Why chlorate occurs in potable water and processed foods: a critical assessment and challenges faced by the food industry

Abstract

Recently, reports have been published on the occurrence of chlorate mainly in fruits and vegetables. Chlorate is a by-product of chlorinating agents used to disinfect water, and can be expected to be found in varying concentrations in drinking water. Data on potable water taken at 39 sampling points across Europe showed chlorate to range from < 0.003 to 0.803 mg l(-1) with a mean of 0.145 mg l(-1). Chlorate, however, can also be used as a pesticide, but authorisation was withdrawn in the European Union (EU), resulting in a default maximum residue limit (MRL) for foods of 0.01 mg kg(-1). This default MRL has now led to significant problems in the EU, where routinely disinfected water, used in the preparation of food products such as vegetables or fruits, leaves chlorate residues in excess of the default MRL, and in strict legal terms renders the food unmarketable. Due to the paucity of data on the chlorate content of prepared foods in general, we collated chlorate data on more than 3400 samples of mainly prepared foods, including dairy products, meats, fruits, vegetables and different food ingredients/additives. In total, 50.5% of the food samples contained chlorate above 0.01 mg kg(-1), albeit not due to the use of chlorate as a pesticide but mainly due to the occurrence of chlorate as an unavoidable disinfectant by-product. A further entry point of chlorate into foods may be via additives/ingredients that may contain chlorate as a by-product of the manufacturing process (e.g. electrolysis). Of the positive samples in this study, 22.4% revealed chlorate above 0.1 mg kg(-1). In the absence of EU levels for chlorate in water, any future EU regulations must consider the already available WHO guideline value of 0.7 mg l(-1) in potable water, and the continued importance of the usage of oxyhalides for disinfection purposes.

Chlorate and Other Oxychlorine Contaminants Within the Dairy Supply Chain

“…This recycling practice is common throughout food processing with treatments using active chlorine utilized to keep the microbial quality of the water at an acceptable level. The further chlorination of the rinse water can cause a concentration of chlorate residues, which leads to residual contamination within the food chain (EFSA, ; Kettlitz et al., ). In the case of the water industry, chlorate is considered to come from hypochlorite reagents (Garcia‐Villanova et al., ).…”

“…The addition of oxidants as part of a CIP process generates a variety of DBPs, which have been linked to numerous health effects (Clark, Goodrich, & Deininger, ). The toxicology of chlorate and other chlorine DBPs has become an area of growing interest, due to the wide distribution of these micropollutants in food and water used for public consumption worldwide with established health‐based guidance values summarized in Table (Asami et al., ; EFSA, , ; Erdemgil, Gözet, Can, Ünsal, & Özpınar, ; Kettlitz et al., ).…”

“…Therefore, the use of water in the preparation of food is a major source of chlorate entry into numerous food products (CVUA, ). This can have a substantial impact on chlorate levels in dairy products that must be rehydrated before consumption, namely infant milk formula and nutritional protein powders (Kettlitz et al., ).…”

Advanced hybrid electro-oxidation & O3 technology for water reuse in the fruit and vegetable process industry

“…However, hyperchlorination of water with high total organic carbon (TOC) content may produce unacceptably high levels of disinfection by-products (DBPs) such as trihalomethanes. Accordingly, the use of chlorine is being gradually reduced and, in some countries such as Germany, even banned (Kettlitz et al 2016). Some alternatives to the use of chlorine have been investigated (Gopal et al 2010) but none of them have gained widespread acceptance due to economic competitiveness limitation compared to inexpensive chlorine-based reagents or some limitations that must be overcome.…”

Microbial transformation of organic and inorganic halogen compounds

“…Organic and inorganic halogen compounds are usually manufactured in large volumes for a broad range of industrial and agricultural applications due to their extensive structural, chemical-physical varieties, and desirable properties. For example, carbon tetrachloride is manufactured as fire extinguishant (Langford 2005), chloroethenes as solvents (Stringer and Johnston 2001), chlorofluorocarbon as refrigerant (Watanabe and Tsuru 2008), chloropropionates and chlorate as pesticides (Kettlitz et al 2016, Lin et al 2011, and chloramphenicol and vancomycin as drugs (Eliopoulos and Wennersten 2002, Piontek et al A B C D E 2018). As a result of the massive anthropogenic production of organohalogens and inorganic halogen compounds, each year large quantities of these compounds are accidentally and/or deliberately released into the environment.…”