Artificial Christmas Trees: How Real Are the Lead Exposure Risks?
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ATVRES
Artificial Christmas Trees: How Real
Are the Lead Exposure Risks?
Richard P. M.ids, I'li.n.
Stcvra C. Patch, Ph.D.
Tamara J. Pandolio
Preschool and Prinnary Scale of Intelligence) as
Abstract Exposure to lead has long been recognized as a major public
health issue in the United States and other industrialized na-
BLLs increased from I to 10 M^dL. This find-
ing strongly suggests that neurological damage
may be caused at even lower BLLs. This latest
tions. The health risks associated with low lead levels mean that consumer products (such
study, which tested 172 children ranging in age
as those made from polyiiuyl chloride |PVC| plastic, which often incorporates lead as from six months to five years and measured
a stahilizer) with even moderate lead exposure risks could he dangerous. The purpose nine confounding lactors, further underscores
the importance of identifying and addressing
of the experiments reported in this article was to test for lead exposure from artificial
even relatively small lead exposure concerns.
Christmas trees made of PVC, which are now present in an estimated 50 million U.S. Several meta-analyses have been done to
households. The first phase of experimentation tested artificial Christmas trees in the further investigate the connection between
lahoratory for lead content in branches, lead transfer from hand contact, and lead dust BLLs and IQ deficits. Some researchers
(Kaufman, 2001; Pocock, Smith, &Baghurst,
levels under the tree. The second phase was based on a field-testing sur\ey of house- 1994) suggest that although there is some
holds with artificial Christmas trees. Results from these experiments show that, while evidence that supports the connection, other
the average artificial Christmas tree does not present a significant exposure risk, in explanations need considering before defini-
tive conclusions can be drawn on the subject.
the worst-case scenarios a suhstantial health risk to young children is quite possible. These researchers fear ihat recent sludies
have not adequately allowed ior confounding
factors and that other shortcomings in the
Introdurtion performance associated with blood lead levels studies may lead to improper conclusions.
L.xposure lo lead has long been recognized as a as low as 2.5 micrograms per deciliter (pg/dL) Other researchers (Needleman & Bellinger,
major public heallh issue in the United States (l^nphear, Dietrich, Auinger, & Cox, 2001). 2001) argue that meta-ana!ysis shows thai
and other industrialized nations. During the Thus, lead-containing products with even mod- lead does indeed have a negative impact on
late 1980s and early 1990s, it was discovered erate potential to cause human exposure are IQ, even when multiple variables have been
that lead would cause permanent and irrevers- becoming recognized as having public health controlled for in different statistical models.
ible neurological damage, especially in infants significance. One particular study found that In addition to intellectual effects, studies
and young children, at far lower exposure lev- even children whose blood lead levels (BLLs) have connected lead exposure with behavior-
els than previously believed (McMichael et al., never exceeded the Centers for Disease Con- al and emotional problems, such as aggressive
1988; Sciarillo, Alexander, & Farrell, 1992). trol and Prevention (CDC) level of concern (10 or anxious behavior, in children (Burns, Ba-
Although recent data show that baseline blood pg/dL) could have decreases in lQ of 2.6 points ghurst. Sawyer, McMichael, &r Tong, 1999).
lead levels have been declining over the last per 10 pg'dL increase in BLLs (Winter, 2001). Lead may also affect the growth of children,
two decades (Mattuck, Beck, Bowers, & Co- In the most recent study of the neurological ef- as was documented in a study that measured
hen, 2001), lead is still a significant threat to fects of low-level lead exposure, Canfield and decreases in height, head circumference, and
health, particularly in children. co-authors (2003) found a 7.4-point IQ deficit chest circumference with increasing lead lev-
A recent study involving multivariate analy- (with a 95 percent confidence interval of 3.2- els (Kafourou et a l , 1997).
sis of 4,853 study subjects ranging in age from 12.9 points, as measured hy the Stanlord-Binct Within the past 10 years, it has become
6 to 16 years found reductions in cognitive Intelligence Scale and the Revised Wechsler recognized that polyvinyl chloride (PVC, or
20 Volume 67 • Ntjmber 5
experiments addressing surface dust deposi-
tion, each tree was disassembled and placed
back into its storage box by a subject, with the
hands wiped before and after disassembly (as
Lead Content of Artificial Christmas Tree Needles
noted above for the assembly procedure) to
determine how much lead was transferred to
ID Type Manufacturer Length of Service (Years) Pb (Mg/g)
the hands during disassembly
CH 01 New The Christmas House 0 *ND All digested uipe satnples were analyzed
CH 02 New Holiday Tree and Trim 0 m lor lead according to Standard Method 3113B
CH 03 Used Puleo 13 1.527 (Clesceri, Greenberg, & Eaton, 1998) for
CH 04 New Christmas Direct 0 ND electrothermal atomic absorption spectrom-
CH 05 New Tree Classics 0 ND etry (EAAS). This method basically involves
CH06 Used American Tree 17 7.IM digesting the wipe in a hot concentrated mix-
CH 07 Used Hudson Valley Tree 6 ND ture of nitric acid and 30 percent hydrogen
CH 08 Used General Form Plastic 7 ND peroxide followed by EAAS analysis. Calcula-
Blank ND tions were then made to express the amount
of lead on the gloved hands in terms of the
*ND: less than 25 |ig/g. total mass (in pg). The lead content in the
plastic needles themselves was calculated as
micrograms of lead per gram of needle (i.e.,
vinyl) plastic products often contain relatively were employed for part of this study Four |.ig/g, or ppm), and the lead in the settled dust
large amounts of lead added as stabilizers. In of these trees were newly purchased, and the beneath the trees was expressed as pg/cm' of
1995, it was discovered that imported vinyl other four had heen in residential use for peri- surface area.
mini-blinds contained so much lead that the ods ranging from 7 to 17 years. The new trees
surface dust produced as a result of direct sun- were sent directly from the manufacturer, and Experiment 2
light and heat was resulting in cases of acute length-of-service documentation for the used In this experiment, research testing kits were
lead poisoning of young children who han- trees was provided by Foundation F.A.R.T.H. mailed to 127 households that had ordered
dled and played with them {Norman, 1996; of St. Louis, Missouri. The manufacturer and the kits from Foundation E.A.R.T.H, The
B.C. Lee of U.S. Consumer Products Safety tree specifications are summarized in Table 1. availability of the research kit was announced
Commission, personal communication to A sample of ihc needles (0.25 grams |gl-0.69 to the public primarily through a Christmas
M.F Toro, July 24, 1996). Studies conducted g) was cut from each tree for subsequent lead season evening news story carried by 73 NBC
in 1997 found that several commonly used analysis. Tree needle samples were ashed for news affiliate stations across the United States.
children's products, such as PVC raincoats, five hours at 400°C before acid/hydrogen Hach testing kit contained instructions, a re-
hook hags, and beach bags accumulated high peroxide digestion. search questionnaire, sample identification la-
levels of lead on surfaces after exposure to F;ach tree was then assembled in the labora- bels, a laboratory' wipe, one plastic headspace
sunlight (DlGangi, 1997; Maas, Smith, Patch, tory by an investigator after a thorough hand- vial, and a pair of laboratory gloves. Individu-
& Thornton, 1997). washing. Before and after assembly, the sub- als were instructed, upon receipt of the kit, to
Artificial Christmas trees made of PVC jects hands were wiped with a laboratory wipe open the plastic vial to have it ready to accept
have become very common in the United to remove all metal/dust material present on tbeir wipe sample. Next, participants put on
States; out of the 76 million family groups in the hands. Each wipe was hot-block-digested the gloves and removed imd unfolded the lab-
the country, an estimated 50 million house- according to National Institute for Occupa- orator>- wipe. A Christmas tree branch section
holds own and use them (Fields & Casper, tional Safety and Healtli (NIOSH) Method approximately 30 cm in length was selected,
2001). Nearly 20 million of the trees in these 7082 (NIOSH, 1994) with concentrated nitric and the wipe was carefully wrapped around
households are nine years or older (U.S. Bu- acid and 30 percent hydrogen penwide, and the branch section. The participants took the
reau of the Census, 2000). Thus, there is a the digestate was analyzed for lead. wipe sample by applying pressure and pulling
potential for lead exposure from the handling Following assembly, a new clean laboratory' the wipe over the entire 30 cm section. After
of the trees during assembly disassembly, and paper surface 120 centimeters (em) x 120 cm the first wipe sample was completed, the wipe
routine usage, as well as from contact with ar- was placed under each tree. Investigators took was folded in half so that any dust was on the
eas underneath the trees. The purpose of this wipe samples weekly for four weeks by wiping inside of the iold. A second pass was made
investigation was lo begin to determine the the entire area with a laboratory wipe. They with the same wipe; it used a second 30-cm
potential lead exposure from typical house- took control samples by wiping an immediately branch section following the same methods.
hold usage of these products. adjacent treeless laborator)' paper surface 120 The wipe was folded a second time and placed
em X 120 em. All viipe samples were digested into the plastic vial, which was then capped. A
as described above with nitric acid and hydro- sample identilication label was affixed to the
gen peroxide. The laboratory where the trees vial, and the kit was mailed back to the authors'
Experiment 1 were erected had windows only along a long laboratory, where the wipes were analyzed lor
Eight 7-foot artificial (PVC) Christmas trees, north-facing wall, so no direct sunlight stmck lead. Digestion and analysis of the wipes were
each from a different major manufacturer, the trees. At the conclusion of the four-week conducted with the same methodology as in
December 2004'lottrniil of Environmental Hoallh 21
BLE2
Lead in Settled Dust Beneath Standing Christmas Trees
ID Manufacturer Week 1 Week 2 Week 3 Week 4 Total
(Mg/IOOcm^) (Mg/IOOcm^) (Mg/IOOcm^) (Mg/IOOcm^) (Mg/lOO cm^)
CH 01 The Christmas House 0.127 0.0980 2.66 0.171 3.06
CH 02 Holiday Tree and Trim 0.0538 0.0258 0.157 0.539 0.775
CH03 Puleo 0.424 1.71 4.98 1.16 8.28
CH 04 Christmas Direct 0.114 0.207 0.107 0.170 0.596
CH 05 Tree Classics 0.298 0.0893 0.157 0.114 0.658
CH06 American Tree 2.43 3.20 5.39 5.94 17.0
CH07 Hudson Valley Tree 0.0807 0.109 0.133 0.IS7 0.479
CH08 General Form Plastic 0.0129 0.475 0.0635 0.151 0.701
Blank 0.0107 0.0151 0.02S8 0.0732 0.125
Experiment I. Calculations were made lo ex- can be made under the assumption that young The mass of lead transferred to subjects'
press [he amount of lead in each wipe in terms children might crawl and otherwise place their bands during assembly and disassembly of
of ihe total mass (in micrograms). hands on the affected under-tree surface (floor. PVC Christmas trees is summarized in Table
Participants also were asked to fill out a re- wrapped presents, etc.) once per week during 3. Again, the results are consistent with the
search questionnaire. The questionnaire was a four-week Christmas tree season and pick up needle lead concentrations shown in Table I,
used to determine the number and ages of perhaps 25 percent of the total dust in the 1.49 with trees CH06 and CH03 showing the high-
children in the household, child involvement n r area, for a total of 630 pg. The U.S. Consum- est handling transfer levels. Sample CH06 re-
in handling of the Christmas tree, length of er Products Safety Commission (CPSC) has sulted in a total lead transfer from assembly
tree ownership, manufacturer of the tree, estimated, based on various bebavioral stud- and disassembly of 30.4 pg, which, spread
counir)' of origin, approximate age of tree, ies, tbat approximately 50 percent of hand-ab- over a four-week Christmas season, translates
and location of tree storage in ihe off-season. sorbed material will be ingested by a child three to a daily exposure of about 1 pg per day and,
The questionnaire also asked what the partic- years of age or younger (U.S. Consumer Prod- spread over an entire year, to about 0.1 (.ig/day
ipant would do with the tree if it was found to uct Safety Commission, 1997), which would Actual ingestion would most likely be only 10
have high lead levels. The choices included entail, in this case, in an approximate acute in- percent of these amounts for an adult and 50
•"discard iree and buy a real tree," "dispose of gestion of 315 ^g. This figure would equate lo percent for a young child. Thus, lead exposure
tree and buy another artificial tree," or "take approximately 0.86 pg/day ingestion spread out from assembly and disassembly would appear
extra care to avoid lead exposure when set- over an entire year. Califomias Proposition 65 to be relatively minor compared witb exposure
ting up and using the tree." requires a warning label if a consumer product to a child playing around and under a tree.
results in an average daily lead exposure of 0.5
Results and Discuvsion jig'day or greater. CPSC does not classify a con- Experiment 2
sumer product as hazardous unless it exposes A total of 127 in-service trees were tested in
Experiment 1 the average user to at least 15 H^day of lead; tbis part of the experiment, and 42 trees, or
Table 1 summarizes the metal concentrations neither regulation specifies a limit for acute 33.1 percent, were observed to have detect-
found in the \ inyl needles themselves. Two of short-term lead exposures. The dust-wipe data able levels of lead in their PVC needles. The
ihe used trees exhibited relatively high levels lor the Puleo brand tree give an annual expo- lower limit for the analytical method was
of lead, with the used American Tree sample sure estimate of about 0.42 ^g/day, just below 1.5 ]xg of lead, Analysis of the questionnaire
having high levels of lead. The levels of lead the Proposition 65 limit, while the remaining data showed that 66.7 percent of the house-
were nondetectable in the other six trees. products produce estimated daily exposures holds with detectable levels of lead had chil-
These results suggest that lead was used more between 0.02 and 0.16 pg'day, It is important dren living in the household. Of this number,
commonly as a PVC stahilizer in die pasl. to note that even the six trees with nondetect- 47.6 percent had children five years of age or
The results of dust wipe samples taken be- able lead content produced dust lead levels 4 younger, while 23.8 percent had children two
neath the laboratory-erected trees are sum- to 24 times background control levels, which years of age or younger in the residence. Many
matized in Table 2, Only used-tree specimens suggests that all of the trees probably contained volunteer participants were not able to deter-
CH03 and CHOb exhibited relatively high lead at least some lead stabilizer. These tests provide mine the tree manufacturer or manulacturer
levels in the settled dust, which is consistent only very rough exposure estimates because location, and thus no conclusions regarding
with the metal-assay results shown in Table 1. only a single tree of each brand was tested, but the relationship between ibe amount of lead in
A scenario oi actual lead exposure for the sam- they do suggest at least some lead exposure po- the tree and the tree's manufacturer or country
ple with the highest lead level, American Tree, tential even from new trees. of origin can be made from the data.
22 \'olume 67 • Number 5
stabilizer used has apparently been reduced
BLE5 to a rnuch larger extent.
The last two columns in Table 4 deal with
Lead on Hands After Assembly and Disassembly of Artificial Christmas Trees possible lead exposure from the artificial
Christtnas trees. Direct mouthing exposure
was calculated on the assumption of once-
Blank (\ig) Wipe Transfer {(jg) Blank {\ig) Wipe Transfer (pg) daily 100 percent transfer of lead from a
30-cm tree branch to a child's tnouth over a
ChOI
of these children lived in a home with an arti- needles. These levels are well in excess of the to have the potential for causing lead exposures
ficial Christmas tree, ihe most exposed I per- less than 400 ng/g that CPSC recommends of considerably greater health significance.
cent ol this populalion (a combination of the children's products contain, and ingestion Data collected from the second phase of the
most dangerous child behavior and the trees calculations indicate that trees of these two authors' research generally confirm that on
with ilie highest lead content) would have a types probably expose young children lo lead average, lead exposure from artificial Christ-
much higher exposure level than estimated for levels at least in the range of California Prop- mas trees is relatively low. A worst-case sce-
ihc typical child; mathematically, ihis percent- osition 65 limits. nario, however, would result in very harmful
age would translate to ahoul 57.500 children. While clearly not an acute loxicity threat by lead exposure. For the safety of all children,
themselves, a significant traction ol older arti- it is probabl)' appropriaic to request that PVC
Conclusions ficial trees are probably exposing children and Christmas tree manufacturers formally com-
rhf experiments conducted in the first phase adults 10 enough lead [o be at least a notewor- mit to banning ihc use of lead in the PVC
of the research do not support the conten- thy public health issue. The experiments de- formations employed in these products. Un-
tion ihiit the PVC Christmas trees currently scribed in this paper indicate that it is probably til they do so, it would be wise to limit ihc
hcing manufactured represent more than a appropriate to caution families—especially amount ofphysical contact thai children have
relatively small lead exposure hazard across families with older PVC Christmas trees, but with artihcial Christmas trees. ' ^
ihe entire population of U.S. children. This even families with new ones—to thoroughly
conclusion is iempcrcd hy fbe fact that only wash hands immediately after tree assembly Corresponding Author: Richard P Maas,
one iree of each major brand was tested. and disassembly, and especially to limit the ac- Co-director, UNC-Asheville Environmental
In contrast, two of the four older used trees cess of children to areas under erected trees. Quality Institute, CPO #2331. One Univer-
ihat were tested contained relatively high lev- Direct mouthing contact, frequent branch han- sity Heights. Asheville, NC 28R04. E-mail:
els of lead (1,527 and 7,184 pg/g) in the PVC dling, or both by young children would appear maas@unca.edu.
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