Migration of aluminum from food contact materials to food—a health risk for consumers? Part II of III: migration of aluminum from drinking bottles and moka pots made of aluminum to beverages

Abstract

Background
Drinking bottles and stove-top moka pots made of aluminum have become very popular. Storing drinks in bottles and preparing coffee in a moka pot may result in the migration of aluminum to the beverage.

Results/Conclusions
In a systematic study of aluminum drinking bottles, it has been shown that drinking a mixture of apple juice and mineral water in an aluminum bottle may reach 86.6% of the total weekly intake (TWI) for adults, and drinking tea from an aluminum bottle may exceed the TWI (145%) for a child weighing 15 kg. In contrast, preparing coffee in an aluminum moka pot results in a maximum of 4% to TWI, if an average of 3.17 L coffee is consumed per week, even if the pots are washed in the dishwasher, against the explicit instructions of the manufacturer.

Full text

Stahl et al. Environ Sci Eur (2017) 29:18
DOI 10.1186/s12302-017-0118-9
RESEARCH
Migration ofaluminum fromfood
contact materials tofood—a health risk
forconsumers? Part II ofIII: migration
ofaluminum fromdrinking bottles andmoka
pots made ofaluminum tobeverages
Thorsten Stahl1*, Sandy Falk2, Alice Rohrbeck2, Sebastian Georgii2, Christin Herzog1, Alexander Wiegand1,
Svenja Hotz3, Bruce Boschek4, Holger Zorn3 and Hubertus Brunn5
Abstract
Background: Drinking bottles and stove-top moka pots made of aluminum have become very popular. Storing
drinks in bottles and preparing coffee in a moka pot may result in the migration of aluminum to the beverage.
Results/Conclusions: In a systematic study of aluminum drinking bottles, it has been shown that drinking a mixture
of apple juice and mineral water in an aluminum bottle may reach 86.6% of the total weekly intake (TWI) for adults,
and drinking tea from an aluminum bottle may exceed the TWI (145%) for a child weighing 15 kg. In contrast, prepar-
ing coffee in an aluminum moka pot results in a maximum of 4% to TWI, if an average of 3.17 L coffee is consumed
per week, even if the pots are washed in the dishwasher, against the explicit instructions of the manufacturer.
Keywords: Aluminum drinking bottles, Aluminum moka pots, Simulants, Coffee preparation, Release limits, Total
weekly intake
© The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License
(http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,
provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license,
and indicate if changes were made.
Background
A list of possible sources of exposure to aluminum can
be found in Part I of this report (Exposure to aluminum,
release of aluminum, Tolerable Weekly Intake (TWI),
toxicological effects of aluminum). Also included there
are the release or migration limit values [3] for aluminum
of 5.00 mg/kg or 5.00 mg/L food or drink, the toler-
able weekly intake (TWI) of 1.00 mg aluminum/kg body
weight and week [4] as well as the toxicological effects of
aluminum. e present Part II deals with the migration of
aluminum from drinking bottles and moka pots to bev-
erages. Drinking bottles were tested with tap water, tea
made from tea bags, soluble tea drink, and a mixture of
apple juice and mineral water. Stove-top moka pots were
tested by preparation of coffee as typically performed
by consumers and rinsing the pots with water after each
use, according to the instructions of the manufacturer.
To replicate a worst-case scenario, the moka pots were
washed in a household dishwasher after every fifth use,
contrary to the recommendation of the manufacturer.
Methods
A detailed description of sample preparation and analysis
can be found in Part I. erefore, only the experimental
details regarding the measurement of aluminum migra-
tion from drinking bottles and moka pots to beverages
will be presented here.
Aluminum drinking bottles
Five models of drinking bottles from different manufac-
turers were tested. ree models were lined with a clear
plastic coating and two were not. ree units of each
Open Access
*Correspondence: thorsten.stahl@lhl.hessen.de
1 Hessian State Laboratory, Am Versuchsfeld 11, 34128 Kassel, Germany
Full list of author information is available at the end of the article
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Page 2 of 7
Stahl et al. Environ Sci Eur (2017) 29:18
model were tested. e following tests were performed
with tap water (pH 7.58) to replicate typical use by con-
sumers. e water was stored at 8°C in a cold room for
1week in a 100-Lpolyethylene (PE) canister with an out-
let tap. e canister was rinsed 3 times with 5L of tap
water before use. is water was used to wash and fill the
drinking bottles as well as for preparation of tea from tea
bags and to dissolve the granulated tea. ree samples of
the tap water were stored in 250-mL PE1 sample bottles
(Heinz Gero Duhme GMBH, Frankfurt, Germany) for
blank value testing. Sample bottles were rinsed three
times with 100mL tap water before filling.
Tap water
e aluminum drinking bottles were first rinsed with
about 200mL tap water and then filled to the top with
tap water from the canister as mentioned above. ey
were allowed to stand for 24h at room temperature. An
aliquot was then removed and transferred to 250-mL
sample bottles and stored at 8°C until subsequent analy-
sis could be performed.
Tea fromtea bags
Tea (fruit tea mixture from Meßmer) was prepared twice
in a 5-L beaker that had been rinsed with tap water, each
time using 3.5L hot (90°C) tap water from the canister
and 14 tea bags (according to the instructions printed on
the package of tea bags: 4 bags per liter water). e tea
(pH 3.65) was allowed to steep for 10min before the bags
were removed. e two batches of tea were then poured
together and shaken in a 10-L PE canister with outlet tap
that had been rinsed three times with 1L tap water for
each rinse. e drinking bottles were then filled to the
closure with 40°C warm tea and the bottles closed with
their lids. After a 24-h contact period, aliquots of the tea
were transferred to 250-mL sample bottles and stored at
8°C for subsequent analysis.
Granulated tea (instant lemon tea drink)2
Two batches of granulated instant lemon tea drink
were prepared in a 5-L beaker that had been previously
rinsed 3 times with 500 mL tap water. For each batch,
one packet (400g) of granulate was dissolved in 4L tap
water at room temperature. e two batches of the bev-
erage (pH 3.33) were then poured together and shaken
for one minute in a 10-L PE canister with outlet tap that
had been rinsed three times with 1L tap water for each
1 In the following, the term “250-mL sample bottles” will be used since all
bottles are made of polyethylene.
2 List of ingredients according to the manufacturer: sugar, glucose, acidi-
fier citric acid, black tea extract cold-water soluble 1.28%, vitamin C, lemon
extract powder (maltodextrin, lemon juice concentrate), aroma.
rinse. e beverage was then allowed to stand for 12h at
room temperature to assure complete dissolution. e
aluminum drinking bottles were filled to the closure with
this solution and closed. After a 24-h contact period, ali-
quots were transferred to 250-mL sample bottles to be
used for analysis.
Apfelsaftschorle (apple juice withmineral water)3
Six 1.5-L bottles of a commercial apple juice and mineral
water drink (pH 3.65) were mixed in a 10-L PE canister
with outlet tap that had been rinsed three times with 1L
tap water for each rinse and shaken for 1min. e alu-
minum drinking bottles were filled to the neck and closed
with their lids. After a contact period of 24 h, aliquots
(250mL) of the apple juice and mineral water mixture
were transferred to 250-mL sample bottles to be used for
subsequent analysis.
Moka pots
Four different brands of stove-top moka pots were tested
by preparing coffee (three repetitions for each pot)
(Fig.1).
e pots from three manufacturers were made of
aluminum and the fourth, for the sake of comparison
of potential aluminum migration, was made of stain-
less steel. Coffee was prepared six times in each pot to
determine the difference between a new pot and one that
has been used a number of times, on the migration of
aluminum.
To emulate the worst-case scenario, the pots were
washed in the dishwasher after the fifth preparation of
coffee.
Before preparing coffee in the pots, the aluminum
content of the coffee itself was determined. To this end,
1.5kg ground coffee (3×0.5kg packets) was placed in
a dry plastic tray that had been rinsed with tap water.
e ground coffee was then stirred to homogeneity with
a plastic spoon that had also been rinsed with tap water
and dried. Care was taken when purchasing the cof-
fee to make certain that all packets had the same batch
number. After stirring, three samples of this coffee were
removed to be used for determination of aluminum con-
tent of the coffee itself. All necessary laboratory equip-
ment was rinsed with tap water before use in order to
remove any residual aluminum contamination. Tap water
was also used for preparation of the coffee. irty liters
of tap water were stored in a PE canister with outlet tap
that had previously been rinsed with tap water. Coffee
was prepared in the aluminum moka pots in exactly the
3 List of ingredients according to the manufacturer: apple juice from apple
juice concentrate, carbonated drinking water, and 60% fruit concentration.
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Stahl et al. Environ Sci Eur (2017) 29:18
same manner as in the stainless steel pots: 12-g portions
of ground coffee were measured out with an accuracy of
two decimal places into the strainer basket of the moka
pot. e 150mL water for brewing was drawn from the
canister mentioned above through the outlet tap, meas-
ured in a graduated cylinder, and poured into the bot-
tom chamber of the coffee maker. Coffee was prepared
a total of six times in a row per moka pot. e brewing
time was 7min for all moka pots heated on an electric
plate with a temperature of 270°C. After brewing was
complete, the coffee was left in the collecting chamber of
the pots for 5min before transfer to 250-mL sample bot-
tles for subsequent analysis. Allowing the coffee to stand
before transfer served to let any particulate coffee to set-
tle in the finished drink. Of the original 150mL, aliquots
of 100mL were poured through a funnel into the sample
bottles. is method assured that no residual coffee par-
ticles would find their way into the samples. e remain-
ing coffee in the collection chambers was disposed of and
the complete moka pots were rinsed three times each by
shaking for 30s. After the 5th brewing cycle, the moka
pots were washed in a standard household dishwasher
for 22min at 50°C (normal wash cycle with standard
household dishwasher detergent tablets). is treatment
is specifically not recommended by the manufacturers
of the pots and serves as a worst-case condition. Before
the pots were reused, they were also rinsed three times
each in tap water by shaking for 30s in order to remove
any residue from the dishwasher detergents and to assure
that the conditions were the same as for the other brew-
ing cycles.
Evaluation of the moka pot experiments was performed
by pairwise comparison of the aluminum concentrations.
On the one hand, samples from the individual coffee
preparations were compared between brands (independ-
ent samples), and on the other hand for each brand
the potential differences in aluminum concentration
(dependent samples) after the individual coffee prepa-
rations were compared. Analysis of possible differences
between the brands was performed using the t test for
independent samples. e t test for dependent samples
was used to analyze the possible differences between the
different coffee preparations from individual brands.
Results
e aluminum concentrations in the control samples
without contact to aluminum-containing equipment
(blank values, arithmetic means of n=6) were as follows:
in tap water 0.7µg/L, in tea from teabags 0.72mg/L, in
tea drink made from granulated product 1.74 mg/L, in
the apple juice and mineral water mix 0.294mg/L, and in
the ground coffee 5.75mg/kg. For the sake of clarity, only
the blank value-corrected data are shown and were also
used for calculations of the aluminum concentration.
Drinking bottles
ree units of each of the bottles from five different
manufacturers were tested. e aluminum insides of the
bottles from brands 1, 2, and 3 were lined (with a clear
plastic coating) and brands 4 and 5 were not lined. e
results of the tests are shown in Fig.2.
It can be seen from Fig. 2 that the unlined bottles
(brands 4 and 5) release more aluminum (0.125 mg/L
tap water in brand 4, 14.8mg/L tea (maximum concen-
tration) prepared from bags in brand 5) into the bever-
ages than the lined bottles, brands 1, 2, and 3 (<LOQ tap
water in brand 2 and 7.8 mg/L tea (maximum concen-
tration) from bags in brand 1). Based on the arithmetic
mean of the results for bottles that were lined and per
beverage, the aluminum uptake and percentage to TWI
were calculated for a child weighing 15kg and an adult
weighing 70kg, assuming a daily portion of 500mL for a
period of 1week (Table1).
Table 1 shows that an adult will not reach 100% of
the TWI with any of the beverages tested in any of the
drinking bottles, regardless of whether they are lined or
unlined (0.17% for water in a lined bottle, 31.1% for tea
made from tea bags in an unlined bottle). A child will
reach from 0.8% (water) to 36.3% (tea) of the TWI drink-
ing from a lined bottle. With unlined bottles, a child will
exceed the TWI, both with tea from tea bags (145%) as
well as with apple juice with mineral water (101%).
Moka pots
Coffee is the favored drink in Germany with 165L cof-
fee being consumed per person and per year, exceeding
the amount of bottled water (140L) per year. e aver-
age German consumes 7.29 kg ground coffee per year
(Deutscher Kaffeeverband “[5]” 2014). Brewing coffee in
Fig. 1 The moka pots tested were made of aluminum or stainless
steel (Stainless steel The right-hand row)
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Stahl et al. Environ Sci Eur (2017) 29:18
a moka pot is a common and popular method of coffee
preparation. According to a market and opinion research
poll on the preferred method of coffee preparation in
a study from 2014, 4.23 million Germans from age 14
upward most commonly use a moka pot to prepare cof-
fee [6]. Figure3 shows the arithmetic means of aluminum
concentrations in coffee from the moka pots tested. Cof-
fee was brewed six times in each of the four different
brands of moka pot. It can be seen from the figure that
the mean of aluminum concentrations drops consider-
ably after the first and second brewing. e differences
are then minimal between the second and fifth brewing.
After the fifth brewing, the pots were washed in a dish-
washer, resulting in a considerable increase in aluminum
concentration in the sixth brewing.
In order to determine whether there were significant
differences in the migration from the different pots, the
aluminum concentrations from all six brewings from the
pots made of aluminum were compared pairwise with all
Fig. 2 Aluminum concentration in mg/L in the various drinks (TW tap water, TB tea bag, GT granulated tea, AS apfelschorle (apple juice mixed with
mineral water) after 24-h contact in lined (left side brands 1, 2, 3 with n = 3) and in unlined drinking bottles (right side brands 4 and 5 with n = 3)
Table 1 Aluminum uptake fromdrinking bottles-child/adult andthe respective percentage toTWI
a The results shown here are the arithmetic means of the results from three repetitions of experiments on bottles from all ve manufacturers
b Data for a child weighing 15kg consuming a daily portion of 500mL for a period of 1week (7days)
c Data for an adult weighing 70kg consuming a daily portion of 500mL for a period of 1week (7days)
Beverage in
aluminum bottle Mean concentration
(mg/L)aAluminum uptake-
childb (mg/week) Percentage
toTWI child aluminum uptake-
adult (mg/week)cPercentage
toTWI adult
Lined drinking bottles
Water (n = 9) 0.03 0.12 0.80 0.12 0.17
Tea from bags (n = 9) 1.56 5.45 36.3 5.45 7.78
Granulated tea (n = 9) 0.44 1.54 10.3 1.54 2.20
Apple juice and mineral water mix (n = 9) 1.02 3.58 23.8 3.58 5.11
Unlined drinking bottles
Water (n = 6) 0.30 1.06 7.06 1.06 1.51
Tea from bags (n = 6) 6.22 21.8 145 21.8 31.1
Granulated tea (n = 6) 2.30 8.05 53.6 8.05 11.5
Apple juice and mineral water mix (n = 6) 4.34 15.2 101 15.2 21.7
Fig. 3 Arithmetic means of aluminum concentration in coffee
brewed 6 times in four different brands of moka pots. Pots from
brands 1, 2, and 3 were made of aluminum and that from brand 4
was made of stainless steel. After the fifth brew the pots were washed
in a dishwasher
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Stahl et al. Environ Sci Eur (2017) 29:18
six brewings from the coffee being made using the stain-
less steel pots. In all of the pairwise comparisons, it is
shown that the arithmetic mean of aluminum concentra-
tions in coffee from the aluminum pots was greater than
that in coffee from the stainless steel pots. A statistically
significant p value (p< 0.05) was found in 13 of the 18
comparisons made. To determine whether the amount
of aluminum migrating varied with the increasing num-
bers of brews, Nos. 1–6 of the individual results for each
brewing were combined (=brand independent). Table2
summarizes the paired comparisons of coffee from the
aluminum pots between the numbers of brewings.
A statistically significant difference in aluminum con-
centration was found in three of the six pairwise com-
parisons of samples from the serial brewing processes.
e difference of the arithmetic mean between the first
and second brews was significant. Differences were also
observed between the second and third uses; however,
these were not statistically significant. e differences
between the third and fourth uses were again statistically
significant. Concentration decreased consistently until
the fifth brewing. e differences were highly significant
between Brew Nos. 5 and 6, showing that cleaning in the
dishwasher results in significantly higher aluminum con-
centrations in the coffee. In fact, the concentration was
higher after cleaning in the dishwasher than in the brand-
new pots (compare Brew Nos. 1 and 6); however, this dif-
ference was not statistically significant.
To summarize the results of this series of tests, it must
be noted that aluminum migration occurs from alu-
minum moka pots into the beverage. e arithmetic
means of the aluminum concentrations in all pairwise
comparisons of coffee from aluminum pots were
observed to be higher than those in the coffee from stain-
less steel pots. is difference was statistically significant
(significance level α=0.05) for 13 of 18 pairwise com-
parisons. e number of times the new aluminum pots
were used had a significant influence on the migration:
e highest concentration of aluminum was observed the
first time the pots were used. From the second to the fifth
use, the aluminum concentration in coffee was at a lower
level, which can be explained by a passivation of the pot
surface. Cleaning the pots in the dishwasher increased
the aluminum concentration in the coffee significantly
(Brew No. 6). Based on the arithmetic mean of all results
per aluminum moka pot (calculation of mean, brand
independent) and the stainless steel moka pot for Brew
Nos. 1, 3, and 6, the aluminum uptake was calculated for
an adult4 weighing 70kg along with the resultant per-
centage of TWI (Table3).
An average yearly coffee consumption of 165L, equiva-
lent to 3.17L per week [5] at the maximum concentration
of aluminum (Brew No. 6 after washing the pot in the
dishwasher, aluminum concentration 0.795mg/L coffee)
would result in reaching 4% of the TWI.
Discussion
Studies in a number of European countries (Nether-
lands, Hungary, Germany, Sweden, and Italy) show
that the average aluminum dietary uptake per adult
(not including job-related exposure) is between 1.6 and
13mg per day. is amount corresponds to an exposure
of 0.16 to 1.3mg/kg body weight per week for an adult
weighing 70kg [1, 4] which is equivalent to 16–130% of
the TWI. It must be noted, however, that there are large
differences in the average contamination between indi-
vidual countries, and it is not always evident in the vari-
ous studies whether or not drinking water was included
in the calculations. A large variation in individual expo-
sure certainly can be expected as a result of differences
in environment, soil contamination, dietary habits, or
the consumption of foods with additives that contain
aluminum [1, 4]. Children consume more nourish-
ment per body weight than adults and therefore repre-
sent the group with the highest potential for exposure
to aluminum per kilogram body weight [1, 4]. Studies
in France show that the estimated exposure for chil-
dren between 3 and 15years amounts to 0.7mg/kg BW/
week (corresponding to 70% of the TWI), and for infants
and toddlers between 1.5 and 4.5years the exposure is
23mg/kg BW/week (corresponding to 230% TWI). In
the UK, studies show that the value is 1.7mg/kg BW/
4 e percentage to TWI was not calculated for a child weighing 15 kg
under the assumption that children do not drink coffee.
Table 2 Comparison ofaluminum concentration incoee fromaluminum moka pots dependent uponnumber oftimes
used
Pair-wise comparisons of coees from the aluminum moka pots (independent of brand) dependent upon the number of times used to brew (BN)
Signicant dierences are labeled with an*. The>(<) symbol shows in which of the comparison groups the arithmetic mean was higher (lower). α=0.05. All n=9
Brew number
(BN) BN1–2 BN2–3 BN3–4 BN4–5 BN5–6 BN6–1 BN1–5
Aluminum-
moka pot 1 > 2* (p = 0.025) 2 > 3 (p = 0.055) 3 > 4* (p = 0.030) 4 > 5 (p = 0.533) 5 < 6*
(p = 0.000) 6 > 1 (p = 0.173) 1 > 5* (p = 0.011)
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Page 6 of 7
Stahl et al. Environ Sci Eur (2017) 29:18
week for children in the age group of 4–18years (cor-
responding to 170% TWI).
In Health Evaluation No. 033/2007 [2], the German
Federal Institute for Risk Assessment (BfR) clearly
states “No danger of contracting Alzheimer’s disease
from aluminum in household utensils.” Furthermore,
this document states that there is no scientific evidence
indicating a connection between aluminum uptake
from foodstuffs, including drinking water, pharma-
ceuticals, or cosmetics, and Alzheimer’s disease. No
increases in the frequency of amyloid plaques in the
brain have been found in dialysis patients or in alu-
minum workers, both groups of people with extensive
contact with aluminum. e BfR, therefore, does not
recognize a health danger for consumers through alu-
minum uptake from food and cooking utensils or cos-
metics [2]. e BfR does recommend that consumers
avoid the use of aluminum pots or dishes for acidic or
salted foodstuffs such as apple sauce, rhubarb, tomato
puree, or salt herring due to the increased solubility of
aluminum under the influence of acids and salts, thus
prophylactically avoiding the “unnecessary ingestion”
of aluminum [2].
In the present study, two household utensils, drinking
bottles and moka pots made of aluminum, were exam-
ined in regard to the migration of aluminum to food or
drink. To summarize the results presented here, it can
be said that human exposure with aluminum result-
ing from properly used drinking bottles is negligible.
Acidic beverages such as apple juice with mineral water
or tea should not be used in aluminum drinking bot-
tles. is is particularly important for children. e
tests here show that the TWI will be (145%) exceeded
for a child weighing 15kg drinking 500mL brewed tea
from an unlined aluminum bottle. Migration of alu-
minum from lined bottles is much less. e specific
release limit (SRL) of 5.00mg/kg or 5.00mg/L was not
exceeded by any of the lined bottles tested. Unlined
bottles, in contrast, did exceed these limits when filled
with acidic beverages. Additional human inner alu-
minum exposure through the proper use of aluminum
moka pots is negligible. Even under the worst-case sce-
nario of washing the moka pots in a dishwasher, the
uptake amounts to only 4% of TWI. e manufacturers
expressly warn not to clean the aluminum moka pots in
the dishwasher.
Authors’ contributions
TS, SF, SG, HZ and HB performed the data calculations, participated in the
study coordination, and drafted the manuscript. SH, AR, AW, and CH partici-
pated in the study design and coordination. BB revised the manuscript. All
authors read and approved the final manuscript.
Author details
1 Hessian State Laboratory, Am Versuchsfeld 11, 34128 Kassel, Germany.
2 Hessian State Laboratory, Glarusstr. 6, 65203 Wiesbaden, Germany. 3 Institute
of Food Chemistry and Food Biotechnology, Justus Liebig University Giessen,
Heinrich-Buff-Ring 17, 35392 Giessen, Germany. 4 Institute of Medical Virology,
Justus Liebig University, Schubertstraße 81, 35392 Giessen, Germany. 5 Hessian
State Laboratory, Schubertstr. 60, 35392 Giessen, Germany.
Acknowledgements
None.
Competing interests
The authors declare that they have no competing interests.
Availability of data and materials
“The datasets supporting the conclusions of this article are included within
the article.”
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in pub-
lished maps and institutional affiliations.
Received: 10 January 2017 Accepted: 29 March 2017
References
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Table 3 Aluminum uptake andthe resultant percentage ofTWI
a The values shown are the arithmetic means of the results of three repetitions for each of three brands of moka pot
b The weekly uptake is based on an adult weighing 70kg and a daily uptake of 500mL coee over a time period of 1week (7days)
Coee Test conditions Mean concentration
(mg/L) Aluminum uptake
adult (mg/week)bPercentage
toTWI adult
First brew Al-pot (n = 9) 0.564a1.97 2.81
Stainless steel pot (n = 3) 0.150 0.525 0.750
Third brew Al-pot (n = 9) 0.133a0.469 0.670
Stainless steel pot (n = 3) 0.018 0.063 0.090
Sixth brew Al-pot (n = 9) 0.795a2.79 3.98
Stainless steel (n = 3) 0.278 0.973 1.39
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Page 7 of 7
Stahl et al. Environ Sci Eur (2017) 29:18
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