Abstract
This paper applies probabilistic risk assessment in quantifying risks from cumulative and aggregate risk pathways for selected goitrogens in water and food. Results show that the percentages of individuals with a Hazard Index (HI) value above 1 ranges between 30% and 50% both with and without serum half-life correction when a traditional regulatory assessment approach based on establishment of a No Observed Effects Level (NOEL) is used. When an exposure-response curve is instead used and a threshold of 50% inhibition is assumed, 1.1% or less of the population exceeds an HI value of 1 with no serum half-life correction, rising to as high as 11% when serum half-life correction is applied. If 0% to 5% threshold for iodide uptake inhibition is assumed for production of adverse effects, the percentage of the population with an HI above 1 is 46.2% or less with no serum half-life correction, and 47.2% or less when serum half-life correction is applied. The probabilistic analysis shows that while there are exposed groups for whom perchlorate exposures are the primary cause of individuals having HI values above 1, these constitute significantly less than 1% of the population. Instead, the potential risk from exposure to goitrogens is dominated by nitrates without serum half-life correction and thiocyanates with serum half-life correction, suggesting public health protection is better accomplished by a focus on these and other goitrogens expect in highly limited cases where waterborne perchlorate is at unusually high concentrations.
Highlights
There is increasing attention in the US and EU on perchlorate as a potential public health risk in both food and water [1]
Perchlorate shares a mode of action with a broad class of goitrogens, or compounds that suppress the function of the thyroid gland through interfering with iodide uptake
Risk of adverse effect is modelled here through calculation of the inter-subject variability distribution of the Average Daily Rate of Intake (ADRI) of a risk agent. Note that this is the same set of units as the daily intake associated with safe levels of consumption (RfD, or the units of TDI or PMTDI can be used when placed onto a per-unit-body-mass basis) that underlies the traditional approaches to regulatory risk assessment
Summary
There is increasing attention in the US and EU on perchlorate as a potential public health risk in both food and water [1]. That attention began with a focus on waterborne exposures, there are significant exposure routes through food. The issue of perchlorate exposure is at least one of aggregate risk assessment [2], with attention directed towards all routes of exposure to perchlorate when considering protection of the public health. Perchlorate’s mode of action is primarily through inhibition of uptake of iodide into the thyroid, largely through the sodium-iodide symporter mechanism. In this regard, perchlorate shares a mode of action with a broad class of goitrogens, or compounds that suppress the function of the thyroid gland through interfering with iodide uptake. Perchlorate exposures should be seen in a framework of cumulative risk assessment, where it is one of a number of goitrogens that act collectively in reducing thyroid function and producing adverse health impacts on metabolism and development
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