Low carbon concrete & Health: what science says…
& what we still
need to know 

I welcome open, constructive conversations that move the building industry forward, and I’m grateful to Dean Ipaviz for the opportunity to explore low-carbon concrete on The Built Environment podcast. With the innovation and momentum we’re seeing across the sector, this is an important moment to elevate the conversation on material health.

You can listen to part I of my chat with Dean on the podcast here: (listen to the episode here).

You can listen to part 2 in which we specifically discuss low carbon concrete here

As our understanding of the health and environmental impacts of building materials deepens, it’s natural, and necessary, that questions arise. These questions are raised to support informed decision-making.

Environmental Product Declarations (EPDs) and certifications play an essential role. They assess many important environmental and health-related criteria and have significantly lifted industry standards.

However, as far as I’m aware, current certification frameworks do not routinely include radon or heavy
metal testing of coal-derived cement replacements, such as fly ash and slag. This is not a criticism of certifiers or manufacturers, it simply reflects where the industry is today. As next-generation materials continue to evolve, expanding testing requirements to include these parameters would only strengthen confidence and help future-proof innovation.

What global research tells us

Coal-fired power stations can release trace levels of naturally occurring radioactive materials (NORM) and heavy metals such as mercury. When coal is burned, by-products like fly ash and slag can sometimes contain between three to ten times higher concentrations of certain naturally occurring elements than the original coal (Pak et al., 2025; World Nuclear Association, 2024), depending on geology, plant operations, and processing methods.

International studies have shown:

  1. concrete can contribute low-level radon emissions, depending on mix design, curing, and indoor conditions, particularly in airtight or below-grade spaces (Bulut & Şahin, 2024).

  2. While Australia’s radon risk is generally considered low, testing remains limited, we cannot assume they are zero.

  3. Research has examined mercury release from fly ash cement mixes under specific high-heat or high-moisture scenarios. These studies don’t point to widespread concern, but they do underline the value of proactive testing, robust data, and dee

Collectively, this research reinforces the need for better  visibility, not panic, or rejection of low-carbon pathways, simply better data.

Are we improving health, or shifting the burden?
As the race to decarbonise intensifies, it’s easy to slip into tunnel vision. But not all “low-carbon” substitutions are created equal. In some instances, when I’ve asked manufacturers exactly what cement is being replaced with, I’ve often been met with silence or vague answers. Without transparency, we can’t assume we're making healthier choices.

Cement is one of the highest-emission materials on the planet, and the industry deserves credit for innovating rapidly, experimenting with alternatives, and actively reducing embodied carbon.

These materials are not inherently unsafe. But independent testing, and publicly accessible reporting of radon and heavy metals in raw materials and finished mixes strengthens confidence and accelerates innovation. 

This is an opportunity for industry-wide collaboration between manufacturers, environmental scientists, and building-health specialists that will build alignment across disciplines and support adoption and innovation of materials that are lowest-impact in every sense of the word. 

Summary

Low-carbon concrete technologies, particularly those incorporating industrial by-products, represent an important step forward in reducing environmental impact. To strengthen trust and outcomes, I believe the most constructive path is transparent, independent testing of both raw materials and finished products. This is a brilliant opportunity for the industry to lead not just on carbon, but also on health transparency, and to work together toward materials that are low-impact in every sense of the word.

The building industry, homeowners, and occupants, benefits when we understand not just carbon, but the full picture of how next-generation materials can influence indoor air quality and occupant health. I’ll be unpacking the research in relation to fly ash, slag and heavy metals in concrete in more detail in an upcoming deeper-dive article.

👉 To receive it straight to your inbox when it goes live, [share your details here].

In the meantime

👉 Take the Healthy Building Materials IQ Scorecard a quick and insightful way to gauge your current knowledge and spot your biggest growth opportunities.
👉 Explore the Healthy Building Materials Mastermind our game-changing program for builders and designers ready to lead in health-centred construction.

This signature program deep dives into:

  • The health and environmental impacts of building materials, through the lens of Building Biology and Building Science

  • Mould and electroclimate risks

  • Indoor air quality and thermal performance

  • Construction-stage practices to reduce mould risks and improve air quality – going beyond NCC 2022

  • Health-focused considerations not yet addressed in industry standards

References

Jew, A.(2015). Mercury Interaction with the Fine Fraction of Coal-Combustion Fly Ash in a Simulated Coal Power Plant Flue Gas Stream. Energy Fuels 2015, 29, 9, 6025–6038 https://doi.org/10.1021/acs.energyfuels.5b01253

Pak, Y., Pak, D., Ibragimova, D., Matonin, V., & Tebayeva, A. (2025). Assessment of Natural Radioactivity and Trace Element Composition of Coals and Ash and Slag Waste in Kazakhstan. Atmosphere, 16(2), 125. https://doi.org/10.3390/atmos16020125 https://www.mdpi.com/2073-4433/16/2/125

World Nuclear Association (2024). Naturally Occurring Radioactive Materials. https://world-nuclear.org/information-library/safety-and-security/radiation-and-health/naturally-occurring-radioactive-materials-norm

Zara D’Cotta is a Building Biology New Build Consultant, Electromagnetic Radiation Specialist, Keynote Speaker and Founder of The Healthy Home.

With a clear vision to make health-focused building the new standard, she’s been empowering award-winning, time-strapped building, architects, and designers, to lead the movement towards healthier building practices since 2021.

Her work is grounded in a decade of lived experience with environmental sensitivities, internationally recognised certifications from the Building Biology Institute (USA), extensive research, and collaboration with award-winning builders, and designers, and world-leading experts in environmental health and building science, in Australia, the USA and Canada, bridging the gap between research and real-world application.

Read more about Zara here and listen to podcast’s Zara has been featured on here.