BLOG: The Environment and Breast Cancer
Published 11 Oct 2017
A state of the evidence review published recently suggests there is more and more evidence linking environmental risk factors to breast cancer.
The ‘state of the evidence’ review was published by members of California-based Breast Cancer Prevention Partners, who campaign on the prevention of breast cancer linked to toxic chemicals and radiation.
Breast Cancer Prevention Partners publish state of the evidence reviews periodically, to assess the weight and strength of evidence on environmental risk factors for breast cancer. Although a state of the evidence review simply pulls together existing data and therefore doesn’t necessarily tell us anything new, it does help to demonstrate how much the evidence is growing, and can help to strengthen the case for action.
Lead author, Dr Janet Gray and her team conclude that the state of the evidence justifies the prioritisation of prevention both through public awareness raising and through further research. The review brings together evidence from over 800 scientific papers and is over 60 pages long, containing a wealth of information and opinion on the key environmental risk factors for breast cancer. Here’s a quick overview of what the paper had to say on the most topical issues.
What increases breast cancer risk:
- Shift work: Although experts have disagreed in the last couple of years on the issue of shift work (2, 3) the authors of the review are clear that there is now enough evidence to show a link between shift work and breast cancer risk, due to the harmful effects of regularly being exposed to light at night for a number of years.
- Smoking: Recently we have also seen contradictory, and sometimes confusing reports about the effect of smoking on breast cancer risk (4, 5). After weighing up the evidence the authors of this review are clear that smoking does increase breast cancer risk, and that it has a negative influence on outcomes after diagnosis.
- Endocrine Disrupting Chemicals: The review confirms that there is increasing scientific evidence that endocrine disruption may be an unintentional side effect of many synthetic substances which are present in everyday products including personal care products, plastics, and food. Breast Cancer UK has worked on the issue of endocrine disrupting chemicals for many years and although the link is difficult to prove conclusively, state the evidence reviews such as these help to demonstrate not only a large and growing body of evidence, but also the gaps in the data. One such gap identified by the review is an assessment of the endocrine disrupting effects of mixtures of compounds. This is a gap that we at Breast Cancer UK have already noted, and it’s one of the reasons why we were pleased to fund research by Dr Elisabete Silva from Brunel University into the effects of mixtures of EDCs on breast cancer.
- Radiation: The review states that there is enough evidence to confirm a link between breast cancer and radiation exposure, especially if exposure is at a young age, or if the person carries a BRCA1 /2 mutation. Exposures to very small amounts of extra radiation can occur through the use of X-rays, CT scans, mammography, and radiological procedures.
Other environmental risk factors discussed in the review include hormones in food, which may occur naturally, hormones in medicines such as HRT and the pill and carcinogenic industrial chemicals.
What can reduce your risk of breast cancer?
On a more positive note, the authors found evidence that dietary lignans (polyphenols) from seeds, whole grains and pulses, and soya consumption especially early in life, may have a protective effect against breast cancer.
You can check out a short and full version on the Breast Cancer Prevention Partners website.
1.Gray, J. M. et al. (2017). State of the evidence 2017: an update on the connection between breast cancer and the environment. Environmental Health 16:94 DOI 10.1186/s12940-017-0287-4 https://www.ncbi.nlm.nih.gov/pubmed/28865460
2.Lin, X. et al. (2015). Night-shift work increases morbidity of breast cancer and all-cause mortality: A meta-analysis of 16 prospective cohort studies. Sleep Med. 16:1381–7. https://www.ncbi.nlm.nih.gov/pubmed/26498240
3.Travis, R. C. et al. (2016) Night shift work and breast cancer incidence: Three prospective studies and meta-analysis of the published studies. J Natl Cancer Inst. 108:djw241. doi:10.1093/jnci/djw169.https://www.ncbi.nlm.nih.gov/pubmed/27758828
4.Catsburg, C. et al. (2015). Active cigarette smoking and risk of breast cancer. International Journal of Cancer 136(9): 2204-2209. https://www.ncbi.nlm.nih.gov/pubmed/24929357
5.Yang, Y. et al. (2013). Lack of an association between passive smoking and incidence of female breast cancer in non-smokers: evidence from 10 prospective cohort studies. PLoS One 8(10): e77029. https://www.ncbi.nlm.nih.gov/pubmed/24204725
6.Zota, A. R. et al. (2014). Temporal trends in phthalate exposures: Findings from the National Health and nutrition examination survey, 2001–2010. Environ Health Perspect. 122:235–41. https://www.ncbi.nlm.nih.gov/pubmed/24425099
7.Calafat, A. M. et al. (2010). Urinary concentrations of four parabens in the U.S. population: NHANES 2005–2006. Environ Health Perspect. 118:679–85. https://www.ncbi.nlm.nih.gov/pubmed/20056562
8. Russo, J. and Russo, I. H. (2004). The breast as a developing organ. In: Molecular basis of breast cancer. Berlin: Springe-Verlag. https://link.springer.com/chapter/10.1007%2F978-3-642-18736-0_2