is related to breast cancer and ovarian cancer incidence. The recommended reading for this topic is a study funded by the charity, Cancer Research UK, on the fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010, and we will discuss each of these different types of risk factor in greater detail.

Environmental factors

Dr Louise Blakemore outlines some of the factors that predispose us to cancer.

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This video is from the free online course:

Cancer in the 21st Century: the Genomic Revolution

University of Glasgow

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