I am cognisant there is a new generation of reader who may not be aware of the seminal work conducted by American-born Rachel Carson who, in the 1950s, brought to light the detrimental effects of pesticides, particularly DDT (dichlorodiphenyltrichloroethane), on the environment. The insecticidal action of DDT was discovered in 1939 by the Swiss chemist Paul Müller (earning him a Nobel Prize), leading to the chemical’s use during World War II to clear South Pacific islands of malaria-causing insects and for managing head and body lice for U.S. troops. After the war, DDT was used in US civilian life to reduce pests and disease-carrying insects courtesy of aerial spraying programs in urban areas. In 1962, Rachel Carson, a nature author and former marine biologist with the U.S. Fish and Wildlife Service, published her book “Silent Spring” exposing the hazards of DDT - describing how it entered the food chain and accumulated in the fatty tissues of animals, including human beings, to detrimental effect – and generally warning of the dangers associated with misuse of chemical pesticides . Carson and her book, while vilified by chemical companies as being alarmist and irresponsible, elicited quick response by the John F. Kennedy administration resulting in a 1963 investigation of the book’s claims by the Life Sciences Panel of the President’s Science Advisory Committee (PSAC) and release of a positive report . This report, and her invitation to testify at congressional hearings on pollution and the federal regulation of pesticides did much to silence industry critics. In 1970, the US Environmental Protection Agency (EPA) was established to set tolerance levels for chemical residues, oversee pesticide regulation, and protect public and environment health. In 1972, the EPA banned the licensing of DDT in the US . In Australia, the use of DDT was not banned until 15 years later in 1987 .
In spite of Carson’s advocates throughout the decades, controversy exists to this day about the risks and benefits of DDT use. Such controversy relates particularly to its use in developing countries, predominantly those of Africa, Asia and India, where the pesticide has been responsible for reducing millions of deaths from malaria-carrying mosquitos. The World Health Organisation (WHO), having initially established a DDT program in 1955 in recognition of the pesticide’s effectiveness in controlling malaria-related deaths, moved to eradicate the program in 1969 based on, among other things, concerns that DDT caused serious health effects in humans and observations that pests were becoming tolerant to the pesticide. In 2006, with concerns of once-again increasing incidence of malaria-related deaths, the WHO endorsed the use of DDT for indoor spraying only in malaria-affected countries due to the absence of equally effective and efficient alternatives but shared a “commitment to the global goal of reducing and eventually eliminating the use of DDT while minimizing the burden of vector-borne diseases” , a position being implemented currently .
I share this example of DDT because I believe it is important we weigh in an evidence-based balance of risk versus benefit our personal decisions about using chemicals known to be harmful to human health. Fortunately for most of us, making the choice to not drink from bisphenol A (BPA)-containing plastic bottles or not giving phthalate-containing toys to our toddlers to suck, or discouraging our pre-teen and teenage daughters from using phthalate and paraben-containing cosmetics is not a case of life or death as it is in developing countries attempting to combat malaria-related deaths with DDT. Minimising exposure to chemicals is, for us, a pretty simple decision.
I would like to introduce you briefly to another important book entitled “Our Stolen Future”, which was published in 1996 by Dr Theo Colborn and her colleagues . In his foreword to the first edition, then US Vice President Al Gore, made reference to the book as being in many respects the sequel to “Silent Spring”. “Our Stolen Future” describes how scientist Theo Colborn, during her tenure at the World Wildlife Foundation (WWF) in Washington DC, pieced together a series of disparate reports by naturalists and scientists who described reproductive, developmental and behavioural abnormalities in wildlife populations in the US and Europe – and her belief that these events were somehow linked to each other, and to chemical pollution. In its introductory chapter, “Our Stolen Future” describes the initial omens that something was seriously wrong - to cite only a few, the impaired courtship, mating and chick-raising behaviour of bald eagle populations in Florida resulting in reduced births (1952), the unhatched eggs, dead chicks, abandoned nests and developmental deformities in herring gull colonies in Canada discerned to be due to dioxin exposure (1970), the abnormally small penises in Florida’s Lake Apopka alligators associated with the Tower Chemical Company dicofol pesticide spill (1980), and the notable decline in the average human sperm count of men in Denmark and possibly other countries (1992) .
In 1991, Theo Colborn organised a group of scientists at the Wingspread Conference held in Racine, Wisconsin where concerns about the prevalence and effects of environmental chemicals were discussed for the first time and where the term “endocrine disruptor” was coined. Theo Colborn continued to be a leading contributor to the field of endocrine disruptors and established The Endocrine Disruptors Exchange, an international, non-profit organisation dedicated to compiling and disseminating scientific evidence on health and environmental problems caused by low-dose exposure to endocrine disrupting chemicals .
There have been, and continue to be, detractors of the claims that low doses of synthetic chemicals, doses to which we are exposed daily, have a detrimental impact on human health. However, key scientific bodies have aligned increasingly with the observations described by the scientists and naturalists whose stories I have shared in this blog. Notably, the Endocrine Society, a premier professional organisation for basic and clinical endocrine research and the treatment of endocrine disorders, released a scientific statement in 2009 outlining the mechanisms and effects of endocrine disruptors on “male and female reproduction, breast development and cancer, prostate cancer, neuroendocrinology, thyroid, metabolism and obesity, and cardiovascular endocrinology,” and showing how experimental, epidemiological and clinical studies “implicate endocrine disrupting chemicals as a significant concern to public health.” The Society statement noted it can be difficult to demonstrate unequivocally that endocrine disruptors cause human diseases, but it recommended that the precautionary principle should be followed .
I will leave you with the definition of the precautionary principle pertaining to endocrine disruptors as defined in the Wingspread statement of 1998, a principle by which I choose to make personal decisions regarding exposure of myself and my family to environmental chemicals: “When an activity raises threats of harm to the environment or human health, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically."
In my next blog, I look forward to sharing with you the case of BPA, its prevalence in our environment, observed effects on animal and human health, and ways to minimise exposure.
1. Carson R. (1962). Silent Spring Houghton Mifflin, Boston, Massachusetts, USA.
2. http://www.environmentandsociety.org/exhibitions/silent-spring/us-federal-government-responds Accessed 29 March 2016
3. https://www.epa.gov/aboutepa/epa-history Accessed 29 March 2016
4. http://www.atse.org.au/Documents/Publications/Reports/Climate%20Change/Pesticide%20Use%20in%20Aust%202002.pdf Accessed 29 March 2016
5. http://apps.who.int/iris/bitstream/10665/69945/1/WHO_HTM_GMP_2011_eng.pdf Accessed 29 March 2016
6. http://apps.who.int/iris/bitstream/10665/116902/1/EMROPUB_2014_EN_1605.pdf Accessed 30 March 2016
7. Colborn T, Dumanoski D, Myers J. (1996). Our Stolen Future. Penguin Group, New York, New York, USA.
8. http://www.endocrinedisruption.org/ Accessed 29 March 2016
9. Diamanti-Kandarakis E, Bourguignon J-P, Giudice L, Hauser R, Prins G, Soto A, Zoeller R, Gore A (2009). Endocrine-Disrupting Chemicals: An Endocrine Society Scientific Statement. Endocr Rev 30(4): 293-342.
Ever since working as a biological scientist at Tufts University School of Medicine in Boston, I have been aware of the abundance of synthetic and natural chemicals in our environment that have significant potential for adversely impacting human health.