Diatomaceous earth is made of silicon dioxide, It's also known as amorphous silica and silica powder among other names. The name diatomaceous earth refers to the source of the material as a powder made up of the crushed fossilised skeletons of prehistoric creatures. Both coarse and fine ground diatomaceous earth is available as a food grade substance.
Food grade diatomaceous earth is not poisonous to humans and many food manufacturers use it in food preparation. The diatomaceous earth has chemical properties which prevent food from caking so it can flow properly and liquids from foaming. It also affects the germination of seeds and can be part of a filtration process. The material is hygroscopic so it also plays a role in keeping foods dry. The powder is also not dangerous to touch.
The major danger of food grade diatomaceous earth arises from the fact that it is a powder and is made from silica. A person can inhale powder into the lungs and become ill. The Centers for Disease Control and Prevention states that inhaled silica can cause a range of diseases such as silicosis. Other diseases of the lungs can also be made more likely from inhaling silica, such as tuberculosis. Exposure to silica may also be involved in the development of other non-lung related diseases such as autoimmune problems and chronic kidney disease. These dangers are more likely to occur with repeated exposures to the substance.
The diatomaceous earth powder particles can also cause irritation because of their small size and abrasive properties. If a person is exposed to the powder, the powder can get into the eyes, which are sensitive to dust. The eyes may become red and scratched, although this effect is temporary. The dust can also irritate the lining of the throat and the inside of the nose.
Food grade diatomaceous earth is not intrinsically carcinogenic, but the changes to the lungs that a person can suffer from through silica exposure can lead to lung cancer.
To negate the inhalation risk of the silica, the dust should be handled in a ventilated area. A person who is exposed to food grade diatomaceous earth dust should move to an area of fresh air. He should wash his eyes out with clean water, drink clean water to remove particles from his throat and blow his nose to remove dust trapped there. The dust can be especially irritating to a person with a pre-existing disease of the airways such as bronchitis, emphysema or asthma.