Citric acid is found in lemons and other fruit. It's a natural antioxidant. If you don't want your bananas to turn brown in a fruit salad, you dip them in lemon juice. The citric acid stops the browning reaction. It can also be added to things like artificial lemonade to give it the bite of natural lemons. I use a dilute citric acid solution on my sprouts to keep them fresh. The only hazard I could find was in the following:
Citric Acid (Acid Regulator 330): Food acid, naturally derived from citrus fruit, although commercial synthesis is by fermentation of molasses. It is used in food as an antioxidant as well as enhancing the effect of other antioxidants, and also as an acidity regulator. Present in virtually all plants, it was first isolated in 1784 from lemon juice, by the Swedish chemist Carl Wilhelm Scheele, and has been used as a food additive for over 100 years. Used in biscuits, canned fish, cheese and processed cheese products, infant formulas, cake and soup mixes, rye bread, soft drinks, fermented meat products. Damages tooth enamel. When citric acid is produced from corn, manufacturers do not always take out the protein which can be hydrolysed and create MSG (621) causing reactions in MSG-sensitive people.
I wouldn't worry about it.
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