Re: Woods Hole Scientists Link Influenza A (H1N1) Susceptibility to Arsenic Exposure
Re: Woods Hole Scientists Link Influenza A (H1N1) Susceptibility to Arsenic Exposure
Arsenic round the world: a review
Badal Kumar Mandal, Kazuo T. Suzuki *
Graduate School of Pharmaceutical Sciences, Chiba Uniersity, Chiba 263 -8522, Japan
Received 7 December 2001; received in revised form 8 February 2002
4.1.1. Taiwan incident
The arsenic contamination incident in well water
on the south-west coast of Taiwan (1961?
1985) is well known [278?280]. The population of
endemic area is about 140,000. In the villages
surveyed, the arsenic content of the well water
examined, ranges from 0.01 to 1.82 mg l−1. Most
of the well water in the endemic area has arsenic
content around 0.4?0.6 mg l−1. The predominant
arsenic species in the well waters is iAsIII with an
average iAsIII to iAsV ratio of 2.6. Chronic arsenicism
is observed in a population of 40,421 in 37
villages, and 7418 cases of hyperpigmentation,
2868 of keratosis, 360 of BFD patients [281], and
some cases of cancer (liver, lung, skin, prostate,
bladder, kidney) [281?285] are observed. The
source material of the arsenic is likely to be
pyretic material or black shale occurring in underlying
geological strata [278]. It is thought at beginning
that arsenic alone is responsible for BFD
of the area [286]. The discovery in 1975 of fluorescent
compounds in these well waters leads to the
isolation of humic substances, which in combination
with arsenic is thought to be probable cause
for the BFD [287]. To save the people of the
Taiwan endemic areas, a water treatment plant is
run to remove arsenic from groundwater before
use.
4.1.2. Antofagasta, Chile incident
About 130,000 inhabitants of the city has been
drinking supplied water with high content of arsenic
(0.8 mg l−1) for 12 years from 1959 to 1970
[288]. The source of the high arsenic content in
water is the Tocance River, of which water comes
from the Andes Mountain at an altitude of 3000
m and is brought 300 km to Antofagasta. At the
beginning of 1960s, the first dermatological manifestation
was noted, especially in children [288].
Peripheral vascular manifestations in these children
included Raynaud?s syndrome, ischemia of
the tongue, hemiplegia with partial occlusion of
the carotid artery, mesenteric arterial thrombosis
and myocardial ischemia. One autopsy showed
hyperplasia of the arterial media. In a survey of
27,088 school children, 12% are found to have the
cutaneous changes of arsenicism, one-fourth to
one-third of these has suggestive systematic symptoms.
Eleven percent has acrocyanosis. Of the
Antofagastan residents, 144 have abnormal skin
pigmentation, compared with none in the 98 control
subjects. Recent studies [212,289] also document
arsenic-induced skin lesions, and increased
bladder and lung cancer mortality in Northern
Chile.
To save the people, a water treatment plant is
run to remove arsenic from drinking water before
use. The sources of arsenic have been reported as
quaternary volcanogenic sediments, minerals and
soil [290]. Samples taken from 23 locations at
Aracamenan settlements near Calama range from
less than 100 to more than 800 g As l−1. Most
of the arsenic is present as arsenate, but some
arsenite is also determined. Five soils irrigated
with high arsenic waters range from 86 to 446 mg
As kg−1 compared to 64 mg As kg−1 in one
control sample.
4.1.3. West Bengal-India incident
Around 1978 various aspects of arsenic groundwater
contamination and arsenicosis among people
in some villages of West Bengal first came to
the notice of Government of West Bengal [291].
Several recent studies [22,63,67,151,291?294] report
that about 6 million people of 2600 villages
in 74 arsenic-affected blocks of West Bengal, India
are in risk and 8500 (9.8%) out of 86,000
people examined are suffering from arsenicosis,
while the source is oxidation of arsenic rich pyrite
or anoxic reduction of ferric iron hydroxides in
the sediments to ferrous iron and thereby releasing
the adsorbed arsenic to groundwater.
4.1.4. Mexico incident
Chronic arsenic exposure via drinking water is
reported in six areas of Region Lagunera, situated
in the central part of North Mexico with a population
of 200,000 during 1963?1983 [295]. The
range of total arsenic concentrations is 0.008?
0.624 mg l−1, and concentrations greater than
0.05 mg l−1 are found in 50% of them. Most of
the arsenic is in inorganic form and pentavalent
arsenic is the predominant species in 93% of the
samples [61]. In 36% of the rest samples, however,
variable percentages (20?50%), of trivalent arsenic
are found. It is also observed that high
concentrations of fluoride in the range of 0.5?3.7
mg l−1 and concentrations greater than 1.5 mg
l−1 are found in 20% of the analysed samples
[296].
The symptoms observed in this area are cutaneous
manifestations (skin pigmentation changes,
keratosis and skin cancer), peripheral vascular
disease (BFD), gastrointestinal disturbances and
alteration in the coporphyrin/uroporphyrin excretion
ratio [297]. It is found that the proportion of
individuals (per age group) affected with cutaneous
lesion increase with age until the age of 50.
The shortest is 8 years for hypopigmentation, 12
years for hyperpigmentation and palmo-planter
keratosis, 25 years for papular keratosis and 38
years for ulcerative lesions [298]. The source of
arsenic is assumed to be geological (volcanic sediment)
[61].
4.1.5. Argentina incident
Similar incident of arsenic contamination in
groundwater is also reported in Monte Quemado
of Cordoba province, north of Argentina [62].
The occurrence of endemic arsenical skin disease
and cancer is first recognized in 1955. Total population
of the endemic area is about 10,000. From
the observations in the Cordoba, it is concluded
[62,209] that the regular intake of drinking water
containing more than 0.1 mg l−1 of arsenic leads
to clearly recognizable signs of intoxication and
ultimately might develop into skin cancer. Biagini
followed 116 patients with clear signs of chronic
arsenic disease over a number of years [299]. After
15 years of follow-up, 78 had died, 24 from cancer
(i.e. 30.7% of total deaths). In Monte Quemado,
the problem seems to be ultimately solved by
building a canal that supplies the town with arsenic
free water from Salta province.
Again, elevated concentrations of arsenic in
surface waters, shallow wells and thermal springs
are reported from the Salta and Jujay provinces in
northwestern Argentina [300]. This natural contamination
is related to Tertiary-Quaternary volcanic
deposits, together with post-volcanic geysers
and thermal springs. Waters abstracted for drinking
supplies for the population of 5000 in the
town of San Antonio de los Cobres ranges from
0.47 to 0.77 mg l−1. Thermal springs range from
0.05 to 9.9 mg l−1 of arsenic.
A strong natural contamination of groundwater
with arsenic and selenium is reported in the
Pampa Province of Cordoba, southeast Argentina.
The arsenic content of nearly 50% of the
water samples from this area ranges from 0.1 to
0.316 mg l−1 with a maximum value of 3.81 mg
l−1 [64,301]. Groundwater contamination is
caused from loess, which differed in composition
to loess from Europe, Asia and North America
[64], with arsenic concentrations ranging from 5.5
to 37.3 mg kg−1, and rhyolitic volcanic glass
ranging from 6.8 to 10.4 mg kg−1.
4.1.6. Millard County, Utah, USA incident
West Millard County is a desert area with low
population density and around 250 people drinking
well water of arsenic content between 0.18 and
0.21 mg l−1 and the predominant arsenic species
is arsenate (86% As5+) [302]. Participants are
examined for specific signs of arsenic toxicity including
palmer and plantar (palms and soles)
keratoses, diffuse palmer and plantar hyperkeratoses
and skin suggestive of arsenic toxicity is
rare, with only 12 of 149 participants having any
signs associated with arsenic ingestion. Participants
from Deseret have the highest average arsenic
in urine concern of 0.211 mg l−1 (n=40)
and that of Hinckley participants have 0.175 mg
l−1 (n=95) compared to control from Delta of
0.048 mg l−1 (n=99). The highest average arsenic
concentration in hair is 1.21 mg kg−1 (n=80)
from Hinckley residents and that of Deseret residents
is 1.09 mg kg−1 (n=37) compared to control
from Delta of 0.32 mg kg−1 (n=68). Lewis
et al. [303] recently reports hypertensive heart
disease, nephritis, nephrosis, and prostate cancer
among the people of the arsenic-affected areas in
Utah.
4.1.7. Lane County, Western Oregon, USA
incident
Well water in Central Lane County [304], located
in Western Oregon about midway between
the Colombia river and the northern boundary of
California gets contaminated with arsenic during
November 1962?March 1963. The concentration
range of arsenic in wells is 0.05?1.7 mg l−1. Wells
in Eugene, Creswell, and Grove districts in Central
Lane County which were known to yield
arsenic rich groundwater are in an area underlain
by a particular group of sedimentary and volcanic
rocks, which geologists have named the Fisher
formation [305]. The largest concentrations of
arsenic are found in samples from the Creswell
district.
4.1.8. Lessen County, California, USA incident
In the Lessen County, California, similar arsenic
poisoning in well water is observed. The
range of arsenic in the well water is 0.05?1.4 mg
l−1. It is found that arsenic is present in drinking
water above 0.05 (0.03) mg l−1 and an increased
level of arsenic in their hairs reflects body
burden due to arsenic exposure [306].
4.1.9. Ontario, Canada incident
In 1937, Wyllie [307] reported that water from
some deep wells in Rocky Mountain areas of
Ontario, Canada were known to contain large
amounts of arsenic. The source of arsenic in well
water is ferrous arsenate where arsenic in water
varies from 0.10 to 0.41 mg l−1 as As2O3. Preliminary
experiments show that arsenic as arsenate is
the primary source of arsenic, which contaminated
the well water. One person died of arsenic
dermatosis. The whole family members of the
victim died are also afflicted due to this arsenic
poisoning.
4.1.10. Nova Scotia, Canada incident
In 1976, several wells in Halifax County, Nova
Scotia are contaminated with arsenic [308] with
concentration greater than 3 mg l−1. More than
50 families have been affected due to arsenic
poisoning [309]. Recently, Boyle et al. [310] reports
also occurrences of elevated arsenic concentrations
in bedrock groundwaters used for
individual and municipal water supplies in the
mainland coast of southern British Columbia,
Canada.
4.1.11. Hungary incident
In Hungary also similar arsenic contamination
in the well water is observed [311,312] in the years
1941?1983. The amount of arsenic present in the
well water is in the range of 0.06?4.00 mg l−1.
Recently, concentrations of arsenic above 50 g
l−1 are identified in groundwaters from alluvial
sediments associated with the River Danube in
the southern part of the Great Hungarian Plain.
Concentrations up to 150 g l−1 (average 32 g
l−1, 85 samples) are found by Varsa?nyi et al. [54].
The Plain, some 110,000 km2 in area, consists of a
thick sequence of subsiding Quaternary sedi
ments. The groundwaters have highest arsenic
concentrations in the lowest parts of the basin,
where the sediment is fine-grained [54]. A few
thousand people are affected and several symptoms
of arsenic poisoning viz, melanosis, hyperkeratosis,
skin cancer, internal cancer, bronchitis,
gastroenteritis, haematologic abnormalities are
found among them [313].
4.1.12. New Zealand incident
In 1939, Grimmet and McIntosh described arsenic
contamination of groundwater and the resulting
effects on the health of livestock [314].
Later on in 1961, high levels of arsenic were
found in water from areas of thermal activity.
Thermal waters in New Zealand contain up to 8.5
mg As l−1 [315]. Aggett and Aspell [316] studied
the chemical forms of arsenic in water samples. In
the geothermal bores, more than 90% of the arsenic
is present in the trivalent form.
4.1.13. Poland incident
A small case is observed in Poland in 1898 [317]
with some skin cancer among the arsenic affected
persons. It is interesting to note that there is no
published data on this incident.
4.1.14. Fairbanks, Alaska incident
In the well water, spring of Fairbanks, Alaska,
arsenic is found above 0.05 mg l−1. The study is
initiated to evaluate the arsenic content of streams
and groundwaters of the Pedro-Dome Cleary
Summit area approximately 30 km north of Fairbanks,
Alaska in the heart of the historic Fairbanks
Mining District. Arsenic is associated with
gold mineralization here and is believed to reach
the water of the area through weathering of arsenic
containing rocks.
The arsenic concentrations in 53 water samples
from wells and springs range from less than 0.005
to 0.07 mg l−1. Eighty percent of the samples
contain less than 0.01 mg l−1 and 95% of the
samples contained less than 0.05 mg l−1 [318].
The arsenic levels in 243 well water range from
less than 0.05 to greater than 0.10 mg l−1. About
28% of the samples contain arsenic less than 0.05
mg l−1, 40% of the samples contained less than
0.10 mg l−1 and about 20% of the samples contain
greater than 0.10 mg l−1. Well water arsenic
concentrations in the Ester Dome study area
range from less than 1.0 to 14 mg l−1 and for the
study population range from less than 1.0 to 2.45
mg l−1 with a mean of 0.224 mg l−1. An epidemiological
study was made in 1976 [319], which
suggested no clinical or haematological abnormalities
among these people. Urine arsenic levels
above 0.02 mg l−1 are found in 130/198 (66%),
hair arsenic levels above 1 mg kg−1 occur in
74/181 (41%) and nail arsenic levels above 4 mg
kg−1 in 49/132 (37%) of the study population.
4.1.15. Sri lanka incident
In a clinical study of 13 cases of polyneuropathy
connected with arsenic poisoning, in Srilanka,
Senanayake et al. [320] found Mee?s line, i.e.
transverse white bands across finger nails, to be
the constant feature at least 6 weeks after the
onset of initial symptoms. In seven of these cases,
the source of arsenic was contaminated well water,
four others had a long history of consuming
illicit liquor.
4.1.16. Spain incident
Manzano and Tellow summarized their experiences
in treating arsenic poisoning caused by well
water in certain areas of Spain [321].
4.1.17. China incident
During the 1980s, the endemic arsenicosis was
found successively in many areas on mainland
China such as Xinjiang Uygur A. R., Inner Mongolia,
Shanxi, Liaoning, Jilin, Ningxia, Qinghai,
and Henan provinces [322?328]. The arsenic concentration
in the groundwater in these affected
areas is in the range of 220?2000 g l−1 with the
highest level at 4440 g l−1. Consequently, a large
sector of the rural population has been exposed to
chronic arsenic poisoning (CAP) resulting from
consuming well water with naturally occurring
high levels of arsenic during the past decades. At
present, the population exposed to high amounts
of arsenic is estimated to be over 2 million and
more than 20,000 arsenicosis patients are confirmed
[328]. The water of the deep-wells, however
contains fluoride and arsenic [323]. Fluorosis was
first found in the 1970s and arsenicism in 1980.
One of the characteristics of the Kuitun case is the
fact that there are three groups of patients among
the residents who drank the same well water for a
long time. Namely, one group suffers from fluorosis,
the second group from arsenicism and the
third group from both fluorosis and arsenicism
combined.
The cause of contamination is considered to be
geological. Major clinical symptoms observed are
keratosis, pigmentation, melanosis or leucoderma
on the skin, often accompanied with peripheral
neuritis, gastroenteritis, and hypertrophy of the
liver, bronchitis or cardiac infarction. At later
stages skin cancer and gangrene are also found.
Feng et al. [329] recently reports DNA damage in
buccal epithelial cells from individuals from this
arsenic-affected area. Various measures are taken
to supply clean water.
4.1.18. Northern India incident
In Ropar, Manimajra, Chandigarh, N. Garh,
Patiala and Ambala around Chandigarh of Punjab
and Haryana of India, the arsenic concentration
in water from wells and springs were higher
than the WHO limit of safety for human consumption
[330] with 0.05?0.545 mg l−1 of arsenic.
Cirrhosis (adult and childhood), non-cirrhotic
portal fibrosis and extra hepatic portal vein obstruction
in adults are very common in India and
suggests that consumption of arsenic-contaminated
water may have some role in the pathogenesis
of these clinical states [331]. The patients who
consumed the water containing arsenic 0.545 mg
l−1 throughout life are suffering from non-cirrhotic
portal fibrosis (N.C.P.F.), whereas their
two relatives consuming same water reveal gross
splenomegaly, but with normal liver function tests
[332]. The source of arsenic is still unknown.
4.1.19. Bangladesh incident
Several recent studies [23,216,292,333] report
that about 25 million people of 2000 villages in
178 arsenic-affected blocks of Bangladesh are in
risk and 3695 (20.6%) out of 17,896 people examined
are suffering from arsenicosis, while the
source is oxidation of arsenic rich pyrite or anoxic
reduction of ferric iron hydroxides in the sediments
to ferrous iron and thereby releasing the
adsorbed arsenic to groundwater. To combat the
situation, Bangladesh need a proper utilization of
its vast surface and rainwater resources and
proper watershed management.
4.1.20. Fallon, Neada Incident
In 1984, Viz et al. [334] were unable to detect
any increase in chromosomal aberrations or sister
chromatid exchange in residents of Fallon, Nevada,
where drinking water contained about 0.10
mg As l−1. From literature it is found that the
health status of these arsenic exposed populations
is not adversely affected [335].
4.1.21. Fukuoka Prefecture, Japan incident
In March 1994, arsenic over the permissible
level for drinking use (0.01 mg l−1) is detected in
well waters in the southern region of Fukuoka
Prefecture, Japan [71]. The highest concentration
found is 0.293 mg l−1, being quite high compared
to other arsenic-containing well waters reported in
Japan as a geological process. The mechanisms of
arsenite/arsenate elution from the soil proposed
are which involved: (i) anion exchange with OH−;
and (ii) reductive labialization of arsenic through
conversion of arsenate to arsenite.
4.1.22. New Hampshire, USA incident
Arsenic concentrations are measured in 992
drinking water samples collected from New
Hampshire households and in randomly selected
households, concentrations ranged from 0.0003
to 180 g l−1, with water from domestic wells
containing significantly more arsenic than water
from municipal sources. Water samples from
drilled bedrock wells have the highest arsenic
concentrations, while samples from surficial wells
has the lowest arsenic concentrations. The authors
[336] suggested that much of the groundwater
arsenic in New Hampshire was derived from
weathering of bedrock materials and not from
anthropogenic contamination. The spatial distribution
of elevated arsenic concentrations (50
g l−1) correlates with Late-Devonian Concordtype
granite bedrock. Analysis of rock digests
indicates arsenic concentrations up to 60 mg kg−1
in pegmatites, with much lower values in surrounding
schists and granites.
4.1.23. Vietnam incident
This is the first publication on arsenic contamination
of the Red alluvial tract (Mekong delta
region) in the city of Hanoi and in the surrounding
rural districts [72]. The contamination levels
vary from 1 to 3050 g l−1 in rural groundwater
samples from private small-scale tube-wells with
an average arsenic concentration of 159 g l−1. In
a highly affected rural area, the groundwater used
directly as drinking water has an average concentration
of 430 g l−1. Analysis of raw groundwater
pumped from the lower aquifer for the Hanoi
water supply show arsenic levels of 240?320 g
l−1 in three of eight treatment plants and 37?82
g l−1 in another five plants. Aeration and sand
filtration that are applied in the treatment plants
for iron removal lowers the arsenic concentrations
to levels of 25?91 g l−1, but 50% remains above
the Vietnamese Standard of 50 g l−1. The arsenic
in the sediments may be associated with iron
oxyhydroxides and releases to the groundwater by
reductive dissolution of iron. The high arsenic
concentrations found in the tube-wells (48%
above 50 g l−1 and 20% above 150 g l−1)
indicate that several million people consuming
untreated groundwater may be at a considerable
risk of CAP. No people were found in these
affected regions with symptoms of chronic arsenic
toxicity.
4.2. Arsenic contamination from industrial sources
4.2.1. Ronphibun, Thailand incident
In 1987, the skin manifestation of CAP was
first diagnosed among the residents of Ronphibun
district, Nakorn Srithammarat Province [337]. It
is seen that 85% of all reported of CAP are from
Ronphibun sub-district of Ronphibun district.
Most cases are of relatively mild disease, with
21.6%, however having very significant lesions
[338]. Rophibun district has eight sub-districts
and 65 villages with a population of 14,085. Three
out of 14 villages of Ronphibun sub-district with
19.9% of the population of the sub-district account
for 60.9% of the cases. These villages use
water with drains from the high-contaminated
area of Suan Jun and Ronna Mountains. Their
attack rate is 8.8 times, the rate in the remainder
of the sub-district. This area has 0.1% arsenopyrite.
Recently, Oshikawa et al. [339] reports the
long-term changes in arsenical skin lesions among
this population. At many sites, the arsenic content
of water exceeds by 8?100 times the 0.05 mg l−1
concentration, which is the accepted safety level
set down by WHO for occasional exposure [15].
4.2.2. Mindanao Island, Philippines incident
Soon after the construction of a geothermal
power plant on Mt. Apo started in January 1992,
people living downstream along the Matingao and
Marbol rivers which run through the construction
site, complained of symptoms such as eruption,
headache or stomach-ache. An environmental investigation
carried out in August 1993, which
revealed that river water downstream of the construction
site contained 0.1 mg l−1 of arsenic and
hair samples of some residents showed high concentrations
of mercury and manganese as well as
arsenic [340]. As a result, the construction of the
geothermal power plant is suspected as the cause
of arsenic contamination. In 1995, a medical survey
of 39 residents who had rashes on their skin
reveals that a few of them are suspected to be
patients suffering from CAP [341].
4.2.3. Nakajo, Japan incident
Waste water from a factory producing arsenic
sulfide contaminated nearby well water in Nakajo,
Japan in 1960 [342,343]. In this place a very small
number of people drank the well water, which was
contaminated with arsenic (0.025?4.00 mg l−1).
Melanosis, hyperkeratosis, cardiovascular disease,
hepatopathy, haematologic abnormalities were
observed among the residents of Nakajo.
4.2.4. Toroku and Matsuo, Japan incident
Toroku is a small mountain village to the north
of Miyazaki prefecture with a population of
about 300 where arsenious acid was produced by
roasting arsenopyrite ore from 1920 to 1962 [344].
Similarly, Matsuo is a small mountain village in
the north of Miyazaki prefecture. Here, white
arsenic was produced by calcinating arsenopyrite
at very primitive stone-made furnaces for nearly
half a century since about 1920. In this system
about 10% or more of As2O3 was lost as fumes
through the refining process. The arsenic-rich remains
of calcinated ore were dumped into the
river. Many mine workers and nearby residents
died from acute and sub-acute arsenic poisoning.
A 6-year follow-up study reveals a high prevalence
of malignant neoplasms especially in respiratory
tract, which was the main cause of death
in the patient [345]. A total of 147 persons are
examined in the study. Out of them, 125 are
diagnosed as CAP. A total of 58 malignant skin
tumors are noted out of 125 patients with skin
lesions of CAP and out of these 58 malignant skin
tumors, 51 occur on trunk and times. The appearance
of multiple malignant tumors was noted in
24 cases (58.5%), including 15 cases of double
cancers. The phenomenon is noted in 14 cases
(42.4%) among cases of malignant skin tumor.
Multiple Bowen?s disease is found in 12 cases
(37.5%). As of 1995, there were 153 patients in
Toroku and 64 in Matsuo who are recognized by
the government as suffering from CAP [346].
4.2.5. Other incidents in Japan
A severe cutaneous manifestations of CAP are
detected in seven out of 28 male Japanese workers,
who are exposed to arsenic in the form of lead
arsenate and Ca3AsO4 in the manufacture of insecticides
[347]. The lesions are symmetric punctuated
palmo-planter hyperkeratosis and bronze
hyper-pigmentation.
A retrospecific cohort study of a Japanese population
in between 1954 and 1959 used well water
contaminated with arsenic from a dye factory.
During the follow-up period until 1987, there
were 18 deaths from cancer, of which seven from
lung cancer and six in the high exposure group
[348].
4.2.6. P.N. Mitra Lane, Behala, Calcutta, India
incident
Arsenic contamination episode in residential
area of Behala, Calcutta during 1969?1989 is well
known [68,92,349]. The concentration of arsenic
in the tube-well water varies from 0.05 to 58 mg
l−1. Chronic arsenic toxicity, resulting from
household use of arsenic contaminated water occurs
in 53 out of 79 members (67% of 17 families)
residing near this factory area within age range
1?69 years. Typical skin manifestations are found
in all of them but pulmonary symptoms are
present in 40% and neurological symptoms in 65%
of cases. Hematomegaly (2?6 cm) is found in 80%
of cases and splenomegaly (1.5?2.6 cm) in 35% of
cases. A few died due to arsenicosis.
4.2.7. Rajnandgaon district, Madhya Pradesh,
India incident
Arsenic contamination of groundwater in
Koudikasa village of Rajnandgaon district, Madhya
Pradesh-India with a population of 1.5 million
was reported first on 1999 [350]. Most of the
villagers of Koudikasa used water from a forest
dug-well (0.52 mg As l−1) along with a PHED
tube-well (0.88 mg As l−1). Out of the total
number of adults (150 nos.) and children (58 nos.)
examined at random, 42 and 9%, respectively,
have arsenical skin lesions. The source of arsenic
contamination is speculated to be due to percolation
of gold and uranium mine?s tailings.
4.2.8. Australia incident
In Australia, old stocks of lead arsenate, that
was used as pesticides prior to 1970 remained in
sheds and caused chronic poisoning among the
workers [351].
4.2.9. Czechosloakia incident
People living near a plant burning arsenic contaminated
coal containing 900?1500 mg As kg−1
was responsible for the episode [352].
4.2.10. Toronto, Ontario, Canada incident
Vegetation and soil samples collected in 1974 in
the vicinities of two secondary lead smelters located
in a large urban area near Toronto, Ontario,
Canada showed arsenic concentrations over
30 times higher than normal urban background
levels of arsenic in unwashed plant foliage and
200 times higher than normal soil which were
found about 200 m away from the smelters. A
large number of people were found suffering from
arsenic toxicity in this region [353].
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