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The Benefits and Risks of Consuming Brewed Tea: Beware of Toxic Element Contamination


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Background. Increasing concern is evident about contamination of foodstuffs and natural health products. Methods. Common off-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 30 different teas by analyzing (i) tea leaves, (ii) tea steeped for 3-4 minutes, and (iii) tea steeped for 15-17 minutes. Results were compared to existing preferred endpoints. Results. All brewed teas contained lead with 73% of teas brewed for 3 minutes and 83% brewed for 15 minutes having lead levels considered unsafe for consumption during pregnancy and lactation. Aluminum levels were above recommended guidelines in 20% of brewed teas. No mercury was found at detectable levels in any brewed tea samples. Teas contained several beneficial 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. There 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.
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Hindawi Publishing Corporation
Journal of Toxicology
Volume , Article ID , pages.//
Research Article
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˚
a, Sweden
Correspondence should be addressed to Gerry Schwalfenberg;
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 foodstus 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  dierent 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 benecial 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.
1. Introduction
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 aer WWII.
Tea or i g inate s f r o m t he pl a n t Camellia sinensis,atreethat
require signicant 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 aecting the development of children, with lead resulting
in signicant decrease in social and average developmental
quotients [].
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 benets of tea as well
as the toxicants found in tea. e possible benecial and
medicinal aspects of tea as well as the detrimental eects 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 caeine 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 eects of drinking tea which are outlined below.
2.1. Cardiovascular Eects. Many reports in the literature
suggest benet to the cardiovascular system by reducing
cholesterol, reducing coronary artery disease, ameliorating
hypertension, and inammation. Green tea has been shown
to reduce total and LDL cholesterol signicantly 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 benet from
green tea with a % risk reduction. However, more robust
studies are needed []. As well green tea may have some
antithrombotic eects [,]. A randomized control study
in obese hypertensive patients showed that green tea extract
may signicantly reduce hypertension (both systolic and
diastolic BP), insulin resistance, total and LDL cholesterol,
inammation, and levels of markers of oxidative stress [].
2.2. Anticancer Eects. ACochranereview()foundcon-
icting evidence that green tea drinking prevents cancer [].
More recent studies again show conicting results with
benet for some cancers but not for others. Green tea may
reduce risk in developing breast cancer. is eect 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 coee
2.3. Weight Loss and Diabetes. ACochranereviewongreen
tea preparations []andweightlossshowedasmallnon-
signicant loss of weight in obese or overweight adults likely
In regard to diabetes green tea may result in lower fasting
glucose levels but no signicant HbAc 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 Eects. 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
same [].
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 eects 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
eects 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 classied as persistent toxicants
[]. As some toxic elements appear to persist because
of enterohepatic recycling [,], even smaller levels of
exposure can bioaccumulate and eect 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 [,].
4. Methods
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). Aer
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-
Scientic) using combination of internal standardization and
external calibration.
is analytical method is simple, ecient, and environ-
mentally friendly. e results in this study are consistent with
those found in other studies [].
5. Results
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
requirement  mg
- minute steeping .–.
– minute steeping .–.
Magnesium Daily requirement
– mg
- minute steeping .–.
– minute steeping .–.
Potassium Daily requirements
– mg
- minute steeping –
– minute steeping –
Phosphorus Daily requirement
of  mg
- 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 signicant 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
 minutes.
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)  .
. inorganic
. methyl
. (methyl Hg in children) . for methyl Hg
Lead   NE 
Concern at low levels.
. established for
reproductive toxicity
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 aer 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
Organic green
𝑁=10 None
SD ±.
MX .
SD ±
MX 
SD ±.
MX .
SD ±.
MX .
SD ±.
MX .
SD ±
MX 
SD ±.
MX .
SD ±.
MX .
Regular green
𝑁=7 None
SD ±.
MX .
SD ±
MX 
SD ±.
MX .
SD ±.
MX .
SD ±.
MX .
SD ±
MX 
SD ±.
MX .
SD ±.
MX .
Organic oolong
𝑁=2 None
detected . 
MX  . . None
MX .
MX  . .
Standard oolong
𝑁=2 None
MX .  . . None
MX .  . .
Organic white
𝑁=3 None
MX .  . . None
detected .  . .
Organic black
𝑁=1 None
detected .   None
detected .  . None
Standard black
𝑁=5 None
MX .
MX  . . None
MX .
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 aer subtracting the level found aer
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
for  minutes.
All tea leaves had detectable levels of cadmium.  teas
had detectable levels aer  minutes brewing while only 
teas had detectable levels aer  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 nonsignicant 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
of concern.
6. Discussion
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 benets of green tea as outlined above are multiple,
and tea may contribute to the daily intake of essential miner-
als and benet 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 signicant 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-
term bioaccumulation.
e organic teas had signicantly higher levels of lead
contamination if le steeping for more than  minutes than
the regular teas. Otherwise there was no signicant dierence
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 signicant 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
This Study
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 signicant 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 signicant 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-
nicantly 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
be avoided.
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 detoxication 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.
9. Conclusions
To move forward in diminishing the risk of toxic element
contamination a few points are oered 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 ocials should
consider mechanisms to limit exposures that add to the total
burden. It is insucient 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 insucient 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 eective 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 foodstus 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 ocials.
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
Authors’ Contributions
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
ALS labs.
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... Most available literature gives results based on procedures involving organic solvents, yet for consumption, tea is usually prepared using boiling water for around four minutes. Steeping for longer than four minutes may cause intolerable amounts of metallic ions to drain into the tea [21], although maximum phenolic extraction from green tea occurs in 40 minutes [22]. Te current study determined the efect of the extraction period (four and 40 minutes) on the aqueous total phenolic content of primary black grades, green tea, and teas from diferent regions in Uganda. ...
... Several reports indicate that tea leaves are rich in antiinfammatory, anticancer, antihypertensive, antibacterial antidiabetes, antiobesity, neurologic health, and antioxidant properties [28]. Most literature on TPC, TFC, and antioxidant capacity of teas globally is based on procedures involving organic solvents, yet for consumption, tea is usually boiled in water for four minutes to avoid the accumulation of intolerable amounts of metallic ions [21]. However, maximum phenolic extraction may occur in 40 minutes' steeping [22]. ...
... Hence, for a better extraction outcome, it would have been better and more efective to increase the extraction time from the usual India, black tea is boiled for more than 15 minutes before consumption [30]. However, the advantage of a short extraction time of 4 minute is that it doesn't allow the draining of heavy metals, such as aluminium and lead, common in prolonged extraction procedures, thus posing a health risk [21]. Fernando and Soysa [31] reported that 83% of tea brewed for 15 minutes had lead levels that were unsafe for pregnant and lactating mothers. ...
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Introduction. Globally, the consumption and production of tea are on the rise because of its beneficial constituents. Scarce literature exists on the effects of extraction periods on the contents of the biologically important and protective phytochemicals such as phenolics, flavonoids, and antioxidants in locally produced teas in Uganda. Aim. This study determined the effects of extraction periods on the aqueous total phenolic content (TPC) of local Camella sinensis, black primary grades and green tea, and their ecological differences, their total flavonoid content (TFC), and antioxidant capacities (AOC). Methods. Samples of local tea were collected from Kigezi, Ankole, and Buganda regions, and those of green tea were purchased from a local supermarket in Uganda. Four- and 40-minute infusions were separately prepared for each sample. Total phenolic and flavonoid contents were determined using the Folin–Ciocalteu and aluminium chloride methods using garlic acid and quercetin as standards, respectively. Antioxidant content was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing assay power (FRAP) methods, using ascorbic acid as the standard. Results. Green tea had the highest total phenolic content both with four-minute (9.50 ± 0.25 mgGAE/g) and 40-minute (25.81 ± 1.13 mgGAE/g) extractions, followed by D1 (4.14 ± 0.33 mgGAE/g) at four minutes and PF (23.60 ± 2.37 mgGAE/g) at 40 minutes. Regionally, Kigezi (4.71 ± 0.09 and 22.13 ± 0.85 mgGAE/g) at four and 40 minutes, respectively, gave the highest TPC. In TFC, tea from Buganda (4,371 ± 0.00 μgQE/g) was the highest. In DPPH and FRAP, GT (93.82 ± 0.03%, 39.04 ± 0.02 AAEμg/mL) was the best, followed by Buganda tea (88.71 ± 0.03%, 36.99 ± 0.01 AAEµg/mL), respectively. Conclusion. Longer extraction periods increase TPC in all teas. Green tea generates approximately twice the TPC generated by black tea in four-minute infusions. Green tea gives higher TPC, DPPH, and FRAP but less TFC than some black teas and is perhaps the best in terms of protection against oxidative damage to the body.
... Traditional tea, produced from the leaves of Camellia sinensis, can be categorised based on the degree of fermentation of the leaves during its processing. Green teas are nonfermented, oolong teas are semi-fermented and black teas are fully fermented (Karak and Bhagat 2010;Schwalfenberg et al. 2013). Additionally, there are herbal teas containing fresh or dried flowers, fruit, leaves, seeds or roots from various herbs or mixtures of herbs which may or may not include C. sinensis leaves ...
... In addition to the occurrence of polyphenols, tannic acid and antioxidants, the regular consumption of tea can be considered a source of dietary essential elements (i.e. calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P) and zinc (Zn) (Schwalfenberg et al. 2013)). However, several studies have also shown the presence of potentially toxic trace metals like lead (Pb), cadmium (Cd) and metalloids, such as arsenic (As) in herbal teas and their infusions (Han et al. 2006;Shekoohiyan et al. 2012;Schwalfenberg et al. 2013;Milani et al. 2018). ...
... calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P) and zinc (Zn) (Schwalfenberg et al. 2013)). However, several studies have also shown the presence of potentially toxic trace metals like lead (Pb), cadmium (Cd) and metalloids, such as arsenic (As) in herbal teas and their infusions (Han et al. 2006;Shekoohiyan et al. 2012;Schwalfenberg et al. 2013;Milani et al. 2018). In a recent study, de Oliveira et al. (2018) measured As, Cd, Cr and Pb in 47 traditional teas and herbal teas commercialised in the U.S. The authors found that the mean concentrations of As (0.26 mg kg −1 ), Cd (0.19 mg kg −1 ) and Pb (2.32 mg kg-−1 ) in tea leaves were higher in herbal teas compared to traditional teas but in all cases the levels were below the WHO limits for medicinal plants, except for one sample. ...
Over the last decade, the consumption of tea and herbal tea has gained more and more popularity across the globe, but the potential presence of chemical contaminants (e.g. pesticides, trace elements, synthetic drugs) may raise health concerns. This study analysed selected teas available in Belgian retail stores and performed a risk assessment for these samples. No chemical adulteration could be detected in dry tea material. More than 38% of the dry leaves samples contained at least one pesticide exceeding the maximal residue level (MRL) set by the EU. However, further risk assessment, based on the values of pesticide residues and the toxic trace elements encountered in the brew, demonstrate that the consumption of these teas will not give rise to health concerns. Nonetheless, attention should be given to the leaching potential of nickel from teas and the presence of arsenic in brews from algae containing teas.
... Several researchers across the globe have reported the elemental composition of tea based on the analysis on atomic absorption spectrophotometer (AAS) [3,[7][8][9][10][11][12][13][14][15][16], inductively coupled plasma optical emission spectroscopy (ICP-OES) [17], inductively coupled plasma mass spectrometry (ICP-MS) [18][19][20][21][22], and hand-held X-ray fluorescence spectrometer [22,23]. Some of them have reported on the north-east Indian tea [3,[7][8][9] or south Indian tea [11,16] and the other compared the Indian tea with the other tea-producing countries in regard to elemental composition of tea [19,24,25]. ...
... Several researchers across the globe have reported the elemental composition of tea based on the analysis on atomic absorption spectrophotometer (AAS) [3,[7][8][9][10][11][12][13][14][15][16], inductively coupled plasma optical emission spectroscopy (ICP-OES) [17], inductively coupled plasma mass spectrometry (ICP-MS) [18][19][20][21][22], and hand-held X-ray fluorescence spectrometer [22,23]. Some of them have reported on the north-east Indian tea [3,[7][8][9] or south Indian tea [11,16] and the other compared the Indian tea with the other tea-producing countries in regard to elemental composition of tea [19,24,25]. So far, most of the researchers from India used AAS for final estimation of the elements in tea. ...
... Barooah et al. [7] reported the concentrations of Hg (< 0.05 mg/kg) of the made tea samples from north-east India. The study result corroborate with the study reported by Gerry et al. [19] who reported no mercury was found at detectable levels in any brewed tea samples from India, Sri Lanka, China, and Japan. Arvay et al. [36] also reported the level of Hg for the teas of China, India, Japan, Nepal, and Taiwan at 0.0027 ± 0.0010 mg/kg for green tea and for Black tea 0.0022 ± 0.0014 mg/kg. ...
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Tea is a perennial crop that requires acidic soil for better plant growth. Due to the acidic nature of tea-growing soil, metals can be easily absorbed by tea plants from growing medium. Other anthropogenic activities are also the major contributor of element in the tea. This study provided a comprehensive database of 24 elements which were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Selected 24 elements belong to alkali metal (Li, Rb, Cs), alkaline earth metal (Be, Sr, Ba), transition metal (V, Cr, Mn, Co, Ni, Cu, Zn, Ag, Cd, Hg), basic metal (Al, Ga, Sn, Tl, Pb), metalloid (As), non-metal (Se), and actinide (U). Total 321 drier mouth samples were collected during 2020–2021 from eight different regions (Darjeeling, Terai, Dooars, North Bank, Upper Assam, South Bank, Cachar, and Tripura) of north-east India. No inorganic mercury as well as uranium was detected in any tested tea samples. Mean concentrations of Be, As, Ga, Tl, Li, Se, Cd, Ag, Cs, V, Co, and Pb were at trace level, whereas macro-element mean concentrations were distributed in the manner of Al > Mn > Rb > Ba > Zn > Cu > Sr > Cr > Ni > Sn. Human health risk for non-carcinogenic and carcinogenic metals was also assessed for the studied elements. Hazard quotients (HQs) and hazard index (HI) values (< 1) for non-carcinogenic elements indicated no risk. The incremental lifetime cancer risk (ILCR) values for carcinogenic elements indicated no risk for As, Cd, and Pb and medium level risk for Ni. Study concluded that north-east Indian tea would not pose any health hazard.
... A previous study reported that concentrations of both total and inorganic As in green tea leaves were higher than those in black tea (Mania et al. 2014). Another study that investigated green, black, and Oolong brewed teas found that the concentration of total As was highest in Oolong tea (0.88 μg L -1 ), followed by green tea (0.43 μg L -1 ) and black tea (0.34 μg L -1 ) (Schwalfenberg et al. 2013). The results of the current study were consistent with the previous study. ...
... A previous study reported that the average Pb concentrations in brewed Oolong tea samples (3.05 μg L -1 ) were higher than those in green or black tea (Schwalfenberg et al. 2013). We found the same findings in the current study that Oolong teas have the highest GM of Pb concentrations than the other tea types. ...
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Tea is the most frequently consumed beverage worldwide and is obtained from the leaves Camellia sinensis. The traditional way of tea consumption through brewing is gradually being replaced by the consumption of bottled and hand-shaken tea. Despite the different ways of tea consumption, trace elements accumulation and contamination of tea leaves have caused concerns. However, limited studies have reported trace element concentrations in different types of tea in bottled or hand-shaken tea and their health risks. This study aimed to determine the level of trace elements (V, Cr, Co, As, Cd, Pb, Mn, and Zn) in green tea, black tea, and Oolong tea in two varieties of products (bottled and hand-shaken tea). The health risks associated with tea consumption in various age subgroups among Taiwan’s general population were also estimated. A Monte Carlo simulation was applied to estimate the distribution of daily trace elements intake through bottled and hand-shaken tea consumption. As to the non-carcinogenic risks, the Monte Carlo simulation showed that hand-shaken green tea had a higher percentage of hazard index (HI) >1 (1.08%~6.05%) among all age groups. As to carcinogenic risks, the Monte Carlo simulation showed that the risks of As exposure from bottled Oolong tea and hand-shaken black, green, and Oolong teas in the 90th percentile in >18 to ≤65 and >65-year-old groups were higher than 10⁻⁶. The current study findings provided some information about trace elements of both bottled and hand-shaken tea and human health risks in the general population of Taiwan.
... As we can see with phytic acids, the advantages frequently exceed the drawbacks. We should take into account the potential that the whole is greater than the sum of its chemical components rather than excluding ever more things from our diet, such as wheat, cereals, nuts, and seed because of one or two chemical constituents (Schwalfenberg et al., 2013, Wu et al., 2014, Carvajal-Millan et al., 2021. ...
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The occurrence of adverse reactions to food is quite low, despite the fact that many foods contain toxins as a naturally occurring component or as a result of being handled or processed. Toxins can be created in either of these ways. The United States Food and Drug Administration (FDA) and other regulatory agencies came up with some creative solutions to reduce the incidence of adverse effects. These solutions included the innovative use of specifications, action levels, tolerances, warning labels, and prohibitions. As a result, the incidence of adverse effects has been reduced significantly. The manufacturers have also played a part by establishing limitations on specific compounds and devising techniques for mitigating the effects of process-induced toxins in their products. In spite of the precautions that have been taken by government agencies and food manufacturers to safeguard consumers from the effects of naturally occurring poisons in food, people will nonetheless unavoidably absorb some of these substances, albeit in trace amounts. There is always the possibility of toxicity owing to contamination, overconsumption, allergy, or an unforeseen idiosyncratic response, despite the fact that the risk of toxicity due to the consumption of food toxins is quite low. The goal of this article is to provide a toxicological and regulatory overview of some of the toxins that are present in some commonly consumed foods and to discuss, to the extent that this is possible, the steps that have been taken to reduce the exposure of consumers to these toxins.
... Loose-leaf single-herb domestic tea products were preferred, when available, in hopes that appearance and flavor could be used to guard against counterfeiting and adulteration [88][89][90]. I also reoriented a longstanding container-gardening hobby to focus more heavily on mint family herbs. ...
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Recent lines of evidence suggest the intriguing hypothesis that consuming common culinary herbs of the mint family might help prevent or treat Covid. Individual citizens could easily explore the hypothesis using ordinary kitchen materials. I offer a philosophical framework to account for the puzzling lack of public health messaging about this interesting idea.
... Ngoài yếu tố về chất lượng trà hay loại trà sử dụng, sự phóng thích của các nguyên tố và sự hiện diện của chúng trong nước trà phụ thuộc nhiều yếu tố dễ thay đổi và điều chỉnh như lượng trà dùng để pha, thể tích nước, nhiệt độ nước pha trà và thời gian ngâm trà. Trên thế giới, có rất nhiều các nghiên cứu liên quan đến hàm lượng của nguyên tố trong trà và cả trong nước trà [8][9][10][11][12]. Tuy nhiên, tại Việt Nam, nghiên cứu về kim loại trong trà nói chung và cho các loại trà Việt Nam nói riêng khá hạn chế. ...
Trà (Camellia sinensis L.) được xem là một loại thức uống phổ biến trên thế giới. Trà có giá trị dinh dưỡng và dược tính cao do chứa nhiều các hợp chất có tính kháng oxi hóa, các amino acid và nhiều nguyên tố dinh dưỡng đa vi lượng cần thiết. Trong nghiên cứu này, phương pháp plasma ghép cặp cảm ứng cao tần - đầu dò khối phổ (ICP-MS) được thẩm định nhằm đánh giá sự phóng thích của các nhóm nguyên tố dinh dưỡng đa vi lượng và nguyên tố không thiết yếu trong nước Trà ở các nhiệt độ pha và thời gian ngâm trà khác nhau. Kết quả cho thấy, sự gia tăng nhiệt độ của nước pha trà đóng vai trò quan trọng trong việc làm tăng tỉ lệ phóng thích của nguyên tố vào trong nước hơn là khi cố định nhiệt độ pha tại 70 0C và kéo dài thời gian ngâm trà. Phần trăm phóng thích của các nguyên tố dinh dưỡng vi lượng còn lại giảm dần theo thứ tự B > Mn > Zn > Cu > Fe > Ni, trong đó Fe và Ni cho tỉ lệ phóng thích thấp hơn hẳn so với các nguyên tố còn lại. Giá trị nồng độ Al cao nhất trong nước trà ghi nhận ở mẫu trà đỏ (khoảng 2,5mg/L), đều nằm trong giới hạn cho phép của WHO.
Conference Paper
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The aim of the study is to determine the effects of tea type, tea concentration and infusion time on the Aluminum (Al) content in tea infusions. Ceylon and Turkish black tea, Ceylon and Turkish green tea infusions were prepared by adding 100 mL of boiling distilled water to 1, 2 and 3 g of tea leaves. The tea infusion was mixed using a glass rod, covered by watch glasses to extract the components of tea leaves and allowed to brew for 2, 5, 10, 20, 30, 45 and 60 minutes. The infusion was filtered through filter paper (Whatman 42, 125 mm) into test tube, cooled, acidified and analyzed immediately for Al. The results showed that the Al content in tea infusion were significantly affected by tea type, tea concentration, infusion time, interactions of tea type x tea concentration, tea type x infusion time, tea concentration x infusion time and tea type x tea concentration x infusion time (P<0.001).
Conference Paper
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The aim of the study is to determine the effects of tea type, tea concentration and infusion time on the manganese (Mn) content in tea infusions. Ceylon and Turkish black tea, Ceylon and Turkish green tea infusions were prepared by adding 100 mL of boiling distilled water to 1, 2 and 3 g of tea leaves. The tea infusion was mixed using a glass rod, covered by watch glasses to extract the components of tea leaves and allowed to brew for 2, 5, 10, 20, 30, 45 and 60 minutes. The infusion was filtered through filter paper (Whatman 42, 125 mm) into test tube, cooled, acidified and analyzed immediately for Mn. The results showed that the manganese content in tea infusion were significantly affected by tea type, tea concentration, infusion time, interactions of tea type x tea concentration, tea type x infusion time, tea concentration x infusion time (P<0.001) and tea type x tea concentration x infusion time (P<0.01).
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Objective: Dietary Fe deficiency has a high incidence in Pakistani children and may be associated with increased gastrointestinal absorption of trace metals such as Mn. Therefore, children residing in heavily polluted cities like Karachi may be prone to Mn toxicity. The present study investigated blood Mn concentrations in Karachi children of different Fe statuses. Design: A prospective observational study was conducted where children were classified into different categories of Fe status – normal Fe, borderline Fe deficiency, Fe deficiency and Fe-deficiency anaemia – using WHO criteria supported by measurements of soluble transferrin receptors. Blood Mn was determined for children in each category using graphite atomic absorption spectroscopy. Setting: Three hospital outpatient departments in Karachi, Pakistan. Subjects: A total of 269 children (156 males, 113 females) aged 6–60 months from low-income families of Karachi. Results: Blood Mn concentrations were significantly higher in children with Fe-deficiency anaemia and Fe deficiency compared with those of normal Fe status (both P,0?01). Blood concentrations of soluble transferrin receptors were higher in children with Fe-deficiency anaemia compared with those of borderline or normal Fe status (both P,0?05). Conclusions: These findings report for the first time high blood Mn concentrations in Fe-deficient children of this age group. There is therefore an urgent need to identify and remove environmental exposure to Mn in combination with health strategies aimed at eradicating childhood Fe deficiency.
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Over the years, anthropogenic factors have led to cadmium (Cd) accumulation in the environment causing various health problems in humans. Although Cd is not a Fenton-like metal, it induces oxidative stress in various animal models via indirect mechanisms. The degree of Cd-induced oxidative stress depends on the dose, duration and frequency of Cd exposure. Also the presence or absence of serum in experimental conditions, type of cells and their antioxidant capacity, as well as the speciation of Cd are important determinants. At the cellular level, the Cd-induced oxidative stress either leads to oxidative damage or activates signal transduction pathways to initiate defence responses. This balance is important on how different organ systems respond to Cd stress and ultimately define the pathological outcome. In this review, we highlight the Cd-induced oxidant/antioxidant status as well as the damage versus signalling scenario in relation to Cd toxicity. Emphasis is addressed to Cd-induced pathologies of major target organs, including a section on cell proliferation and carcinogenesis. Furthermore, attention is paid to Cd-induced oxidative stress in undifferentiated stem cells, which can provide information for future therapies in preventing Cd-induced pathologies.
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Objective: To determine the in vitro inhibitory activity of green tea extract on some clinically isolated cariogenic and periodontopathic bacteria. Materials and methods: Twenty strains of each of Streptococcusmutans, Aggregatibacteractinomycetemcomitans, Porphyromonasgingivalis, and Prevotellaintermedia were isolated from carious teeth and periodontal pockets of patients with dental caries and periodontal diseases. Green tea extract was prepared by aqueous extraction method and diluted from 50 to 1.56 mg/ml. Standard techniques of agar disk diffusion and broth microdilution assays were applied for qualitative and quantitative determinations of antibacterial activity of green tea extract on each isolates. Results: All clinical isolates of S. mutans (100%) were sensitive to green tea extract at concentrations 6.25, 12.5, 25, and 50 mg/ml producing inhibition zones ranging from 10 to 38 mm. All periodontopathic isolates (A. actinomycetemcomitans, n = 20, P. intermedia, n = 20, and P. gingivalis, n = 20) (100%) tested were sensitive to 12.5, 25, and 50 mg/ml of this extract. The minimal inhibitory concentration of green tea extract for S. mutans was 3.28 ± 0.7 mg/ml and for A. actinomycetemcomitans 6.25, for P. gingivalis and P. intermedia 12.5 mg/ml. Conclusions: Our findings showed that green tea extract exhibited strong antibacterial activity on S. mutans,A. actinomycetemcomitans,P. gingivalis and P. intermedia and therefore may be used in mouthwashes or dentifrices for prevention of dental caries and periodontal diseases.
This paper presents a study of the counts of lymphocytes, (CD3+)T-cells, (CD4+)T-helper and (CD8+)T-suppressor and (CD16+)NK-cells in the peripheral blood of 101 males with a history of occupational exposure to metallic mercury vapours (Hg0) and in 36 males without this exposure. These workers were divided depending on the duration of exposure: 37 males with a short-term history of exposure to Hg0 (up to 10 years) and 64 males with a history of long-term exposure (10 to 37 years). For the determination of T-cell populations monoclonal antibodies were used in indirect immunofluorescence tests. The time weighted average of mercury concentrations in air was 0.028 mg m–3. Mercury concentration in the urine of the exposed subjects ranged from 20–260 µg dm–3, and in blood it was from 4 to 72 µg dm–3. Stimulation of the T-cell line was noted as evidenced by increased numbers of (CD3+)T-cells, (CD4+)T-helper and (CD8+)T-suppressor cells in the workers with <10 or >10 years’ exposure to Hg0. Lower increase count of (CD3+)T-cells and (CD4+)T-helper cells than (CD8+)T-suppressor cells was the cause of decreased values in the (CD3+)T/(CD8+)T-suppressor ratio and (CD4+)T-helper/(CD8+)T-suppressor ratio in the workers with <10 or >10 years’ of exposure. Moreover, no changes were observed in the T-cell populations between workers with <10 and those with >10 years’ exposure. In addition, statistical analysis of the effects of age and duration of exposure to Hg0 on the studied immunological parameters indicates that exposure duration may affect some of the values. These quantitative changes of T-cell population as well as changes of the (CD3+)T/(CD8+)T-suppressor and (CD4+)T-helper/ (CD8+)T-suppressor ratio have been proposed as immunological indicators of exposure to Hg0, which can be used for monitoring and to explain the origin of autoimmunity disorders induced by metallic mercury.
As, Cr, and Cu represent one potential combination of multiple metals/metalloids exposures since these three elements are simultaneously leached from chromated copper arsenate (CCA)-treated wood, a common product used for building construction, at levels that can be potentially harmful. This study investigated the neurotoxicity of As associated with CCA-treated wood when accompanied by Cr and Cu. The toxicity was evaluated on the basis of a cytotoxicity model using human neuroblastoma cell line SK-N-SH. The cells were cultured with CCA-treated wood leachates or with solutions containing arsenate [As(V)], divalent copper [Cu(II)], trivalent chromium [Cr(III)] alone or in different combinations of the three elements. The toxicity was evaluated using variations in cell replication compared to controls after 96h exposure. Among the three elements present in wood leachates, As played the primary role in the observed toxic effects, which were exerted through multiple pathways, including the generation of oxidative stress. DOM affected the absorption of metals/metalloids into the test cells, which however did not obviously appear to impact toxicity. As toxicity was enhanced by Cu(II) and inhibited by Cr(III) at concentrations below U.S. EPA's allowable maximum contaminant levels in drinking waters. Thus assessing As toxicity in real environments is not sufficient if based solely on the result from As.