Occurrence of Bromine, Lead, and Zinc in Synthetic Turf Components
Philip Dickey, Staff Scientist, Washington Toxics Coalition
Summary
As part of San Francisco Department of the Environment’s (SFE’s) evaluation of
synthetic turf products, we used a handheld X-ray Flourescence Analyzer (XRF) to
screen representative samples of turf, backing, infill, and shock pads for bromine that
might indicate the presence of brominated flame retardants. Because most of the sample
materials tested are heterogeneous in nature, the results described here should be
interpreted as a qualitative screening rather than accurate quantitative measurements of
the concentrations of chemical elements in the materials under test. Experimental errors
quoted are statistical only and do not take account of lack of homogeneity in the samples.
The testing did not indicate the presence of bromine in any samples of the turf yarn or
backing material itself, but bromine was detected in some of the infill and shock pad
samples. The highest level of bromine measured was 4340 ppm (0.4%). The XRF
analyzer simultaneously tests for up to 25 different elements. A few samples had rather
high levels of lead, ranging up to 1990 ppm. Most of the infill samples contained
significant amounts of zinc, usually in the 4-10% range.
These tests show that brominated flame retardants are not present in the brands of turf
and backing tested. The bromine that was detected in infill material was at rather low
concentrations, in the hundreds of parts per million. The highest levels of bromine (10004340 ppm) were found in the shock pad for the ARMS ProPlay turf system. According to
the manufacturer, the pad “does contain less than 1% of a flame retardant.”1 The amount
of bromine found in the samples is lower than we have seen in some electronic
equipment and foam cushions.
Methodology
Turf samples were obtained from selected manufacturers by SFE and shipped to
Washington Toxics Coalition, where they were catalogued. Most of the products arrived
with the turf/backing component and the infill material separately packaged. The
SprinTurf samples, however, were composite samples in which the turf was already
mixed with the crumb rubber and contained in a plastic box. The ARMS and Motz
products had a separate shock pad. Because of the diversity of materials, we did not
attempt to completely separate all components for testing. For this reason, some of the
test results may include contributions from more than one component of the turf system
Turf/backing samples were X-rayed from each side so that one test would pick up
primarly the yarn, while the other would pick up primarily the backing. Figure 1 shows a
typical turf/backing sample being tested from the turf side. Each of these test results
contains a small but unknown contribution from the material on the other side. Given the
screening nature of these tests, this was not considered a problem and no attempt was
made to separate the yarn and backing to obtain a pure test of each component.
2
Figure 1. A turf/backing sample undergoing testing
Crumb rubber samples were poured into a glass bowl and X-rayed from the top into a
thickness of 1 to 1-1/4 inches of rubber, as shown in Figure 2. The ARMS shock pad
appears to be made of an aggregate of several materials, with chunks of various sizes and
colors. It also has a thin backing. This material was sampled at three different places on
the aggregate side and two places on the backing side. The Motz shock pad appeared
uniform in color and texture and so was sampled only from one side.
Figure 2. Infill sample test
Figure 3. Mixed turf/infill sample
The SprinTurf samples contained the infill already mixed with the turf, and we did not
attempt to separate the two components. The X-ray gun was aimed into the mixture from
3
the top, as shown in Figure 3 and several samples of each were taken to include areas
with more or less infill present. We were not able to test the backing on these products.
Table 1. Description of Synthetic Turf Samples Tested
Manufacturer
Forever Green
Forever Green
Forever Green
Product
Component
SmartGrass 5020 XPS
turf/backing
SmartGrass 4020 L
turf/backing
10-30 mesh crumb rubber infill
Testing Performed
X-rayed from each side
X-rayed from each side
X-rayed 1-1/4” thickness
SprinTurf
Ultrablade*
turf/backing/infill X-rayed composite
SprinTurf
Ultrablade M*
turf/backing/infill X-rayed composite
SprinTurf
Ultrablade DF*
turf/backing/infill X-rayed composite
*all samples have infill already poured over the top of grass
ARMS
ARMS
ARMS
ProPlay Field
ProPlay Field
EnviroFill
turf/backing
X-rayed from each side
shock pad/backingX-rayed from each side
infill
X-rayed 1” thickness
Motz
Motz
Motz
Motz
24/7 PE
24/7 PE/Nylon
24/7 shock pad
8-25 mesh crumb rubber
turf/backing
turf/backing
shock pad
infill
X-rayed from each side
X-rayed from each side
X-rayed from one side
X-rayed 1” thickness
The XRF Analyzer
The XRF Analyzer uses a technology known as X-ray fluorescence (XRF) spectrometry
to detect certain chemical elements. The XRF analyzer has three major components: an
X-ray tube, a spectrometer, and a data collection/processing unit. To test a sample, the
front end of the analyzer is placed against the object to be tested and held there for the
duration of the test, which typically runs from one to two minutes. Longer tests give
better statistical accuracy. The XRF Analyzer is manufactured by Innov-X Systems, Inc.,
located in Woburn, Massachusetts. Their website contains more information about the
analyzer and the company, at www.innov-xsys.com. The Washington Toxics Coalition
has been using this equipment to examine electronics, furniture, and clothing for the
presence of bromine and lead.
The X-ray tube inside the gun emits 10-40 kev X-ray photons that exit through a small
winow on the gun and strike the sample being analyzed. These photons dislodge electrons
from the innermost orbitals of some atoms in the sample, making the atoms unstable. As
electrons move from outer orbitals to the vacant space closer to the nucleus of the atom,
they emit energy in a secondary X-ray photon through a process known as fluorescence.
The analyzer measures the amount of energy in these X-rays. Typically, two main peaks
are visible in the spectra for each element. The analyzer quantifies the energy and uses a
lookup table to associate the energy of the emitted X-rays with particular elements. The
energy of the emitted X -rays identifies the material, and the intensity of the emitted X rays quantifies the amount of each element in the sample.
4
The XRF was operated in RoHS/WEEE2 mode, which is optimized for analyzing lead,
cadmium, bromine, and other elements commonly found in electronic equipment. The
sensitivity of the instrument varies, with the highest sensitivity for elements in the middle
of the periodic table. It cannot detect elements lighter than phosphorus or heavier than
americium. Detection limits for the device are a function of testing time, sample matrix,
and the presence of interfering elements. Because of known interferences between
particular X -ray lines of elements in the data library, the XRF analysis software is
programmed to select for identification and quantification only those x-ray lines with the
least possibility of interference. Penetration of the X -ray beam is dependent on the
sample matrix and the X-ray energy. For low-density materials such as polyethylene, a
thickness of 6 mm (~1/4”) will attenuate 90% of 20 kev X-rays.3
Calibration and QA/QC
The XRF analyzer performs energy calibration checks on startup, and the software does
not permit the analyzer to be used until the standardization is complete. Instrument
amplitude calibrations were performed on standard samples of plastic with known
concentrations of cadmium, arsenic, and lead. The table below shows measured results of
QA tests versus known composition of the calibration standard.
Material
Cadmium
Arsenic
Lead
Composition Average of 10 tests
140.8 ppm
121.3 ppm
30.9 ppm
28.9 ppm
107.6 ppm
118.1 ppm
Deviation
-13.9%
-6.5%
+9.8%
Sampling
The turf component samples were placed against a wooden backing, and the exit window
of the XRF gun was placed in contact with the sample surface but not pressed hard
against it. (For the turf samples, the grass yarn was gently flattened to maximize contact
area with the blades.) In general, the samples were thick enough that it is unlikely that
much of the x-ray beam penetrated all the way through to the wooden backing, and the
spectrum recorded for the wooden backing alone showed no peaks at the energies of the
elements of interest. Each data run lasted 60 seconds. Several duplicates were run to
check for consistency. The XRF analyzer records the X-ray spectra and identifies
elements according to an internal lookup table. The spectra and analyses were exported
from the XRF to a computer. All peaks in the spectra associated with elements of interest
were examined visually to determine whether background or interference peaks from
other elements might be confounding the analysis.
Results
The following elements were not found in any turf samples and are not shown in the data
tables that follow: chlorine <1-1.5%, molybdenum <22-30 ppm, cadmium <50-65 ppm,
gold <4-27 ppm, and bismuth <4-18 ppm. The lack of detected chlorine indicates that no
measurable PVC vinyl is contained in any of the materials.
Although bromine was the main focus of this investigation, several other elements of
5
concern were apparently found in some samples at quite high concentrations. These
included arsenic, mercury, lead, and zinc. However, on examining the spectra closely, we
consider it likely that the arsenic and mercury results were artifacts. Elements of no
concern that were found in the percent range included calcium and iron. Table 2 shows
measured concentrations of bromine, lead, and zinc. Zinc is included here as well because
it is a known constituent of rubber used in automobile tires. Zinc toxicity to humans is
low, but it is more toxic to aquatic life, which could be a concern if it leaches in sufficient
amounts from athletic fields. All concentrations have been rounded to a number of
significant figures appropriate to the statistical uncertainties.
Table 2. Bromine, Lead, and Zinc Concentrations in All Samples (Units = ppm)
Product
Area Tested
Wooden board backing front surface
SmartGrass 5020XPS
SmartGrass 5020XPS
SmartGrass 4020L
SmartGrass 4020L
Br
3.9 ±0.6
<LOD
<LOD
<LOD
SmartGrass 4020L
Forever Green
Forever Green
turf side
backing side
turf side
backing
between stitches
backing on stitches
infill
infill
ARMS ProPlay
ARMS ProPlay
ARMS ProPlay
ARMS ProPlay
ARMS ProPlay
ARMS ProPlay
ARMS ProPlay
ARMS ProPlay
ARMS ProPlay
turf side
backing side
pad: aggregate side
pad: aggregate side
pad: aggregate side
pad: backing side
pad: backing side
infill
infill
<LOD
<LOD
1360
4340
1000
994
1412
<LOD
<LOD
Motz 24/7 PE
Motz 24/7 PE
Motz 24/7 PE/nylon
Motz 24/7 PE/nylon
Motz 24/7 PE/nylon
Motz
<LOD
<LOD
<LOD
<LOD
<LOD
Motz
turf side
backing side
turf side
backing side
turf side
pad: side opposite
lettering
infill
SprinTurf Ultrablade
SprinTurf Ultrablade
SprinTurf Ultrablade M
SprinTurf Ultrablade M
Sprinturf Ultrablade DF
Sprinturf Ultrablade DF
mainly turf
mainly infill
mainly turf
mainly infill
turf/infill well mixed
turf/infill well mixed
80
82
213
185
235
110
Note: LOD = limit of detection.
<LOD
<LOD
794 ±11
576 ±8
<LOD
363
±20
±50
±13
±12
±18
Pb
<LOD
Zn
<LOD
<LOD
<LOD
7.7 ±2.2
<LOD
27
28
16.3
6.8
23.5
99.2
±2.2
±2
±3.3
±5
<LOD
<LOD
34.5 ±4
<LOD
26.4 ±3.4
534 ±10
692 ±14
<LOD
<LOD
<LOD
<LOD
1950 ±20
974 ±15
1990 ±25
±7
<LOD
<LOD
±2.4
±2.7
±4
±4
±4
±3
18.1
59
60
<LOD
38
8.6
±6
±7
50
±7
51
±6
67500 ±720
68100 ±730
18
18
9350
19730
28200
8250
7480
<LOD
<LOD
±6
±5
±120
±240
±310
±100
±110
22.6 ±6
40.3 ±6
24
±7
125 ±10
43.3 ±8
59300 ±560
93300±1050
±2.3
±3.3
±3.5
±3
±2
40280
57200
42860
69670
44830
53910
±380
±545
±420
±750
±430
±515
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Figure 4. Sample X-ray Spectra (note that intensity scales are not all the same)
Run #12
Run #17
120
450
Fe
Zn
400
100
X-ray intensity
X-ray intensity
350
80
60
40
300
250
200
150
Br
100
20
50
0
0
0
5
10
15
20
25
30
35
40
0
5
10
15
Energy (kev)
a) Forever Green SmartGrass 5020XPS turf side
25
30
35
40
25
30
35
40
25
30
35
40
b) Forever Green infill material
Run #22
140
20
Energy (kev)
Run #26
100
Br
90
120
80
70
X-ray intensity
X-ray intensity
100
80
Zn
60
60
50
40
30
40
20
20
10
0
0
0
5
10
15
20
25
30
35
40
0
5
10
15
Energy (kev)
c) ARMS ProPlay shock pad, aggregate side
d) ARMS ProPlay infill material
Run #32
Run #39
100
300
Zn
90
250
80
Fe
X-ray intensity
70
X-ray intensity
20
Energy (kev)
60
50
Pb
40
30
20
200
150
100
Fe
50
Br
10
0
0
0
5
10
15
20
25
30
Energy (kev)
e) Motz PE/nylon turf/backing, turf side
35
40
0
5
10
15
20
Energy (kev)
f) SprinTurf Ultrablade DF mixed turf/infill sample
The spectra in Figure 4 show examples of the X-ray line pairs indicating iron (Fe), zinc
(Zn), bromine (Br), and lead (Pb) in selected samples where these elements were
prominent. Identifications were made by the XRF analyzer and confirmed by visual
examination of the spectra. The broad hump towards the center-right in each spectrum is
caused by X-ray photons from the source that scatter off the test sample and back into the
detector. The amount of this scattering that occurs relative to the sharply defined
fluorescence lines depends on the nature of each each sample matrix, e.g. plastic versus
7
metal. For purposes of individual detecting elements, the scattered photons are
considered a background radiation that must be subtracted.
Bromine
Bromine was not found in any of the pure turf/backing samples. It was found in the
hundreds of parts per million level in some infill samples (e.g. Figure 4b) but not
including the ARMS ProPlay, as well as in all of the SprinTurf samples, in which the
infill was not completely separated from the yarn (e.g. Figure 4f). The highest
concentrations of bromine (about 1000 to 4300 ppm) were found in the shock pad of the
ARMS ProPlay system (e.g. Figure 4c). The wide variation in this last material can be
explained by the fact that this shock pad seems to be made of flakes of several different
materials of different colors. According to ARMS, the material is closed celled crosslinked polyethylene (PEX), with the different colors indicating different grades of the
material.1 The samples taken on the aggregate side were targeted at three different colors
of material, with the highest reading coming from a flake of the gray-colored material.
The presence of bromine does not necessarily indicate that a material contains
brominated flame retardants, or polybrominated diphenyl ethers (PBDEs) in particular,
but the absence of bromine does rule it out. Deca-BDE, for example, contains 83.3%
bromine by weight, so if a substance does contain Deca, the concentration of bromine is
nearly the same as that of the compound. Six television set cabinets made of plastic tested
by WTC were found to contain from 13.7 to 15.2% bromine.4 Other objects likely to
contain PBDEs that we have tested with the XRF analyzer include a couch cushion (3.2%
bromine), a modem case (938 ppm bromine), a laptop computer case (7438 ppm), a
padded office chair (1.1%), the foam pad of an infant car seat (2.1%), an infant carrying
basket (3.2%), and a VCR (13.5%).
Lead
Lead was found at 1952 to 1993 ppm in two measurements of the Motz 24/7 PE/nylon
turf/backing sample when X-rayed from the turf side (e.g. Figure 4e). The reading
dropped to 974 ppm when X -rayed from the backing side, indicating that the lead is
probably in the turf rather than the backing. This particular turf has a nylon fiber threaded
through the polyethylene yarn. The Motz PE turf (without the nylon) did not show any
lead.
Lead was also found at 534 and 692 ppm in duplicate tests of the ARMS ProPlay pad
when X -rayed from the backing side (spectrum not shown). When x-rayed from the
aggregate side, lead readings were 34.5, <LOD, and 26.4 ppm. It is important to realize,
however, that because of the heterogenous character of this material, the tests are not true
replicates because the X-ray beam was seeing different parts of the sample in each. This
test does suggest, however, that most of the lead detected is in the backing material rather
than the aggregate itself.
Lead contamination is of particular concern because lead has no useful function in the
body but it harms children’s intelligence at quite low concentrations in the body. Since
1973, the action level of lead in children’s blood (the point at which exposure reduction is
8
recommended) has been lowered from 40 to 10 ug/deciliter, and the argument has been
made that it should be lowered even further to 2 ug/deciliter.5 Toxicologist Steven Gilbert
notes, “Currently, there appears to be no safe level of lead exposure for the developing
child.”6 Lead is listed as a carcinogen and developmental toxicant by the State of
California.
Ideally, lead exposure would be zero, but lead is present in soils at background levels,
usually lower than 50 ppm, although ambient concentrations, especially in urban areas,
can be much higher. A reasonable level of concern can be estimated by comparing to
allowed levels of lead in soil amendments such as compost and to cleanup levels required
for hazardous waste sites. Table 3 summarizes these reference concentrations.
Table 3. Standards and Guidelines for Lead
Source
EPA
EPA
WA
EPA
EPA
Medium/location
Soil/children’s play areas
Soil/rest of yard
Soil/residential cleanup standard
Biosolids (Class A/high quality)
Biosolids (ceiling)
Compost products
Level (ppm)
4007
12007
2508
3009
40 CFR Part 503
8509
15010
From a risk perspective, if the lead is inaccessible the risk is negligible. Therefore the
presence of lead in padding or other layers below the turf may not be a concern for users
of the turf. However, a precautionary principle approach to purchasing would seek to
avoid products containing lead.
Zinc
Zinc was detected at 6.75% and 6.81% in two tests of the Forever Green infill material
(Figure 4b) and at 9.33% in the Motz infill (spectrum not shown). It was also detected at
between 4.03% and 6.97% in the SprinTurf samples (e.g. Figure 4f), which were turf and
infill mixed. Zinc was also detected at lower levels in the ARMS ProPlay shock pad
(Figure 4c). It was not detected in the ARMS infill material (Figure 4d). Note that the
ARMS infill material is coated silica sand rather than rubber. Our non-detects for zinc
and lead in this material are consistent with testing commissioned by the manufacturer
(Pb <1.5 ppm, Zn 0.425 ppm).11
Zinc oxide or zinc stearate are used as activators in rubber used in car tires.12 The
concentrations we measured in infill material are higher than the percentages implied by
Wik and Goran (2-5% zinc oxide + fatty acid or zinc stearate). A typical MSDS for
crumb rubber lists the following zinc components: zinc oxide fume <3% and zinc oxide
total dust <3%.13 It also lists approximately 20% naphthenic/aromatic oil. Another MSDS
cryogenic rubber lists zinc oxide at 1-5%.14
Zinc is a necessary human nutrient that has relatively low toxicity to humans but is more
toxic to aquatic life. A recent study for the Norwegian government used data from
laboratory measurements of zinc leachate from artificial turf fibers and rubber infill to
9
calculate total zinc leached from a hypothetical turf pitch. A measured leachate
concentration of 3290 ppb lead to a prediction of 18.95 grams of zinc leached per year,
assuming a field of 7200 m2 and annual rainfall of 800 mm (31.5 inches).15 The authors
concluded that “the concentration of zinc poses a significant local risk of environmental
effects in surface water which receives runoff from artificial turf pitches.”
Note on XRF versus Laboratory Analysis
XRF technology has the enormous advantages that it is quick and non-destructive.
However, these advantages would be moot if the results were could not be verified by
other methods. There are several reasons why XRF testing might give different results
than another technique, such as acid digestion followed by ICP (inductively coupled
atomic spectroscopy). The major sources of discrepancy between the two techniques
occur if the part of the material being sampled is not the same. Because the X-ray beam
penetration through the test material is limited in both depth and diameter, a comparable
sample prepared for laboratory analysis must be carefully chosen to include the same
portion. If a test material is not homogeneous, there is also the possibility that the X-ray
beam may not srike the same exact percentage of the various components. In the testing
described here, we acknowledge this possibility and caution against reading our results as
a definitive test of the bulk material properties.
A second source of discrepancy has been recently described in measurements of
contaminants in packaging materials. In that work, laboratory measurements yielded as
much as an order of magnitude lower concentrations than those of the XRF.16 In addition
to the factors described above, there is also the possibility that the samples were
incompletely digested in the laboratory analysis. It is important to verify the methods
used to ensure that the spectrometry will “see” all of the substances of concern in the
samples.
Acknowledgement
I would like to thank my colleague Maria Mergel for performing the data collection and
assisting with the analysis. Also, many thanks to Jack Hanson of HMC Analytical
Instrumentation for help with technical questions.
1
Description of the ProPlay™ Shock/Drain Pad included in the compilation of materials
provided to Deborah Fleischer by Mike VanBrocklin, Sales & Marketing Manager,
ARMS Building & Maintenance, Inc. Undated.
2
Restriction on Hazardous Substances (RoHS) and Waste from Electrical and Electronic
Equipment (WEEE), two European directives.
3
J.H. Hubbell and S.M. Selzer. “Tables of X-ray mass attenuation coefficients and massenergy-absorption coefficients.” National Institute of Standards and Technology. NISTIR
5632. 1996. http://physics.nist.gov/PhysRefData/XrayMassCoef/cover.html
4
Erika Schreder. “Results of X-ray testing for toxic chemicals in Washington homes and
offices.” Washington Toxics Coalition. February 2007.
http://www.watoxics.org/files/xrf-analyzer-report
10
5
Steven G. Gilbert and Bernard Weiss, “A Rationale for Lowering the Blood Lead
Action Level from 10 to 2 ug/dL,” NeuroToxicology 27 (June 29, 2006): 693-701.
6
Steven G. Gilbert, A Small Dose of Toxicology (Boca Raton, Fla.: CRC Press, 2004),
92.
7
ATSDR. Lead toxicity: What are U.S. standards for lead levels?
http://www.atsdr.cdc.gov/csem/lead/pb_standards2.html
8
Washington State Department of Ecology. Chapter 173-340 WAC, Model Toxics
Control Act—Cleanup—Code Reviser Version.
http://www.ecy.wa.gov/biblio/wac173340.html
9
USEPA. 40CFR Part 503.
10
King County Natural Resources and Parks. Biosolids Compost Quality.
http://dnr.metrokc.gov/wtd/biosolids/grocoquality.htm
11
Analytical Industrial Research Laboratories. Test results for Envirofill-W coated sand.
August 2006.
12
Anna Wik and Dave Goran. “Environmental labeling of car tires—toxicity to Daphnia
magna can be used as a screening tool.” Chemosphere 58: 645-651, 2005; Erik Smolders
and Fien Degryse. “Fate and effect of zinc from tire debris in soil.” Environ Sci Technol
36: 3706-3710, 2002.
13
Texas Tire Recycling Inc. Material Safety Data Sheet for crumb rubber. Undated.
14
Recovery Technologies (Canada) Inc. Material Safety Data Sheet for styrene-butadiene
rubber. January 22, 2002.
15
Torsten Kallqvist. “Environmental risk assessment of artificial turf systems.”
Norwegian Institute for Water Research. 2005.
http://www.isss.de/conferences/Dresden%202006/Technical/NIVA%20Engelsk.pdf
16
Northeast Recycling Council. “An assessment of heavy metals in packaging: Screening
results using a portable X-ray fluorescence analyzer.” Final Report prepared by The
Toxics in Packaging Clearinghouse. June 20, 2007.