Researchers at Hebrew University of Jerusalem and the Icahn School of Medicine at Mount Sinai updated their landmark 2017 analysis, now including studies from all continents collected through 2018. The updated dataset covered 223 studies and 57,168 unselected men.

They found total sperm count declined by 52.4% from 1973 to 2011 among Western men. The rate of decline accelerated after 2000, reaching 2.64% per year compared to 1.16% per year from 1972 to 2000. For the first time, the updated analysis found significant declines in South America, Asia, and Africa as well.

The acceleration coincides with the period of greatest increase in global plastic production, which grew from about 100 million tons per year in 1990 to over 400 million tons by 2022. The authors concluded that something in the modern environment is driving the decline, with endocrine-disrupting chemicals from plastics among the leading suspected causes.

Researchers at the University of New Mexico analyzed testicular tissue from 23 human cadavers and 47 neutered dogs using pyrolysis-gas chromatography mass spectrometry to identify and quantify microplastics.

Microplastics were detected in 100% of both human and dog testes. Human testes contained a mean of 328.44 micrograms of microplastics per gram of tissue, roughly three times higher than the dog samples (122.63 micrograms per gram). Twelve different polymer types were identified, with polyethylene being the most prevalent.

In the dog samples, where sperm counts were available, PVC concentration was significantly negatively correlated with sperm count. The researchers noted that because dogs share the same living environment as humans, the dog findings provide a relevant model for human reproductive effects. The concentration difference between species may reflect humans'' longer lifespan and greater cumulative exposure.

Published in eBioMedicine (a Lancet journal) in 2024, researchers recruited 113 men from three different Chinese regions and analyzed their semen for microplastic contamination using laser direct infrared spectroscopy.

Polystyrene microplastics were detected in 100% of participants. Most men were exposed to 2-7 different polymer types simultaneously. PTFE (polytetrafluoroethylene, the material in Teflon coatings) showed a statistically significant association with reduced sperm quality parameters including motility and concentration.

The multi-site design strengthened the findings by showing consistent patterns across geographically distinct populations with different diets and environmental conditions. The researchers noted that the ubiquity of microplastic contamination in semen makes it impossible to find an unexposed control group, which likely means the true effect size is underestimated.

Researchers at the University of Salerno used Raman microspectroscopy to analyze semen samples from 10 healthy men living in a polluted area of Campania, Italy. They identified 16 pigmented microplastic fragments across the samples.

Microplastics were found in 6 out of 10 samples. The particles ranged from 2 to 6 micrometers in size and included six different polymer types: polypropylene, polyethylene, polyethylene terephthalate (PET), polystyrene, polyvinyl chloride, and polycarbonate. The researchers identified ingestion and inhalation as the most likely routes of exposure.

This was one of the first studies to directly visualize and chemically identify microplastic particles in human semen using a method that preserves the particles intact. The diversity of polymer types found in a single body fluid suggests multiple simultaneous exposure routes from food packaging, water bottles, synthetic clothing fibers, and airborne dust.

Researchers at a Chinese fertility center collected and analyzed semen from 45 men seeking fertility evaluation. Using micro-Fourier transform infrared spectroscopy, they detected microplastics in 34 of 45 samples (75.6%).

Men whose semen contained PET (polyethylene terephthalate) microplastics had significantly lower progressive motility at 20.6%, compared to 34.9% in men without PET contamination. PET accounted for 35.9% of total microplastics identified, making it the most common polymer type. Other detected polymers included polystyrene, polyamide, and polypropylene.

Progressive motility is one of the most clinically important sperm parameters because it measures the proportion of sperm swimming forward effectively, which directly affects the ability to reach and fertilize an egg. A difference of 14.3 percentage points between exposed and unexposed groups represents a clinically meaningful reduction in fertility potential.

Published in Frontiers in Cell and Developmental Biology in 2025, researchers exposed male mice to 60-nanometer polystyrene particles at 20 mg/kg body weight daily for 35 days via oral gavage.

Exposed mice showed more than a 20% decrease in progressive sperm motility compared to controls, along with significantly increased numbers of static (non-moving) sperm. Testicular tissue analysis revealed disrupted glycerophospholipid metabolism, impaired DNA repair pathways, and activation of immune-inflammatory responses.

The 35-day exposure period corresponds to one full cycle of mouse spermatogenesis, equivalent to approximately 74 days in humans. The nanoplastic particles were small enough (60nm) to cross biological barriers that block larger microplastics, suggesting that the smallest plastic fragments may pose the greatest reproductive risk because they can penetrate the blood-testis barrier that normally protects developing sperm cells.

Published in Scientific Reports (Nature) in 2026, researchers exposed male rats to polystyrene microplastics at low doses via oral administration for 45 days, then assessed reproductive parameters at multiple dose levels.

Results showed clear dose-dependent effects: as microplastic dose increased, sperm count and motility decreased while the proportion of morphologically abnormal sperm increased. Serum testosterone levels dropped significantly at higher doses, while follicle-stimulating hormone (FSH) and luteinizing hormone (LH) rose, indicating the testes were struggling to maintain normal function.

Histological examination of testicular tissue revealed oxidative stress markers and mitochondrial damage in the cells responsible for producing sperm. The dose-response relationship strengthens the case for causation because it follows a fundamental toxicological principle: more exposure leads to more damage in a predictable, graded pattern.

Published in Frontiers of Environmental Science and Engineering in 2025, this review synthesized findings from dozens of animal and human studies on microplastic effects on male reproductive health.

The review identified multiple converging mechanisms of harm: microplastics physically accumulate in testicular tissue where they disrupt the blood-testis barrier (a protective layer that shields developing sperm from toxins). They impair mitochondrial function in sperm cells via the Sirt1-Pgc1a pathway, reducing the energy available for sperm motility. They lower testosterone production by damaging Leydig cells. And they trigger oxidative stress that damages sperm DNA.

The convergence of multiple independent mechanisms helps explain why microplastics affect nearly every measurable sperm parameter simultaneously, rather than targeting just one aspect of function. The review concluded that reproductive toxicity from microplastics represents an emerging public health concern requiring urgent regulatory attention.

Researchers in Jinan, China, collected semen samples from 40 healthy men who had no occupational exposure to plastics. Using Raman spectroscopy, they detected microplastic contamination in every single sample tested.

The particles ranged from 0.72 to 7.02 micrometers in size, with an average of 2 particles identified per sample. The most common polymers were polystyrene, polyethylene, and polyvinyl chloride. The 100% detection rate in men with no known occupational exposure suggests that microplastic contamination of the male reproductive tract is now universal in the general population.

The study controlled for potential laboratory contamination by processing blank samples alongside the semen samples. The universal contamination finding is significant because it means that no truly "unexposed" control group exists, making traditional epidemiological study designs difficult and likely causing studies to underestimate the true effect of microplastics on sperm parameters.

Published in Frontiers in Public Health in 2023, this review synthesized evidence on how endocrine-disrupting chemicals leaching from plastics affect male reproductive hormones and sperm production.

Phthalates, which leach from PVC and other plastics as they degrade into microplastics, were associated with 10-15% decreases in serum testosterone levels in epidemiological studies of exposed men. Men in the highest quartile of phthalate exposure showed approximately 12% lower testosterone than those in the lowest quartile. Bisphenol A (BPA), another plastic-derived chemical, showed similar anti-androgenic effects.

The review described disruption at multiple levels: hypothalamic signaling, Leydig cell steroidogenesis (testosterone production), Sertoli cell support of developing sperm, and direct DNA damage to mature sperm cells. This multi-level disruption explains why microplastic exposure affects sperm count, motility, and morphology simultaneously rather than impacting only one parameter.