Rust, or iron oxide, is a common reddish-brown compound that forms when iron reacts with oxygen and moisture. Its widespread presence on metal objects often raises concerns if accidentally swallowed.
Understanding Ingested Rust
In small quantities, swallowed rust is generally not highly toxic. Rust, or iron oxide, is not readily absorbed by the body in its oxidized form. The human body primarily absorbs iron in its ionized form, so most ingested rust will pass through the digestive system undigested and be excreted. The U.S. Food and Drug Administration (FDA) approves iron oxide as a food coloring, indicating its low acute toxicity.
The primary concern with ingesting a rusty item often stems from the object’s physical properties, not the rust itself. A sharp or large rusty object could cause physical injury to the digestive tract. Rust itself is considered a benign substance in small quantities.
What to Expect After Swallowing Rust
If a small amount of rust is ingested, individuals may experience mild stomach upset or no symptoms. Rust has a gritty texture and a bitter, metallic taste, but these sensory experiences do not indicate severe harm. The stomach’s dilute hydrochloric acid can partially dissolve rust, but most of it typically passes through the digestive system.
Medical attention is necessary if a large, sharp, or contaminated rusty object was swallowed. Signs like persistent vomiting, severe abdominal pain, choking, or blood in the stool warrant immediate evaluation. While tetanus spores can be found on rusty objects, a tetanus infection from ingesting rust is rare; the risk is primarily associated with deep puncture wounds.
Specific Scenarios of Rust Exposure
Rust can appear in various everyday scenarios. Drinking water from old, corroded pipes can contain rust particles. While this may cause discoloration or a metallic taste, small amounts of iron oxide in drinking water are generally not harmful and are considered an aesthetic issue by the EPA. However, prolonged intake of heavily rust-contaminated water may contribute to elevated iron levels in susceptible individuals, potentially leading to conditions like hemochromatosis.
Rust on the outside of food cans is common. Cans with surface rust that can be wiped off are safe to use, provided the can’s integrity is not compromised. If rust has eaten through the can, or is on the inside, the food should be discarded as it may have been exposed to bacteria. For small, non-sharp household items with surface rust, the risk from accidental ingestion of tiny rust flakes is minimal.