Trisodium phosphate is probably safe in food.
Trisodium phosphate is a non-toxic white salt that has many different applications. Tiny amounts are used in food to control acidity levels, and to mix oil and water as an emulsifier. In concentrated form, trisodium phosphate is used in a couple of industrial processes. Because it's extremely basic, it works well as a cleaning agent - you can use it for everything from wiping down a floor to disinfecting a wine barrel.
Understandably, that scares some people - why would a cleaning agent be used in their food? Seattleorganicrestaurants.com has a page to that effect, claiming that your kids (your kids!) are daily exposed to dangerous amounts of trisodium phosphate and that the only reason it hasn't yet been banned is that the experiments would be so gruesome as to never get the green light. Naturalsociety.com took the same argument a step further, calling trisodium phosphate an "industrial strength paint thinner" and implying that it's in your food at, well, industrial paint-thinning levels.
That's a dishonest argument. Trisodium phosphate, as discussed above, is very basic. It's also useful for emulsifying oils - breaking them up into tiny suspended droplets so they mix well with liquid solutions. The FDA has approved it as a food additive at a fraction of a percent of the overall product; thus, small amounts are used to make cereal dough less acidic (cereal dough is very acidic - it has a very low pH).
The reasons for small amounts of trisodium phosphate being useful in food - their high pH and emulsifying properties - are the same that much higher amounts are useful in cleaning. Get together hundreds or thousands of times as much trisodium phosphate as you consume in a week, and you can use it to thin paint by emulsifying the oils therein or to scrub grime off of a surface. The Clean Water Act regulates the release of these industrial concentrations of trisodium phosphate into bodies of water, just as they do with any concentrated substance that's very basic or acidic (The EPA regulates streams, not food, and this isn't an inter-agency disagreement between them and the FDA).
The key here is concentration - as they say, the difference between medicine and poison is the dose. A Coca-Cola once in a blue moon won't kill you; concentrate the phosphoric acid therein, however, and you can use it to clean your toilet. There's not enough trisodium phosphate in cereal to hurt you - because it's basic, it actually makes the cereal a bit less acidic, and thus slightly easier on your teeth or stomach ulcers. Provided you don't eat the concentrated salts you find at the hardware store, you'll be fine.
Commonly found in
- processed meats
- processed cheeses
- canned foods
- cleaning agents
- stain removers