Environ Geochem Health (2011) 33:389–397
DOI 10.1007/s10653-011-9384-4
ORIGINAL PAPER
Does iodine gas released from seaweed contribute to dietary
iodine intake?
P. P. A. Smyth • R. Burns • R. J. Huang
T. Hoffman • K. Mullan • U. Graham •
K. Seitz • U. Platt • C. O’Dowd
•
Received: 28 June 2010 / Accepted: 11 January 2011 / Published online: 23 March 2011
Ó Springer Science+Business Media B.V. 2011
Abstract Thyroid hormone levels sufficient for brain
development and normal metabolism require a minimal
supply of iodine, mainly dietary. Living near the sea
may confer advantages for iodine intake. Iodine (I2) gas
released from seaweeds may, through respiration,
supply a significant fraction of daily iodine requirements. Gaseous iodine released over seaweed beds was
measured by a new gas chromatography–mass spectrometry (GC–MS)-based method and iodine intake
assessed by measuring urinary iodine (UI) excretion.
Urine samples were obtained from female schoolchildren living in coastal seaweed rich and low seaweed
P. P. A. Smyth (&) C. O’Dowd
School of Physics and Environmental Change Institute,
National University of Ireland, Galway, Ireland
e-mail: [email protected]
P. P. A. Smyth R. Burns
UCD School of Medicine and Medical Science,
University College Dublin, Dublin, Ireland
R. J. Huang T. Hoffman
Institute of Inorganic and Analytical Chemistry,
Johannes Gutenberg University of Mainz,
Duesbergweg 10-14, 55128 Mainz, Germany
abundance and inland areas of Ireland. Median I2
ranged 154–905 pg/L (daytime downwind), with higher
values (*1,287 pg/L) on still nights, 1,145–3,132 pg/L
(over seaweed). A rough estimate of daily gaseous
iodine intake in coastal areas, based upon an arbitrary
respiration of 10,000L, ranged from 1 to 20 lg/day.
Despite this relatively low potential I2 intake, UI in
populations living near a seaweed hotspot were much
higher than in lower abundance seaweed coastal or
inland areas (158, 71 and 58 lg/L, respectively). Higher
values[150 lg/L were observed in 45.6% of (seaweed
rich), 3.6% (lower seaweed), 2.3% (inland)) supporting
the hypothesis that iodine intake in coastal regions may
be dependent on seaweed abundance rather than
proximity to the sea. The findings do not exclude the
possibility of a significant role for iodine inhalation in
influencing iodine status. Despite lacking iodized salt,
coastal communities in seaweed-rich areas can maintain
an adequate iodine supply. This observation brings new
meaning to the expression ‘‘Sea air is good for you!’’
Keywords Atmospheric gaseous iodine Thyroid Urinary iodine Seaweed Iodine
K. Mullan U. Graham
Royal Victoria Hospital, Belfast, N. Ireland
Introduction
K. Seitz U. Platt
Institute of Environmental Physics,
University of Heidelberg, Im Neuenheimer Feld 229,
69120 Heidelberg, Germany
The thyroid hormones thyroxine (T4) and triiodothyronine (T3) play a vital role in human development
and metabolism. Iodine forms a major constituent of
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390
these hormones (65.3% by weight of T4). A regular
source of iodine intake, principally dietary, is necessary to maintain normal function in all mammals
including humans. Although seawater is relatively
poor in iodine (approx. 58 lg/L; Fuge and Johnson
1986), its massive abundance makes it and forms of
life of marine origin such as seafish, shellfish, and
seaweeds the richest source of iodine on the planet. In
dietary terms, the most efficient source of iodine
intake is the use of table salt or salt used in food
processing of NaCl which has been fortified with KI
or KI03 at a level of 20–40 mg/kg (iodized salt).
Daily intakes of iodine recommended by the WHO
range from 90 lg in infants to 250 lg in pregnant
women with adults requiring 150 lg/day. The use of
iodized salt (universal salt iodization: USI) is the
means of iodine prophylaxis recommended by the
WHO (WHO 2007). However, the policy is not
practiced by all countries, and in those in which salt
iodization is available, it is often on a voluntary basis,
giving rise to wide variations in usage. The use of
seaweeds in cooking, particularly Japanese and
Korean, results in populations in those countries
having extremely high dietary iodine intakes. Japanese
iodine intake has been estimated at about 1 mg/day
(Nagataki 2008), compared with approximately
100 lg/day in European countries (WHO 2007).
Seaweeds have also been used as agricultural fertilizers
resulting in crops of high iodine content. For example,
in Northern Ireland commercial and local harvesting of
seaweed and its application as a fertilizer on agricultural soils may in the past have contributed significant
concentrations of marine-sourced iodine to coastal
soils. Seaweed has also been used as a livestock feed in
Irish coastal communities and is often sold for human
consumption, commonly known as ‘dulse’ (Smyth and
Johnson 2010). However, apart from their occasional
use as fashionable health and cosmetic additives, it is
doubtful if current seaweed consumption makes a
significant contribution to dietary iodine intake.
Since molecular iodine (I2) was suggested to be
the dominant source of coastal reactive iodine in the
marine boundary layer during the 2002 North Atlantic
Marine Boundary Layer Experiment (NAMBLEX)
field campaign at Mace Head (Ireland) (Saiz-Lopez
and Plane 2004), it has become well established by
laboratory studies that the emission of this molecular
iodine from low tidal macroalgal exposure is indeed a
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Environ Geochem Health (2011) 33:389–397
most important process responsible for the observed
tropospheric iodine level (McFiggans et al. 2004;
Küpper et al. 2008). A diagram depicting the ocean–
atmosphere–land part of the iodine cycle (Johnson
2003) is shown in Fig. 1. Significant levels of molecular
iodine have been observed at Mace Head and nearby
sites (*100 parts per trillion (ppt) or *1,000 pg/L)
(Saiz-Lopez and Plane 2004; Saiz-Lopez et al. 2006;
Peters et al. 2005), and at La Jolla, California (*80 pg/
L) (Finley and Saltzman 2008). While most of the above
studies have been located at Mace Head, it should be
noted that Mace Head possesses perhaps the lowest algal
biomass in the region as most of the shore is characterized by bare rocks rather than notable kelp beds. This
study extends the studies at Mace Head to simultaneous
measurements in a nearby algal biomass hotspot,
Mweenish Bay where seaweed abundance of 1–5 kg/
M2 has been recorded (Sellegri et al. 2005). During a
sampling campaign in August and September, 2007,
elevated concentrations of I2 were observed in the
atmosphere, particularly over the exposed seaweed
beds (Huang and Hoffmann 2009; Huang et al.
2010a, b).
What is less well known is the extent to which
gaseous iodine released from seaweeds could contribute to dietary iodine intake through respiration
particularly in populations residing in coastal areas.
There are few studies on this subject, but Vought et al.
(1964) reported atmospheric gaseous iodine at levels
of 0–7.4 lg/m3 which they calculated on the basis of a
concentration of 5 lg/m3 would provide an iodine
intake of 100 lg/day approaching the 150 lg WHO
recommended figure. On the other hand, Johnson
(2003) has postulated an intake of 0.3 lg/day from
breathed air based on an air intake of 20 m3 per day
(Vought et al. 1970) and average atmosphere iodine
content of 10–20 ng/m3 (Whitehead 1984). However,
one of these authors (Vought et al. 1970) emphasized
that much of the discrepancies in accounts of iodine in
the atmosphere could be attribute to poor sampling
methods. It has also been established by Morgan et al.
(1968), in probably never to be repeated experiments
involving human volunteers breathing in radioactive
I2 gas, that the earliest and most important site for
inspired I2 deposition was the nasopharyngeal passage. An important feature of I2 inspiration might be
improved bioavailability from the lungs to the bloodstream in contrast to potential losses via the gastric
Environ Geochem Health (2011) 33:389–397
391
Fig. 1 The ocean–
atmosphere–land part of the
iodine cycle updated from
Fuge (1996). Reprinted
from Johnson (2003) with
permission
route (e.g. malabsorption, fecal loss). However, such
pathways are unproven.
It has long been assumed that populations residing
near the sea would enjoy superior iodine nutrition
compared with those in inland areas primarily due to
the consumption of marine-environment foodstuffs.
However, iodine deficiency has been demonstrated to
exist even in coastal communities on the Portuguese
Atlantic islands of Madeira and the Azores (Limbert
et al. 2010) with median UI values being lower than
on the Portuguese mainland. These islands support
very little seaweed growth (Limbert, Private Communication). It is the objective of this study to test the
hypothesis that gaseous iodine measured in seaweedrich coastal ‘‘hotspots’’ contributes significantly to
iodine intake, as assessed by urinary iodine (UI)
excretion, in comparison with coastal areas with lessabundant seaweed growth or inland areas.
Subjects and methods
Study populations
Subjects studied were female schoolchildren (aged
\15 years) attending schools in areas of both the
Republic of Ireland and Northern Ireland. Areas
selected are shown in the accompanying map
(Fig. 2). Informed consent was obtained from children, parents, and teachers. The study was carried out
with collaboration of the Section of Primary, Community & Continuing Care, Health Services West,
Ireland.
Subjects (N) were subdivided into groups on the
basis both of proximity to the sea and local seaweed
abundance:
Group A (N = 93): Inland, Rochfortbridge, Co
Westmeath: [100 km from the coast.
Group B (N = 28): North Coast (Irish Sea; lesser
seaweed abundance) Ballycastle, Co Antrim, within
10 km of the coast.
Group C (N = 46): West Coast, Seaweed Hotspot,
Carna, Co Galway.
In general, the Atlantic West coast of Ireland
displays the greatest abundance of seaweed growth
(Hession et al. 1998). The seaweed hotspot at
Mweenish Bay adjacent to Carna and the marine
Research Station at Mace Head has been used in many
experiments on iodine release by seaweeds (Huang
et al. 2010a, b). This is an area of high seaweed
density being a sheltered bay where seaweeds can
readily attach to rocks (Fig. 3). Seaweed density is in
the region of 1–5 kg/m2 (Sellegri et al. 2005). It
should be noted that exposure to extensive wave
action can reduce the abundance or even occurrence
of kelp (Hession et al. 1998). Ballycastle, Co Antrim,
an area with a long tradition of kelp harvesting, lies on
the more exposed Northern Irish Coast where seaweed
beds might be expected to produce and maintain less
iodine vapor.
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Environ Geochem Health (2011) 33:389–397
Fig. 2 Map of Ireland,
showing sites where urine
samples were collected
from schoolchildren. Group
A (N = 93): Inland,
Rochfortbridge, Co
Westmeath: [100 km from
the coast. Group B
(N = 28): North Coast
(Irish Sea; lesser seaweed
abundance) Ballycastle, Co
Antrim: within 10 km of the
coast. Group C (N = 46):
West Coast (Coastal;
seaweed hotspot), Carna,
Co Galway: on coast
Fig. 3 Mweenish Bay, Co Galway, Ireland. Seaweed hotspot
Methods
Atmospheric molecular iodine (I2)
The field measurements of I2 in the atmosphere were
made at the Mace Head Atmospheric Research Station
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(53.32o N, 9.90o W) and Mweenish Bay (53.31o N,
9.83o W), in Co. Galway Ireland. The latter is located
about 7 km southeast of the Mace Head research
station. Measurements were made between 6th August
and the 4th of September 2007 (Huang et al. 2010a).
Molecular iodine (I2) was measured by a diffusion
denuder system in combination with a gas chromatography–mass spectrometry (GC–MS) method,
which provides ‘‘single-point’’ in situ concentrations
of I2 at the sampling site (Huang and Hoffmann 2009).
The diffusion denuder can separate gases and particles
in the same air mass and quantitatively collect gaseous
I2 by the formation of inclusion complex between
the trapped I2 and the denuder coating materials
á-cyclodextrin/129I- (Huang and Hoffmann 2009;
Huang et al. 2010a, b). Since I2 is rapidly photolyzed
to iodine atoms during daytime, the denuder tubes
were set up directly above the algal beds with a very
short vertical distance of around 5 cm between the
seaweed and the denuder inlet to minimize the
potential influence of photolysis. The denuder method
Environ Geochem Health (2011) 33:389–397
393
has also been used to detect iodine species other than I2
including reactive iodine species HOI and ICI (Huang
and Hoffmann 2009). Measurements were made
between 7th August and 27th August, 2007 (Huang
et al. 2010b).
Urinary iodine excretion
Urinary iodine (UI) was measured using the ammonium persulfate digestion microplate method followed
by Sandell-Kolthoff colorimetry as described by
Ohashi et al. (2000). This method measures total
iodine in urine. Results were expressed as lgI/L urine
(lg/L). Quality control was assessed under the Centre
for Disease Control (CDC, Atlanta, Georgia, USA)
EQUIP (Ensuring the Quality of Urinary Iodine
Procedures) programme (Caldwell et al. 2005). Study
group values were expressed as medians and percentage of individual values indicative of iodine deficiency (\50ug/L) or higher iodine intake ([150 lg/L)
as recommended by the WHO (2007).
Statistical analysis was performed using Wilcoxon’s rank sum test for unpaired samples and the chi
squared test (Fischer’s exact test).
Results
Figure 4 shows daytime I2 values (pg/L) measured
in Mweenish Bay over the seaweed bed (hotspot)
and 150 m downwind. Measurements were taken in
five inconsecutive days over a campaign period of
30 days, and as shown, the I2 values measured over
the hotspot varied from 1,145 to 3,132 pg/L during
this period. Much lower values were observed at
the site 150 m downwind of the seaweed bed where
I2 ranged 155–905 pg/L. The variations observed in
Fig. 4 could be attributed to the properties of
different seaweeds or the surrounding atmosphere
(Huang et al. 2010). Since the inlet of the denuder
was set up very close to the seaweed beds (*5 cm)
during sampling, it is reasonable to treat these data as
local source strength. This significant decrease of I2
mixing ratio observed downwind of (i.e. further away
from) the seaweed beds could be attributed to the
rapid photolysis of I2 that has a photolytic lifetime of
10 s (Saiz-Lopez et al. 2006). Note that during these
measurements, the wind (from sea direction) passed
over the seaweed beds with a speed of 3.7–7.7 m s-1
Fig. 4 Gaseous I2 measured by a diffusion denuder system in
combination with a gas chromatography–mass spectrometry
(GC–MS) method, which provides ‘‘single-point’’ in situ
concentrations of I2 at the sampling site (Huang and Hoffmann
2009). Measurements taken in daylight at low tide over, and
150 m downwind of, the Mweenish Bay seaweed hotspot
corresponding to a transport time of about 20–41 s.
Wind directions and speeds were as follows:- 07/08/
2007, 299°, speed 6.1 m/s; 08/08/2007, 198°, speed
7.4 m/s; 15/08/2007, 330°, speed 7.7 m/s; 22/08/
2007, 316°, speed 6.8 m/s; 27/08/2007, 342°, speed
3.7 m/s. Therefore, during the 5-day measurements,
the winds were almost blowing from northwest,
except on 8th Aug (southwest). In all cases, the winds
passed over seaweed beds before reaching the sampling point. However, the averaged night-time I2
mixing ratio downwind of the seaweed beds
(*1,287 pg/L) is comparable to the levels found
directly above the seaweed beds (source strength),
although the values drop to around * 300 pg/L in
several episodes. A mixing ratio is defined as that
concentration in which one molecule of species is
present per one million molecules of air. As suggested
by Huang et al. 2010b, coastal background I2 mixing
ratios of 156–187 pg/L could be maintained even in the
face of strong ([10.8 m s-1) westerly winds (i.e. from
the sea).
Figure 5 shows the relationship of sampling time
(day v night) and tidal height to I2 released at 150 m
downwind of the seaweed bed. The maximum tidal
heights related to these data ranged from 0.5to 3.8 m.
The two factors, time and tidal height, combine to
produce the lowest values in daytime samples
(58–464 pg/L). As shown in Fig. 5, the combination
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Environ Geochem Health (2011) 33:389–397
Fig. 5 Influence of time (Nighttime (closed circle) Daytime
(open circle)) and tidal height on atmospheric I2 measured
150 m downwind of a seaweed hotspot at Mweenish Bay. Note
different scales on nighttime and daytime axes
Table 1 Possible contribution of atmospheric I2 to daily
iodine requirements
Approx.
average I2 lg
inspired/24 h
Sampling time
and location
Atmospheric
I2 pg/L
(range)
Daytime
381 (155–905)
Still night
1287
12.8
Over seaweed mass
1934 (1145–3132)
19.6 (11.5–31.3)
Coastline background
155–186
3.8 (1.5–9.0)
1.5–1.8
Amount of I2 inspired arbitrarily set at 10,000 L/day
Adapted from Huang et al. (2010a). Atmos. Chem. Phys. 10.
4823–4833
of nighttime with the lowest tide (0.5 m) gave the
highest atmospheric I2 values (1,150 and 2,000 pg/L).
In contrast, the apparent absence of photolysis (i.e.
chemical changes brought about by the influence
of light) of I2 in nighttime samples gave values of up
to orders of magnitude higher (121–2,006 pg/L). As
expected, lowest values were seen at high tide when
the seaweed was covered and therefore subject to less
stress.
Table 1 shows an approximation of possible iodine
intake from inspired gaseous I2. Calculations are
based on the average I2 (pg/L) and an assumed daily
respiration of 10,000 L of air. This is a resting level
which would be significantly increased during vigorous exercise. Using a daily intake of 10,000 L of air,
the calculated daily intake on the basis of atmospheric
I2 levels would range from 3.8 to 19.6 lg/day. This
would be significantly diminished further away from
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Fig. 6 Urinary iodine (UI) excretion expressed as median (lg/
L) and % of values \50 and [150 lg/L in the three groups of
female schoolchildren. Group A (inland); Group B (Coastal,
lesser seaweed abundance); Group C (Coastal, seaweed
hotspot)
the seaweed bed. Inland measurements were not taken
at this time. At an ambient coastal background level of
155–186 pg/L, it would only amount to a daily intake
of approximately 1–2 lg. Even using a daily air intake
of 2,000L (Vought et al. 1970) would only increase
iodine inhalation at ambient coastal background
to 2–4ug. However, it is known that children have
higher respiration rates (California EPA Research
Note 1994), which can result in their greater exposure
to pollutants and perhaps to iodine (Bateson and
Schwartz 2008).
The calculated iodine intakes shown in Table 1 are
not very significant in terms of the WHO recommended intake of 150 lg/day. However, it does not
take account of vigorous exercise, where air intake
could be several multiples of resting intake (California
Environmental Protection Agency 1994), or indeed of
possible greater bioavailability of lung rather than
gastric absorption.
The distribution of urinary iodine excretion in
different study populations is shown in Fig. 6. The
highest median UI (158 lg/L; Range 30–567 lg/L)
occurred in Group C, residing near the seaweed
hotspot. This value was significantly higher than those
of 71 lg/L (range 31–175) and 58 lg/L (range
40–303) in Groups A and B (p \ 0.01 in each case).
These findings were reflected in the number of values
indicative of iodine deficiency (\50 g/L) which
amounted to 8.7% in Group C but reached 14.5% in
Group B and was highly significantly elevated (37.6%)
in the inland population (Group A) (p \ 0.01). In
contrast, higher UI values ([150ug/L) predominated
Environ Geochem Health (2011) 33:389–397
in Group C (45.6% v 3.6% and 2.3% in Groups B and
A) (p \ 0.01).
Discussion
The use of the diffusion denuder system in combination with GC–MS measurement has demonstrated
substantially higher levels of gaseous I2 over seaweed
beds than was hitherto reported (Saiz-Lopez and
Plane 2004; McFiggans et al. 2004; O’Dowd and
Hoffmann 2005; Sellegri et al. 2005; Pirjola et al.
2005). As the values recorded in the present study
were single point in situ measurements, not surprisingly the highest values were observed over the
seaweed beds with lower values downwind. The
results obtained were of course highly variable being
dependent on wind direction and strength as well as
time of sampling (day v night) and tidal height. The
gaseous I2 levels recorded varied from a coastal
background low of 155 pg/L to a high over the
seaweed mass of 3,132 pg/L.
Attempts to apply these values to potential ingestion
by humans are fraught with difficulty. It could be
argued that the majority of people reside somewhat
inland from the coast and therefore would only be
exposed to coastal background I2 levels. On the basis of
breathing in an arbitrary daily 10,000L of air, only
1–2 lg of I2 would be ingested even in coastal areas
which in terms of the WHO recommended 150 lg/day
(WHO 2007) would be inconsequential even in an area
of borderline dietary iodine intake such as Ireland
(Nawoor et al. 2006; Lazarus and Smyth 2008). This
may indeed be the case, but the possibility of exposure
to much higher seaweed derived I2 levels cannot be
ignored. A much higher contribution of atmospheric I2
(*100 lg/day) was suggested by Vought et al. (1964).
However, the higher atmospheric values potentially yielding a dietary intake of up to 30 lg/day
could if inhaled make a significant contribution,
particularly in the context of an estimated average
requirement (EAR) of 95 lg/day (Zimmermann
2009). A major difficulty in assessing such exposure
are the many factors which could affect seaweed
derived atmospheric I2. In addition to wind direction
and strength, time of sampling and tidal height
previously mentioned, density and seaweed species
differences in iodine content and bioavailability
could determine how much gaseous I2 was available
395
for ingestion. Firstly, there is almost certainly a
difference between the coastal and inland atmospheric
iodine backgrounds with iodine levels presumably
declining with distance from the sea. Unfortunately in
this study, inland atmospheric iodine was not measured. One method of deposition would be ingestion of
sea spray which could potentially equal or exceed
gaseous iodine. However, even allowing for inhalation
of large amounts of sea spray through ingestion,
unlikely during the calm periods of study, an increment
over gaseous iodine of significant magnitude to alter
iodine nutrition does not seem probable.
The efficiency of the lung in absorbing gaseous I2
remains uncertain. The earlier work of Morgan et al.
(1968) suggested deposition of particle-associated
I2 in the nasopharyngeal tract as the major source
of ingestion. As the sodium iodide transporter NIS
has only rarely been demonstrated in lung tissue
(Spitzweg et al. 1998; Harun-Or-Rashid et al. 2010),
deposition may indeed be the most efficient pathway.
However, more recent work by Harvey et al. (2006;
Harvey 2009) documented differences in gas uptake
from that occurring as a result of particle deposition.
In particular, the inhalation dose coefficient (DC) is
much greater in younger age groups (Harvey et al.
2006) supporting findings in the present study conducted in girls aged less than 15 years. This is
consistent with the evidence that children have greater
rates of inhalation than do adults (California Environmental Protection Agency 1994; Bateson and Schwartz
2008).
However, in view of the very low atmospheric I2
recorded, it must be emphasized that some extremely
preferential I2 absorption by the lungs would be
necessary to make a significant contribution to daily
iodine intake. On the other hand, such a contribution
would be proportionally greater when iodine intake
from other sources was restricted as in individuals
with low UI (\50 lg/L). Despite the apparently low
potential contribution of seaweed-derived gaseous I2
to daily iodine intake, the findings that median UI and
% of lower and higher values in the three study
groups A-C were consistent with the presence of a
seaweed mass support some form of marine related
iodine intake. Particularly noteworthy was the finding
that 45.6% of female children living adjacent to
the seaweed hotspot had UI [ 150 lg/L compared
with 3.6% in the coastal area with lesser seaweed
abundance and 2.3% in an inland community. It is of
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396
course possible that some undetected dietary preference of the Group C children contributed to the
finding particularly in view of the large range of UI
values encountered in all three study groups. However, there was no evidence of such an intake. A wide
distribution of UI values is characteristic of this mode
of investigating iodine status, since it reflects iodine
intake over the previous 24 h rather than long-term
intake (WHO 2007; Zimmermann 2009). For this
reason, the distribution of low (\50 lg/L) and high
([150 lg/L) UI values as shown in this study
provides a useful index of iodine status.
Regional differences in food intake might in the
past have provided a satisfactory explanation for
variance in dietary intake when food consumed was
almost exclusively locally sourced, but is less likely
in the era of supermarkets with widely sourced
products. It is unclear from the results in this study
if the iodine content of air, ingested by respiration,
makes a significant contribution to overall daily iodine
intake in populations living near to, in comparison with
remote from, the sea. Interestingly Limbert et al.
(2010) reported on UI levels being lower on the Azores
and Madeira Islands where it might be expected that
iodine intake would be higher in populations residing
near the sea than in continental Portugal. As previously
stated, these islands have a very low seaweed
abundance.
This finding is supportive of the hypothesis that
iodine intake in coastal regions may be dependent on
seaweed abundance rather than simply proximity to
the sea. Certainly larger studies with greater control
of dietary input and the form of iodine inhalation
would add weight to the hypothesis as would a better
understanding of the efficiency of lung absorption
of seaweed-derived iodine. Nonetheless the findings
do not exclude the possibility of a significant role for
iodine inhalation in influencing iodine status and may
help explain why despite the absence of a regular
source of dietary iodine intake such as iodized salt,
coastal communities residing in seaweed-rich areas
can maintain an adequate dietary iodine supply. This
observation may bring new meaning to the expression
‘‘sea air is good for you’’.
Acknowledgments The authors gratefully acknowledge the
cooperation of the parents and schoolchildren of participating
schools in both the Republic of Ireland and Northern Ireland.
We greatly appreciate the assistance of the HSE, West, Dr
Karla Kyne, Area Community Medical Officer for the Carna
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Environ Geochem Health (2011) 33:389–397
Area, Dr Mary FitzGerald, Senior Medical Officer Primary,
Community & Continuing Care. Dr John O’Donnell of Galway
and Richard Fitzgerald of the Martin Ryan Institute, NUI,
Galway. Thanks to Professor Edward Limbert for helpful
discussion re Portuguese data. Financial assistance was
provided by the Health Research Board, Ireland and the Clinical Endocrinology Trust.
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