Iodine nutritional status & prevalence of goitre in Sundarban delta of
South 24-Parganas, West Bengal
Amar K. Chandra, Smritiratan Tripathy, Dishari Ghosh, Arijit Debnath & Sanjukta Mukhopadhyay
Endocrinology & Reproductive Physiology Laboratory, Department of Physiology,
University College of Science & Technology, University of Calcutta, Kolkata, India
Received April 27, 2004
Background & objectives: In post salt iodization phase endemic goitre and associated iodine
deficiency disorders (IDD) were found prevalent in a randomly selected rural area of Sundarban
delta and its adjoining areas of West Bengal. The present investigation was thus undertaken to
study the total goitre rate, urinary iodine and thiocyanate excretion pattern of the school going
children, iodine content in edible salt and drinking water in the Sundarban delta of South
24-Parganas in West Bengal.
Methods: A total of 4656 school children (6-12 yr) were clinically examined for goitre from 13 different
areas in the delta region. Urinary iodine and thiocyanate levels were measured in 520 (40 from each
area) samples collected randomly to evaluate the iodine nutritional status and consumption pattern
of dietary goitrogen. Simultaneously iodine content was determined in 104 (8 from each area) drinking
water samples and 455 (35 from each area) edible salt samples collected from the areas.
Results: Children of all the areas were affected by endemic goitre. The prevalence rates were in
the ranges from 25-61 per cent; overall goitre prevalence was 38.2 per cent (grade 1 - 34.0%; grade
2 - 4.2%). Median urinary iodine level in the studied areas was 225 µ µ µ µ µg/l (range 115-525 µ µ µ µ µg/l)
indicating no biochemical iodine deficiency in the region. Mean urinary thiocyanate levels were in
the range from 0.326 - 1.004 mg/dl. Iodine content in drinking water samples were in the ranges
from 22 - 119 µ µ µ µ µg/l, and 55.6 per cent edible salt samples had iodine level above the recommended
15 ppm at the consumption point.
Interpretation & conclusion: The severity of endemic goitre was high in the studied population
though the iodine nutritional status was found satisfactory in the region indicating no biochemical
iodine deficiency. The people of the region consumed iodine through iodized salt but about 44 per
cent of the salt samples at household level contained inadequate iodine, however their iodine intake
was compensated through iodine in water and food. They also consumed dietary goitrogen.
Environmental factors other than iodine deficiency may have possible role for the persistence of
endemic goitre in the region. More investigations are thus necessary to arrive at certain definite
cause of high goitre rates in this population.
Key words Endemic goitre - goitrogens - school children - urinary iodine - urinary thiocyanate
Indian J Med Res 122, November 2005, pp 419-424
Iodine deficiency disorders (IDD) are a major
public health problem all over India1. It is not only
restricted to the Himalayan mountain areas, but has
been reported from the sub-Himalayan mountain
areas, the sub-Himalayan flat lands (Tarai), plains,
riverine areas, deltas and even coastal regions2. Iodine
deficiency as an environmental determinant in the
development of endemic goitre, has been established.
However, the possibility that factors other than iodine
deficiency contribute to the development of endemic
goitre has been known for a long time3. Seventy five
per cent of people with goitre live in less developed
countries where iodine deficiency is prevalent
whereas remaining 25 per cent of live in more
developed countries where goitre occurs in certain
areas despite iodine prophylaxis4.
The Sundarban delta is the largest mangrove
ecosystem of maximum bio-diversity in India. A
random study in the Madhabnagar village under
Patharpratima Community Development Block in
the delta on a population of 3814 covering all age
groups showed overall goitre prevalence 44.5 per
cent along with associated disorders viz., feeble
mindedness (49%), hypothyroidism (29%), stunted
growth (12%), deaf mute (6.6%), reproductive
failure (18%), and stillbirth (4%)5. Another study
on iodine nutritional status among school children
conducted in an adjoining rural area of the Gangetic
West Bengal showed that in spite of adequate iodine
intake as evidenced by urinary iodine level, the total
goitre prevalence was about 38 per cent6.
Systematic studies on the iodine nutritional status
of the population in the delta region are not
available. The present investigation was therefore
undertaken to study the goitre rate, urinary iodine
and thiocyanate excretion pattern in school going
children, iodine content in edible salt and drinking
water in the Sundarban delta of South 24-Parganas
in West Bengal.
Material & Methods
Selection of study area: The Sundarban delta is spread
amidst the two districts of North and South 24-
Parganas in West Bengal. It has as its boundaries the
Hooghly river in the west, Bangladesh in the east,
Bay of Bengal in the south and Dampier Hodges line
in north, and covers an area of 9630 sq. km of land
in West Bengal7. It is an archipelago of 54 islands,
full of unnumbered rivers and creeks. It has
population of 31,20,986 (2001 Census Report) living
under 19 community development blocks (CD
Blocks) of which 13 are in the district of South 24-
Parganas and the rest are in North 24-Parganas
district. Most of the people are engaged in
agricultural activities. The diet is mainly non-
vegetarian and consists of cereals (rice), pulses and
both sweet water and sea fish. They also consume
vegetables of Brassica family with others.
Selection of population: To get the representatives
population from the studied region 13 areas were
selected from 13 CD Blocks of Sundarban delta
located in South 24-Parganas by purposive sampling
method8. From each selected area, one school was
randomly chosen where the students (age group
6-12 yr) of both sexes (as recommended by WHO/
UNICEF/ICCIDD9) were available. In areas where
children of both sexes in the age group 6-12 yr were
not available in one school, more than one school
(one primary and one secondary or one boys school
and one girls school) were chosen at random.
Clinical goitre survey: The study was conducted
between May 2003 and September 2004. All the
students of the recommended age group who were
present on the day/days of survey were clinically
examined for goitre by trained research staff. Goitre
grading was done according to the recommended
criteria of WHO/UNICEF/ICCIDD9 (grade 0, no
goitre; grade 1, thyroid palpable but not visible; and
grade 2, thyroid visible with neck in normal
position). The age of the students was recorded from
the school register and was rounded off to the
nearest whole number. In this way 4,656 students
were clinically examined for the enlargement of
Iodine in urine: To evaluate the state of iodine
nutrition of the locality, spot casual urine samples
were collected from 40 children irrespective of their
thyroid status from the clinically examined enrolled
students at a definite interval maintaining
proportionate representation from the entire
population of the studied school(s) following
420 INDIAN J MED RES, NOVEMBER 2005
ICCIDD/UNICEF/WHO criteria10 in wide mouth
screw capped plastic bottles adding a drop of toluene
to inhibit bacterial growth and minimize bad odour.
Iodine in urine was determined by the arsenite method
following dry ashing in presence of potassium
carbonate11 maintaining internal quality control
having a known concentration range of iodine content
with each batch of test samples. In case of higher
values, samples were diluted two to five times with
double distilled water to get the appropriate result.
Thiocyanate in urine: Urinary thiocyanate
concentration was measured from the same collected
urine samples used for the analysis of iodine by the
method of Aldridge12 as modified by Michajlovskij
& Langer13. To identify the source of thiocyanate,
people of the studied areas were interviewed
regarding the consumption of cyanogenic foods and
the information was recorded.
Iodine in salt and water: The sources of dietary
iodine are water, food and the iodised salt available
in the studied areas. Iodine content in water in a
region truly reflects the bioavailability of iodine14.
To cover the entire region, 104 drinking water
samples were collected at random taking 8 samples
from each area from the shallow tube wells (150-
200 feet depth), in the screw capped plastic bottles,
brought to the laboratory, kept at 4°C and iodine
level was measured following the method of
Karmarkar et al11.
To monitor the iodine content of salt samples
available in the area, 35 marked airtight plastic
containers were distributed15 at random to the
students of the studied schools and they were asked
to carry samples of edible salt from their household
the next day. The salt samples were kept at room
temperature in the laboratory and iodine content was
measured within a week following the iodometric
Data analysis: One-tailed Student's-t test was
performed to find out the level of significance of
correlation coefficient (r) that was computed to
establish the relation between median urinary iodine
and mean iodine content in drinking water.
Results & Discussion
Prevalence of endemic goitre in school children
(6 -12 yr) is the most widely accepted marker to
evaluate the severity of IDD in a region. According
to WHO/UNICEF/ICCIDD15 recommended criteria,
CHANDRA et al: GOITRE PREVALENCE & IODINE NUTRITIONAL STATUS IN SUNDARBAN DELTA421
Table I. Goitre prevalence in different study areas of Sundarban delta, District South 24-Parganas
No. (%) of children with goitre Severity as
problem Grade-1Grade-2 Total (1+2)
Severity of public health problem: 5.0 - 19.9 per cent mild; 20.0 - 29.9 per cent moderate; >30 per cent severe15
a prevalence rate of 5.0 - 19.9 per cent is considered
mild; 20.0 - 29.9 per cent as moderate and above
30 per cent is considered as a severe public health
problem. No earlier data on goitre prevalence, urinary
iodine level or salt iodization status were available
in the studied areas, therefore necessary precautions
have been taken during goitre survey and in the
analysis of urine and salt. The total goitre prevalence
was found to be 38.2 per cent indicating that
clinically IDD was a severe public health problem
in the studied region. Though in most of the children
goitre was palpable (34.0%), but the prevalence of
visible goitre (4.2%) among the children during post
salt iodization period further signifies the severity
of the problem (Table I).
Urinary iodine is the most important biochemical
indicator that shows current state of iodine nutrition.
It is also used as a valuable indicator for the
assessment of IDD because 90 per cent of body’s
iodine is excreted through urine10. The indicator of
iodine deficiency elimination is a median value for
urinary iodine (MUI) concentration of 100 µg/l, i.e.,
50 per cent of the samples should be above 100 µg/l,
and not more than 20 per cent of samples should be
below 50 µg/l17. In all the 13 studied areas MUI was
well above 100 µg/l (Table II). In addition, urinary
iodine values <50 µg/l in more than 20 per cent
sample was not found in any of the areas suggesting
that as per WHO/UNICEF/ICCIDD criteria there was
no biochemical iodine deficiency or no inadequacy
in iodine intake of the overall population.
It has been recommended that 90 per cent of the
household should get iodized salt at the
recommended level of 15 ppm17. Our study showed
that overall 55.6 per cent of households were
consuming salt with adequate iodine level (Table II).
Inspite of that, MUI of the population was more than
100 µg/l. This indicated that the population must be
having some other sources of dietary iodine. The
people mainly consumed crops cultivated and
available in the region. Iodine content in the crop of
a region is known to be dependent on iodine content
of the soil. Iodine content in the drinking water
indicates that the region is environmentally iodine
422INDIAN J MED RES, NOVEMBER 2005
Table II. Urinary iodine and thiocyanate excretion of studied population and iodine content in salt and drinking water of Sundarban
delta, South 24 Parganas
Urinary iodine levels (µg/l)
(Mean ± SD)
0.643 ± 0.30
0.715 ± 0.41
0.392 ± 0.15
0.326 ± 0.22
0.471 ± 0.15
1.004 ± 0.32
0.497 ± 0.23
0.408 ± 0.28
0.452 ± 0.16
0.690 ± 0.34
0.738 ± 0.36
0.412 ± 0.31
0.744 ± 0.35
0.577 ± 0.34
100.4 ± 4.5
22.9 ± 4.1
68.4 ± 13.9
63.6 ± 6.5
80.6 ± 5.2
78.9 ± 5.8
105.3 ± 8.4
42.3 ± 1.9
119.6 ± 15.9
40.9 ± 5.8
68.6 ± 4.3
53.5 ± 4.2
60.4 ± 7.2
66.4 ± 42.8
No. of urine samples from each area- 40; total urine samples- 520
No. of salt samples from each area- 35; total salt samples- 455
No. of drinking water samples from each area- 8; total water samples- 104
sufficient or the soil rich in iodine according Zeltser
et al18. The people often consumed river/sea fish that
was also a rich source of iodine. In addition, the
people consumed iodized salt. Therefore, the high
MUI levels in the study areas were due to
consumption of food and water containing sufficient
iodine. A positive correlation (r = 0.7274; P<0.05)
found between the iodine content in drinking water
and urinary iodine level further showed that
consumption of iodine rich food and water was
perhaps responsible for high MUI of the population
and was enough to compensate the inadequacy of
iodine in salt available in the region.
The consumption of cyanogenic plant foods was
also evident from the urinary excretion of
thiocyanate (SCN). In India, large numbers of
cyanogenic plants (SCN precursors) are used as
common vegetables and IDD thus persists in
many such regions inspite of recommended iodine
intake19-22. In India cyanogenic plant foods used as
common vegetables have potent anti-thyroid activity
and supplementation of extra iodine usually fails to
counteract their effect23. Thus the involvement of
thiocyanate or thiocyanate precursors present in
foods consumed by the people of the region may
not be ruled out because the people of the region
often consume such foods.
In conclusion, the findings revealed that inspite
of high iodine intake, endemic goitre was prevalent
in the region indicating that goitrogenic or
antithyroidal substance might have a role in the
persistence of this disorder. More investigations are
necessary to arrive at a definite cause of high goitre
rates in the population of this area.
The financial assistance by the Department of Science &
Technology and Nonconventional Energy Sources (NES) (Govt.
of West Bengal) is gratefully acknowledged. The authors
acknowledge the co-operation received from the staff and
students of the schools studied.
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