The Truth Behind the 'Toxic Potato Gas' Myth
The idea that potatoes can produce a mysterious, fatal toxic gas is a common urban legend, often stemming from tragic incidents in places like root cellars. The reality, as revealed by science, is more nuanced. Potatoes are not bombs of solanine gas; the dangers come from two distinct and entirely separate issues: asphyxiation from carbon dioxide ($CO_2$) in rotting potatoes and poisoning from a solid toxin called solanine found in green or sprouted potatoes.
The Decomposing Potato: A Real Gas Hazard
The primary gaseous threat from decomposing potatoes is not an exotic neurotoxin but a very common, simple gas: carbon dioxide. As with any rotting organic matter, decay is a biological process fueled by bacteria and fungi. During this process, they consume oxygen and release $CO_2$. The danger arises when large quantities of potatoes are stored in a poorly ventilated, enclosed area, such as a basement, bin, or root cellar.
- Carbon Dioxide ($CO_2$): This gas is heavier than air, so it sinks and pools in low-lying areas. In a confined space with poor air circulation, it can build up to lethal concentrations, displacing the breathable oxygen. A person entering such an area would be at risk of asphyxiation without warning, as carbon dioxide is odorless.
- Anaerobic Fermentation: In severe cases of wet, packed decay, bacteria can perform anaerobic fermentation, producing other, more foul-smelling gases like hydrogen sulfide ($H_2S$), which famously smells like rotten eggs. These are also toxic in high concentrations but, unlike $CO_2$, their odor provides a strong deterrent.
The infamous root cellar fatalities linked to potatoes are almost certainly cases of $CO_2$ asphyxiation, not solanine poisoning from a gas, as solanine has a high melting point and does not vaporize into a cloud.
The Green Potato: A Toxin, Not a Gas
The second, and perhaps more well-known, danger comes from solanine. This is not a gas but a solid, toxic glycoalkaloid that potatoes naturally produce as a defense mechanism against pests. Its concentration increases significantly under certain conditions:
- Exposure to Light: When potatoes are exposed to sunlight or artificial light during storage, they begin to produce chlorophyll, which causes the skin to turn green. Simultaneously, the production of solanine is also stimulated. The green color serves as a visual indicator of potentially higher solanine levels, but the two compounds are produced independently.
- Sprouting and Damage: The highest concentrations of solanine are found in the sprouts ("eyes"), the green skin, and around damaged areas of the potato. As a potato ages and begins to sprout, its solanine content rises.
- Bitter Taste: Solanine has a distinctly bitter flavor, a natural warning sign. A cooked potato that tastes bitter or causes a burning sensation in the mouth should not be eaten.
Symptoms of solanine poisoning, while rare, can include gastrointestinal issues like nausea, vomiting, and diarrhea, as well as neurological effects like headaches and confusion. In extremely rare instances involving very high doses, it can be fatal.
Gas vs. Toxin: A Comparison Table
| Feature | Rotting Potatoes (Gas) | Green/Sprouted Potatoes (Toxin) |
|---|---|---|
| Type of Hazard | Asphyxiation and potential toxicity from decay gases ($CO_2$, $H_2S$). | Ingestion poisoning from glycoalkaloids (solanine). |
| Primary Chemical | Carbon Dioxide ($CO_2$), Hydrogen Sulfide ($H_2S$). | Solanine and Chaconine. |
| Cause | Anaerobic decomposition by bacteria. | Exposure to light, aging, or physical damage. |
| Danger | Displaces oxygen in enclosed spaces, leading to suffocation. Odorless $CO_2$ is the most insidious risk. | Ingestion of sufficient quantities can cause illness or, in rare cases, death. |
| Sensation/Warning | None from $CO_2$. A very foul, sulfurous smell from $H_2S$. | Visually apparent green color and a bitter taste. |
Safe Handling and Storage Best Practices
By following these simple steps, you can prevent both the gaseous risks of rotting and the toxic issues of solanine build-up:
- Store Properly: Always store potatoes in a cool, dark, and dry place. A pantry or cabinet is ideal. This prevents light exposure and slows the natural aging process.
- Ensure Ventilation: Use a breathable container like a paper bag or a burlap sack, and do not store potatoes in sealed containers.
- Avoid Onions: Keep potatoes and onions separate. The ethylene gas released by onions can accelerate potato sprouting.
- Inspect and Discard: Regularly check your potatoes. Immediately discard any that are soft, rotten, moldy, or emitting a bad odor.
- Trim Green Parts and Sprouts: If a potato has small green spots or sprouts, you can peel away the skin and trim them away, as solanine is concentrated there. If the potato is extensively green or tastes bitter after cooking, throw it out completely.
What to Do in an Emergency
- For Suspected Gas Exposure: If you enter a confined space and notice a foul smell or feel lightheaded, leave immediately and seek fresh air. In cases of unconsciousness, do not enter to rescue; call emergency services and let trained professionals with proper equipment handle the situation.
- For Suspected Solanine Poisoning: If someone has ingested a green or bitter potato and experiences symptoms like vomiting, abdominal pain, or headache, contact a poison control center immediately for guidance. For expert advice, you can use the webPOISONCONTROL online tool or call 1-800-222-1222 in the US, which is a free and confidential service.
Conclusion
Can potatoes cause toxic gas? Yes, but not in the way many believe. The danger of "potato gas" comes from the odorless asphyxiant carbon dioxide released by rotting tubers in confined spaces, not a vaporized form of solanine. Green or sprouted potatoes, on the other hand, contain the non-gaseous toxin solanine, which is only dangerous if ingested. By understanding these two separate risks—$CO_2$ asphyxiation from rot and solanine poisoning from greening—you can practice safe storage and handling, ensuring your potatoes are a delicious meal and not a hidden household hazard.
Resources
For more information on the dangers of sprouted potatoes and solanine toxicity, visit the Poison Control website: Are Sprouted Potatoes Safe to Eat?.
What to remember for safety
- Rotting potatoes create $CO_2$: In confined spaces like root cellars, rotting potatoes release carbon dioxide, which can cause asphyxiation by displacing oxygen.
- Solanine is a solid toxin: The toxic compound in green or sprouted potatoes is solanine, a solid glycoalkaloid, not a gas.
- Green means higher solanine: The green color on a potato, caused by chlorophyll, indicates increased levels of the toxin solanine beneath the skin.
- Peeling can help: Removing the skin and any green parts or sprouts can significantly reduce the solanine content in a potato.
- Bitter taste is a warning: If a potato tastes bitter, it indicates high levels of solanine, and it should be discarded, regardless of its appearance.
- Cooking doesn't eliminate toxin: Boiling, baking, or frying does not effectively remove solanine from potatoes.
- Store potatoes properly: To prevent greening and rotting, store potatoes in a cool, dark, and dry place, away from onions.
FAQs
Is the gas from rotten potatoes really dangerous?
Yes, the gas from rotten potatoes can be dangerous. The primary risk comes from the colorless and odorless carbon dioxide ($CO_2$) released during decomposition. In poorly ventilated, enclosed spaces like root cellars or bins, this gas can accumulate and displace oxygen, posing a severe risk of asphyxiation.
Do green potatoes give off toxic gas?
No, green potatoes do not release toxic gas. The danger from greening is not from a gas but from a solid toxic compound called solanine, which increases in the potato when exposed to light.
What are the symptoms of solanine poisoning?
Symptoms of solanine poisoning from eating green or sprouted potatoes can include nausea, vomiting, diarrhea, stomach cramps, headaches, and dizziness. More severe, though rare, cases can cause neurological symptoms.
Does cooking green potatoes make them safe?
No, cooking does not effectively remove or destroy solanine. While peeling away the green parts and sprouts can significantly reduce the toxin, boiling, baking, or frying will not make a heavily green or bitter potato safe to eat.
What should I do if I find a rotten potato in my storage?
If you find a rotten potato, especially if you have a large batch, check for proper ventilation before entering the storage area. Discard any potatoes that are soft, moldy, or smelly. If the area is enclosed and poorly ventilated, open it up and allow plenty of fresh air to circulate before retrieving the rest of your potatoes.
How can I tell if a potato has too much solanine?
The best indicators of high solanine levels are the potato turning green under the skin or tasting noticeably bitter, especially in the skin and just beneath it. Any sprouts or "eyes" also have higher concentrations.
What is the best way to store potatoes safely?
The safest way to store potatoes is in a cool, dark, and dry place with good air circulation, such as a pantry or cabinet. Avoid storing them in plastic bags or near onions, which can speed up sprouting and decay.
Is there a difference between the danger of rotting potatoes and green potatoes?
Yes, there is a fundamental difference. The danger of rotting potatoes comes from carbon dioxide ($CO_2$) gas causing asphyxiation in enclosed spaces, while the danger of green or sprouted potatoes comes from ingesting the solid toxin solanine. They are two entirely separate hazards requiring different safety precautions.
