by Vincent Garcia
Executive Summary
Surface heat is one of the most common concerns raised about synthetic turf, and it’s a fair one, anyone who has walked barefoot across a field on a hot afternoon has felt the difference. In 2024, researchers from Southern Cross University, Central Queensland University, and the University of Sydney published the first systematic review to formally examine this question: how does the thermal environment around synthetic grass actually compare to natural grass, and how much does the type of synthetic system matter?
The review, published in the International Journal of Biometeorology, screened the existing peer-reviewed literature under PRISMA guidelines and synthesized what is, and isn’t, established about synthetic turf and heat.
Key Findings
What Was Consistently Higher on Synthetic Grass
- Surface temperature was consistently higher on synthetic grass than natural grass, with studies reporting differences ranging from 9.4°C to 33.7°C in direct sunlight. This was the most pronounced and consistent finding across the reviewed studies.
- Air temperature just above the surface was also consistently higher, but by a much smaller margin, 0.5°C to 1.2°C.
What Infill and System Type Changed
- Systems using styrene butadiene rubber (SBR) infill or a shock pad showed increased surface temperatures.
- Systems using thermoplastic elastomer (TPE) infill, cool-climate fiber technologies, or HydroChill-type treatments showed measurably lower surface temperatures than standard SBR systems.
- This is a meaningful finding for field owners: infill and fiber selection is not just a performance and durability decision, it is also a heat management lever.
What Did Not Show a Clear, Consistent Difference
- Mean radiant temperature, humidity, and wind velocity were similar between synthetic and natural grass across the studies reviewed, or the available data was insufficient to determine whether a real difference exists.
- The authors’ own conclusion: it remains uncertain whether the measured surface and air temperature differences are large enough to meaningfully increase an individual’s heat stress risk during play. The review found a real physical difference in surface heat — it did not find, and does not claim, a proven increase in athlete heat-related illness risk.
Important Limitations
- This is a systematic review of existing studies, not new field testing. Its conclusions are only as strong as the underlying studies it screened, which varied in methodology, climate, and measurement approach.
- Heat stress is a whole-body, whole-environment question. Surface temperature is one input. The review found the broader thermal environment picture (radiant heat, humidity, wind) was largely similar or under-studied, meaning surface temperature alone should not be treated as a proxy for athlete heat risk.
- Findings on infill/fiber-specific temperature reduction come from a smaller subset of studies than the general turf-vs-grass surface temperature comparison, and product-specific performance should still be verified against independent testing for a given system.
- The review does not address mitigation strategies (irrigation, cooling infill treatments, scheduling) in depth, that is a separate, practical question for field operators.
Why This Matters
Surface heat is consistently one of the first questions architects, athletic directors, and parents ask about synthetic turf, and it deserves a straight answer rather than either dismissal or alarm. This review confirms the physical reality: synthetic grass surfaces do run measurably hotter than natural grass in direct sun. It also confirms something field owners can act on: not all synthetic systems heat up the same way, and infill/fiber choice is a legitimate design lever for managing it.
What the review does not support is a blanket claim that synthetic turf categorically increases heat-related health risk to athletes, the authors are explicit that this remains an open, unresolved question requiring further research.
Act Global Perspective
Surface heat is a real design consideration, not a talking point to spin in either direction, and we think field owners are better served by a straight account of what’s established and what isn’t. This review reinforces why Act Global treats heat management as part of the system specification conversation for every project, climate, usage pattern, and infill/fiber selection all factor into how a field is designed, not as an afterthought once a field is already installed.
We also think it’s worth being direct about what this research doesn’t settle: whether measured temperature differences translate into meaningfully different heat stress outcomes for athletes is still an open scientific question, and Act Global will continue to track this research as it develops rather than get ahead of what the science currently supports.
Related Resources
Access the Original Study
This review is Act Global’s independent summary of publicly available peer-reviewed research, prepared for educational purposes. Act Global does not host or reproduce the original article. Read the full systematic review directly from the publisher:
This is an Act Global Research Review, an independent interpretation of publicly available peer-reviewed research prepared for educational purposes only. It does not constitute medical, legal, or engineering advice.
by Vincent Garcia
Executive Summary
In 2016, the U.S. Environmental Protection Agency (EPA), the Centers for Disease Control and Prevention (CDC), the Agency for Toxic Substances and Disease Registry (ATSDR), and the Consumer Product Safety Commission (CPSC) launched the Federal Research Action Plan (FRAP) to study recycled tire crumb rubber used as infill on synthetic turf fields and playgrounds. The goal was to answer a question parents, coaches, and communities had been asking for years: what is actually in tire crumb rubber, and how much of it do people come into contact with while playing on it?
The research was released in two parts. Part 1 (2019) characterized what chemicals are present in tire crumb rubber. Part 2 (2024) measured how people are actually exposed to those chemicals during real play and practice, including a biomonitoring study comparing athletes on synthetic turf to athletes on natural grass.
This is the most comprehensive government-led exposure study on tire crumb rubber conducted in the United States to date, and it is the study most frequently cited in public conversations, and public concerns, about turf safety. Any credible synthetic turf authority resource has to engage with it directly, not around it.
Key Findings
- Chemicals are present, as expected. Tire crumb rubber contains a range of metals and organic chemicals, and all fields tested positive for bacteria at levels the agencies compared to those commonly found on household surfaces.
- Actual exposure was measured as low. Across both outdoor and indoor fields, next-to-field air concentrations for most analytes were not meaningfully different from background (non-field) air samples. Some compounds — including benzothiazole and certain PAHs, were measurably higher near the field, and indoor field air concentrations were generally higher than outdoor.
- Very little of what’s in the material transfers to the body. In simulated biological fluid testing, only a small fraction of metals in tire crumb rubber were bioaccessible (roughly 3% in simulated gastric fluid, less than 1% in simulated sweat and saliva), far below the conservative default assumption of 100% used in early risk models.
- Biomonitoring found no meaningful difference between turf and grass athletes. In the supplemental biomonitoring study (132 synthetic turf field users compared to 29 natural grass field users), there was no significant difference in urinary PAH metabolite levels between the two groups. Metal levels in blood were consistent with the general U.S. population, with the exception of selenium — a finding the agencies noted was not explained by the field material itself, since selenium wasn’t detected above threshold in the tire crumb or surrounding field environment.
- Agencies’ own bottom line: across Part 1 and Part 2 combined, the federal researchers concluded that exposures to chemicals from tire crumb rubber during normal play activity “are likely limited.”
Important Limitations
Act Global believes a research review is only useful if it’s honest about what the underlying study does not say. Several limitations matter here:
- This was not a risk assessment. The EPA and ATSDR are explicit that the FRAP characterizes exposure, what’s in the material and how people come into contact with it, but does not draw conclusions about health risk or set safety thresholds. Exposure data is an input to a future risk assessment, not a substitute for one.
- Sample sizes were small. The pilot exposure and biomonitoring study involved measurements at only three fields and a limited number of participants. The supplemental biomonitoring study was larger (161 total participants) but still modest relative to the number of fields and athletes nationwide.
- The study measured typical use, not worst-case scenarios. Conditions like extreme heat, unusually long exposure durations, or non-standard field maintenance were not the focus.
- Some compounds showed elevated readings that remain only partly explained, including the selenium finding in blood and several compounds with next-to-field air concentrations above background. The agencies flagged these as areas for continued attention rather than closed questions.
Why This Matters
For architects, athletic directors, municipalities, and parents evaluating a synthetic turf project, tire crumb rubber has been one of the most persistent public concerns in the category, and one of the most frequently misrepresented, in both directions. This study doesn’t provide a simple “safe” or “unsafe” verdict, and any source claiming it does is misrepresenting a study that explicitly declined to make that determination.
What it does provide is the most rigorous exposure data collected to date, from real fields under real play conditions, using biomonitoring, not just surface sampling. That data consistently points toward low measured exposure and no meaningful biological difference between turf and grass athletes on the metrics tested. For decision-makers, that’s a meaningfully different, and more useful, starting point than either alarm or blanket reassurance.
Act Global Perspective
Act Global uses tire crumb rubber as one infill option among several offered across our systems, and we think field owners deserve a straight answer on what the best available federal research actually shows, not a marketing summary in either direction.
The FRAP findings are consistent with the exposure characterization research Act Global relies on when evaluating infill options for a given project, and they reinforce why we present infill choice as a genuine tradeoff conversation with each client, climate, usage pattern, maintenance program, and budget all factor in, rather than a single default answer. We think the responsible position is the one the federal researchers themselves take: this research substantially narrows the uncertainty around tire crumb rubber exposure, and it does not close the door on further study. Where the agencies flagged open questions, like the elevated selenium and next-to-field air readings, we think field owners are better served by knowing that than by not.
Related Resources
Access the Original Study
This review is Act Global’s independent summary of publicly available federal research, prepared for educational purposes. Act Global does not host or reproduce the original reports. Readers can access the full findings directly from the source:
This is an Act Global Research Review, an independent interpretation of publicly available peer-reviewed research prepared for educational purposes only. It does not constitute medical, legal, or engineering advice.
