Look closely at many synthetic lawns and you will see small granules settled between the blades. That layer is the infill. Artificial turf infill comes in many materials, and the choice affects what is in the lawn, how it handles heat and what questions to ask a seller.
Most research on infill comes from athletic fields rather than home yards. The findings still help homeowners read product claims with a careful eye.
What Infill Is Made Of
A 2017 overview from the Massachusetts Toxics Use Reduction Institute, posted by the University of Massachusetts Lowell, describes the main infill materials. It says the most commonly used infill is made from recycled tires, often called crumb rubber or styrene butadiene rubber (SBR).
The overview groups alternatives into a few families.
- Synthetic. EPDM rubber, thermoplastic elastomer (TPE) and products made from waste athletic shoe materials.
- Mineral or plant based. Sand, cork and coconut hulls, among others.
- Combinations. One example is acrylic coated sand.
The report notes that mineral and plant based materials may be used in combination with one another or with other materials. Many products on the market blend more than one ingredient.
Why Labels Can Be Hard to Compare
Broad names cover a lot of ground. The TURI overview explains that EPDM, TPE and shoe based materials each include a variety of specific materials, additives and toxicological profiles.
Given that range, the report says it is difficult or impossible to make broad statements about the safety of a product in those categories without more detailed information. Additives can include cross linking agents, accelerators, stabilizers, plasticizers, fillers or antimicrobials.
The full list of additives is frequently not disclosed, according to the overview. It adds that it may be possible to obtain assurances that specific additives are absent or below a set threshold.
Crumb Rubber Research in California
California has studied tire crumb directly. The Office of Environmental Health Hazard Assessment published a summary of revisions to its Synthetic Turf Study in March 2026. Its title points to health risks from exposure to chemicals in crumb rubber infill.
OEHHA says it tentatively identified over 400 organic chemicals in combined analyses of air and crumb rubber samples. The summary describes the work as a risk assessment, not a health impact study or an epidemiological evaluation.
OEHHA’s work covered 35 synthetic turf fields with crumb rubber infill. Its findings apply to those fields, so a home lawn with a different infill or design may not match.
Infill and Surface Heat
Heat is a common question. Many alternative infills are marketed as cooler. Penn State’s Center for Sports Surface Research tested that idea in a 2012 synthetic turf heat evaluation.
The researchers compared fibers and infills, including black, green and tan rubber, an organic based product and TPE. Tested on their own, components differed by up to 20 degrees. Once combined into full turf systems, differences shrank to 12 degrees or less.
All tested systems exceeded 150 degrees F under the lab heat lamp. The report concluded that no product in the study produced a substantial reduction in surface temperature compared with a standard green fiber and black rubber system. Outdoor tests in summer 2011 showed similar results.
The same report notes that marketing materials may claim lower surface temperatures, but at the time no scientific reports substantiated those claims. It also cites earlier work showing that irrigation drops surface temperatures right after watering, though temperatures quickly rebound.
OEHHA Field Temperatures
OEHHA’s revised study also measured heat on crumb rubber fields. It found that maximum surface temperature occurred at midday on all fields and was at least 20 degrees higher than ambient air temperature for most fields at that time.
Nearby off field surfaces, including grass, concrete and dirt, were about 20 degrees lower than the turf surfaces. For more on heat, see why artificial grass gets hot in full sun.
Questions About Artificial Turf Infill
Clear questions help when comparing products. Ask each seller for written answers.
- What is the infill made of, by name and by share of the mix?
- Is the material new or recycled?
- Which additives are present, and can the maker confirm any that are absent?
- Has the product been tested for surface temperature, and by whom?
- How much infill does the system use, and how often does it need topping up?
Answers backed by independent testing carry more weight than general claims. The Penn State report is a useful reminder that a “cooler” label may not hold up once the infill sits in a full turf system.
Reading Product Sheets
Product sheets for artificial turf infill often lead with words like natural, organic or cool. Those terms do not tell you the full makeup of the product. Look for the specific material names that the TURI overview uses, such as SBR, EPDM, TPE, sand, cork or coconut hulls.
Check for test reports too. Ask who ran the test, when it was done and whether the infill was tested alone or installed with fibers and backing. The Penn State results show why that last point matters, since component differences shrank once materials were combined.
Keep copies of any documents you receive, including product names and lot details. Those records help when comparing bids and if questions come up after installation.
Infill and the Rest of the System
Infill works with the fibers, backing and base below it. Penn State found fiber color and type also played a part in surface temperature, which is why the full system matters more than any single part.
Pile height and drainage shape the system as well. Read what pile height means on an artificial turf sample and how turf drainage works during winter rain.
Weighing Real and Synthetic Grass
Infill is one of many factors in deciding between real and synthetic grass. Heat, water use, maintenance and use patterns all matter too. The comparison in artificial grass and real grass for busy households covers those tradeoffs.
Infill research keeps changing, and most studies focus on sports fields. Check the date and setting of any study you rely on. A study from a decade ago may not cover products sold today. More guides sit in the artificial turf category.