> Worldwide, iodine deficiency affects two billion people and is the leading preventable cause of intellectual and developmental disabilities.[1][2] According to public health experts, iodisation of salt may be the world's simplest and most cost-effective measure available to improve health, only costing US$0.05 per person per year
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https://en.wikipedia.org/wiki/Iodized_salt#In_public_health_...
> Worldwide, iodine deficiency affects two billion people and is the leading preventable cause of intellectual and developmental disabilities.[1][2] According to public health experts, iodisation of salt may be the world's simplest and most cost-effective measure available to improve health, only costing US$0.05 per person per year