Outbreaks of foodborne diseases have raised concerns about the safety of U.S. food supply. The CDC estimates that each year, approximately 48 million people in the U.S. get sick, and 3,000 die, from foodborne diseases. The addition of chlorine-based disinfectants (e.g., chlorine, chloramines) is a promising strategy for disinfection of water used for vegetable irrigation and produce washing to control pathogen risks by preventing cross-contamination. However, disinfectant exposures need optimization, as high disinfectant concentrations may lead to an increased formation of chemical disinfection byproducts (DBPs). In particular, inorganic DBPs, such as bromate and chlorate, have received significant attention, in part because the European Union (EU) has considered a maximum residue level (MRL) of 0.01 mg/kg for chlorate in food, and concerns over chlorate accumulation are threatening exports to the EU. Previous studies have demonstrated that chlorate concentration in water increases during produce processing, but have primarily focused on the washing step.  In this study, we investigate the effect of sunlight on the formation of chlorate and bromate in irrigation water and on produce surface, as UV irradiation has been demonstrated to increase the production of radicals, and correspondingly chlorate, in chlorinated water. We evaluate the extent to which sunlight enhances DBP formation, and whether (1) sunlight illumination of irrigation droplets containing chlorine/chloramine forms chlorate and bromate, and (2) chlorate and other DBPs occurring in the irrigation water can be taken up through the leaves. Our results suggest that sunlight enhances the formation of both chlorate and bromate from irrigation waters containing chlorine and chloramine.

Effect of sunlight on the formation of inorganic disinfection byproducts in water and on produce surfaces

ACS Fall 2021

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