Hindawi Publishing Corporation
Journal of Toxicology
Volume , Article ID , pages
The Benefits and Risks of Consuming Brewed Tea:
Beware of Toxic Element Contamination
Gerry Schwalfenberg,1Stephen J. Genuis,2and Ilia Rodushkin3
1University of Alberta, Number 301, 9509-156 Street, Edmonton, AB, Canada T5P 4J5
2University of Alberta, 2935-66 Street, Edmonton, AB, Canada T6K 4C1
a University of Technology, Aurorum 10, 977 75 Lule˚
Correspondence should be addressed to Gerry Schwalfenberg; firstname.lastname@example.org
Received July ; Accepted September
Academic Editor: Lucio Guido Costa
Copyright © Gerry Schwalfenberg et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
Background. Increasing concern is evident about contamination of foodstus and natural health products. Methods.Common
o-the-shelf varieties of black, green, white, and oolong teas sold in tea bags were used for analysis in this study. Toxic element
testing was performed on dierent teas by analyzing (i) tea leaves, (ii) tea steeped for - minutes, and (iii) tea steeped for –
minutes. Results were compared to existing preferred endpoints. Results. All brewed teas contained lead with % of teas brewed for
minutes and % brewed for minutes having lead levels considered unsafe for consumption during pregnancy and lactation.
Aluminum levels were above recommended guidelines in % of brewed teas. No mercury was found at detectable levels in any
brewed tea samples. Teas contained several benecial elements such as magnesium, calcium, potassium, and phosphorus. Of trace
minerals, only manganese levels were found to be excessive in some black teas. Conclusions. Toxic contamination by heavy metals
was found in most of the teas sampled. Some tea samples are considered unsafe. ere are no existing guidelines for routine testing
or reporting of toxicant levels in “naturally” occurring products. Public health warnings or industry regulation might be indicated
to protect consumer safety.
more than years ago. It has a relatively recent history in
the west beginning in the th century when it was introduced
to Portuguese priests and merchants. It became popular in
Britain in the th century. e use of tea bags was not
common until aer WWII.
Tea or i g inate s f r o m t he pl a n t Camellia sinensis,atreethat
require signicant rainfall of inches a year and grow in
acidic soil. Contaminants may vary in the soil, air, or water in
which the plants are grown. Acidic soil may result in excess
available aluminum and uoride . An acid or alkali soil
pH also enhances leaching of toxic heavy metals from the
soil . Increasing pH with soluble calcium would reduce the
absorption of uoride . Environmental pollutants such as
uoride and aluminum have been found in tea in part due to
the tea plants absorption and deposition and concentration
of these compounds in the leaves . e drinking of more
than liters of tea per week may result in dental or skeletal
uorosis . Mercury, lead, arsenic, and cadmium as well
as other toxic elements have been found in tea leaves as
described in the literature [,]. Lead, arsenic, and cadmium
have also been found in brewed black tea . ese soil and
air contaminants may be directly related to the use of coal
red power plants. e use of coal in China has increased
to . billion tons or about % of global coal consumption.
Coal burning power plants supply % of the energy in China
. Pollutants such as lead and mercury from power plants
are aecting the development of children, with lead resulting
in signicant decrease in social and average developmental
Teas are commonly grouped into major categories:
readily available at most supermarkets in Canada except
yellow tea. For the purposes of this study common o the
Journal of Toxicology
were obtained as well as some that were available in health
food stores. All teas used were in tea bags used for brewing in
individual cups. e four types of tea sampled in this study
are white, green, oolong, and black tea.
() White tea: young leaves or new growth buds, with-
ered, uncured, baked dry;
() Green tea: steamed or dry cooking in hot pans to
prevent oxidation; dried tea leaves may be separate
leaves or rolled into pellets (gunpowder tea);
() Oolong tea: withering of leaves under sun and warm
winds with further oxidation standard between green
and black teas;
() Black tea: leaves are completely oxidized, withered,
resulting in catechins being transformed to complex
is study will look at some of the benets of tea as well
as the toxicants found in tea. e possible benecial and
medicinal aspects of tea as well as the detrimental eects of
heavy metals in tea are discussed below.
2. Medicinal Value of Green Tea
Green tea provides a small amount of magnesium, calcium,
potassium, phosphorus, and other trace elements considered
necessary for health. e results in our study are reported
below. Tea contains catechins, which are a type of antioxidant.
preparation. Tea also contains caeine which may vary from
to mg/cup depending on the type of tea and method of
brewing. Other medicinal ingredients are theobromine and
theophylline found in smaller quantities. ere are many and
varied eects of drinking tea which are outlined below.
2.1. Cardiovascular Eects. Many reports in the literature
suggest benet to the cardiovascular system by reducing
cholesterol, reducing coronary artery disease, ameliorating
hypertension, and inammation. Green tea has been shown
to reduce total and LDL cholesterol signicantly as shown in
a recent meta-analysis . Total cholesterol was reduced by
. mg/dL and LDL by .mg/dL. A dose response curve
has been observed. Black tea has not been associated with
decreased risk of coronary artery disease, as outlined in a
recent meta-analysis, but there may be some benet from
green tea with a % risk reduction. However, more robust
studies are needed . As well green tea may have some
antithrombotic eects [,]. A randomized control study
in obese hypertensive patients showed that green tea extract
may signicantly reduce hypertension (both systolic and
diastolic BP), insulin resistance, total and LDL cholesterol,
inammation, and levels of markers of oxidative stress .
2.2. Anticancer Eects. ACochranereview()foundcon-
icting evidence that green tea drinking prevents cancer .
More recent studies again show conicting results with
benet for some cancers but not for others. Green tea may
reduce risk in developing breast cancer. is eect has been
ascribed mostly to the phytochemicals which can modify
the metabolism of estrogens . ese include polyphenols
(catechins) such as epigallocatechin gallate (EGCG), which
appears to be most potent, epigallocatechin, epicatechin
gallate, and epicatechin. Green tea drinking does not appear
to reduce the risk of developing prostate cancer and black tea
may increase prostate cancer risk .Amostrecentmeta-
analysis shows that the consumption of green tea and coee
2.3. Weight Loss and Diabetes. ACochranereviewongreen
tea preparations andweightlossshowedasmallnon-
signicant loss of weight in obese or overweight adults likely
In regard to diabetes green tea may result in lower fasting
glucose levels but no signicant HbAc changes . ere
is some evidence that insulin resistance may be improved by
the antioxidant protective function of the polyphenols .
As well there is evidence that these antioxidants may protect
the retina from neurodegenerative changes seen in diabetic
retinopathy  and protect against nephropathy .
2.4. Anti-Infective Properties. Green tea extract potentially
decay and periodontal disease because of its strong antibac-
terial properties . Epigallocatechin gallate, the most active
component of green tea, has antiviral, antibacterial, and
antifungal properties .
2.5. Miscellaneous Eects. Tea may reduce mercury absorp-
tion [,] and provide protection of nephrotoxicity [–
e consumption of greater quantities of tea, or more
cups compared to or less, may provide some protection from
depression . Another study in elderly patients suggests the
ere is some evidence that the polyphenols in green
tea may be protective against Alzheimer’s; however further
studies are required .
3. Detrimental Effects of Heavy Metals in Tea
ere is an abundance of literature demonstrating the adverse
health eects of various heavy metal and metalloid ele-
ments on the human organism. By numerous mechanisms,
including endocrine disruption , cytotoxicity , mito-
chondrial dysfunction , and oxidative stress [,], a
spectrum of toxic elements is able to disturb cellular and
metabolic homeostasis and induce clinical illness. e liter-
ature is replete with many common disease processes such
as carcinogenesis , insulin resistance , neurodegen-
eration , and immune dysregulation [,]. ese may
result from exposure to and bioaccumulation of various
heavy metals and metalloids. In addition, recent literature has
Journal of Toxicology
elucidated that various toxic compounds can have epigenetic
eects with the potential for transgenerational damage [,
]. Rather than isolated incidents of single exposures, it is
apparent that toxic metal contact is a widespread phenome-
non  with many potential sources including tainted food
air. Many toxic metals such as cadmium and lead have very
long half-lives and thus are classied as persistent toxicants
. As some toxic elements appear to persist because
of enterohepatic recycling [,], even smaller levels of
exposure can bioaccumulate and eect long-term harm.
e toxic elements discussed in this paper include lead,
mercury, aluminum, and cadmium. e extremely low levels
of lead accepted in Proposition during the prenatal period
come from our knowledge of the accumulation in the brain
and resultant impairment of cognitive development [,].
allowed to stand in ne bone china cup for minutes. e
steeping of the teas was done in the ne china cups as might
be done in the real world.
All tea leaves were analyzed to determine the presence or
absence of metals.
All teas were steeped using one tea bag (containing - gm
of tea) in mL of distilled water in ne bone china cups. All
teas had two samples taken, one steeped for - minutes and
another steeped for – minutes.
4.1. Sample Preparation for Analysis. Wat e r : s am p l es w e re
diluted -fold with .M HNO3(SP grade).
fold with . M HNO3(SP grade).
Solids: approximately . g of sample was subjected to
closed-vessel MW-assisted digestion (MARS- oven, W
h holding time) using mL concentrated HNO3(SP grade),
. mL H2O2(PA grade) and . mL HF (SP grade). Aer
digestion, solutions were diluted with . M HNO3(SP grade)
providing nal dilution factor of approximately . A set
of digestion blanks and matrix-matched CRM were prepared
together with each digestion batch.
All solutions were spiked within (internal standard, at
𝜇g/L) and analyzed by ICP-SFMS (ELEMENT, ermo-
Scientic) using combination of internal standardization and
is analytical method is simple, ecient, and environ-
mentally friendly. e results in this study are consistent with
those found in other studies .
5.1. Minerals Found in Tea. In our study cups of tea may
supply as much as % of daily calcium requirements, % of
magnesium requirements, -% of daily potassium require-
ments and –.% of phosphorus requirements using distilled
water. See Table . e use of regular tap water may provide
more magnesium, calcium potassium, and phosphorus than
using distilled water.
T : Healthy minerals found in teas in this study mg/L.
Calcium Daily minimum
- minute steeping .–.
– minute steeping .–.
Magnesium Daily requirement
- minute steeping .–.
– minute steeping .–.
Potassium Daily requirements
- minute steeping –
– minute steeping –
Phosphorus Daily requirement
- minute steeping .–.
– minute steeping .–.
were boron – 𝜇gm/L, cobalt .–. 𝜇gm/L, copper
– 𝜇gm/L, chromium .–. 𝜇gm/L, iron –
. 𝜇gm/L, manganese – 𝜇gm/L, molybdenum
.–. 𝜇gm/L, phosphorus – 𝜇gm/L, selenium
<.–. 𝜇gm/L, vanadium <.–. 𝜇gm/L, and zinc
5.2. Heavy Metals in Tea. ere are established upper limits of
ingestion on a daily basis of heavy metals from various orga-
nizations. e most stringent are from Proposition in Cal-
ese limits have been outlined in Tab l e along with
other accepted limits.
e levels of toxic elements in this study for mercury
(Hg), lead (Pb), aluminum (Al), arsenic (As), and cadmium
(Cd) are outlined in Tab l e .
Of the teas tested none had detectable levels of mercury
as brewed teas although / tea leaves had detectable
mercury present (as high as ng/g of tea). It appears that
the mercury is bound in the leaf in a way that it does not
make its way into the brewed tea at levels that are detectable
(detectable limit in this assay is . 𝜇gm/L).
All teas contained signicant amounts of aluminum. Tea
leaves contained from to ng/g of tea. All brewed
teas steeped for or minutes contained detectable levels of
aluminum. e range was 𝜇gm/L to 𝜇gm/L steeping
for minute and 𝜇gm/L to 𝜇gm/L steeping for
minutes. Only teas had levels above acceptable limits at
minutes of brewing but of the teas had levels greater than
the upper acceptable daily limit of 𝜇gm/L. C learly letting
tea steep for longer than minutes is not advisable. Two of the
organicgreenteashadlevelsabove,𝜇gm/L brewed for
All brewed tea and tea leaves had detectable lead levels
with Chinese oolong teas having the highest levels, followed
by green tea and regular black tea having lower levels. Organic
Journal of Toxicology
T : Established toxicant limits in supplements (𝜇gm/day) adapted from .
Tox ic element US California Proposition (P)
and Environmental Protection Agency
union Australia World Health Organization Gestational limits
Mercury (Hg) .
. (methyl Hg in children) . for methyl Hg
Concern at low levels.
. established for
Cadmium . NE
Arsenic . NE . NE
Aluminum , , , NE NE
NE: not established.
European/WHO/Australian levels were established by convention as representing % of the daily total toxicant intake aer conversion of values expressed in
mg/kg/week for an average adult weight of kg.
T : Toxic element contaminants in teas.
TEAS Steeped - minutes Steeped – minutes
Ave rag e 𝜇g/LHgPbAlAsCdHgPbAlAsCd
MX . . None
MX . .
MX . . . None
MX . . .
MX . . . None
detected . . .
detected . None
detected . . None
MX . . None
MX . .
SD is standard of deviation. None detected is below the limit of detection or <. ng/L and MX is maximum level detected.
. 𝜇gm/L to . 𝜇gm/L aer subtracting the level found aer
brewing distilled water in ne china cups.
All brewed tea and tea leaves had detectable arsenic with
Chinese oolong teas (organic or regular) having the highest
levels. Levels in all teas ranged from . 𝜇gm to . 𝜇gm/L of
tea steeped for minutes to . to . 𝜇gm/L of tea steeped
All tea leaves had detectable levels of cadmium. teas
had detectable levels aer minutes brewing while only
teas had detectable levels aer minutes brewing suggesting
that there is further leaching of this toxicant into the water
over time. e highest level was . 𝜇gm/L found in
standard oolong tea from China.
All tea leaves and brewed teas had detectable levels of
cesium with one organic tea having ng/g in the dry leaf,
. 𝜇gm/L at minutes of brewing and . 𝜇gm/L at
minutes of brewing.
All tea leaves had detectable levels of tin but only two
brewed samples had nonsignicant levels detected in the teas.
All tea leaves and all teas had detectable levels of barium,
antimony and thallium but none had levels considered to be
Heavy metal contamination in tea has been described in the
literature before using the same method of analysis . Lead
levels in the previous study were found to be the highest
in Chinese samples as seen in our study. Infusion for
minutes increased the amount of toxicants in the previous
study similar to this study.
Journal of Toxicology
e benets of green tea as outlined above are multiple,
and tea may contribute to the daily intake of essential miner-
als and benet overall health. However, in the real world of
tea drinking it is important to look at several other factors to
minimize exposure to heavy metals.
First the source of tea and where it was grown (country of
origin) must be considered; see Tab l e . It would be optimal to
drink tea with minimal exposure to toxicants in ground water,
soil, air, and rain. Second one must consider the water that
the tea is brewed with that may contain contaminants. Tap
water does contain more contaminants than distilled water.
ird the vessels that the water is boiled in may contribute
to toxicants and the cups either glass or ne china used for
this study the leaching of lead from the ne china cups into
distilled water alone resulted in a lead level of . 𝜇gm/L.
is was subtracted from all the analysis results of the teas
to obtain the true level contributed by the brewed tea.
Of the trace minerals manganese is the only mineral
found in substantial amounts in teas and some teas will supply
more than the total daily requirements. Black tea achieved
the highest level in this study. Excess manganese can result in
interference with the absorption of iron andmayresult
in ADHD-like symptoms in children exposed in utero .
In regard to toxic elements tested only aluminum and lead
had levels that were unacceptable. Unacceptable aluminum
levels were found in % of teas brewed for minutes and
% of teas brewed for minutes. e lead levels that were
present are a signicant concern during pregnancy in that
% of the samples brewed for minutes and % of samples
brewed for minutes were above . 𝜇gm/L. Despite smaller
amounts of cadmium and arsenic there is concern for long-
e organic teas had signicantly higher levels of lead
contamination if le steeping for more than minutes than
the regular teas. Otherwise there was no signicant dierence
in levels of contaminants between organic teas and regular o
the shelf teas. Organic teas did not appear to have less toxic
element contamination than regular teas even from the same
7. Limitations of the Study
A limitation of this study is that this is a sample of conve-
nience using samples readily available in supermarkets and
health food stores in Canada. is study did not look at u-
oride, which is a very common and signicant contaminant.
e particular method of analysis used here would not allow
for uoride analysis. e scope of this analysis did not look at
pesticides, herbicides, or other organic contaminants, which
are addressed in some of the organic labeling.
8. Recommendations Associated with
Although manganese is an essential trace mineral, levels in
black tea are quite high and may result in toxic levels when
adjusted for total daily intake from multiple sources.
e acceptable limit of lead in reproductive health is
. 𝜇gm on a daily basis. All but teas or % of teas had
levels above this limit when consuming cups of tea daily.
Consumption of tea needs to be severely limited during
pregnancy. e consumption of this and some prenatal
vitamins  may easily exceed this daily limit and result
in signicant bioaccumulation over time especially in the
fetus. As well when the additional lead from the tea cup was
added, % of all teas had more than the acceptable limit of
of the teas had . 𝜇gm/L of lead. Since tea is only part of
Some nutritional supplements also have high levels of lead
especially Chinese and Ayurvedic herbal remedies . In
combination it would be easy to exceed this daily limit. Chi-
nese oolong teas had the highest levels of lead and although
this is below the acceptable standard of 𝜇gm/day are best
All teas had signicant levels of aluminum and out of
teas brewed for minutes had unacceptably high levels.
Drinking more than cups of tea a day may contribute sig-
nicantly to a toxic load.
Brewed tea appears to contain numerous toxic elements
such as arsenic and cadmium. However, none of these toxi-
cant levels were above present day acceptable standards.
Steeping tea for longer periods of time increases the
levels of these contaminants by to % over steeping for
minutes. erefore steeping for longer than minutes should
Although mercury is found in the tea leaves no mercury
was detected in the brewed tea even when steeped for longer
periods of time. is raises an interesting question: would tea
be useful for detoxication from mercury?
e source of water used for brewing may contain some
contaminants and add to the toxic load.
One must know the manufacturing source and processing
of the cups in which the tea is brewed especially ne china
cups that may contain lead in the glaze. ere are manu-
factures that advertise having no lead glaze and glassware is
unlikely to have lead.
To move forward in diminishing the risk of toxic element
contamination a few points are oered for consideration.
When determining regulatory standards as well as individual
and public health recommendations, it is important to con-
sider the cumulative total load of toxic elements as some of
these agents including cadmium and lead have long half-lives
 and constitute persistent pollutants within the human
body. As such, it is important to consider means to diminish
exposure as well as to facilitate elimination of toxic elements
from all sources, including beverages. Precautionary avoid-
ance is paramount as individuals and public ocials should
consider mechanisms to limit exposures that add to the total
burden. It is insucient to simply look at isolated exposures
Journal of Toxicology
T : Toxicant (heavy metal) levels according to country of origin.
Tea typ e Tea country of origin High levels Moderate levels Low levels
Green tea organic China Pb, Al As Cd
Green tea organic Sri Lanka Low in Pb, Cd, Al, As
Green tea organic Japan As, Pb, Cd, Al
Green tea standard China High in Al Pb, As Low in Cd
White tea India LowestinAl,Pb,Cd,As
White tea China Pb, Al, As Low in Cd
Oolong tea organic China HighestinAs,highinPb,Al LowinCd
Oolong tea standard China Highest in Pb Al, Cd, As
Black tea organic Blend India
Sri Lanka Al Pb Low in Cd, As
Black tea standard India
Sri Lanka Al Lowest Pb, low in Cd, As
Pb: lead, Cd: cadmium, Al: aluminum, As: arsenic.
to toxic elements, but rather to look at the total cumulative
As such, if individuals are being exposed to lead, for
example, from drinking polluted tea as in this study, from
taking tainted supplements , from consuming contami-
nated drinking water from lead pipes , from eating or
drinking from dinnerware containing lead , and so on,
the total daily exposure may be enormous. Simple regulation
to control the exposure from one source is insucient to
secure safety from toxic element bioaccumulation and thus
education in precautionary avoidance from all main sources
needs to be implemented.
Education to medical trainees about exposures to toxic
elements and persistent organic pollutants has been limited
in most medical centers thus far. Recognizing the escalating
problemoftoxicantbioaccumulation, it would be pru-
dent to commence education of health professionals, inline
with recommendations from the World Health Organization
 and other notable health bodies.
Public awareness campaigns may be eective in alerting
individuals to concerns related to toxic element bioaccumu-
lation and potential sources of exposure. Such awareness may
facilitate further avoidance as well as medical intervention to
eliminate accrued toxicants .
In response to the Pediatric Academic Societies admoni-
tion that “low level exposure to environmental toxicity may
be impacting the functioning of the current generation,” 
education programs in schools may have some role in pro-
tecting and guiding developing children and their families.
Routine inspection and testing of foodstus and bever-
ages to rule out contamination—with results being made gen-
erally available—might identify compounds that are heavily
tainted and thus preclude contaminants from being con-
sumed. is might include a self-regulatory process that is
overseen by government ocials.
Original source labeling of products would provide con-
sumers with information about the geographic origins of
products. As some jurisdictions appear to have a greater prob-
lem with contamination , this will give consumers choice
in their acquisitions and the opportunity to provide feedback
to jurisdictions which consistently demonstrate contamina-
Conflict of Interests
Gerry Schwalfenberg conceived and designed the experi-
ments. Gerry Schwalfenberg and Ilia Rodushkin performed
the experiments. Gerry Schwalfenberg and Stephen J. Genuis
analyzed the data. Gerry Schwalfenberg and ALS labs con-
tributed reagents/materials/analysis tools. Gerry Schwalfen-
berg, Stephen J. Genuis, and Ilia Rodushkin wrote the paper.
e authors would like to express gratitude to Cheryl
Schwalfenberg who carefully reviewed and edited this paper.
e rst author paid the fee for the toxicological testing at
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