Dr Shanna Swan on Chemicals, Hormones and the Global Fertility Crisis
WHO IS DR SHANNA SWAN
Dr Shanna Swan is a Professor of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai in New York City, and one of the world's leading environmental and reproductive epidemiologists. She has published more than 200 peer-reviewed scientific papers focusing on how chemicals in food, water, cosmetics and household products affect hormones and reproductive health. In 2017 she co-authored a landmark study demonstrating that sperm counts among men in Western countries had fallen by more than 50% in the preceding five decades. Her 2021 book Count Down, co-written with science journalist Stacey Colino, brought this research to a mainstream audience for the first time.
This interview, recorded for the Huberman Lab podcast with neuroscientist Andrew Huberman, runs over two hours. The interview covers how compounds in food, water, cosmetics and household items impact the developing fetus, children and adults at the level of their reproductive biology, specifically testosterone, oestrogen and the pathways affected by both. Her emphasis throughout is on practical steps people can take, which she describes as very simple.
Watch on YouTube
Huberman Lab with Dr Shanna Swan
Full interview, over 2 hours
What This Interview Covers
Dr Swan explains what endocrine disrupting chemicals are and why the timing of exposure matters as much or more than the dose. She covers her research into phthalates and their effect on fetal development, including her work measuring anogenital distance as a marker of prenatal phthalate exposure, and the correlation between shorter anogenital distance and lower sperm count in adult men.
A substantial portion covers the global sperm count decline data, how it was measured and why lifestyle factors alone cannot explain it. She discusses the parallel decline in fertility across animal species as evidence that the cause is environmental rather than simply social or economic. The interview also covers polycystic ovarian syndrome, which she notes is increasing in women, and the broader picture of declining testosterone levels across the population.
In the practical section, Dr Swan describes what she personally does to reduce exposure, pulled directly from the interview. She distils her own water using a tabletop steam distiller, storing it in glass containers. She checks all personal care products using the Environmental Working Group database before using them. She always buys organic produce. She leaves shoes at the door to avoid tracking PFAS containing dust indoors. And she is increasingly paying attention to chemicals in clothing, particularly synthetic workout wear, which she notes may be absorbed more readily because the skin is warm and sweaty during exercise, noting she is airing toward cotton as opposed to synthetic materials.
"The chemicals I am most concerned about are those that alter our hormones. I am especially concerned with those that affect reproduction."
Dr Shanna Swan, Huberman Lab
Why This Matters for Purify The World
Dr Swan's research underpins almost every claim about phthalates, endocrine disruptors and fertility that appears across this site. This interview is the clearest single resource we can point someone toward if they want to understand the full picture of why the choices covered on Purify The World genuinely matter, explained directly by the scientist who has spent decades establishing the evidence.
Related reading: Beauty and Skincare covers phthalates in personal care products in detail. Home and Living addresses water filtration and plastic free storage. Food and Nutrition covers the organic produce guidance Dr Swan references and practices herself.
Video source: Huberman Lab with Andrew Huberman, featuring Dr Shanna Swan. All rights to the original interview content belong to the original creators. Linked here for educational reference with original commentary provided by Purify The World.