Do You Know What Your Child Is Playing On?
An Overview of Playground Surface Materials
By Wendy Priesnitz
Playground surfaces are important for our children's
health. After all, kids
can get badly hurt if they fall on concrete or other paved surfaces. And,
let’s face it, kids fall a lot, especially when they’re playing on
playground equipment or school and community play fields. An estimated
eighty percent of injuries on playgrounds are as a result of falls. So it’s
a good thing that many playgrounds provide a surface that’s softer than
pavement. Unfortunately, it appears not to be such a good thing that some of
those surfaces could be providing health effects much worse than a skinned
knee or even a broken arm. Here is an overview of the pros and cons of
playground surface materials, a topic that is slowly coming onto the public
Rubber mulch chips and rubber mats are manufactured
from recycled tires and sold as shock-absorbing materials for playgrounds.
The chips are also sold as garden mulch. Since tires are made of vulcanized
rubber, the mulch made from them is said by its manufacturers to be
virtually indestructible, so it won’t crumble or disintegrate.
However, in some jurisdictions, rubber tires are
classified as “hazardous waste” and can’t be disposed of without a permit.
That’s because tires contain a variety of toxins, including carcinogens,
chronic lung irritants, and endocrine disruptors. Various studies have
identified the chemicals found in tires, which are made of forty to sixty
percent rubber polymers, carbon black (twenty to thirty-five percent),
silicas, process and extender oils (up to twenty-eight percent),
vulcanization chemicals and chemical antidegradents, plasticizers and
softeners, and heavy metals.
In 2007, Environment and Human Health, Inc. (EHHI) –
a non-profit organization composed of doctors, public health professionals,
and policy experts – released a report about potentially harmful exposures
to recycled tire products used on playgrounds and soccer fields. Informed by
studies that found cancer in workers in rubber fabrication and reclamation
industries, EHHI undertook an exploratory study with the Connecticut
Agricultural Experiment Station to examine what the materials were and
whether they out-gassed harmful chemicals into the air or were capable of
leaching into ground water.
The four compounds confirmed to be found in the
Connecticut Agricultural Experiment Station study were: benzothiazole (skin
and eye irritant); butylated hydroxyanisole (carcinogen, endocrine toxicant,
immunotoxicant, neurotoxicant, and more); n-hexadecane (severe irritant);
and 4-(t-octyl) phenol (corrosive and destructive to mucous membranes). And
approximately two dozen other chemicals were found at lower levels.
In a press statement at the time of the study, David
Brown, Sc.D., EHHI’s public health toxicologist, said, “Health endpoints of
concern are numerous. Some are acute irritation of the lungs, skin, and
eyes, and chronic irritation of the lungs, skin, and eyes. However,
knowledge is more limited about the effects of semi-volatile chemicals on
the kidney, endocrine system, nervous system, cardiovascular system, immune
system and development.”
A 2019 study published in the Proceedings of the National Academy of
Science USA added to the general body of knowledge about the effects of
these toxins on the brain and cardiovascular system. CR leachate injected
into the yolks of chickens caused mild to severe developmental
malformations, reduced growth, and specifically impaired the development of
the brain and cardiovascular system, which were associated with gene
dysregulation in aryl hydrocarbon receptor, stress-response, and thyroid
hormone pathways. The authors wrote, “The observed systematic effects were
probably due to a complex mixture of toxic chemicals leaching from CR, such
as metals (e.g., Zn, Cr, Pb) and amines (e.g., benzothiazole). This study
points to a need to closely examine the potential regulation of the use of
CR on playgrounds and artificial fields.”
Artificial or synthetic turf is manufactured from
polymers such as polypropylene or polyethylene. It was developed in the
mid-1960s by Monsanto and has since gained
widespread popularity as a replacement for grass. Originally used in
stadiums and on athletic fields for college and professional sports teams,
it now is also used in municipal parks, golf courses, playgrounds, cruise
ships, and airports. There is also a growing residential market for
Artificial turf has some issues, including
overheating (as high as two hundred degrees) on hot days. It has also been
reported to increase ankle injuries and skin abrasions. It requires the
application of harmful disinfectants and sprays to reduce static cling and
odors. In the past, many synthetic turf companies used lead paint to make
the plastic blades of “grass” green, a practice that is now thought to have
been stopped after a series of lawsuits against the industry.
But one of artificial turf’s biggest health drawbacks
is that many brands use a finer version of tire mulch, called crumb rubber
as in-fill between the blades of “grass” to provide stability, uniformity,
and resiliency to the synthetic turf fields. Crumb rubber is a pellet-like
substance the size of a cracker crumb. Like tire mulch, it contains heavy
metals and other chemicals, but due to its fine consistency, it sheds dust that can easily get
into a person’s mouth, nose, shoes, and clothing. Many public health
organizations have concerns about the use of tire crumb in artificial turf.
Doctors from New York’s Mt. Sinai Children’s
Environmental Health Center have written: “Exposures to chemicals present in
crumb rubber at very high levels, typical of animal or occupational studies,
are known to cause birth defects, neurologic and developmental deficits, and
some can even cause cancer.”
David Brown, Sc.D., EHHI’s public health
toxicologist, says, “It is clear the recycled rubber crumbs are not inert,
nor is a high temperature or severe solvent extraction needed to release
metals, volatile organic compounds, or semi-volatile organic compounds. The
Connecticut Agricultural Experiment Station study conclusively demonstrates
that the tire crumbs and tire mulch release chemical compounds into the air
and ground water. Thus, tire crumbs constitute a chemical exposure for
humans and the environment.”
The Ecology Center, a nonprofit environmental
research group based in Michigan, has tested artificial turf blades
and found levels perfluoroalkyl and polyfluoroalkyl substances (PFAS)
chemicals, members of a class of chemicals associated with multiple health
problems, including cancer.
The California-based Center for Environmental Health
points out that children are particularly vulnerable to toxic
threats: “Children have increased exposure to toxic chemicals due to the
unique way they interact with their environment. Because they are growing
and developing, their bodies are also more susceptible than adults’ to
Unfortunately, children’s exposure to these chemicals
while using artificial turf fields has not been adequately studied. The U.S.
Environmental Protection Agency (EPA), in an evaluation of its study of
crumb rubber, determined that it was not possible for the agency to reach
“comprehensive conclusions without the consideration of additional data.”
According to Dr. Joel Forman, an associate professor
of pediatrics and preventive medicine at New York's Mt. Sinai Hospital,
these data gaps make it difficult to draw firm conclusions. He says, “None
of [the studies] are long term, they rarely involve very young children, and
they only look for concentrations of chemicals and compare it to some sort
of standard for what’s considered acceptable. That doesn’t really take into
account subclinical effects, long-term effects, the developing brain, and
Some jurisdictions, like New York City and
the Los Angeles Unified School District, have removed crumb rubber from play
areas for young children, or are using alternatives in new installations.
The Center for Environmental Health recommends that schools, when feasible,
replace crumb rubber infill with natural materials such as cork, coconut
fibers, and even sand. In spite of these concerns, which have been around
for close to ten years and were recently revived by an investigative report
by NBC news, the industry claims that research demonstrates no negative
health effects from scrap tire materials.
Aside from the possible health effects, in a 2007
report on the safety of rubber playground chips, California officials found
that nearly seventy percent of rubber surfaces weren’t shock-absorbent
enough to actually cushion falls, possibly due to lack of maintenance. Wood
chips were found, in one study, to do a better job of protecting children
from head trauma than surfaces using recycled rubber.
Wood chips are natural and inexpensive; some
municipalities have them in abundance due to tree trimming. However, the
U.S. Department of Interior (DOI) has determined that ordinary wood chips
are not considered an accessible playground surface. In its place, the
International Play Equipment Manufacturers Association (IPEMA) prefers
Engineered Wood Fiber (EWF). This is wood ground to a fibrous consistency,
randomly sized but not typically over two inches in length. The fibers knit
together to provide a surface springy enough to cushion falls, yet firm
enough for wheelchairs, and they tend not to cause splinters. Besides
meeting ASTM International safety and accessibility standards, EWF is a
totally natural product and is not chemically treated.
Sand and Pea Gravel
Grass is still found in some playgrounds. (And there
can be problems with grass, too, if herbicides are used.) However, research
has found that impactable, absorbant materials, such as sand or pea gravel,
provide better protection than grassy surfaces, with one study finding that
risk of injury is reduced by 1.7 times when playgrounds are surfaced with
sand rather than grass.
Researchers at The Hospital for Sick Children and
York University, both in Toronto, have found that using granite sand as
playground surfacing reduced the risk of arm fractures, compared to wood
chip surfaces. The study published in 2009 in the open-access journal PLoS
Medicine, showed the risk of an arm fracture from a fall off playground
equipment was almost five times higher on a wood chip surface compared to
sand. Risks of other types of injuries were also higher on wood-chip
However, playground designers don’t favor sand
because it hardens quickly, gets tracked into schools on students’ shoes,
and attracts animals who use the play area like a litter box.
An alternative is pea gravel – smooth, round,
pea-sized stones that slide over each other’s surfaces to absorb shock. It
is relatively inexpensive, clean, doesn’t track into buildings (especially
important for school playgrounds), and drains well.
Whatever type of loose fill is used on a playground,
it should be present in sufficient quantities. The Canadian Standards
Council, which produces a nationally recognized standard for playground
safety, stipulates the material be used at a depth of at least 15 cm (6 in)
for preschool equipment and 30 cm (12 in) for full-sized equipment. That
means regular maintenance is almost as important as the choice of material.
While we cannot and, I think, should not inhibit our
children’s free outdoor play by being fearful – or, worse, instilling fear
in them – we can ensure that the playgrounds they use are as safe as
Helping Kids Play Safely
- Avoid tire crumb playgrounds in favor of wood
chip or grass sites.
- Use well-maintained playgrounds, because any
loose surface material can become scattered and thin, exposing your
child to a hardened, compressed surface.
- If you and your kids can’t avoid using synthetic
turf fields, remove the crumb rubber pellets from clothing, bodies, and
equipment after playing.
- Do not use synthetic turf on extremely hot days.
- Don’t let kids lie down or eat on a surface that
uses recycled tire rubber.
- Teach your children the importance of frequent
hand washing after playing.
- Lobby for the use of wood chips, EWF, pea
gravel, or sand surfaces rather than artificial turf or recycled rubber.
- Reduce the risk of falling by having children
use age-appropriate equipment.
- Avoid dressing children in scarves and clothing
with drawstrings or cords that could catch on playground equipment.
- Supervise very young children on playground
Wendy Priesnitz is
Natural Life Magazine's founding editor. She is a journalist with forty
years of experience, the author of 13 books about green living, natural
parenting, and learning without school, and the mother of two adult
daughters. An earlier version of this article was published in
Child's Play Magazine.