Environews Focus

A 116 VOLUME 116 | NUMBER 3 | March 2008 • Environmental Health Perspectives

Synthetic turf field at Cadman Plaza Park, Brooklyn, New York

Environmental Health Perspectives • VOLUME 116 | NUMBER 3 | March 2008 A 117

Focus | Synthetic Turf

Synthetic TurfHealth DebateTakes Root

In Little League dugouts, community

parks, professional athletic organiza-

tions, and international soccer leagues,

on college campuses and neighborhood

playgrounds, even in residential yards, the

question being asked is “grass or plastic?”

The debate is over synthetic turf, used to

blanket lawns, park spaces, and athletic

fields where children and adults relax and

play; the questions are whether synthetic turf

is safe for human and environmental health,

and whether its advantages outweigh those

of natural grass. Despite or perhaps because

of the fact that it is too early to definitively

answer those questions, the debate is fierce.

New York City, which buys the largest

amount of synthetic turf of any U.S.

municipality, held a hearing 13 December

2007 on the use of synthetic turf in city

parks. There is a clear need for open space

in the city. The 28,700 acres of land con-

stituting some 4,000 parks are distributed

unevenly throughout the city. “Many dis-

tricts have no green parks, not even one,”

said Helen Sears, a city council member

representing the Jackson Heights neighbor-

hood, during the hearing.

New York City Department of Parks &

Recreation commissioner Adrian Benepe

wants to address the need for parks and ath-

letic fields by installing not only natural grass

fields and lawns but also synthetic turf.

“With quality recreational facilities—which

means, in some cases, synthetic turf fields—

we will be able to better confront this issue,”

he says. In New York City, he points out, at

least 35 synthetic turf fields are or will be a

replacement for asphalt surfaces.Josh

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Others oppose the move toward syn-thetic turf. “Grassroots organizations havebeen working hard to have pesticide usereduced or banned in places where it isunnecessary,” says Tanya Murphy, a boardmember of Healthy Child, Healthy World,an advocacy organization. “Now we’regoing from the frying pan and into the firewhen replacing grass with synthetic turf.”

The debate leaves many on the fence.Orlando Gil, an assistant research scientistat New York University and soccer coach,is weighing both alternatives: “We wantchildren to play outside, exercise, and playsports, but with pesticides and fertilizers ingrass and chemicals in artificial turf, I don’tknow which to choose.”

Indeed, a dearth of research on thenonoccupational human health effects ofexposure to the constituents of syntheticturf hampers the ability to make thatchoice with any degree of confidence. Onthe basis of limited toxicity data, somereports have concluded the health risks areminimal. Most agree, however, that farmore research is needed before the ques-tion can be definitively answered. In the13 December 2007 issue of Rachel ’ sDemocracy and Health News, WilliamCrain of the City College of New YorkPsychology Department and JunfengZhang of the University of Medicine &Dentistry of New Jersey School of PublicHealth called conclusions of minimal risk“premature.”

A Turf HistoryDuring the 1950s, the Ford Foundationstudied ways to incorporate physical fit-ness into the lives of young people, partic-ularly in cities where outdoor play areaswere scarce. Ford joined MonsantoIndustries to create an artificial surface onwhich children could play sports. In 1964the first artificial playing surface was mar-keted under the name Chemgrass.

Meanwhile, the first domed stadiumwas being built in Houston, Texas. TheAstrodome, with its retractable translucentplastic ceiling, let in enough sunshine tomaintain a natural grass field. But after thefirst baseball season, it was clear there was aproblem. The plastic panes produced aglare that made it difficult for players to seethe ball. This problem was solved by paint-ing the panes black—but then the grassbegan to die from lack of sunlight. By thebeginning of the second season, the Astroswere playing on dead grass and painteddirt. At this time, production of Chemgrasswas limited, but what little was availablewas installed in the Astrodome. By the endof the 1966 season, the material had been

renamed AstroTurf. The green nylon car-pet was a success.

The popularity of AstroTurf grewsteadily during the 1970s and 1980s, withmost of its use in professional sports arenas.However, a backlash began to unfold whenplayers started to complain about the sur-facing. The English Football Associationbanned synthetic turf in 1988, mainlybecause of complaints from athletes that itwas harder than grass and caused moreinjuries. Similar concerns were growing inthe United States. A poll conducted by theNational Football League Players Associa-tion in 1995 showed that more than 93%of players believed playing on artificial sur-faces increased their chances of injury. Thissentiment was famously expressed by base-ball player Dick Allen: “If a horse won’t eatit, I don’t want to play on it.”

The movement against AstroTurfgained traction, and many ballparks wereconverted to natural grass during the 1990s.One example was Giants Stadium in NewJersey, which had used AstroTurf since itsconstruction in 1976. The stadium wasrefitted with a system of 6,000 removabletrays of natural grass. Even the new stadiumin Houston, built to replace the originalAstrodome, was surfaced with grass.

In this story of grass, the balance is tilt-ing once more against the natural kind.Natural grass, under some circumstances,cannot consistently withstand the demandsof sports where a lot of running is involved.Parallel to this back-and-forth controversyover which is best have come new develop-ments in the manufacture of synthetic turf.Several companies, including the makers ofthe original AstroTurf, have come on themarket with new playing surfaces.

FieldTurf, for example, is made of ablended polyethylene–polypropylene mate-rial woven to simulate blades of grass. The“grass” is held upright and given somecushioning by adding a layer of infill madeof recycled tires, rubber particles 3 mm indiameter or smaller. This crumb rubberinfill is sometimes mixed with silica sand.Many stadiums that switched to grass fromAstroTurf have since switched back toFieldTurf-style synthetic turf.

F igures f rom the Synthet ic TurfCouncil, a trade organization based inAtlanta, show that 10 years ago there were7 new-generation fields installed in theUnited States. Today there are 3,500. SaysGeoffrey Croft, president of the nonprofitNew York City Parks Advocates, whichpromotes public funding and increasedpark services, “There are millions of squarefeet of synthetic turf already installed onfields around the country, and not one

environmental impact statement has beenissued.”

Human Health QuestionsGiven the relatively recent development ofnew-generation synthetic turf, there areunanswered questions regarding its poten-tial effects on health and the environment,with the rubber infill one of the mainsources of concern. The crumbs becomeairborne and can be breathed in andtracked into homes on clothes and athleticgear. There are also questions about der-mal and ingestional exposures, and aboutecosystem effects.

For athletes, the little black rubber pel-lets may seem little more than a nuisance.Others express more concern, especiallywhen it comes to children’s exposure tothe infill. Patti Wood, executive director ofthe nonprofit Grassroots EnvironmentalEducation, argues, “This crumb rubber is amaterial that cannot be legally disposed ofin landfills or ocean-dumped because of itstoxicity. Why on earth should we let ourchildren play on it?”

Recycled crumb rubber contains anumber of chemicals that are known orsuspected to cause health effects. The mostcommon types of synthetic rubber used intires are composed of ethylene–propyleneand styrene–butadiene combined with vul-canizing agents, fillers, plasticizers, andantioxidants in different quantities, depend-ing on the manufacturer. Tire rubber alsocontains polyaromatic hydrocarbons(PAHs), phthalates, and volatile organiccompounds (VOCs).

According to the Rubber Manu-facturers Association, only 8 states have norestrictions on placing tires in landfills.Most of these restrictions have to do withpreventing pest problems and tire fires,which release toxicants such as arsenic,cadmium, lead, nickel, PAHs, and VOCs.

Some studies suggest that the samechemicals that can be released profuselyduring a tire fire may also be released slow-ly during deterioration of crumb rubber.For instance, researchers at the NorwegianInstitute of Public Health presented areport at the 2006 meeting of the Inter-national Association for Sports SurfaceSciences on turf-related chemicals in indoorstadiums. The report, Artificial TurfPitches: An Assessment of the Health Risksfor Football Players, showed that VOCsfrom rubber infill can be aerosolized intorespirable form during sports play. Theauthors calculated health risk assuming theuse of recycled rubber granulate, whichreleases the lowest amounts of these chemi-cals of any type of rubber infill.

Focus | Synthetic Turf

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Focus | Synthetic Turf

The report concluded that, given cur-rent knowledge, the use of synthetic turfindoors does not cause any elevated healthrisk, even in vulnerable populations such aschildren. However, the report continues, “Itshould also be noted that little or no toxico-logical information is available for many ofthe volatile organic compounds which havebeen demonstrated as being present in theair in the [indoor stadiums]. . . . [Further-more], not all organic compounds in the[stadium] air have been identified.” In par-ticular the report called for more informa-tion regarding the development of asthmaand airway allergies in response to exposureto the latex in many tires.

Similarly, the California Office ofEnvironmental Health Hazard Assessment(OEHHA), in the January 2007 reportEvaluation of Health Effects of Recycled WasteTires in Playground and Track Products, con-cluded that 49 chemicals could be releasedfrom tire crumbs. Based on an experimentsimulating gastric digestion, the OEHHAcalculated a cancer risk of 1.2 in 10 millionassuming a one-time ingestion over a life-time—well below the 1 in 1 million di min-imis risk threshold. In a hand-wipe experi-ment, the OEHHA calculated an increasedcancer risk of 2.9 in 1 million for ingestionof chrysene (a suspected human carcinogenfound in tire rubber) via hand-to-mouthcontact with crumb rubber infill. This esti-mate assumed regular playground use for thefirst 12 years of life and was termed by theauthors to be “slightly higher” than the diminimis level.

In the summer of 2007, Environmentand Human Health, Inc. (EHHI), a non-profit organization headquartered in NorthHaven, Connecticut, commissioned a studyfrom the Connecticut Agricultural Experi-ment Station to determine whether toxiccompounds from crumb rubber could bereleased into air or water. The reportArtificial Turf describes identifying 25 chem-ical species with 72–99% certainty usingmass spectrometry–gas chromatography.Among those definitively confirmed werethe irritants benzothiazole and n-hexade-cane; butylated hydroxyanisole, a carcinogenand suspected endocrine disruptor; and4-(t -octyl) phenol, a corrosive that can beinjurious to mucous membranes.

The Synthetic Turf Council said in astatement issued on 13 December 2007 that“Claims of toxicity [in the EHHI report] arebased on extreme laboratory testing such asthe use of solvents and high temperatures togenerate pollutants.” But the EHHI standsby its studies. Artifical Turf author DavidBrown, EHHI’s director of public healthtoxicology, says, “It is clear the recycled

Environmental Health Perspectives • VOLUME 116 | NUMBER 3 | March 2008 A 119

Weighing costs and benefits. High-impact sports take a toll on natural grass fields(above), but concerns about the unknown health effects of crumb rubber infill (seenbelow spraying upon impact) and other environmental health concerns keep somestakeholders from wholeheartedly buying in to the benefits of synthetic turf.

rubber crumbs are not inert, nor is a hightemperature or severe solvent extractionneeded to release metals, volatile, or semi-volatile organic compounds.” Brown assertsthat the laboratory tests approximate condi-tions that can be found on the field, and thatno solvent besides water was used.

According to Brown, the basic barrier toaccurately assessing the safety of recycled tirerubber is the high variability in tire construc-tion and the lack of chemical characteriza-tion of the crumb rubber. “Very few sampleshave been tested,” he says. “There is nostudy with sufficient sample sizes to deter-mine the potential hazard.” He adds, “Sincenew tires contain vastly different amounts ofthe toxic materials, based on the intendeduse, it is impossible to ensure players or gar-deners and others that their personal expo-sure is within safe limits.”

Another debated health issue is that ofinjuries. Several studies published in a sup-plement to the August 2007 issue of theBritish Journal of Sports Medicine reportedno differences in the incidence, severity,nature, or cause of injuries in soccer teamswho played on grass versus new-generationsynthetic turf. However, injuries maydepend on the type of sport being played. Afive-year prospective study of footballinjuries among high school teams published1 October 2004 in The American Journal ofSports Medicine showed that there wereabout 10% more injuries when games wereplayed on synthetic turf than when playedon grass surfaces. Conversely, the risk ofserious head and knee injuries was greateron grass fields.

Injuries lead to another concern: infec-tion with methicillin-resistant Staphylococcusaureus (MRSA), which is thought to spreadespecially easily among athletes because ofrepeated skin-to-skin contact, frequency ofcuts and abrasions, and sharing of lockerroom space and equipment. A study con-ducted by the Centers for Disease Controland Prevention and published in the3 February 2005 issue of the New EnglandJournal of Medicine showed that, althoughsynthetic turf itself did not appear to harborMRSA, the greater number of turf burnscaused by the abrasive friction of this type ofsurface increased the probability of MRSAinfection, especially among professional ath-letes playing on hard surfaces.

There is, however, some evidence tosuggest that synthetic turf may harbormore bacteria. For example, an industrystudy sponsored by Sprinturf, a maker ofsynthetic turf, found that infill containinga sand/rubber mixture had 50,000 timeshigher levels of bacteria than infill made ofrubber alone. To address this, the companymarkets synthetic turf that is “sand-free” asa safer alternative and offers sanitation forthose fields already installed.

Proper maintenance of synthetic turfrequires that the fields be sanitized toremove bodily fluids and animal droppings;manufacturers market sanitizing productsfor this purpose. According to SyntheticTurf Sports Fields: A Construction andMaintenance Manual, published in 2006 bythe American Sports Builders Association,some synthetic turf owners disinfect theirfields as often as twice a month, with more

frequent cleanings forsideline areas, wherecontaminants concen-trate.

Different Shades ofGreenCultivated naturalgrass carries plenty ofenvironmental bag-gage. According to“Water Managementon Turfgrass,” a paperon the Texas A&MUniversity Coopera-tive Extension website(http://plantanswers.tamu.edu/), naturalgrass sports fields canrequire up to 1.5 mil-lion gallons of waterper acre per year. Thef r e q u e n t m o w i n grequired for naturalgrass lawns and fields

also results in emissions of hydrocarbonsand carbon monoxide (up to 5% of suchemissions in the United States, according tothe Environmental Protection Agency).

Natural grass does offer tangible bene-fits, however. According to TurfgrassProducers International, these includeincreased pollution control, absorption ofcarbon dioxide, a cooling effect, water fil-tration, and prevention of soil erosion.There are also perhaps intangible benefitsto a field of grass. Crain presents the ideathat replacing grass with synthetic turf canhinder children’s creative play and affecttheir development. “Today’s children large-ly grow up in synthetic, indoor environ-ments,” he says. “Now, with the growingpopularity of synthetic turf fields, theirexperience with nature will be less thanever.”

Adds Croft, “Although there is animportant need for open spaces, the issuehere is not open space but active recreation-al facilities. I don’t see the connectionbetween open space and installing syntheticturf fields.”

Synthetic turf does offer certain advan-tages over natural grass. A New Turf War:Synthetic Turf in New York City Parks, areport released in 2006 by the advocacygroup New Yorkers for Parks, points out,“Proponents of synthetic turf fields tout thereduction of allergy and asthma triggers.The removal of natural pollens and grassesmay be beneficial to children and adultswith these afflictions.”

One of the main arguments used infavor of synthetic turf is that it can be

A 120 VOLUME 116 | NUMBER 3 | March 2008 • Environmental Health Perspectives

Focus | Synthetic Turf

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Moratorium introduced. Cadman Plaza Park in Brooklyn, New York, boasts a picture-perfect blanket of syn-thetic turf. In fall 2007 the New York State Assembly has introduced a moratorium on the sale and installa-tion of synthetic turf containing crumb rubber until the state completes a comprehensive study on itspotential health effects.

Environmental Health Perspectives • VOLUME 116 | NUMBER 3 | March 2008 A 121

installed relatively quickly and, once func-tional, can be used almost continuously. Incontrast, grass fields need time to take rootand must be closed periodically for propermaintenance. For example, the CentralPark Conservancy, a private philanthropythat maintains New York City’s CentralPark, closes grass fields all winter; duringthe summer and spring, fields are closed ona rotating basis for restoration. Also, tacklefootball and cleated shoes are prohibited onall of the fields, and the fields are closedwhenever it rains or they are wet. Accordingto estimates from the New York CityDepartment of Parks & Recreation, syn-thetic fields can be open for use 28% moreof the time in a year than natural grassfields because they can withstand heavy use,which the department estimates has dou-bled in the last eight years.

Lower cost for long-term maintenanceis another argument that is made for syn-thetic turf, although the degree of the sav-ings is disputed. It is generally agreed thatinstallation costs of synthetic turf can bealmost double those of natural grass. Forinstance, a synthetic turf soccer field cancost almost $1.4 million compared with anatural grass field at about $690,000. Butwhen the costs are prorated over the expect-ed lifespan of the field, including mainte-nance, the difference in cost narrows to lessthan $15,000 more for the natural grass,according to A New Turf War.

Although some, like Benepe, considerthis cost savings to be substantial, othersconsider it insignificant. As ChristianDiPalermo, executive director of NewYorkers for Parks, puts it, “The amount ofmoney saved is negligible considering themany unknowns about artificial turf.”

One drawback that both fans and criticsof synthetic turf agree on is that these fieldscan get much hotter than natural grass.Stuart Gaffin, an associate research scientistat the Center for Climate Systems Researchat Columbia University, initially becameinvolved with the temperature issues of syn-thetic turf fields while conducting studiesfor another project on the cooling benefitsof urban trees and parks. Using thermalsatellite images and geographic informationsystems, Gaffin noticed that a number ofthe hottest spots in the city turned out to besynthetic turf fields.

Direct temperature measurements con-ducted during site visits showed that syn-thetic turf fields can get up to 60° hotterthan grass, with surface temperatures reach-ing 160°F on summer days. For example,on 6 July 2007, a day in which the atmos-pheric temperature was 78°F in the earlyafternoon, the temperature on a grass field

that was receiving direct sunlight was 85°Fwhile an adjacent synthetic turf field hadheated to 140°F. “Exposures of ten min-utes or longer to surface temperaturesabove 122°F can cause skin injuries, so thisis a real concern,” said Joel Forman, med-ical director of the Pediatric Environ-mental Health Specialty Unit at MountSinai School of Medicine, speaking ata 6 December 2007 symposium on the issue.

Many physical properties of syntheticturf—including its dark pigments, low-den-sity mass, and lack of ability to vaporizewater and cool the surrounding air—makeit particularly efficient at increasing its tem-perature when exposed to the sun. This isnot only a hazard for users, but also cancontribute to the “heat island effect,” inwhich cities become hotter than surround-ing areas because of heat absorbed by darkman-made surfaces such as roofs andasphalt. From many site visits to both blackroofs and synthetic turf fields, Gaffin hasconcluded that the fields rival black roofs intheir elevated surface temperatures.

Although it is often argued that one ofthe advantages of synthetic turf is that it

does not need irrigation, some installationsmust be watered to control the excessiveheat. Benepe stated in public hearings thatwater misters may have to be installed insome fields to help remedy the heat prob-lem. According to Gaffin, synthetic turf is soefficient at absorbing sunlight, that coolingwith water is only temporarily effective.

“After a short while of watering, I expect thetemperature should rebound and the surfacebecome intolerably hot again,” he says.

In addition to heat control, the Inter-national Hockey Federation requires thatcollege teams saturate synthetic turf fieldsbefore each practice and game to increasetraction, according to an article in the19 October 2007 Raleigh (North Carolina)News & Observer. The article, which exam-ined why local universities were wateringtheir synthetic turf fields in the midst ofsevere ongoing drought in the U.S.Southeast, noted that Duke Universityreceived a business exemption to water thefields provided overall campus water con-sumption decreased by 30%.

The EHHI study addressed the ques-tion of whether synthetic turf fields cancontribute to increased water contamina-tion from rain or from spraying or misting.The study found that 25 different chemicalspecies and 4 metals (zinc, selenium, lead,and cadmium) could be released into waterfrom rubber infill. Moreover, because syn-thetic turf is unable to absorb or filter rain-water, chemicals filter directly into storm

drains and into the municipal sewer systemwithout the beneficial filtration that livevegetation provides. Benepe and othersagree this can be an issue that New YorkCity would need to address, as water runofffrom synthetic turf fields could overwhelmstorm drains, thus contributing to the esti-mated 27 billion gallons of raw sewage and

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Thermal effect. An image taken 14 August 2002 by NASA’s Landsat satellite(left) shows surface temperatures in upper Manhattan (red indicates warm tem-peratures, and blue indicates cool temperatures). A large synthetic turf field cre-ated high temperatures similar to those on a large black roof (see Google Earthimage, right). Cool spots almost always correspond to urban vegetation, such asparks, street trees, and water bodies.

stormwater that discharge from 460 com-bined sewer overflows into New YorkHarbor each year.

Finally, what happens to synthetic turffields when they are no longer usable?Industry estimates that synthetic turf fieldshave a lifespan of 10 to 12 years, where-upon the material must be disposed ofappropriately. Rick Doyle, president of theSynthetic Turf Council, says the infill couldbe cleaned and reused; put to another pur-pose, such as for rubber asphalt; incinerat-ed; used in place of soil to separate landfilllayers; or otherwise recycled. Typically,however, it is landfilled.

AlternativesOne of the benefits of synthetic turf is thatit can serve as a way to reuse old tires, a realproblem given the 1 billion–plus tires thatare sold every year. Doyle says the syntheticturf industry currently recycles one-twelfthof the 300 million auto tires that are with-drawn from use each year. The average soc-cer field can contain crumb rubber madefrom 27,000 tires at a density of about 4 to15 pounds of infill per square foot.

Europe has launched an aggressive tirerecovery campaign in which tires that meetquality criteria can be retreaded and reused.

End-of-life tires that cannot be reused arerecycled for other uses including someindustrial energy-generating applications,the production of rubberized pavement, andrecycling into materials for the car industry(in addition to some use in producing syn-thetic turf). In western Europe, recoveryrates of used tires have increased from 65%in 2001 to almost 90% in 2005.

Whereas end-of-life tires add tons ofwaste a year for disposal in many areas, inEurope they are turning into a potentiallylucrative secondary raw material. “There areincreasingly numerous applications,” saysSerge Palard, head of the end-of-life tirerecovery department at Michelin, one of thelargest tire manufacturers in the world. “Insome countries where we did not know whatto do with end-of-life tires a few years ago,now we do not have enough to meet thedemand of all the reprocessors.”

In accordance with the EuropeanUnion’s recently implemented REACH(Registration, Evaluation, Authorisation andRestriction of Chemicals) regulations, whichwill require more testing of industrial chemi-cals, companies such as Michelin are work-ing to reduce the use of harmful chemicalsin tires in order to facilitate recycling intoother products.

European companies are also findinginnovative ways to address concerns regard-ing recycled tire infill in synthetic turf. InItaly, for example, there is an effort to mar-ket synthetic turf fields that feature infillmade of a new thermoplastic material that isthought to be nontoxic. Mondo, a manufac-turer of floor surfaces, produces Ecofill, apatented polyolefin-based granule used insynthetic turf. According to the company,this material disperses heat more efficiently;is highly shock absorbent; does not containpolyvinyl chloride, chlorine, plasticizers,heavy metals, or other harmful chemicals;and is 100% recyclable.

Another alternative is infill made fromplant-derived materials. Synthetic turf man-ufacturer Limonta Sport produces Geo SafePlay, an infill made from coconut husks andcork. Company spokesperson DomenicCarapella says, “There are certainly alterna-tives to crumb rubber. There is no longer areason to sacrifice the playing quality andmore importantly the health of children[playing on synthetic turf].”

Why can’t the alternative to bad grassfields simply be well-maintained grass fields,asks Croft. Certain varieties of turf grasseshave been bred for resistance to stress, abilityto withstand trampling and low water condi-tions, and other characteristics that makethem appropriate for athletic field use.

But according to Doyle, increasedmaintenance is not the answer. “Moremaintenance cannot overcome overusage ofa natural grass sports field,” he says. “Andoverusage of a natural grass sports field orusage during a rainstorm or in months ofdormancy will produce an unsafe playingsurface.” Adds Benepe, “Even the wealthi-est professional sports teams and IvyLeague universities have concluded thatgrass fields are a losing proposition forintense-use sports such as football or soc-cer. . . .There is also the reality that naturalturf fields used for high-intensity sportsmust be replaced every few years, unlessyou severely restrict use.”

For now, New York State Assembly-members Steve Englebright, WilliamColton, and David Koon have proposed leg-islation to impose a six-month moratoriumon the installation of synthetic turf until thestate health and conservation departmentshave better studied the pros and cons of nat-ural and synthetic grass. Said Englebright ina 5 November 2007 statement, “Before wetake risks with our children’s health anddrinking water quality, we need to makesure that the uncertainties . . . are fullyinvestigated.”

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Growing demand. Expanding markets for the reuse of scrap tires have enabled thestate of Ohio (home to this recycling site) to reduce its stockpiles faster than anticipated.In Europe, some countries are having trouble meeting the demand for end-of-life tiresto recycle.