Biomonitoring Equivalents for interpretation of urinary iodine
- DOI
- Language of the publication
- English
- Date
- 2018-01-28
- Type
- Article
- Author(s)
- Hays, Sean M.
- Poddalgoda, Devika
- Macey, Kristin
- Aylward, Lesa
- Nong, Andy
- Publisher
- Elsevier
Abstract
Iodine is an essential nutrient whose deficiency or excess exposure can cause adverse health effects. The primary sources of iodine exposure in the general population are iodized salt, dairy products, bread and sea food. Urinary iodine concentrations (UIC) have been measured by Canadian Health Measures Survey (CHMS) and US National Health and Nutrition Examination Survey (NHANES). The Institute of Medicine (IOM), the US Agency for Toxic Substances and Disease Registry (ATSDR) and World Health Organization (WHO) have established exposure guidance values for nutrition (IOM Estimated Average Requirement (EAR), Recommended Dietary Allowance (RDA), WHO Recommended Nutrient Intake (RNI)) and toxicity (IOM Tolerable Upper Intake Level (UL); ATSDR Minimal Risk Level (MRL), WHO International Programme on Chemical Safety (IPCS) Tolerable Daily Intake (TDI)). Using a urinary excretion fraction of 0.9, Biomonitoring Equivalents (BE) for the EAR, RDA, UL and MRL were derived for adults (60, 100, 730 and 450 μg/L, respectively) and children (50, 80, 580 and 360 μg/L, respectively). The population median UIC values from NHANES and CHMS for adults (140–181, 122–126 μg/L, respectively) and children (232, 189 μg/L, respectively) were above the criteria for assessing iodine nutrition, indicating that US and Canadian populations are likely to have adequate population iodine nutrition. The median UIC from NHANES and CHMS do not exceed BE values derived from exposure guidance values for toxicity.
Plain language summary
Several studies have been recently conducted to measure the levels of chemicals in the blood and/or urine of Canadians. These biomonitoring surveys generate increasing data on chemicals that are found within the general population; however, the presence of a chemical within the body does not necessarily indicate there is the potential for harm. The concept known as Biomonitoring Equivalents (BE) has been developed to aid in interpreting and communicating biomonitoring results in the context of potential risks to health. A BE is defined as the concentration of a chemical in blood or urine that corresponds to a health-based exposure value. By comparing biomonitoring data for a chemical with its BE, one can assess whether population exposures to the chemical are below or above a level that is not considered to be harmful. To inform Health Canada’s risk assessment of iodine-containing substances, this study reviewed several available health-based exposure guidance values and calculated a BE in urine. Iodine is an essential nutrient if intake is within a narrow range of concentrations. As such, health authorities have established guidance values to help people avoid either insufficient or excessive iodine exposure. Different BE values were derived for various guidance levels for adults and children. The population median iodine concentrations in urine measured in the US National Health and Nutrition Examination Survey (NHANES) and Canadian Health Measures Survey (CHMS) for adults and children were above the World Health Organization (WHO) epidemiological criteria for assessing iodine nutrition. In addition, NHANES and CHMS results suggest that the US and Canadian populations are likely to have adequate iodine intake. The population median urine levels from NHANES and CHMS do not exceed the BE values derived exposure guidance values for toxicity. The outcome of this work will assist Health Canada in the prioritization of any further iodine-related risk assessment or management actions, in a public health context. This study was conducted in collaboration with Summit Toxicology, LLP.
Subject
- Health,
- Health and safety