Which chemicals are considered harmful?
Not all chemicals are harmful. However, some are capable of causing cancer (carcinogens) and some can interfere with normal hormone functions in humans or animals (so-called hormone disrupting chemicals) (1) which can increase our risk of developing cancer.
Carcinogens cause cancer by directly damaging our DNA, the genetic material present in all our cells, or by disrupting our cells’ metabolic processes (chemical reactions). Cancerous cells divide in an uncontrolled manner and are capable of spreading to other sites in the body (2). Well known carcinogens include nicotine (a chemical used in cigarettes), ionising radiation from X-rays or sunlight, and certain industrial chemicals for example benzene (3).
Infectious agents, such as the hepatitis B virus, may also be carcinogenic (4). Lesser known carcinogens include plant toxins such as those found in bracken. Chemicals that cause cancer (or other developmental abnormalities) in utero are known as teratogens (5). Examples include diethylstilbestrol (DES) a synthetic estrogen which causes reproductive cancers in exposed offspring in later life (6) and high levels of mercury which can affect neural development (7).
Hormone disrupting chemicals (also called endocrine disrupting chemicals or EDCs) can mimic, inhibit or interfere with natural hormones leading to cell changes that may increase the risk of developing cancers and other diseases (8, 9). For example, some hormone disrupting chemicals bind to oestrogen receptors and trigger reactions that would normally be associated with the female sex hormone, oestrogen.
Where are they found?
Carcinogens and suspected hormone disrupting chemicals can be found in a range of every day products including food, cosmetics, hair products, deodorants, nail polish, kitchen cleaners, packaging, pesticides and new baby equipment. They may be used as preservatives, plasticisers, UV filters in sunscreen, or as pesticides. They are widespread in the environment so are in our air, soil and water. Carcinogens and hormone disrupting chemicals have been routinely detected in bodily fluids including blood, urine and breast milk (10).
1. IPCS. (2002). Global assessment of the state-of-the-science of endocrine disruptors. Geneva, Switzerland, World Health Organization, International Programme on Chemical Safety. Accessed February 5 2015
2. Freeman, S. (2011). Biological Science. 4th edition, Pearson Benjamin Cummings, San Francisco.
3. IARC list of group 1 human carcinogens http://monographs.iarc.fr/ENG/Classification/ClassificationsAlphaOrder.pdf Accessed February 5 2015
4. Cougot, D. et al., (2005). HBV induced carcinogenesis. Journal of Clinical Virology 34(1): S75-8
5. Gilbert-Barness, E. Review: Teratogenic Causes of Malformations Annals of Clinical and Laboratory Science, 40(2), 99-114.
6. Reed, C.E. and Fenton, S.E. (2013). Exposure to diethylstilbestrol during sensitive life stages: a legacy of heritable health effects. Birth Defects Research Part C Embryo Reviews Today 99(2): 134-46.
7. Bose-O’Reilly et al., (2010). Mercury Exposure and Children's Health. Current Problems in Pediatric and Adolescent Health Care 40(8):186-215.
8. Diamanti-Kandarakis E., et al. (2009). Endocrine- disrupting chemicals: an Endocrine Society scientific statement. Endocrine Reviews, 30(4): 293–342.
9. Soto, A.M. et al. (2013). Does cancer start in the womb? Altered mammary gland development and predisposition to breast cancer due to in utero exposure to endocrine disruptors. Journal of Mammary Gland Biology Neoplasia 18(2): 199-208.
10. UNEP/WHO (2013). State of the science of endocrine disrupting chemicals 2012.Accessed February 5 2015