Over the past twenty years, the issue of certain chemical products – so called ‘endocrine disruptors’ – having a negative effect on hormonal activity in the endocrine system at doses previously considered safe has gained increasing attention in the public debate. These chemical substances with their hormonal effects have the potential to cause not just cancer and reproductive disorders, but also subtle disruption to the way an organism works, in turn another cause of illness.
Known Endocrine Disrupting Chemicals (EDC) are
- Dichlorodiphenyltrichloroethane (DDT, a weedkiller extensively used) and DDE, a metabolite of DDT)
- Polychlorinated Biphenyls (PCBs, a family of more than 200 chemicals, used in electrical installations)
- Diethylstilbestrol (DES, given to women who had high risk of miscarriage)
- Chlordecon (used as a fire retardant)
- Trybutyltin (TBT, used as fungicides and bactericides)
- Bisphenol A (BPA, used widely in the manufacture of polycarbonate products including reusable containers of all types)
In the last decades of the 20th century, the incidence of breast cancer increased greatly throughout the world, though with geographical variations. Even in countries with a low incidence, it is the top ranked form of female cancer.
The influence of endocrine disruptors on the occurrence of breast cancer has been highlighted in several studies.
Studies published in 2006 and 2007 revealed that risk doubles after reaching the age of 40, and triples after reaching 50 for women exposed to DES. A study carried out in 1993 reported a positive link between DDE, the main DDT metabolite, and the risk of developing breast cancer. However, this was contradicted by other studies in the same period.
A study carried out in 2007 in the US measured DDT exposure of the enrolled young women from 1957-1967 (the years in which DDT usage peaked) in a series of studies on reproductive health (the Child Health and Development Study). The study showed an increase in the risk of developing breast cancer, or dying from it, before the age of 50 among women exposed to DDT before the age of 14. Continuing their work, the study authors looked at the risk of developing breast cancer in relation to in utero exposure to DDT among 9,300 women whose mothers had been enrolled in the programme. Published in 2015, the results show that, in 25% of the women whose mothers were most exposed to DDT, the risk of developing breast cancer was 3.7 times higher.1
A number of studies on animals are being carried out on animals to assess impact of BPA on the risk of breast cancer development. In a study using rats, 33% of the animals exposed to 250 micrograms of BPA per kilo of body weight between the 9th day of pregnancy and birth developed cancer of the mammary glands in adulthood. No cancer developed in non-exposed animals.
DES, DDT and BPA are not the only chemical substances with hormonal action involved with developing breast cancer. According to a 2015 report by the Breast Cancer Fund, other substances are under suspicion, (solvents, pesticides, PCBs).
1Cohn B.A. et al (2007) Environmental Health Perspectives, 115 (10) 1406-1414; Cohn B.A. et al (2015), Journal of Clinical Endocrinology and Metabolism, 100 (8) 2865-2872.
With thanks to Endocrine Disruptors: an occupational risk in need of recognition, Mengeot MA with Musu T and Vogel L, European Trade Union Institute 2016