The Scary Future of Human Fertility with Dr. Shanna Swan

In this episode you will uncover the pressing effects of
declining fertility rates on the human population, delve into the
influence of environmental factors, specifically exposure to
harmful chemicals, on reproductive health, gain insights on age,
egg/sperm quality, and environmental influences in fertility,
grasp the effects of phthalates on male reproductive health,
highlighting AGD and sperm count, and also realize the importance
of increased awareness, research, and action to safeguard human
health and fertility.


Dr. Shanna Swan is an Environmental and Reproductive
Epidemiologist. She is Professor of Environmental Medicine and
Public Health at the Icahn School of Medicine at Mount Sinai, New
York, Adjunct Professor in Obstetrics and Gynecology at the
University of California San Francisco and Senior Scientist at
Environmental Health Sciences. Dr. Swan's work examines the
impact of environmental exposures on reproductive health and
neurodevelopment. 
Links for this episode

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Episode Overview

00:07:32 - Population Decline, 
The world's fertility rate has dropped from over five children
per couple to under two now, and a large proportion of the world
is now below replacement. 

00:12:17 - The Roller Coaster of Fertility, 
The declining fertility rate in many countries means that we are
headed towards a maximum world population, which will decrease
and never come back. 

00:15:37 - Social Causes of Fertility Decline, 
The decline in fertility is not just due to social causes like
women entering the workforce and getting educated, but also due
to environmental and lifestyle factors. 

00:22:28 - Environmental and Lifestyle Factors Affecting
Fertility, 
Environmental and lifestyle factors, such as exposure to
phthalates and Bisphenol A, are major contributors to the decline
in fertility. 

00:16:51 - The Challenges of Motherhood and
Fertility, 
Dr. Stephanie and Dr. Shanna discuss the challenges of motherhood
and fertility. The decline in egg quality and sperm quality with
age is a major limiting factor in infertility, which is a concern
for women who choose to have babies later in life. 

00:19:57 - Decline in Male Fertility, 
Dr. Shanna explains that research on the declining rate of male
fertility has been around for 30 years. The first study in 1992
reported that sperm count had decreased by 50% in 50 years.
However, this figure was met with skepticism. 

00:23:30 - Early Puberty in Girls, 
Dr. Stephanie brings up the phenomenon of early puberty in girls,
and Dr. Shanna explains that it is a real concern. Girls are
starting menstruation earlier and earlier, which is not only a
risk for psychological and social challenges but also for
fertility. 

00:25:46 - Environmental Factors Affecting Sperm
Count, 
Dr. Shanna discusses her study on environmental factors affecting
sperm count. She found that exposure to phthalates, a chemical
found in plastics, is linked to lower sperm count. Exposure to
other chemicals like bis

00:34:10 - Factors Affecting Sperm Count, 
The recruitment bias and selection bias of the men in the studies
from 1940 and 1990 were analyzed. The lifestyle factors of
smoking, obesity, exercise, and stress were found to be
important. Chemicals that affect the reproductive system,
particularly testosterone and estrogen, were also
identified.

00:40:16 - Plastic Increase and Endocrine-Disrupting
Chemicals, 
After World War II, scientists were revered, and plastic
production increased rapidly. However, plastic has a large number
of chemicals that can alter hormones. Phthalates are particularly
concerning as they lower testosterone levels and can affect
genital formation during pregnancy.

00:43:45 - Non-Monotonic Dose Response and
Endocrinology, 
Hormones often respond non-linearly to low doses of chemicals,
affecting not just testosterone, but also estrogen and the immune
system. Endocrine-disrupting chemicals can have a significant
effect, regardless of the dose.

00:49:57 - Phthalate Syndrome, 
Phthalates can cause the phthalate syndrome, where exposure in
utero in male rodents can affect genital formation and induce
infertility and other health problems. Humans have phthalates in
their bodies, and pregnant women are particularly at risk for
exposure.

00:51:44 - Development of Genitalia in Male and Female
Fetuses, 
Dr. Swan explains how the genitals of fetuses develop under
genetic regulation, and everything changes during a critical
period of gestation. She highlights how testosterone contributes
to the differentiation of genitalia in male fetuses and explains
how insufficient testosterone exposure can undermasculinize
males.

00:54:27 - The Analogeneital Distance (AGD), 
Dr. Estima and Dr. Swan discuss the AGD and how it is an
important distance that differentiates males and females in
almost every mammal. They also discuss how it can be difficult to
measure the AGD accurately because it is soft tissue and how
standardization of the position of the legs is necessary when
measuring the AGD.

01:02:36 - The Phthalate Syndrome in Humans, 
Dr. Swan discusses how she found the phthalate syndrome in humans
after researching variations in AGD, penile size, and descent of
the testicles. She highlights how many papers have found other
chemicals related to AGD and how she would love to see AGD become
part of the standard of care.

01:05:14 - Implications of AGD on Testosterone and
Longevity, 
Dr. Swan explains how AGD has massive implications on men's
capacity for testosterone, sperm production, and
longevity. 

01:08:09 - The Relationship between AGD and Sperm
Count, 
Dr. Swan discusses her research on the relationship between AGD
(anogenital distance) and sperm count. Her study found a direct
linear relationship between the length of AGD and the number of
sperm, indicating that the longer the AGD, the higher the sperm
count. 

01:13:27 - Phthalate Syndrome and Exposure, 
Dr. Swan explains phthalate syndrome, a condition assigned at
birth that affects the male reproductive system and is caused by
exposure to phthalates. She discusses the common sources of
phthalates, such as plastic tubing, personal care products, and
food packaging. 

01:15:24 - NICU Exposure and Other Hormonal Effects, 
Dr. Swan highlights the dangers of exposure to phthalates and
other hormone-disrupting chemicals in the NICU, where preemies
are especially vulnerable. She also notes that these chemicals
can affect other hormonal systems in the body, such as lung
development, brain development, and blood pressure. 

01:20:28 - BPA-Free Products and Other Chemicals, 
Dr. Swan addresses the issue of manufacturers substituting
BPA-free products with similar chemicals that have the same
effects. She also mentions other chemicals that disrupt hormones,
such as PFAS chemicals in Teflon and sunscreen. 

01:26:10 - Gender Dysphoria and Environmental
Chemicals, 
Dr. Swan explores the relationship between gender dysphoria and
exposure to environmental chemicals. She acknowledges the
complexity of the topic and emphasizes the need for further
research before drawing conclusions.
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