What’s New in Research on Endocrine Disruptors and Testosterone

Over the last few years, research on endocrine disruptors has shifted in an important way. Scientists are no longer asking if these chemicals affect hormones. Instead, they are asking how, which chemicals matter most, and how long-term exposure adds up over time.

Recent studies are helping researchers connect the dots more clearly than ever before.

1. PFAS (“Forever Chemicals”) Continue To Show Strong Links With Lower Testosterone

PFAS are chemicals designed to resist heat, water, and grease. Because they break down very slowly, they can remain in the body for years.

New population studies are now looking at specific types of PFAS, rather than grouping them together. This is a major shift. Researchers are finding that certain PFAS compounds are associated with lower total testosterone and lower free testosterone in adult men.

Free testosterone is especially important because it is the form the body can actually use. Scientists believe PFAS may interfere not only with hormone production, but also with how testosterone is transported and circulated in the body. [1]

2. Flame Retardants Are Still Affecting Hormones Years After Restrictions

Brominated flame retardants were widely used in furniture, electronics, and household materials. Even though many have been restricted, they remain in the environment and can accumulate in body fat.

New research has found associations between specific flame retardants and lower testosterone levels, with the strongest links appearing in older men.

This matters because hormone production naturally becomes less efficient with age. When environmental exposure is added on top of normal aging, the combined effect may become more noticeable. [2]

3. Phthalate Research Is Becoming More Precise

Phthalates are used to soften plastics and help fragrances last longer.

Researchers are now studying dose-response relationships, examining how changes in exposure levels relate to changes in hormone levels. [3]

Higher exposure to certain phthalate metabolites has been associated with:

• Lower total testosterone

• Changes in free testosterone

• Changes in sex hormone–binding globulin (SHBG)

Researchers believe phthalates may interfere with Leydig cells, the cells responsible for producing testosterone.

4. “BPA-Free” Plastics Are Receiving New Scrutiny

When BPA became controversial, many products were reformulated with similar chemicals such as BPS and BPF.

New laboratory and mechanistic research suggests these substitutes may still interact with hormone pathways. Some studies show they can accumulate in reproductive tissue and affect genes involved in hormone production. [4], [5]

This has led to the concept of “regrettable substitution”—replacing one chemical with a closely related compound that may behave in similar ways.

5. Scientists Are Now Studying Chemical Mixtures

One of the biggest changes in research is the move away from studying one chemical at a time.

In real life, people are exposed to many endocrine disruptors simultaneously through food, air, water, and everyday products.

New studies examining chemical mixtures suggest that combined exposures may have additive or synergistic effects on hormone systems. In simple terms, small exposures from many sources may matter more than one large exposure from a single source. [6]

Why This Research Matters

Most human studies in this field are observational and show associations, not direct cause and effect. However, laboratory and animal research help explain the biological mechanisms involved.

The most consistent message across recent research is this:

Hormonal changes are not always the result of one major exposure. They may reflect long-term, repeated exposure to small amounts of chemicals over time.

This shift in understanding is shaping how scientists study hormone health and environmental exposure moving forward.