Abstract
Post Mina
vast amount
Tsuruta, K.,
poisoninig o
Arantes, G.,
of methylme
and sea-wat
is microbiol
biomagni ca
environmen
persons who
of the toxica
children are
through brea
safe mercur
mercury lev
a causative a
genetic. Rec
lateral sclero
of mercury e
' 2005 Elsev
Keywords: M
1. Introduction
In 1950
awares. It h
ways of m
pharmaceu
cern becau
∗
Correspon
E-mail address:
1382-6689/$
doi:10.1016/jEnvironmental Toxicology and Pharmacology 20 (2005) 351 360
Low dose mercury toxicity and human health
Farhana Zahir
a,∗
, Shamim J. Rizwi
a
, Soghra K. Haq
b
, Rizwan H. Khan
b
a
Interdisciplinary Brain Research Centre, JN Medical College, AMU, Aligarh, U.P., India
b
Interdisciplinary Biotechnology Unit, AMU, Aligarh, U.P., India
Received 8 November 2004; accepted 20 March 2005
Available online 17 May 2005
mata incident there has been awareness about mercury toxicity even among the general public. Previous researches contributed a
of data regarding acute mercury exposure, but gradually information about the low dose [Ninomiya, T., Ohmori, H., Hashimoto, K.,
Ekino, S., 1995. Expansion of methylmercury poisoning outside minamata: an epidemiological study on chronic methylmercury
utside of Minamata. Environ. Res. 70 (1) 47 50; Lebel, J., Mergler, D., Lucotte, M., Amorim, M., Dolbec, J., Miranda, D.,
Rheault, I., Pichet, P., 1996. Evidence of early nervous system dysfunction in Amazonian populations exposed to low-levels
rcury. Neurotoxicology 17 (1) 157 167] of mercury toxicity has been trickling in. With mercury contaminating rain-, ground-
er no one is safe. Polluted water leads to mercury laced sh, meat and vegetable. In aquatic environments, inorganic mercury
ogically transformed into lipophilic organic compound methylmercury . This transformation makes mercury more prone to
tion in food chains. Consequently, populations with traditionally high dietary intake of food originating from fresh or marinet have highest dietary exposure to mercury. Extensive research done on
routinely consume sh or a particular species of sh are at an increased
nt to man through multiple pathways air, water, food, cosmetic products
more susceptible towards mercury toxicity. Mothers consuming diet conta
st milk. Decreased performance in areas of motor function and memory ha
y levels. Similarly, disruption of attention, ne motor function and verbal
els. It is an occupational hazard for dental staff, chloralkali factory worke
gent of various sorts of disorders, including neurological, nephrological,
ently heavy metal mediated toxicity has been linked to diseases like Alz
sis, etc. Besides this, it poses danger to wildlife. Therefore, it becomes im
xposure amongst the scientists and masses.
ier B.V. All rights reserved.
ercury pollution; Low dose toxicity; Biomagni cation; Neurodegenerative disorder
, Minamata bay tragedy caught the world un-
as been since recognized that the multiple path-
ercury contamination through air, water, food,
ticals, cosmetic products, etc., pose serious con-
se it persists in the environment and accumu-
ding author.
farhanazahir@rediffmail.com (F. Zahir).
lates in th
the organic
barrier ow
implication
getting wo
review was
adverse he
the require
ment and to
remediatio
see front matter ' 2005 Elsevier B.V. All rights reserved.
.etap.2005.03.007locals across the globe have already established this,
risk of methylmercury poisoning. The easy access
and even vaccines increase the exposure. Foetus and
ining mercury pass the toxicant to foetus and to infants
s been reported among children exposed to presumably
memory was also found in adults on exposure to low
rs and goldminers, etc. Mercury has been found to be
immunological, cardiac, motor, reproductive and even
eihemer s, Parkinson s, Autism, Lupus, Amyotrophic
perative to spread the information regarding the threat
s
e food web. Amongst three forms of mercury,
form is most toxic as it passes the blood brain
ing to its lipid solubility. The damage has vast
s with human beings at the top of food chain
rst of the deal owing to biomagni cation. This
written to focus on recent researches showing
alth effects of low doses of mercury, to instigate
ment for a new era of pharmaceutical develop-
create further awareness regarding environmental
n.

352 351–360
2. Sources of mer
2.1. Mercury in
As a na
vironment
from dega
mately 20,
(Hansen an
coal smoke
and mercu
the mercur
(Zhang et a
ter/sphygm
night lamp
is emitted.
National E
coverage f
accounted
important
nicipal was
plants and
ary interna
commercia
manufactur
(Murray an
mercury si
Amazon (B
is indicated
(Grandjean
tal staff (Ro
ers (Barreg
et al., 1999
2.2. Mercury in
Mercury
oceans afte
With merc
Levine, 20
kowiak, 20
during nine
VT in the n
ber, 1998.
71.8
r cont
conc
ges be
n and
erous
te gro
h ultim
d in a r
t of w
ample
ana, A
gly h
at (H
imes
had 5
dustan
t in el
ce wa
tion in
ercury co
Food of
e emiF. Zahir et al. / Environmental Toxicology and Pharmacology 20 (2005)
cury
air
tural element mercury is ubiquitous in the en-
(Fig. 1), approximately 10,000 tons originates
ssing of earth s crust, to this amount approxi-
000 tons/year is added by anthropogenic activity
d Dasher, 1997). Mercury emissions from the
is the main source of anthropogenic discharge
ry pollution in atmosphere. It is estimated that
y emissions will increase at a rate of 5% a year
l., 2002). When medical devices like thermome-
omanometer or household items like uorescent
s or thermostats are discarded residual mercury
The US Environmental Protection Agency (EPA)
missions Inventory (NEI) had the most complete
or all states. It found coal- red electric utilities
for 52.7% of the region s Hg emissions. Other
contributors to regional emissions included mu-
te combustion (5.6%), mercury-cell chlor-alkali
hazardous-waste incinerators (4% each), station-
l combustion engines (ICEs) (3.5%), industrial,
l and institutional (ICI) boilers (3.3%) and lime
ing (3.0%) and medical waste incineration (1%)
7.5 to
wate
cloud
linka
inatio
Num
pollu
whic
lishe
resul
ter s
Hary
prisin
Panip
268 t
value
(Hin
resul
surfa
mula
2.3. M
2.3.1.
Thd Holmes, 2004). Informal gold mining has used
nce antiquity. High contamination of Brazilian
razil is world s second largest producer of gold)
by the strong presence of mercury in its biota
et al., 1999). It is an occupational hazard for den-
wland and Baird, 1994), chloralkali factory work-
ard and Lindstedt, 1994) goldminers (Grandjean
), etc.
water
in air eventually passes into rivers, lakes and
r travelling long distances together with wind.
ury contaminating rain (Domagalski et al., 2004;
04), ground and seawater (Beldowski and Pemp-
03), no one is safe. Cloud water was collected
non-precipitating cloud events on Mt. Mans eld,
ortheastern USA between 1 August and 31 Octo-
Mercury cloud water concentrations ranged from
an inorgan
carried off
water bodi
microbiolo
pound, me
more prone
population
originating
dietary exp
across the g
lar Eskimo
ular specie
poisoning (
cury intake
exposure o
cause of hi
measuring
sh and she
Canadian a
Fig. 1. Mercury and environment.ng l (−1), with a mean of 24.8 ng l (−1). Liquid
ent explained about 60% of the variability in Hg
entrations (Malcolm et al., 2003). There are also
tween acidic deposition and sh mercury contam-
eutrophication of estuaries (Driscoll et al., 2003).
factories that directly pump untreated ef uents
undwater. The polluted water produces acidic rain
ately contaminates all water bodies. Report pub-
eputed Indian daily, The Hindustan Times showed
ater samples analysed at IIT, Kanpur. Groundwa-
s in India from eight places each from Punjab,
ndhra Pradesh, Gujarat and Kanpur showed sur-
igh levels of Hg in all samples. Water sample from
aryana) had highest level of Hg at concentration
that of safe limit, even the sample with least Hg
8 times more mercury than the upper safe limit
times, 1999). Algal bloom and leaf fall events can
evated methylmercury (MeHg) concentrations in
ters, potentially leading to increased MeHg accu-
sh ( Balogh et al., 2002).
ntamination of food
animal origin
tted mercury both natural and anthropogenic is inic form predominantly metallic vapour, which is
to great distances by winds and eventually falls in
es. In aquatic environments, inorganic mercury is
gically transformed into lipophilic organic com-
thylmercury. This transformation makes mercury
to biomagni cation in food chains. Consequently,
s with traditionally high dietary intake of food
from fresh or marine environment have highest
osure to Hg. Extensive research done on locals
lobe have already established this for instance po-
s. Persons who routinely consume sh or a partic-
s of sh are at an increased risk of methylmercury
Table 1)(Hansen and Dasher, 1997). Since mer-
is expressed on a per kilogram body weight basis
f children under age 14 is two three times high be-
gher food intake per kilogram body weight. After
total mercury in the edible portions of 244 selected
ll sh purchased in Canada at the retail level, the
dvisory to children and women of child-bearing