Bulletin of the World Health Organization

Access to iodized salt in 11 low- and lower-middle-income countries: 2000 and 2010

Thach Duc Tran a, Basil Hetzel b & Jane Fisher a

a. Jean Hailes Research Unit, School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria 3004, Australia.
b. International Council for Control of Iodine Deficiency Disorders, Women's and Children's Hospital, North Adelaide, Australia.

Correspondence to Thach Duc Tran (email: thach.tran@monash.edu).

(Submitted: 13 June 2015 – Revised version received: 07 November 2015 – Accepted: 16 November 2015 – Published online: 01 December 2015.)

Bulletin of the World Health Organization 2016;94:122-129. doi: http://dx.doi.org/10.2471/BLT.15.160036

Introduction

The International Council for Control of Iodine Deficiency Disorders (ICCIDD) estimated recently that 28.5% of the world’s population have insufficient dietary iodine intake as indicated by a urinary iodine concentration less than 100 µg/L.1 Proportions of the population with iodine deficiency are higher in countries in Africa, South-east Asia, the Eastern Mediterranean regions and eastern Europe than in other parts of the world. Among adults, iodine deficiency leads to an enlarged thyroid gland (goitre). Maternal iodine deficiency during pregnancy can cause stillbirth or mental and physical growth deficits among children.2,3

Since 1994, universal salt iodization has been recommended by the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) as a safe and cost-effective strategy to ensure sufficient dietary iodine intake.4 The advantages of using salt as a vehicle of the delivery of iodine to people are as follows: (i) salt is one of the few commodities consumed daily by everyone regardless of geography and culture; (ii) the numbers of salt producers are usually limited in each country, allowing effective monitoring of the quality of salt iodization; (iii) iodization is a well-established method that is relatively easy to transfer and implement at a reasonable cost; and (iv) consumer acceptance is high because iodization does not affect the colour, taste or odour of salt. A recent meta-analysis of 87 studies worldwide showed that iodized salt reduces goitre with a pooled relative risk of 0.30 (95% confidence interval, CI: 0.23–0.41) and cretinism with a pooled odds ratio 0.13 (95% CI: 0.08–0.20).5 Intelligence quotient (IQ) scores increased by an average of 8.18 points, (95% CI: 6.71–9.65) and urinary iodine concentration by an average of 59.22 µg/L, (95% CI: 50.40–68.04) among children.5

Most countries passed salt iodization legislation and introduced salt iodization and iodine deficiency disorders’ control programmes to ensure that more than 90% of households have access to adequately iodized salt, containing 15–40 parts per million (ppm) of iodine.6 However, not all salt iodization laws comply fully with the universal salt iodization strategy.4 In 2013, for example, only 22 of 25 countries in south and east Asia and the Pacific had salt iodization legislation and only 11 had compulsory iodization of salt for use in food processing industries and households.7 Many countries, including Brunei Darussalam, Indonesia, Myanmar, Ukraine and Viet Nam still permit production and sale of non-iodized salt.

Global household coverage of iodized salt increased dramatically during the 1990s from less than 10% to 66%.8 In 2011, approximately 70% of all households globally had access to adequately iodized salt.9,10 Among 128 countries with available data on iodized salt, household coverage is greater than 90% in 37 countries, 50–90% in 52 countries and less than 50% in 39 countries.11 Countries with the least access to iodized salt are in Africa, the eastern Mediterranean and south-east Asia regions.11

Household coverage with iodized salt is a key indicator in Multiple Indicator Cluster Surveys (MICS), which are international household surveys initiated by UNICEF. Here we use MICS data to describe changes in household coverage with iodized salt between 2000 and 2010. We also describe patterns of coverage in relation to socioeconomic factors, within and between countries.

Methods

These surveys involve a nationally representative sample of between 5000 and 40 000 households using a multistage, cluster sampling technique. Data are collected through home visits and structured face-to-face interviews by national data collection teams; household salt samples are tested for iodine content by the interviewer using standardized test kits. The kits contain a starch-based solution that turns blue if iodine is present. The intensity of the colour varies with the amount of iodine and by matching it with the colour chart the iodine concentration can be ascertained. Salt containing 15 ppm or more of iodine is considered to be adequately iodized in MICS. Results are categorized as follows: (i) not iodized; (ii) iodized at more than 0 ppm and less than 15 ppm; (iii) iodized at 15 ppm or more; (iv) no salt in the household; and (v) not tested.

An index of household wealth is constructed on the basis of household characteristics, including the main materials of the dwelling’s floor, roof and exterior walls; main type(s) of fuel used for cooking; source of drinking water; type of sanitation facility; and household assets.

National indicators

The country-level socioeconomic indicators used in this study are gross domestic product per capita (GDP) and the Human Development Index (HDI) – a composite index reflecting life expectancy, education and the proportion of the population living above the international poverty line income.12 HDI ranges from 0 (the worst) to 1 (the best). Country HDIs are reported annually in Human Development Reports from the United Nations Development Programme. Estimates of GDP per capita are provided annually by the World Bank.13 MICS data from rounds two (in 2000), three (in 2005) and four (in 2010) were downloaded from the MICS website.14 We analysed data for the 11 countries with data on household coverage with iodized salt in rounds two and four.

Analysis

Indices of household salt iodization in 2000 and 2010 were calculated, taking into account the sampling weights in each survey. We calculated two indices of the proportion of households with adequately iodized salt: (i) the number of households with salt iodized to at least 15 ppm divided by the total number of households surveyed; and (ii) the proportion of households with adequately iodized salt among households with any iodized salt. These indices were also calculated for urban and rural households and by quintiles of the household wealth index.

We calculated the median proportion of households with adequately iodized salt for the year 2000 and 2010 by national HDI and GDP. Kendall's tau correlation coefficients were calculated to measure the associations among indices.

Results

The total number of households included in the analyses ranged from 3801 to 24 448 in 2000 and from 7736 to 35 635 in 2010 (Table 1). The exclusion rates (missing data or salt not tested) ranged from 0.05% in the Republic of Moldova to 9.28% in Swaziland in 2000 (overall 2.15%), and from 0.18% in Iraq to 5.66% in Chad in 2010 (overall 2.13%).

Indicators

All households

The proportion of households with adequately iodized salt varied widely among the 11 countries (Fig. 1). Between 2000 and 2010, household coverage of adequately iodized salt increased by 6.1% on average, but with regional differences: coverage fell by 13.0% in the Central African Republic but improved by 40.4% in Sierra Leone (Table 2).

Fig. 1. Proportion of households with adequately iodized salt by country, 2000 and 2010
Fig. 1. Proportion of households with adequately iodized salt by country, 2000 and 2010

Coverage was generally higher in urban than in rural areas. Overall, there were greater improvements, but from a lower base, in rural than in urban areas. Coverage was higher in wealthier households; however, the largest improvement in coverage over the 10 years was among the poorest groups (Table 2).

There was a negative correlation between the proportion of households with adequately iodized salt in the year and the change in coverage over 10 years (correlation coefficient = −0.58). There were weak correlations between the changes in coverage from 2000 to 2010 and HDI (correlation coefficient = 0.11) or GDP (correlation coefficient = 0.05). The improvements were slightly higher in the countries with higher HDI and GDP (Table 3). However, coverage was lower in countries where HDI and GDP were high.

Households with adequately iodized salt

Among households with iodized salt, coverage with adequately iodized salt increased by 5.1% on average between 2000 and 2010. Coverage improved slightly more in urban (2.6%) than in rural (1.6%) areas (Table 4). The poorest households had the smallest changes. The countries with higher HDI and higher GDP had greater improvements from lower initial levels (Table 5).

Discussion

We examined the household coverage of adequately iodized salt in 11 countries that have relevant Multiple Indicator Cluster Survey data from both 2000 and 2010. Overall, there has been a remarkable improvement in the proportions of households with adequately iodized salt, but there are substantial inter-country differences. Four countries (Mongolia, the Republic of Moldova, Sierra Leone and Sudan) made improvements, five countries (Chad, the Democratic Republic of the Congo, Kenya, Swaziland and Viet Nam) were relatively stable and two countries (the Central African Republic and Iraq) had reductions in coverage.

The four countries with improvements in coverage all had low initial coverage. In these countries, efforts by national governments, international agencies and the mass media to promote the production and consumption of iodized salt were implemented during this period (Table 6). The Republic of Moldova relies entirely on imports of household salt; in the late 1990s the government released a decree banning the importation of non-iodized salt.15 UNICEF supported the National Maternal and Child Health Programme during 2000 to 2004 in advocacy, communication, monitoring, evaluation and legislation for salt iodization. Iodization equipment for one main salt importer was supplied to enable the initiation of domestic iodization in the Republic of Moldova.20 In 2002, a situation analysis was conducted in the Republic of Moldova, followed by a 3-month mass media campaign. Two national multi-sector workshops developed a collaborative plan of action to eliminate iodine deficiency. As a result, a National Programme to Eliminate Iodine Deficiency Disorder, promoting the supply of iodized salt, was started in 2004.15

In Mongolia, the first National Programme on Elimination of Iodine Deficiency Disorder, from 1996 to 2001, introduced iodized salt for food consumption.21 The second and third stages of this programme were implemented from 2002 to 2010, and included multiple activities to improve use of iodized salt including legislation and public awareness campaigns. The government released national standards for iodized salt (in 2001), legislation (Prevention of Iodine Deficiency Disorder by Salt Iodization, in 2003) and regulations that mandated salt iodization (in 2006).22

The two African countries in this group (Sierra Leone and Sudan) all experienced civil wars during the 1990s, which are likely to have affected implementation of programmes and could account for the low prevalence of households consuming iodized salt in 2000. Government commitments combined with financial and technical support from international agencies including WHO, UNICEF, and ICCIDD contributed to significant changes, in particular in Sierra Leone.

Chad, the Democratic Republic of the Congo and Swaziland had approximately 50% coverage in 2000 and this remained unchanged in 2010. In these countries, no significant changes in the policy and government efforts concerning salt iodization were implemented during this period.

Kenya scaled up its universal salt iodization programme and was successful in sustaining coverage for the decade. In Viet Nam, the National Iodine Deficiency Disorder Control Programme, supported by UNICEF and ICCIDD, was implemented between 1995 and 2005 and led to an increase in the coverage of iodized household salt from 25% in 1993 to 94% in 2005.23 In 2005, the government declared that iodine deficiency had been eliminated in Viet Nam, changed the policy about salt iodization from mandatory to voluntary, and significantly reduced the budget allocated for iodine deficiency disorder control activities.24 As a result, the coverage of iodized household salt in 2010 reversed to almost the same level it had been in 2000.

In the Central African Republic and Iraq, coverage decreased significantly from 2000 to 2010. It is likely that military conflict prevented implementation of public policies and services for the civilian population, since both countries were seriously affected by wars during this period.

There were disparities in access to adequately iodized salt, both between rural and urban areas and the poorest and the richest in 2000 and 2010. In 2000, the coverage in urban areas was 20.9% higher than in rural areas, but the gap reduced to 8.7% in 2010. Similarly, the proportion of households in the richest quintile with adequately iodized salt was 25.0% higher than that of the poorest quintile households in 2000, but this reduced to 19.3% in 2010. Even though the inequalities have been reduced in the past decade, the differences between the poor and the rich and between urban and rural remain substantial in many countries.

We acknowledge that the pooled statistics used in this study are summaries of national data and are not representative of specific populations or resource-constrained countries in general. However, these findings can inform strategies for achieving the global goal of more than 90% of households with adequately iodized salt. First, the largest improvement in the coverage of adequately iodized household salt in the decade 2000–2010 was in the countries that started at very low levels and had buy-in from national governments and support from international donors and other agencies. This group of countries appears to be implementing scaling-up salt iodization programmes effectively. Countries with coverage of 50% or higher, in which salt iodization had been scaled up, appeared to face challenges to make further improvements. Some countries are experiencing significant difficulties, including military conflicts which undermine progress. Second, socioeconomic disparities in access to adequately iodized salt are substantial in many countries, suggesting that equity should be addressed explicitly in salt iodization policies. Finally, countries affected by war require explicit additional support from international agencies to achieve universal salt iodization during and following military conflict.

A combination of sustained commitments from governments, the salt industry, international donors and civil society has resulted in remarkable advances in household salt iodization in the past 20 years.25 Countries with significant achievements had an operational, political and regulatory environment including passing legislation mandating iodization of salt, effective monitoring systems, strong partnerships with the salt industry, and strategic advocacy and communication efforts.9,26 Countries which maintained low coverage or experienced reduced coverage appeared to lack a political will to advance iodization programmes, had poorly developed salt industries reliant mostly on small-scale producers or little local salt production, had weak government inspection and enforcement systems, and/or were involved in military conflict which severely limited the country’s capacity to implement health programmes.

In conclusion, changes in iodized household salt coverage from 2000 to 2010 vary widely among countries. The achievement and maintenance of universal salt iodization appears a remote goal for many resource-constrained countries and requires explicit renewed efforts by governments, bilateral and multilateral agencies and civil society to avoid the burden of iodine deficiency disorders in the population.


Acknowledgements

We thank Pieter Jooste, ICCIDD Regional Coordinator for Southern Africa.

Funding:

JF is supported by a Professorial Fellowship from Monash University and the Jean Hailes Professorial Fellowship which is funded by the L and H Hecht Trust, managed by Perpetual Trustees. TDT is supported by a Bridging Postdoctoral Research Fellowship from Monash University and an Early Career Fellowship from the Australian National Health and Medical Research Council.

Competing interests:

None declared.

References