Endocrine Disruptors and Testosterone (BPA, Phthalates, PFAS)

Testosterone levels in men have been declining for decades -- and the rate of decline significantly exceeds what aging alone explains. A widely-cited 2007 study by Travison and colleagues in the Journal of Clinical Endocrinology & Metabolism analyzed testosterone data from three separate cohorts spanning 1987 to 2004 and found a population-level decline of approximately 1% per year -- meaning a 60-year-old man in 2004 had significantly lower testosterone than a 60-year-old man in 1987, despite matching age.

The study controlled for age, body mass index, smoking, and alcohol use. The decline persisted. Something in the environment was changing men's hormonal profiles across generations.

Environmental endocrine disruptors -- chemicals that interfere with hormone signaling -- are among the most plausible explanations. This post examines the three most evidence-backed categories: BPA, phthalates, and PFAS.

What Endocrine Disruptors Actually Do

An endocrine disruptor is a chemical that interferes with the body's hormonal signaling system. They do this through several mechanisms:

• Receptor mimicry: Binding to hormone receptors (including androgen receptors) and producing effects similar to or opposite to the natural hormone
• Receptor blocking: Occupying hormone receptors without activating them, preventing the real hormone from binding
• Hormone production interference: Disrupting the enzymes that produce or metabolize hormones, including the steroidogenic pathway that produces testosterone
• Transport protein alteration: Affecting sex hormone-binding globulin (SHBG), which determines how much testosterone is bioavailable

Most endocrine disruptors relevant to testosterone are anti-androgenic -- they reduce androgenic signaling either by lowering testosterone production, blocking androgen receptors, or increasing the conversion of testosterone to estrogen.

Related: Want to put this into practice? Try our Experiment Builder to get started, and check out Red Light Therapy & Testosterone: 12 Weeks of Data for more context.

BPA: The Best-Studied Disruptor

Bisphenol A (BPA) is a synthetic estrogen that has been used since the 1950s in polycarbonate plastics and epoxy resins. It is found in water bottles, food can liners, thermal paper receipts, dental sealants, and many other consumer products.

BPA is an estrogen mimic -- it binds to estrogen receptors and produces estrogenic effects. In men, elevated estrogen relative to testosterone suppresses the HPG (hypothalamic-pituitary-gonadal) axis through negative feedback, reducing LH production and downstream testosterone synthesis.

Multiple human studies have documented the association:

• A 2010 study of Chinese factory workers (Hanaoka et al., Occupational & Environmental Medicine) found that men with higher occupational BPA exposure had significantly lower testosterone levels
• Cross-sectional analyses of NHANES data have found that urinary BPA levels negatively correlate with total testosterone, free testosterone, and inhibin B (a marker of testicular function) in adult men
• Animal studies consistently show BPA exposure reduces testosterone production in Leydig cells -- the testicular cells responsible for testosterone synthesis

Where BPA Exposure Is Highest

Thermal paper receipts are among the highest-exposure sources -- a single receipt can transfer micrograms of BPA to your skin within seconds of contact, and absorption increases dramatically if your hands are wet or if you use hand sanitizer first. Canned foods (especially canned soups, tomatoes, and beans) are another significant source, as most can liners use BPA-based epoxy resins.

Phthalates: The Plasticizers in Everything

Phthalates are a family of chemicals used to make plastics flexible and as solvents in personal care products. They are found in vinyl flooring, plastic food wrap, shower curtains, shampoos, lotions, fragrances, and countless other products.

The research on phthalates and testosterone is extensive and consistently concerning:

• A 2014 study in Environmental Health Perspectives analyzed data from 1,499 men in the NHANES database and found that urinary phthalate metabolites were associated with significantly lower total and free testosterone
• A 2014 Human Reproduction study of 463 Danish men found that phthalate exposure was associated with lower testosterone levels and reduced sperm quality
• Shanna Swan's research at Icahn School of Medicine -- published in part in her book Count Down and in peer-reviewed journals -- documents associations between phthalate exposure and reduced anogenital distance in male infants, a marker of androgen exposure during development

Phthalates primarily act by suppressing CYP17A1, an enzyme critical to testosterone synthesis in the steroidogenic pathway. Unlike BPA, they are not primarily estrogenic -- they suppress testosterone production directly at the testicular level.

PFAS: The "Forever Chemicals"

Per- and polyfluoroalkyl substances (PFAS) are a class of over 12,000 man-made chemicals that do not break down in the environment or the human body. They are used in non-stick cookware coatings (PTFE/Teflon), water-repellent clothing, food packaging (microwave popcorn bags, fast food wrappers), fire-fighting foam, and many industrial applications.

PFAS accumulate in human tissue over time -- they have been detected in blood samples from people in every country tested. The half-life of some PFAS compounds in the human body is estimated at 3-8 years.

The testosterone connection:

• A 2019 prospective study in Environmental Research of 1,191 men found that blood PFAS concentrations were inversely associated with testosterone levels, with the relationship strongest in men under 40
• Meta-analyses of available studies have found consistent negative associations between PFAS exposure and testosterone, particularly for PFOS and PFOA (two of the most studied compounds in this class)
• Mechanistically, PFAS appear to interfere with both the HPG axis and directly with steroidogenic enzymes in Leydig cells

PFAS contamination of drinking water is widespread. Environmental Working Group analyses have estimated that a significant portion of U.S. drinking water contains detectable PFAS levels, with contamination found near military bases, industrial sites, and municipal water systems across the country.

The Shanna Swan Research and the Bigger Picture

Shanna Swan's body of work spans three decades and focuses on reproductive health trends in men. Her 2017 meta-analysis in Human Reproduction Update analyzed 185 studies of sperm count trends and found a 59% decline in sperm concentration and 52% decline in total sperm count among men in Western countries from 1973 to 2011. The rate of decline did not slow over time.

Her subsequent research and book (Count Down, 2021) argues that environmental chemical exposures -- particularly phthalates and other endocrine disruptors -- are driving not just testosterone decline but a broader deterioration in male reproductive health that has accelerated over the same decades that chemical exposure has increased.

The strength of Swan's work is in its epidemiological scale. The limitation is that correlation does not prove causation, and disentangling chemical exposure from other concurrent changes (obesity rates, sedentary behavior, diet changes, sleep disruption) remains methodologically difficult.

Practical Exposure Reduction

You cannot eliminate all exposure, but meaningful reduction is achievable with targeted changes.

Tier 1 changes (highest impact, lowest friction):

1. Never heat food in plastic containers. Heat accelerates chemical leaching from plastics into food dramatically. Use glass, ceramic, or stainless steel for hot food and liquids.

2. Switch to a water filter. A reverse osmosis or activated carbon filter with NSF 58 or 53 certification reduces PFAS and other contaminants. Under-sink RO systems provide comprehensive protection.

3. Decline thermal paper receipts. Request email receipts. If you handle receipts, wash hands before eating.

4. Audit personal care products. Check your shampoo, body wash, lotion, and deodorant for "fragrance" as an ingredient and for known phthalates (DBP, DEP, DEHP on labels). The EWG Skin Deep database rates products by ingredient safety.

Tier 2 changes (moderate impact, higher cost):

5. Replace non-stick cookware. Older PTFE-coated pans, especially scratched ones, release PFAS compounds when heated. Stainless steel, cast iron, or ceramic cookware are alternatives.

6. Reduce canned food consumption. Particularly canned tomatoes and soups, which have higher BPA leaching due to acidity. Fresh or frozen alternatives or brands using BPA-free can liners (Eden Organics labels their cans) reduce exposure.

7. Filter shower water. PFAS and chlorine are absorbed through skin and inhaled in steam. Shower head filters reduce but do not eliminate this exposure.