Microplastics, Hormone Health and Fertility: What Does the Evidence Actually Tell Us?

Microplastics and fertility are becoming an increasing area of research, particularly in relation to hormone and reproductive health.

For decades, the plastics conversation has focused mainly on landfill, ocean pollution and recycling.

That conversation is now expanding.

Researchers are investigating whether tiny plastic particles and chemicals associated with plastics may also affect human health, including inflammation, hormonal function and reproductive health.

The subject deserves attention, but it also requires careful language. Microplastics have been detected in human reproductive tissues and fluids, and laboratory and animal studies have raised legitimate concerns. However, current research does not prove that microplastics are responsible for infertility or the broader decline in sperm counts reported worldwide.

What the evidence does support is a stronger case for precaution, better material selection and reducing persistent plastic pollution at its source.

What does the evidence currently say?

Microplastics have been detected in human reproductive tissues and fluids. Animal and laboratory studies also suggest possible effects involving inflammation, oxidative stress and hormone signalling.

However, current human research does not prove that microplastics cause infertility or that they caused the recorded global decline in sperm counts.

The responsible conclusion is that the early findings deserve further research, while manufacturers and product developers should continue looking for practical ways to reduce persistent plastic pollution.

Plastic pollution is no longer only an environmental issue

Microplastics are generally described as plastic particles smaller than approximately five millimetres.

Some are manufactured at a very small size. Others are known as secondary microplastics because they form when larger plastic products progressively break into smaller fragments.

Conventional plastic does not necessarily disappear when it becomes too small to see. It may continue breaking into increasingly small particles that remain in soil, waterways, oceans and the wider environment.

People may be exposed to microplastics through food, drinking water and the air. The World Health Organization has reviewed exposure through all three pathways, while also emphasising that significant uncertainty remains about the level of exposure and its implications for human health.

Food Standards Australia New Zealand, or FSANZ, says scientific evidence about potential exposure through food and the associated health risks is still evolving. Its current position is that plastic contamination of the food chain is unlikely to create immediate health risks for consumers, while further research and ongoing monitoring are still required.

That distinction matters. The presence of an emerging contaminant shouldn’t be dismissed, but detection alone is not the same as proof of harm.

What does the “50% decline in sperm counts” claim mean?

One of the most widely discussed reproductive health findings comes from a major systematic review and meta-analysis examining changes in human sperm counts over several decades.

The updated analysis included 223 studies from 53 countries, covering semen samples collected from 57,168 men between 1973 and 2018.

Among men who had not been selected according to fertility status, the researchers reported:

• A 51.6% decline in average sperm concentration
• A 62.3% decline in total sperm count
• Evidence that the rate of decline had become steeper after 2000

The estimated annual decline in sperm concentration increased from 1.16% across the full period to 2.64% in the analysis restricted to data collected after 2000.

These findings are significant, but they don’t identify one specific cause.

The decline may reflect a combination of environmental exposures, lifestyle factors, occupational conditions, health changes and other biological influences. The review didn’t assess microplastics as the cause of the trend.

It would therefore be inaccurate to say that microplastics have caused sperm counts to fall by approximately 50%.

A more accurate conclusion is that sperm counts have declined substantially, while researchers are still investigating the factors contributing to that decline.

It is also important to recognise that sperm count is only one reproductive health measure. The authors described it as an imperfect proxy for fertility, although lower sperm concentration and total sperm count can be associated with a reduced probability of conception, particularly below certain levels.

Why are researchers looking at microplastics?

Researchers are examining two connected issues.

The first is the possible biological effect of the physical particles themselves.

The second is exposure to monomers, chemical additives, contaminants and other substances associated with plastic materials.

The World Health Organization notes that health questions may relate not only to plastic polymers, but also to additives used during manufacturing, chemicals that attach to plastic particles and biological material carried on their surfaces.

Possible mechanisms being investigated include:

• Oxidative stress
• Inflammation
• Hormonal or endocrine disruption
• Cellular damage
• Changes affecting sperm development or movement
• Changes within reproductive tissue

These mechanisms have been observed most clearly in laboratory and animal studies. Human evidence remains far more limited.

A 2024 systematic review published in BJOG examined studies involving microplastics in reproductive tissues, environmental exposure and fertility or pregnancy outcomes. Its authors concluded that better-quality human observational research is needed before firm conclusions can be drawn about the effect of microplastics on human reproductive health.

Another systematic review assessing digestive, respiratory and reproductive outcomes classified microplastics as suspected of harming reproductive health. That classification signals concern, but it isn’t the same as establishing proven human causation.

Research summary

Research question	What is currently known	What remains uncertain
Are microplastics found in the human body?	They have been detected in several human tissues and fluids, including reproductive samples.	The level of exposure across the wider population and the long-term health implications remain unclear.
Can microplastics affect reproductive systems?	Animal and laboratory studies show plausible effects involving inflammation, oxidative stress and hormone signalling.	Direct causation in humans has not been established.
Did microplastics cause falling sperm counts?	Large studies have reported a substantial decline in sperm counts over several decades.	The research did not identify microplastics as the cause of the decline.
Are all bioplastics biodegradable?	Some materials are designed to biodegrade or compost under defined conditions.	The term “bioplastic” alone doesn’t establish how or where a material will break down.
Should manufacturers respond now?	Persistent plastics can fragment and remain in the environment for extended periods.	The most appropriate alternative depends on the product, performance requirements and available end-of-life pathway.

What has been found in human reproductive samples?

Microplastics have now been reported in several forms of human reproductive tissue and fluid, including semen, testicular tissue and placenta.

A 2024 study led by Ning Li examined semen samples from men without known occupational exposure to microplastics. Microplastic particles were detected in all samples tested.

The researchers identified several polymer types, with polystyrene, polyethylene and PVC among the most common, and reported differing associations with sperm progressive motility.

The study provides important evidence that microplastics can be present in human semen. However, it involved a relatively small sample and cannot demonstrate that the detected particles caused infertility or broader reproductive harm.

Another 2024 study examined semen and urine samples from 113 men across three regions of China. Researchers investigated eight types of microplastics and found that most participants were exposed to several polymer types.

The study reported associations between greater mixed exposure, particularly exposure involving PTFE, and lower sperm count or motility measures. However, this was an observational study. It identified statistical relationships but couldn’t prove that microplastic exposure directly caused the measured changes.

Microplastics have also been detected in testicular tissue. A 2024 study analysed 23 human testicular tissue samples and reported plastic material in all samples examined. The authors highlighted the need for further research into whether accumulation may affect male reproductive function.

Placental research has produced similar detection findings. A 2024 study using tissue from 62 placentas reported measurable microplastic concentrations in all samples, with substantial variation between participants.

Another study examining 50 placentas found particles in 31 samples but didn’t find significant changes in the maternal or neonatal measures it assessed.

These findings show that plastic particles can be detected within human reproductive samples. They don’t, by themselves, establish that the particles caused a particular pregnancy, hormonal or fertility outcome.

What do systematic reviews conclude?

Taken together, laboratory and animal research suggests plausible pathways through which microplastics could affect reproductive health.

Researchers have reported changes involving inflammation, oxidative stress, hormone signalling, reproductive tissue and sperm characteristics in experimental settings.

Human evidence is less developed.

The 2024 BJOG systematic review found that research involving direct human reproductive outcomes was limited and that higher-quality observational studies were required.

A broader review published in 2024 concluded that microplastics were suspected of adversely affecting human reproductive health. This judgement was based on the total body of evidence, including animal studies, rather than conclusive proof of a direct effect in human populations.

The responsible conclusion is therefore not that microplastics definitely cause infertility.

It is that early findings are concerning enough to justify further research, responsible exposure reduction and greater attention to the materials businesses place into the market.

Why this matters for manufacturers

Manufacturers influence future microplastic pollution long before a product reaches a consumer or waste facility.

Important decisions are made during:

• Product design
• Polymer selection
• Additive selection
• Packaging development
• Prototyping
• Tooling and manufacturing
• Decisions about product lifespan
• Repair, reuse and recycling planning
• Disposal or organic recovery
• End-of-life planning

Responsible manufacturing isn’t simply a matter of changing the disposal label printed on a product.

A product needs to be considered across its full lifecycle.

How long is it expected to remain in service? Will it be repeatedly exposed to sunlight, heat, friction or moisture? Can it be collected and recycled? Is there an established end-of-life pathway? Could it fragment if it escapes that pathway?

These questions affect whether a material is appropriate for the product and the conditions in which it will be used.

They also show why one material cannot be treated as the right solution for every application.

“Manufacturers can’t control every part of a product’s life after it leaves the factory, but they can make more informed decisions about its material, expected lifespan and end-of-life pathway before production begins.”

Suggested attribution: Kulbir, Good Plastics

Biodegradation is not the same as fragmentation

This is one of the most important distinctions in the plastics discussion.

A product that breaks into smaller visible pieces has not necessarily biodegraded.

Fragmentation describes the physical breakdown of a material into progressively smaller particles. Those particles may remain plastic, even when they can no longer be easily seen.

Biodegradation involves biological activity converting a material into simpler substances under particular environmental conditions.

For compostable plastics, testing may assess factors including disintegration, biodegradation and the effect on compost quality.

International and Australian standards also distinguish between industrial composting and home composting because the required temperature, moisture, aeration and processing conditions are different.

The term bioplastic can also be misunderstood.

A material may be called biobased because some or all of its carbon comes from renewable biological resources. That description alone doesn’t determine whether it is recyclable, compostable or biodegradable.

Likewise, a material described as compostable may only be suitable for a specific controlled end-of-life environment.

Businesses should therefore avoid assuming that anything described as plant-based, bioplastic or compostable will safely disappear in soil, water, landfill or the natural environment.

Every claim needs to be supported by testing that applies to the specific material, product design and intended disposal conditions.

The Good Plastics perspective

At Good Plastics, we believe material selection should consider more than performance at the point of use.

Businesses also need to understand what their products may leave behind after use, including whether the material persists, fragments or genuinely biodegrades under its intended end-of-life conditions.

Good Plastics works with businesses across:

• Material selection and innovation
• Product design and development
• Prototyping and advanced 3D printing
• Precision tooling
• Injection moulding
• Testing and research
• Sustainable packaging
• Manufacturing support
• End-of-life planning
• Transitioning suitable products away from persistent conventional plastics

That mission doesn’t remove the need for evidence.

Any statement about how a particular material biodegrades, where it biodegrades or what it leaves behind must be supported by the appropriate testing, documentation and conditions relevant to that material and product.

This is how businesses can move beyond vague sustainability language and make decisions grounded in engineering, manufacturing reality and measurable outcomes.

What does the evidence actually tell us?

Scientists are still determining exactly how microplastics interact with the human body.

Current evidence doesn’t allow infertility, hormonal changes or the global decline in sperm counts to be attributed directly to microplastic exposure.

At the same time, it is clear that persistent plastic products can fragment into smaller particles, that people are exposed through multiple pathways and that microplastics have been detected in human reproductive tissues and fluids.

Those facts make prevention and responsible product design worthwhile even while the health evidence continues to develop.

Reducing long-term plastic pollution is already an environmental responsibility. In light of the emerging human health research, it is also a prudent investment in a healthier and more resilient future.

Frequently asked questions

Do microplastics cause infertility?

Current research doesn’t prove that microplastics directly cause infertility in humans. Microplastics have been detected in reproductive tissues and fluids, and animal and laboratory studies have raised concerns, but stronger human research is still needed.

Did microplastics cause the global decline in sperm counts?

No direct causal link has been established. Sperm counts have declined substantially over several decades, but researchers are still investigating the combination of environmental, lifestyle, occupational and biological factors that may be contributing.

Are all bioplastics biodegradable?

No. A material can be biobased without being biodegradable. A compostable or biodegradable claim must also specify the conditions under which the material is expected to break down.

What can manufacturers do to reduce future microplastic pollution?

Manufacturers can consider the complete product lifecycle, including material selection, expected lifespan, exposure conditions, reuse, recycling, disposal and whether an appropriate end-of-life pathway actually exists.

Considering a different material for an existing or new plastic product?

Good Plastics works with businesses to examine product performance, manufacturing requirements and end-of-life goals before recommending an appropriate material pathway.

Contact Good Plastics to discuss your product or packaging project.

Email: [email protected]
Phone: 0403 357 777

References

1. Levine H, Jørgensen N, Martino-Andrade A, et al. Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries. Human Reproduction Update.
2. World Health Organization. Dietary and inhalation exposure to nano- and microplastic particles and potential implications for human health.
3. Food Standards Australia New Zealand. Microplastics in food.
4. Hunt K, Davies A, Fraser A, et al. Exposure to microplastics and human reproductive outcomes: a systematic review. BJOG.
5. Li N, Yang H, Dong Y, et al. Prevalence and implications of microplastic contaminants in general human seminal fluid: a Raman spectroscopic study.
6. Zhang C, Zhang Y, Wang X, et al. Association of mixed exposure to microplastics with sperm dysfunction: a multi-site study in China. EBioMedicine.
7. Hu CJ, Garcia MA, Nihart A, et al. Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis. Toxicological Sciences.
8. Chartres N, Cooper C, Bland G, et al. Effects of microplastic exposure on human digestive, reproductive and respiratory health: a rapid systematic review.
9. International Organization for Standardization. ISO 17088:2021, Plastics: Organic recycling, specifications for compostable plastics.
10. Australasian Bioplastics Association. Guidance on bioplastics and Australian compostability standards.

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