This International Women’s Day, CHEM Trust sat down with Dr Shanna Swan to discuss her research on chemicals, fertility and reproductive health, and her new book, Count Down.
Shanna H. Swan, Ph.D., is one of the world’s leading environmental and reproductive epidemiologists and a Professor of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai in New York City. An award-winning scientist, her work examines the impact of environmental exposures, including chemicals such as phthalates and Bisphenol A, on men’s and women’s reproductive health and the neurodevelopment of children.
Written with Stacey Colino, COUNT DOWN: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race, was published in the U.S. on 23rd February. Read more about Count Down here.
What inspired you to do research in this area?
I became interested in the question of declining sperm count and its causes when I first read Carlsen et al 1992, which stated: “There has been a genuine decline in semen quality over the past 50 years”. I was skeptical but after spending 6 months reanalysing the 61 studies included in this analysis, the rate of decline was unchanged, and I became very interested in what could be causing this. Since the late 1990s I have been pursuing the causes of this decline. Our 2017 meta-analysis, which utilised more sophisticated methods and far more studies, came to a similar conclusion to that reported by Carlsen in 1992.
I decided to write this book after my scientific team’s analysis of four decades of sperm counts, published in 2017, revealed a dramatic decline in the numbers, which sparked enormous interest around the world. But Count Down goes far beyond sperm counts to address disturbing—and at times, even shocking—trends in sexual development in not just men and women but also non-human species.
Your research highlights very important issues, but what has shocked you most from your findings?
First, the persistent and ongoing decline in sperm count (despite the use of different methods and studies). Second, our finding that prenatal exposure to one class of EDCs (the phthalates) could alter male genital development and lead to decreased masculinisation, which we later showed to be related to lower sperm counts.
Throughout your career have you had any pushback from industry?
I’ve been fortunate in feeling little effects from industry pushback. Despite being tagged as a “junk scientist”, “truth disruptor” and “endocrine disruptor cry-baby” my work has been funded and recognised.
How important is it to educate men about these (anti-androgenic) chemicals and where should we start?
It’s important to educate both men and women about endocrine disrupting chemicals and other risk factors that can impair fetal development. Men should be aware that their exposures in the few months prior to conception (or attempted conception) can interfere with fetal development or the success of the conception attempt (in the case of Assisted Reproductive Technology). Women need to understand that their exposures during pregnancy (and particularly early pregnancy) can have life-long consequences for the development of the fetus, changes that may not be detectable till adulthood. And both men and women should be aware that reduced reproductive health has consequences for their own lifetime morbidity and mortality.
What three pieces of advice would you give to younger generations who may be concerned about the impact of chemicals on their fertility?
Become aware of the potential reproductive risks from manufactured products and processed foods. Food is a major source of exposure to phthalates, bisphenols, pesticides, perfluorinated compounds and even flame retardants. Whenever possible, chose unprocessed organic foods! Avoid fragranced products and check out personal care products and cosmetics on one of the many consumer guides available on the web.
Read more about CHEM Trust’s policy work on EDCs, and the impact of chemicals on children’s brain development.
Read about how to reduce your risk of exposure to EDCs and other harmful chemicals on our website.