General Questions
What are phosphates, and what is the difference between phosphorus, phosphates and phosphoric acid
Phosphorus is a mineral that is essential to human, animal and plant life. In your high school chemistry class, it was presented as one of the elements on the Periodic Table. Phosphorus occurs in nature and is often found in combination with other minerals, such as calcium and sodium.

Phosphates are natural compounds – salts containing phosphorus and other minerals. The main minerals in bones and teeth are types of phosphates with the scientific names of hydroxyapatite or tricalcium phosphate. Phosphates are used in a variety of applications including personal care products, water treatment, industrial and institutional cleaning, and building and construction.

Phosphoric acid is an inorganic acid that is used as a starting point to produce many phosphate derivatives. The most common form of phosphoric acid is produced by adding sulfuric acid to phosphate rock. [_/su_spoiler]

Are phosphates natural?
Phosphates are derived from phosphate rock, which is mined from the earth. The rock is crushed and purified to form phosphoric acid, which may be reacted with caustic soda or lime to produce purified phosphate salts. [_/su_spoiler]
How are phosphates formed?
Phosphate rock is mined to obtain phosphorus. The natural phosphate rock includes clay and other minerals, so it must be purified using caustic soda or lime to isolate phosphorus in the form of phosphoric acid. The acid is reacted with alkaline salts to produce purified phosphate salts. [_/su_spoiler]
Why are phosphates used as ingredients in food and also industrial products like paint, drywall and fire extinguishers?
 Great question, because it really gets to the heart of the chemistry of what phosphate compounds can do.  Phosphates have many great qualities, including an amazing ability to keep compounds together that normally want to be separate from each other.  The simplest example for most people to understand is salad dressing.  When you have oil and vinegar, along with herbs and spices, in a salad dressing, the dressing will separate into layers when it sits for a few minutes.  You shake the dressing before you put it on your salad and for the short while that you are pouring everything stays mixed together evenly so you get all the flavors of the dressing on your salad.  When those ingredients are all mixed together, evenly dispersed, that is called an emulsion.  A substance that facilitates a nice, even mixture like that is called an emulsifier.  Some types of phosphates are emulsifiers.  They bring together and keep together substances that normally want to separate into layers.  That kind of function, an emulsifier, is useful for foods, like beverages, but also for paint and other liquid industrial products. Emulsification is just one of the functions of phosphates.  There are other things phosphates can do that have use in both foods and “industrial” products.

The fact that phosphates can bring together and keep together many different kinds of compounds is the nature of their chemistry and has nothing to do with their safety.  People misconstrue this fact, of the different uses of phosphates in foods and in industrial products, as an indication of whether they are safe (or not) for use in foods.  That is like saying that table salt (sodium chloride) is unsafe to eat because it can also melt ice on your driveway.  Yes, the same substance can do something “industrial” but that is not what makes it safe (or not) to put in your food. [_/su_spoiler]

OK, now I understand the chemistry but what I really want to know is whether I am getting industrial chemicals in the foods that I eat.

No, you are absolutely not getting industrial chemicals in the foods you eat.  Different grades of a material are allowed for use in different types of products.  For example, an industrial grade phosphate is produced under different conditions than a food grade phosphate and is not allowed to be used as a food ingredient.  On the other hand, phosphate food ingredients must be made under strict manufacturing conditions, dictated by the laws enforced by the US FDA (which inspects phosphate manufacturers just like other food ingredient manufacturers), and specific for the safety of foods and food ingredients.  In addition, phosphate makers must ensure that their product meets “purity and identity” requirements before they can sell those ingredients to food makers.  “Purity” means that there is nothing in the food ingredient that is going to make it unsafe to use in food and “identity” means that the food ingredient manufactured (and about to be shipped) is actually what the  food maker ordered.  These are all requirements that phosphate food ingredient manufacturers must follow before their sell their products.  There are different requirements for industrial and other grades of phosphates. [_/su_spoiler]

Are phosphates essential to life?
Yes. Phosphates contain essential nutrients that are needed for human, animal and plant life. They have critical functions in key biochemical processes such as metabolism. Our bodies are made of many phosphorus-containing compounds that play a major role in:

  • Genetic material – the DNA and RNA that makes each of us unique
  • Cellular membranes
  • Teeth and bones
  • Human energy systems
  • Cell signaling systems, which regulates diverse functions from the acid-base balance in the body to hormonal responses.
  • Plants also need phosphorus, and phosphorus-containing compounds are vital to photosynthesis.
Environmental Questions
How do phosphates enter the environment?
Many phosphates occur naturally in the environment as minerals and as essential nutrients for plant and animal life. In the phosphorus nutrient cycle, plants absorb phosphates from water and soil. Phosphates are available to animals and humans when plants (and other animals) are consumed and are then returned to the environment through animal and human waste and decomposition of plants and animals.
Where do phosphates go in the environment?
Crops take up phosphates from fertilizer, all of which may not be utilized. Some phosphates remain in the soil in a mineralized form and some are lost by soil erosion and runoff. Agricultural runoff and unprocessed animal waste may reach streams and lakes. Although phosphates are a nutrient compound, and in combination with other nutrients support aquatic life, they can have an adverse effect on ecosystems at higher concentrations. For example, a condition known as “eutrophication” can occur by which a lake or pond becomes rich in plant nutrient minerals and organisms, but often deficient in oxygen in midsummer. This can have a temporary adverse impact, with the situation reversing as the phosphates eventually are precipitated (or re-mineralized).
Why are phosphates used in water treatment facilities?
Municipal water treatment facilities add inorganic phosphates to water at very low levels to act as corrosion inhibitors in metal plumbing lines and help prevent the potential leaching of heavy metals, such as lead and copper, into the water supply. Phosphates are either added in the coating of metal plumbing lines or are flushed through the water system, resulting in very small amounts of phosphates in drinking water. Phosphates also provide other important benefits in the treatment of potable water, including corrosion control and scale inhibition.
Consumer Product Questions
Why are phosphates in fertilizer?
Phosphates contain essential nutrients that are necessary for plant growth and health, and are the most stable compounds to deliver phosphorus to plant roots. When choosing the right fertilizer, the phosphorus content is one of the key properties to consider, along with levels of nitrogen (for growth and greening) and potassium (for drought and disease resistance). Highly soluble ammonium phosphate and potassium phosphate salts can be blended with other sources of nitrogen and potassium to develop a variety of products to meet specific fertilizer needs.
Why are phosphates used in cleaning products and detergents?
Phosphates act as a key ingredient in many cleaning products and detergents. They serve multiple functions, providing properties that increase the effectiveness of a variety of products. Phosphates offer two main benefits for detergents. First, the application of phosphates during the cleaning process helps prepare the water or cleaning environment by removing any hardness ions present in the water (such as calcium, magnesium or iron), which allows other components to work more effectively. Phosphates then trap and hold fine particles such as dirt and oils so they can be effectively removed during rinsing. In addition, due to their unique buffering capabilities, phosphates prevent soil and other cleaning components from shifting the pH of a cleaning solution, which can diminish its optimum cleaning efficiency range.
Why are phosphates used in flame retardants?
Many phosphorus containing materials are used as flame-retardants for textiles, plastics, coatings, paper, sealants and mastics. This includes soluble and insoluble inorganic phosphate salts, organophosphates and phosphonates.

Ammonium phosphates are used to protect steel and building components, intumescent coatings and sealants. In addition, the aerial application of ammonium phosphates are used to control brush fires.

To read more about the use of phosphates in flame retardants, please click here.

Why are phosphates in fire extinguishers?
Several types of phosphates are used in fire extinguishers. Ammonium phosphates are used as chemical powders in fire extinguishers and release non-combustible gases and carbonizing substances, which extinguish the flames. Other dry chemicals used for fire extinguishing, such as sodium and potassium bicarbonate powders, are only effective with Class B (flammable liquids) and Class C (electrical fires). However, these other products are ineffective against fires with Class A compounds, such as paper, wood, and cotton fabrics, since problems of smoldering, flare-up or re-ignition often occur. Chemical powders containing ammonium phosphates are effective against all classes of fires, and, therefore, are the basis for most multipurpose fire extinguishers. Tricalcium phosphate is also used in fire extinguishers and serves as a free-flowing agent for the fire-extinguishing powder.
Why are phosphates used in asphalt modification?
Polyphosphoric acid (PPA) is used as an asphalt binder modifier either individually or in combination with other synthetic polymers. In neat asphalt, PPA increases the high temperature Performance Grade (PG) rating without affecting the low temperature properties. In this application, PPA also helps to improve water sensitivity of the mix. In polymer-modified asphalt, PPA provides the same benefits as in neat asphalt and allows for significant reduction in the level of polymer used to meet elastic recovery requirements.

To learn more about the use of Polyphosphoric Acid in asphalt binders, please click here.

Why are phosphates used in paints?
Polyphosphates are often used in water-based paints and coatings due to their diverse functionality. Tetrasodium Pyrophosphate (TSPP) and Tetrapotassium Pyrophosphate (TKPP) are used to assist in the wetting of pigments and fillers. Potassium Tripolyphosphate (KTPP), Sodium Potassium Tripolyphosphate (SKTP) and TKPP are used to break down agglomerates and stabilize the pigment suspension. Polyphosphates also aid in ensuring stable and controlled viscosity in paint.

Sodium Hexametaphosphate (SHMP), Tetrasodium Pyrophosphate (TSPP) and Sodium Tripolyphosphate (STPP) can be used as kaolin clay deflocculants for paper coatings. These paper coatings reduce ink bleeding and increase the opacity and brightness of paper.

To learn more about the use of phosphates in paint and coatings, click here.

Why are phosphates used for metal treatment?
Phosphoric acid-based chemical polishes are used to polish and brighten aluminum and aluminum alloys. These products can be tailored for specific alloys and smooth the surface of aluminum parts to give a brighter appearance. Phosphoric acid can also be used to protect steel with a phosphate coating which helps to prevent corrosion and can prepare the surface for improved paint adhesion.
Why are phosphates used in ceramic products?
A number of different phosphates are used in various ceramic products, including whiteware, refractory products, specialty cements, specialty glasses and ceramic glazes and enamels. Phosphates can also be used as processing aids in the manufacture of ceramic products to improve the products characteristics.

Sodium Hexametaphosphate (SHMP) and Sodium Tripolyphosphate (STPP) are used as deflocculants in the mining and processing of clay materials and as dispersants in preparing slurries for whiteware, glaze and enamel manufacture. Tetrasodium Pyrophosphate (TSPP), Tetrapotassium Pyrophosphate (TKPP) and Potassium Tripolyphosphate (KTPP) help control ceramic product slurry viscosity, and can be supplemented with Disodium Phosphate (DSP) or Trisodium Phosphate (TSP) to act as buffering agents to control slurry pH and improve stability. Some polyphosphates can also be used as dispersants in wet process cements to improve pump-ability.

Orthophosphates can also be used in ceramic refractory systems as they provide low temperature chemical bonding to strengthen ceramic bonds. Phosphoric acid can also be used to assist with bonding. Orthophosphates are also used for their fluxing and optical properties for specialty glass and ceramic glazes.