We think a lot about what we put into our bodies. We read food labels, look at skincare ingredients and question where the things we consume come from.
But when was the last time you looked closely at what your clothes are made of?
For many of us, the answer is probably not very often.
Most modern wardrobes are filled with synthetic fibres such as polyester, nylon and elastane. They are lightweight, stretchy, durable and particularly common in activewear and underwear - the very clothes we tend to wear closest to our skin.
And while these materials can perform remarkably well, there is a growing conversation around what it means to live in them every day.
Synthetic fibres are plastic
Polyester, nylon and many other synthetic fibres are forms of plastic. They are made from polymers, often derived from fossil-based resources, and are engineered to be durable and resistant to breaking down.
That durability is useful when it comes to making clothes last.
But it also means that these fibres do not simply disappear when a garment reaches the end of its life.
With washing and everyday wear, synthetic textiles can also shed tiny plastic fibres known as microfibres. These can become part of the wider problem of microplastic pollution, making their way into wastewater and eventually into the environment.
So the question is not only what happens to a synthetic garment when we throw it away.
It is also what happens while we are wearing and washing it.
What happens when synthetic materials meet the body?
This is an area where the science is still developing, and we think that distinction matters.
Microplastics are increasingly being detected in the human body, including in tissues and fluids connected to the reproductive system. A 2026 review in Human Reproduction reported that microplastics have been detected in human testes, semen, ovarian follicular fluid and placental tissue. The review also discusses possible biological mechanisms including inflammation, oxidative stress, DNA damage and endocrine disruption.
Researchers are still trying to understand how much exposure people experience in everyday life, which types of particles matter most, and what levels of exposure may actually affect human health.
And what about fertility?
This is perhaps where the conversation becomes particularly important.
Researchers are increasingly investigating whether microplastic exposure could affect reproductive health. The 2026 review found evidence of microplastics in several parts of the human reproductive system and described growing evidence for possible effects on reproductive function. At the same time, it emphasised that the full extent of reproductive toxicity in humans remains poorly understood.
A 2024 systematic review reached a similarly cautious conclusion. It found evidence of microplastics in human reproductive tissues, but concluded that there was not yet enough high-quality evidence to determine whether exposure causes adverse fertility or pregnancy outcomes in humans.
So we cannot say that wearing synthetic clothing causes infertility.
But we can say that the potential relationship between microplastic exposure and reproductive health is an active area of scientific research.
And for something we are exposed to every day, that feels like a conversation worth paying attention to.
Why activewear makes the question even more interesting
Activewear deserves particular attention because of how we use it.
We wear it close to the body, often for extended periods, while our body temperature is elevated and we are sweating. We then wash these garments repeatedly, which can contribute to the release of synthetic microfibres.
Does that mean we should avoid all synthetics?
Not necessarily.
Synthetic fibres have transformed modern clothing and can be incredibly useful. They make garments stretchy, lightweight, durable and capable of drying quickly. There are situations where those properties are exactly what we need.
The point isn't that every synthetic garment is bad.
It is that synthetic doesn't automatically mean harmless simply because we have become used to it.
And natural doesn't automatically mean perfect either.
Every material has an environmental footprint. What matters is understanding the differences, asking better questions and making more considered choices.
Choosing what stays close to the body
At EIR, this is something we have become increasingly interested in.
The closer something is to the body, the more we want to understand what it is made from.
That doesn't mean having all the answers. It means asking better questions.
What is this fibre made from?
How was it produced?
How does it feel against the skin?
What happens when it is washed?
How long will it last?
And what happens when we no longer need it?
We believe those questions deserve more attention - especially when it comes to the pieces we wear closest to our bodies, every day.
Because sometimes, choosing what we wear is about more than how it looks or how it performs.
It is also about what we choose to live in.
Research and further reading
Hyman, S., Kahn, L. G. & Cowell, W. (2026). Microplastics and reproductive health: implications for human health and areas for future research. Human Reproduction, 41(7), 1040–1049.
Read the full review on PubMed
Hunt, K. et al. (2024). Exposure to microplastics and human reproductive outcomes: A systematic review. BJOG, 131(5), 675–683.
Read the systematic review on PubMed
Chartres, N. et al. (2024). Effects of Microplastic Exposure on Human Digestive, Reproductive, and Respiratory Health: A Rapid Systematic Review. Environmental Science & Technology, 58(52), 22843–22864.
Read the systematic review on PubMed