Overlooked Iodo-Disinfection Byproduct Formation When Cooking Pasta with Iodized Table Salt

Abstract

Iodized table salt provides iodide that is essential for health. However, during cooking, we found that chloramine residuals in tap water can react with iodide in table salt and organic matter in pasta to form iodinated disinfection byproducts (I-DBPs). While naturally occurring iodide in source waters is known to react with chloramine and dissolved organic carbon (e.g., humic acid) during the treatment of drinking water, this is the first study to investigate I-DBP formation from cooking real food with iodized table salt and chloraminated tap water. Matrix effects from the pasta posed an analytical challenge, necessitating the development of a new method for sensitive and reproducible measurements. The optimized method utilized sample cleanup with Captiva EMR-Lipid sorbent, extraction with ethyl acetate, standard addition calibration, and analysis using gas chromatography (GC)–mass spectrometry (MS)/MS. Using this method, seven I-DBPs, including six iodo-trihalomethanes (I-THMs) and iodoacetonitrile, were detected when iodized table salt was used to cook pasta, while no I-DBPs were formed with Kosher or Himalayan salts. Total I-THM levels of 11.1 ng/g in pasta combined with cooking water were measured, with triiodomethane and chlorodiiodomethane dominant, at 6.7 and 1.3 ng/g, respectively. Calculated cytotoxicity and genotoxicity of I-THMs for the pasta with cooking water were 126- and 18-fold, respectively, compared to the corresponding chloraminated tap water. However, when the cooked pasta was separated (strained) from the pasta water, chlorodiiodomethane was the dominant I-THM, and lower levels of total I-THMs (retaining 30% of the I-THMs) and calculated toxicity were observed. This study highlights an overlooked source of exposure to toxic I-DBPs. At the same time, the formation of I-DBPs can be avoided by boiling the pasta without a lid and adding iodized salt after cooking.

Water Analysis: Emerging Contaminants and Current Issues

“…Humans are exposed to DBPs through drinking tap water, showering, bathing, washing dishes and clothes, and swimming in pools. New research also shows that there can be exposure through foods, for example, when cooking pasta with iodized salt in chloraminated tap water, where iodo-DBPs are formed by reaction of the iodide with chloramine and organic matter in the pasta . However, adding the salt after cooking or boiling the water without a lid can avoid this.…”

“…Transformation of algal toxins during drinking water oxidation/disinfection processes was the focus of a new review by Dong et al 223 An overview of global algal toxin occurrence and regulation was also provided. Transformation kinetics, formation of DBPs/TPs, and reaction pathways are detailed for ozonation, chlorination, chloramination, UV-based advanced oxidation processes, and permanganate treatment of representative algal toxins (MC-LR, cylindrospermopsin, and βmethylamino-L-alanine (BMAA)).…”

“…New research also shows that there can be exposure through foods, for example, when cooking pasta with iodized salt in chloraminated tap water, where iodo-DBPs are formed by reaction of the iodide with chloramine and organic matter in the pasta. 68 However, adding the salt after cooking or boiling the water without a lid can avoid this. Cooking seaweed (Haidai), which contains natural iodide, in chloraminated tap water also lead to the formation of iodo-DBPs.…”