What is sodium aluminum phosphate, and where do I find it?
Sodium aluminum phosphate is an ingredient commonly found in baking powders and processed cheeses. 6In baking powders, bakers use it as an acid that provides the baked goods' chemical reaction needed to rise. Sodium aluminum phosphate reacts with heat and the other leavening ingredients to allow baked goods to rise. Subscribe for weekly updates_ go.msu.edu/cris-connectManufacturers typically use it in industrial baking for products like cookies, muffins, crackers, waffles, and more.
Baking powders for home use don't typically contain aluminum because the leveling ingredients usually react to moisture rather than heat for the needed chemical reaction. In processed cheeses, manufacturers use it to create a smooth, soft texture with easy melting and slicing characteristics.

Why do some people believe it's harmful?
Sodium aluminum phosphate contains two components that raise some people's concerns: phosphate and aluminum. It's known that excessive phosphorus consumption can cause kidney harm, especially in people with kidney conditions. Sodium aluminum phosphate is considered a phosphorus-containing ingredient. 
Additionally, some studies suggest that excessive aluminum exposure, especially exposure that can occur in occupational settings like aluminum production, may cause adverse reproductive and neurological health impacts. As we know, hazard does not equal risk, and it's unlikely we'd be exposed to harmful levels of aluminum in the ingredients we use in our everyday life.

What does the science say about safety?
The United States Food and Drug Administration (FDA) recognizes sodium aluminum phosphate as a GRAS ingredient that does not pose health risks unless consumed in significant quantities. It would be unlikely for someone to consume sodium aluminum phosphate in the amounts needed to cause harm.  In 2018, the European Food Safety Authority (EFSA) reviewed sodium aluminum phosphate, known in Europe as E 541. In their safety analysis, they took into consideration the bioavailability of sodium aluminum phosphate. Bioavailability, in this case, refers to the amount of E 541 our bodies absorb after consumption. Due to E 541's limited absorption and its limited usage in products, EFSA determined E 541 is safe to consume in typical quantities. 

What should I keep in mind?
Remember, the dose makes the poison. For sodium aluminum phosphate to cause harm, there needs to be significant, repeated exposure to this ingredient. The exposure would need to be many times greater than what we encounter in daily life.  
It's important to note that the FDA and EFSA consider vulnerable populations like young children and individuals with health conditions when making safety recommendations. If an ingredient impacts people's health, it can be banned and no longer sold or may contain additional warnings for people with specific health conditions.