High Flag Guidance Range Proposal for Urinary Inorganic Arsenic in the Canadian Population

Abstract

Background/Aim: A high flag is the concentration of a given biological marker above which a participant should be informed in writing of his/her exposure results and receive information and general advice to help determine, and if necessary control, the sources of exposure. The objective of this study was to propose a guidance biomonitoring value that could be used as a high flag for summed urinary inorganic arsenic species and their metabolites (∑As), as measured in the Canadian Health Measure Survey. Methods: The starting premise of this work is that the Canadian maximum acceptable concentration (MAC) of 10 µg/L for arsenic in drinking water corresponds to a level of exposure that should not be exceeded. Thus, the urinary ∑As concentration in a population consuming drinking water contaminated at the MAC, and exhibiting a background exposure level similar to what is observed in the Canadian population, was estimated. To do so, data describing the relationship between the urinary excretion of ∑As and the As content of drinking water were retrieved from a literature review. Due to the limited number of relevant studies (n=8) and their related uncertainties, a range of significant values of interest was identified. Results: Individuals exposed to arsenic at the background level present in Canada and, additionally, to a water source contaminated at the Canadian MAC of 10 µg/L would have, on average, a urinary ∑As concentration of between 7.5 and 13.3 µg/L. These values are therefore proposed here as respectively the lower and upper limit of a high flag guidance range. Conclusions: This high flag range appears suitable to other population biomonitoring studies around the world in which the background exposure is comparable to the Canadian context. Before selecting a single value from within the proposed range, it will be important to assess the consequences that the determination of a threshold could have on the management and communication of the biomonitoring results.