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Analysis of metals leached from smoked
cigarette litter
J W Moerman,
1
G E Potts
2
ABSTRACT
Background Littered cigarette butts represent potential
point sources for environmental contamination. In areas
with substantial amounts of cigarette litter,
environmental hazards may arise as chemical
components are leached from the filters and smoked
tobacco.
Objective The three main aims of this study were: (1) to
quantify the amount of Al, Ba, Cd, Cr, Cu, Fe, Pb, Mn, Ni,
Sr, Ti and Zn leached from cigarette butts, (2) to
determine the relationship between the pH of the
aqueous soaking solution and metal concentration
leached and (3) to determine the relationship between
the period of soaking in aqueous solution and metal
concentration leached.
Methods Smoked cigarette butts and unsmoked
cigarettes were added to phials containing aqueous
solutions of pH 4.00, 5.00 and 6.00 (60.05). The metal
concentration of the resultant leachates was measured
via inductively coupled plasma optical emission
spectroscopy (ICP-OES) 1 day, 7 days and 34 days after
sample addition.
Results All metals were detected in leachates 1 day
after sample addition (with the exception of Cd) and
were released at varying rates. No clear relationship
between pH within the range typical of precipitation and
metal concentration leached was observed.
Conclusions Based on the gradual release of multiple
metals over the full 34-day study period, cigarette litter
was found to be a point source for metal contamination.
The apparent rapid leaching of other metals may
increase the risk of acute harm to local organisms.
Cigarette butts are among the most common forms
of litter. Worldwide, approximately 4.95 trillion
cigarette butts are estimated to be littered each
year.
1
Of the 10 million pieces of litter collected
during the 2009 International Coastal Cleanup
campaign, 21% were cigarette butts and filters,
2
twice as much as any other type of litter. Water
channelled by sewer systems and streams acts to
accumulate cigarette litter in localised areas and
leach its chemical components into the environ-
ment. Although many may argue that a single piece
of cigarette litter would not inflict serious envi-
ronmental damage, the cumulative effect of many
cigarette butts littered in a centralised area may
present a significant threat to local organisms.
Indeed, several studies
3e5
have found cigarette litter
toxic to some aquatic species.
Although the compounds in cigarettes and
mainstream smoke have been extensively
researched, few studies have attempted to identify
and quantify the components leached from
cigarette butts
3 6
or assess the leaching behaviour of
these components. Micevka et al.
3
suggest that the
toxicity of cigarette butt leachates is in part due to
heavy and trace metals. The occurrence of metals in
cigarettes can largely be attributed to the growth
and cultivation of tobacco (Nicotiana tabacum), as
tobacco is known to readily accumulate metals
from underlying soil.
7
The metal composition of
soil primarily reflects the mineral composition of
the bedrock from which it was derived. Fertilisers,
however, may also introduce metals to soil. Case
studies of the use of municipal sludge containing
heavy metals as fertiliser found significant increases
in the concentration of many heavy metals in the
sludge-amended soils and the plants grown in these
soils.
7
The application of pesticides, insecticides and
herbicides also introduce metals to the tobacco
leaf.
8
Further introduction occurs during cigarette
manufacture, particularly via the addition of casing
materials to the cured leaves
910
and the use of
brightening agents on the wrapping paper.
11e13
The response of biota to metal contamination is
highly varied.
14 15
Whereas increased levels of trace
and heavy metals in soils and water adversely affect
some organisms, contamination enhances the
metal tolerance of other species (eg, bioaccumula-
tors). Environmental conditions, such as pH,
further vary biological responses to contamination
by affecting the mobility of metals in soils and the
bioavailability of metals to plants.
14
To better
predict how metals leached from littered cigarette
butts affect local biota, investigation of their
leaching behaviour is required. The main aims of
this study, therefore, were: (1) to determine the
concentration of Al, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb,
Sr, Ti and Zn leached from cigarette butts in
aqueous solution; (2) to assess the relationship
between pH of the leaching solution and metal
concentration leached; and (3) to assess the rela-
tionship between soaking time and metal
concentration leached. The metals listed above
were selected for study based on their presence
in smoked filters,
12 16 17
toxicity to living
organisms,
18
and/or ability to be reliably analysed
by inductively coupled plasma optical emission
spectroscopy (ICP-OES).
METHODS
Sampling
Smoked cigarette butts were collected from
covered cigarette receptacles adjacent to buildings
on the campus of the University of Tennessee-
Chattanooga, USA. Following collection, the filters
were manually separated from the remnant tobacco
on the cigarette butts. These components were
stored separately in disposable plastic containers.
<Additional materials are
published online only. To view
these files please visit the
journal online (http://
tobaccocontrol.bmj.com).
1
School of Earth and
Atmospheric Sciences, Georgia
Institute of Technology, Atlanta,
Georgia, USA
2
Department of Chemistry, The
University of Tennessee at
Chattanooga, Chattanooga,
Tennessee, USA
Correspondence to
Dr Gretchen E Potts,
Department of Chemistry, The
University of Tennessee at
Chattanooga, 615 McCallie
Avenue, #2252, Chattanooga,
TN 37403, USA;
gretchen-potts@utc.edu
Received 19 September 2010
Accepted 25 January 2011
This paper is freely available
online under the BMJ Journals
unlocked scheme, see http://
tobaccocontrol.bmj.com/site/
about/unlocked.xhtml
i30 Tobacco Control 2011;20(Suppl 1):i30ei35. doi:10.1136/tc.2010.040196
Research paper
Cigarette butts were not collected after local precipitation
events to reduce the loss of analyte prior to sampling. Packs of
the three most popular cigarette brands in the USA
19
were also
purchased from convenience stores. The unsmoked cigarettes
were stored in their original packaging and sealed inside
a disposable plastic container to prevent moistening caused by
humidity in the laboratory.
Leaching procedure
Aqueous solutions were prepared by adding dilute analytical
grade sulfuric acid and/or ammonium hydroxide dropwise to
deionised water. The pH of the solutions (6.00, 5.00 and 4.00)
was determined within 60.05 of the desired unit with a Vernier
LabQuest pH probe (Beaverton, OR, USA). Aliquots (100 ml)
were transferred to 125 ml high-density polyethylene (HDPE)
phials. Leachates of smoked cigarette material were prepared by
adding approximately 2.060.2 g filter and 2.060.2 g remnant
tobacco to the phials of aqueous solution. Leachates of
unsmoked cigarette material were prepared by adding 3.660.1 g
of unsmoked cigarettes (approximately four whole cigarettes) to
the phials of aqueous solution. The cigarette material was
allowed to soak in the aqueous solutions for 1 day, 7 days and
34 days. Individual phials designated for each soaking period
were prepared to avoid changes in the volume of the leaching
solution after successive analyses. This procedure is summarised
in figure 1. Method blanks were prepared in the same manner as
the leachate samples except no cigarette material was added.
Filtration and ICP-OES analysis
The leachates were extracted 1 day, 7 days and 34 days after
sample addition using Luer-lockÔsyringes. Nylon filter tips
(0.22 mm) were attached to the syringes to allow direct filtration
into test tubes for analysis. A new filter (conditioned by the
sample leachate) was used for each sample. The concentration of
each metal in the leachates was measured by ICP-OES. The
operating conditions of the JobineYvon Ultima ICP-OES
(Edison, NJ, USA) are given in table S1, and the emission wave-
lengths of each metal are listed in table S2 (see Supplementary
material).
RESULTS
Metals leached from cigarette material
All 12 of the metals selected for analysis were identified in
quantifiable amounts in the leachates after 1 day of soaking with
the exception of cadmium in the smoked cigarette leachates
(tables 1 and 2). Detection limits, based on 2SD of the analytical
blank, ranged between 0.03 mg/litre (Ba) and 8 mg/litre (Al) and
are given in table S2. The concentration of metal leached was
converted to mg
analyte
/g
sample added
to account for variation in
sample mass added. Data that failed a 90% CI t-test were
excluded from the data set, resulting in sample sets of
varying sizes. The average concentration of metal leached varies
from values below limits of detection (Cd, 1-day analysis,
smoked material) to over 75 mg/g (Fe, 34-day analysis, unsmoked
material).
Metal concentration and pH
Within the pH range studied, no identifiable trend emerged
between pH of the aqueous leaching solution and
metal concentration leached from the smoked cigarette material
(figure 2). Analysis of variance (ANOVA) statistical tests were
performed to determine whether the concentration of metal
leached varied significantly with pH. The results of these tests
indicate that in almost all cases, the difference in the metal
concentration leached with pH is due to random error. Based on
this conclusion, the concentration of metal leached for each
soaking period presented in tables 1 and 2 incorporates samples
from each pH group.
Metal concentration and soaking period
Variable relationships between soaking time and metal concen-
tration leached from the smoked cigarette material were
observed (figure 3). The concentration of Ba, Fe, Mn and Sr
leached increased with soaking time, indicating an increase in
metal contamination over time. The concentration of Ni, Pb, Ti
and Zn did not change significantly after 1 day of soaking,
suggesting all leachable Ni, Pb, Ti and Zn was released within
1 day. The concentration of Al, Cd, Cr and Cu leached was
found to decrease at some point during the time study. The
formation of insoluble compounds and complexes is likely
responsible for the observed decrease since solids were removed
from the leachates by filtration prior to analysis.
DISCUSSION
The sampling and leaching procedures used in this study were
designed to simulate natural conditions as closely as possible.
Littered cigarette butts found in the environment encompass
a wide range of cigarette brands with varying amounts of
tobacco left on the filters. In this study, smoked cigarette
material was collected from actively used butt receptacles to
provide a sample population representative of the local cigarette
litter with respect to brand and amount of remnant tobacco.
A disadvantage of this sampling technique is the introduction of
additional variables, as previous work
16 20
demonstrates that
metal concentrations in cigarettes may vary between brands.
The percentage relative standard deviation associated with the
mean concentration of metal leached given in tables 1 and 2,
however, is relatively low for most sample sets, demonstrating
the reproducibility of this method. By collecting smoked
samples from butt receptacles, the use of human subjects was
also made unnecessary.
The leaching procedure employed in this preliminary study
simulates a closed system environment. Although an open
system is likely more representative of natural conditions,
a closed system was considered the most straightforward
method of obtaining the maximum amount of leachable metal.
For the investigation of how pH affects the leaching behaviour
of the metals studied, a pH range of 6.00e4.00 was selected for
the aqueous solutions because it represents the range of pH
typically observed in natural rainwater.
21
Indeed, the pH of
Figure 1 Schematic of leaching procedure for leachates derived from
(A) smoked cigarette material and (B) unsmoked cigarettes.
Tobacco Control 2011;20(Suppl 1):i30ei35. doi:10.1136/tc.2010.040196 i31
Research paper
rainfall in the Chattanooga, Tennessee area in 2009 was
approximately 4.8e5.0.
22
As illustrated in figure 2, the findings of this study suggest
that differences in pH within the range typical of precipitation
have no appreciable effect on the metal concentration leached
from smoked cigarette material. This result implies that changes
to the pH of precipitation within its natural range likely will
not enhance or reduce the magnitude of metal contamination
from cigarette litter. Further investigation, however, is required
to determine the effect of pH values outside the natural range
of precipitation, such as those measured in areas with highly
acidic rain.
Further, this study finds that the metals studied have different
leaching behaviours over time (figure 3). The direct relationship
between soaking period and the concentration of Ba, Fe, Mn and
Sr leached indicates that a piece of cigarette litter is a point source
of Ba, Fe, Mn and Sr contamination for at least a month and
possibly longer. This result suggests that the longer cigarette
litter remains in the environment, the greater the contamination
of these metals will be. This finding supports the need for timely
Table 1 Concentration of metals leached from unsmoked cigarette material measured after specified period of soaking
Unsmoked cigarette material, mg/g
Al Ba Cd Cr Cu Fe Mn Ni Pb Sr Ti Zn
1 day
Mean value 5.94 6.45 0.130 0.326 3.74 13.8 46.4 0.480 1.36 14.1 0.603 11.1
Error* 60.73 60.46 60.02 60.019 60.38 61.8 64.2 60.07 60.10 61.7 60.037 61.1
Minimum value 5.13 5.76 0.105 0.306 3.23 12.0 41.8 0.387 1.24 11.7 0.559 9.9
Maximum value 7.49 7.05 0.166 0.360 4.38 17.9 54.8 0.585 1.54 15.6 0.671 13.1
RSD (%) 12 6.6 19 5.1 9.8 13 8.7 15 7.2 12 5.4 9.6
n 99789999910119
7 days
Mean value 6.94 10.1 0.123 0.372 1.58 30.3 54.0 0.554 1.53 20.2 0.712 11.6
Error* 60.36 60.8 60.010 60.014 60.18 63.4 63.4 60.044 60.06 60.8 60.027 60.6
Minimum value 6.52 8.9 0.114 0.361 1.39 23.3 49.7 0.483 1.46 19.4 0.686 10.3
Maximum value 7.39 10.9 0.140 0.385 1.83 33.4 57.7 0.611 1.61 21.1 0.741 12.3
RSD (%) 4.3 6.9 8.0 2.5 11 11 5.6 7.5 3.0 2.7 2.6 4.8
n 785 1199108 1199 9
34 days
Mean value 6.90 15.3 0.132 0.283 0.67 75.3 59.6 0.404 1.79 32.8 0.729 9.68
Error* 60.3 61.3 60.038 60.105 60.20 65.7 62.9 60.231 60.40 61.5 60.036 60.71
Minimum value 6.59 13.8 0.092 0.197 0.48 69.2 55.8 0.171 1.34 31.8 0.689 8.82
Maximum value 7.27 18.2 0.176 0.429 1.12 84.7 62.2 0.755 2.55 35.2 0.775 10.7
RSD (%) 4.2 8.1 29 37 30 7.0 3.9 57 22 3.5 4.1 6.8
n 8 9 7 10 10 9 10 9 9 9 9 11
*Error represents square root of the sum of the squared relative errors of the mean concentration (1
s
) and mass.
RSD, relative standard deviation.
Table 2 Concentration of metals leached from smoked cigarette material measured after specified period of soaking
Smoked cigarette material, mg/g
Al Ba Cd Cr Cu Fe Mn Ni Pb Sr Ti Zn
1 day
Mean value 7.83 3.81 e* 0.248 3.96 11.7 25.5 0.313 1.12 9.89 0.646 6.56
Errory61.06 60.41 N/A 60.025 60.59 61.3 63.2 60.079 60.12 61.29 60.066 60.69
Minimum value 7.02 3.56 e* 0.240 3.37 10.9 22.9 0.187 1.08 8.90 0.625 6.20
Maximum value 8.89 3.96 e* 0.257 4.55 12.5 28.2 0.431 1.17 11.1 0.665 6.82
RSD (%) 9.2 4.0 N/A 2.0 11 5.0 7.3 23 2.5 8.4 1.8 3.4
n 9 9 N/A 9 9 9 10 10 9 8 9 11
7 days
Mean value 11.0 6.51 0.149 0.302 2.20 15.2 31.5 0.342 1.35 14.1 0.765 6.58
Errory61.3 60.92 60.044 60.045 60.6 62.4 64.4 60.059 60.16 61.6 60.082 60.68
Minimum value 9.55 5.54 0.103 0.271 1.54 12.4 26.7 0.276 1.25 10.9 0.722 6.26
Maximum value 11.7 7.41 0.184 0.363 3.17 17.7 35.4 0.409 1.51 16.8 0.817 6.78
RSD (%) 6.5 10 28 11 26 12 9.8 14 6.9 5.2 4.0 2.5
n 8 9 3 10 11 8 9 8 11 9 11 10
34 days
Mean value 8.92 10.4 0.142 0.236 1.22 45.3 40.1 0.298 1.42 23.4 0.755 5.87
Errory61.92 63.0 60.057 60.109 60.46 69.7 64.4 60.223 60.32 62.5 60.099 60.96
Minimum value 12.1 7.2 0.079 0.128 0.63 30.3 37.7 0.072 1.10 19.3 0.681 5.06
Maximum value 6.52 15.6 0.221 0.460 1.68 59.0 43.5 0.721 2.06 27.3 0.902 6.92
RSD (%) 19 27 39 45 36 19 4.8 74 20 3.5 8.4 13
n 11 9 11 11 10 10 10 9 11 9 10 10
*Below detection limit.
yError represents square root of the sum of the squared relative errors of the mean concentration (1
s
) and mass.
RSD, relative standard deviation.
i32 Tobacco Control 2011;20(Suppl 1):i30ei35. doi:10.1136/tc.2010.040196
Research paper
and continual litter cleanup to reduce the magnitude of metal
contamination from improperly discarded cigarette butts. In
contrast to the metals discussed above, the concentration of Ni,
Pb, Ti and Zn remained relatively unchanged over the 34-day
study period. One explanation for this observation is that all
leachable metal is released from the cigarette butts after a single
day of soaking. For local organisms sensitive to Ni, Pb, Ti and Zn,
a rapid release of these metals may have implications for acute
biological effects. Because leaching occurred in a closed system,
however, these seemingly static concentrations throughout the
study period may be due to dynamic equilibrium between the
cigarette butt samples and aqueous soaking solution; if so,
greater amounts of Ni, Pb, Ti and Zn may be leached by the
continual removal of saturated aliquots of leachate and
replacement with fresh water at a rate that exceeds that of
equilibrium.
With respect to the metal concentrations previously measured
in whole unsmoked American cigarettes,
16 23
more than half of
Pb and Sr, one-quarter of Cu, and one-fifth of Ba, Mn and Zn
originally contained in cigarettes may potentially be leached
into the environment (table 3). When placed in context of the
estimated amount of cigarette butts littered annually (4.95
trillion),
1
the results of this study indicate that between
0.12060.048 kg (Cd) and 38.168.2 kg (Fe) may enter the
environment each year from cigarette litter alone.
Moriwaki et al.
6
is thus far the only study known that has
also investigated metals leached from cigarette butts. Moriwaki
et al.
6
studied four metals in common with this paper: Cd
(0.2460.60 mg/g), Cr (1.860.34 mg/g), Cu (2160.91 mg/g) and Pb
(7.260.70 mg/g). These values are approximately 2e7 times
greater than those measured in this study, which is likely due
the difference in leaching methods employed. In this study, the
metals were allowed to passively diffuse from the cigarette litter.
Moriwaki et al.
6
however, generated leachates by shaking
suspensions of cigarette litter in 1 N HCl solutions for 2 h. The
shaking action is likely responsible for the leaching of greater
concentrations of metal from the cigarette litter.
Figure 2 Concentration of metals
leached in aqueous solutions with
varying pH after 7 days of soaking.
Figure 3 Variable relationships observed between metal concentration
leached from smoked cigarette material and soaking time in aqueous
solution. A. Increase in metal concentration leached over time. Observed
for Ba (shown), Fe, Mn and Sr. B. No significant change in metal
concentration leached over time. Observed for Ni, Pb, Ti and Zn (shown).
C. Decrease in metal concentration measured over time. Observed for Al,
Cd, Cr and Cu (shown).
Table 3 Percentage of metal leached from cigarette butts with respect
to concentration in whole American cigarettes and annual amount of
metal leached from cigarette butts littered worldwide
Metal
Concentration in
whole cigarette, mg/g Percentage leached
Amount leached
worldwide,* kg/year
Al 9506354
16
1.260.5 9.2661.99
Ba 48.7611.2
16
2168 8.7662.52
Cd 0.9960.49
23
1469 0.12060.048
Cr 1.7862.37
16
17623 0.25460.117
Cu 1160.5
23
3666 3.3361.25
Fe 394613
23
1163 38.168.2
Mn 17868
23
2363 33.863.7
Ni 2.7560.31
23
1263 0.28860.215
Pb 2.3960.32
23
59615 1.2060.27
Sr 39.6614.0
16
59622 19.762.1
Ti 106661
16
0.760.4 0.64460.084
Zn 35.360.7
23
1962 5.5460.91
*Calculated using highest mean metal concentration leached and estimated amount of
cigarette butts littered annually.
1
Tobacco Control 2011;20(Suppl 1):i30ei35. doi:10.1136/tc.2010.040196 i33
Research paper
Leachates of unsmoked cigarettes were investigated in this
study to provide background concentrations of the metals of
interest and to identify possible instances of contamination. In
general, the metal concentrations of the leachates prepared
from unsmoked cigarettes were greater than those measured in
the leachates prepared from smoked cigarette butts. This result
is likely due to the loss of metals in smoke or ash during
cigarette combustion, as cigarette smoke and ash are known to
contain metals.
24e26
This trend was observed for all metals
except Al, Cu and Ti. These exceptions to the trend introduce
the possibility of metal contamination prior to sample
collection.
Sand and cigarette ash in the butt receptacles were investi-
gated as potential sources of contamination, since they may
have adhered to the cigarette wrapping prior to sampling. X-ray
diffraction analyses, however, indicate that these materials do
not contain minerals bearing the metals studied. Non-crystalline
compounds were also detected in the cigarette ash, but their
composition could not be identified. Therefore, the adherence of
additional ash to the cigarette wrapping cannot be ruled out as
a potential contamination source. Sunscreen or lip balm trans-
ferred to the cigarette wrapping during smoking is another
possible contamination source, as these products have been
found to contain many of the studied metals, including Al, Cu
and Ti.
27 28
Contamination from these sources, however, is not
necessarily problematic since cigarette ash, sunscreen and lip
balm are often on littered cigarette butts. Another explanation
for the higher concentrations of Al, Cu and Ti in the leachates of
smoked cigarette material is that these metals are in a more
mobile phase in the cigarette filter than in the tobacco. Greater
mobility would likely yield greater concentrations leached.
Further investigation, however, is required to determine the
mobility of metals in filters versus tobacco.
The finding that greater concentrations of metals were in
general leached from unsmoked cigarettes than smoked cigarette
materials implies that cigarette litter with more remnant
tobacco likely causes greater contamination than butts with
little or no remnant tobacco. This result calls into question
a practice of some environmentally conscious smokers, who
scatter remnant tobacco into the environment but keep the filter
until it can be deposited into a waste container.
Conclusions
The results of this research suggest that littered cigarette butts
are point sources for prolonged metal contamination. Further-
more, the apparent rapid release of multiple metals from littered
cigarette butts increases the potential for acute harm to local
organisms. Given the varying responses of organisms to metal
contamination, knowledge of the leaching behaviour of metals
from cigarette butts is necessary to assess the effect littered
cigarette butts have on local biota and the environment in
general. With a better understanding of the toxicity of cigarette
butts
3e5
and how contaminants are leached from them (see
Micevka et al.
3
Moriwaki et al.
6
and this paper), the environ-
mental hazards posed by littered cigarette butts may no longer
be a subject of debate.
Acknowledgements We would like to thank Dr Robert Mebane and Dr Steven
Symes of UTC for their guidance and valuable suggestions.
Funding This research was funded by the University of Tennessee Chattanooga
Department of Chemistry and the University of Chattanooga (UC) Foundation.
Competing interests None.
Contributors Both authors made contributions to this paper to justify authorship.
Provenance and peer review Not commissioned; externally peer reviewed.
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What this paper adds
<The constituents leached from cigarette butts have been
identified and quantified by only a few studies. This paper
investigates the amount and behaviour of selected trace
metals leached from cigarette butts in aqueous solution over
a range of soaking periods and pH.
<All metals were detected in the leachates after 7 days of
soaking. The results indicate that some metals may be rapidly
released into the environment whereas others are leached
more gradually from littered cigarette butts.
<This study also finds that the amount of metal leached from
cigarette butts does not significantly vary with pH within the
range typical of rainfall.
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