Chemicals and cancer
Cancer is uncontrolled, invasive cellular reproduction
Cancer is a family of around 200 diseases which begin when cells reproduce in an uncontrolled manner, invading and destroying healthy tissue. Chemicals can be carcinogenic by directly damaging DNA, increasing the risk of genetic mutations by altering cellular reproduction cycles, or by interfering with the body’s various fail-safe mechanisms which stop cancers developing.
Chemicals and cancer
The European Union CLP regulation (Classification, Labelling and Packaging of substances and mixtures) has identified 904 substances and substance groups that may cause cancer (R45 or R49), according to the European Commission ESIS database.
The International Agency for Research on Cancer (IARC) classifies 165 agents, many of which are chemicals, as either “definitely” or “probably” carcinogenic to humans, including benzene, vinyl chloride, chromium VI compounds, dioxin and formaldehyde (IARC 2010).
Endocrine disruptors and cancer
There is a growing body of evidence that endocrine disrupting chemicals (EDCs) may increase the risk of cancer by interfering with hormonal signalling in ways which make cancers more likely to initiate or grow (Diamanti-Kandarakis et al. 2009).
Exposure to EDCs during developmental periods can certainly have life-long implications for cancer risk, as was proven by the discovery that the daughters of women who took the oestrogenic drug diethylstilbestrol (DES) during pregnancy had a greatly increased risk of developing rare reproductive cancers (Herbst et al. 1971).
For chemicals we encounter in our everyday environment, studies of female mice exposed in the womb to Bisphenol A (BPA) have found they are more likely, when adults, to develop abnormal breast tissue which is more likely to become cancerous (Vandenberg et al. 2007; Murray et al. 2007).
Males can also be affected by oestrogenic compounds, with rat studies finding that BPA exposure after birth can cause an increase in pre-cancerous prostate growths in adulthood (Prins et al. 2011).
Given that prostate cancer and breast cancer are the most common cancers in men and women respectively, widespread exposure to other oestrogen-like compounds such as parabens and alkylphenols is a matter of concern.
What do we currently know about the occupational and environmental causes of cancer? In this scientific review, researchers from the University of Boston School of Public Health summarise evidence connecting cancer with environmental exposure to a range of agents.
Series of four articles summarising the issues around chemical causes of cancer
- Runaway Growth. Forty years into the “War on Cancer,” casualties are mounting — and we still don’t know what motivates the enemy.
- Soft-Pedalling Prevention. We celebrate those who beat cancer … but ignore efforts to prevent it
- Risk Assessment: Science has a hard time gauging the danger posed by carcinogens. “Genetics loads the gun, environment pulls the trigger.”
- Coming Clean. Can we solve the problem of carcinogens in the environment?
Selection of references
Diamanti-Kandarakis E, Bourguignon JP, Giudice LC, Hauser R, Prins GS, Soto AM, Zoeller RT, Gore AC. Endocrine-disrupting chemicals: an Endocrine Society scientific statement. Endocr Rev. 2009 Jun;30(4):293-342. Review.
Herbst AL, Ulfelder H, Poskanzer DC (1971). “Adenocarcinoma of the vagina. Association of maternal stilbestrol therapy with tumor appearance in young women”. N Engl J Med 284 (15): 878-81.
IARC, The International Agency for Research on Cancer (2010). Agents Classified by the IARC Monographs Volumes 1-100. Retrieved from: http://monographs.iarc.fr/ENG/Classification/index.php
Murray TJ, Maffini MV, Ucci AA, Sonnenschein C, Soto AM. Induction of mammary gland ductal hyperplasias and carcinoma in situ following fetal bisphenol A exposure. Reprod Toxicol. 2007 Apr-May;23(3):383-90
Prins GS, Ye SH, Birch L, Ho SM, Kannan K. “Serum bisphenol A pharmacokinetics and prostate neoplastic responses following oral and subcutaneous exposures in neonatal Sprague-Dawley rats.” Reprod Toxicol. 2011 Jan;31(1):1-9 http://www.ncbi.nlm.nih.gov/pubmed/20887781
Vandenberg LN, Maffini MV, Wadia PR, Sonnenschein C, Rubin BS, Soto AM. Exposure to environmentally relevant doses of the xenoestrogen bisphenol-A alters development of the fetal mouse mammary gland. Endocrinology. 2007 Jan;148(1):116-27.