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When the media breaks news about formaldehyde in the food supply, it sounds scary and threatening to your health. But many news stories on formaldehyde in food focus on foods that have been banned from entering the United States due to their unusually high levels of formaldehyde.
Although formaldehyde is a dangerous chemical when ingested or inhaled in high doses, the small amount in foods is generally harmless. The compound is found naturally in minimal amounts in food and is even produced by your own body.
Formaldehyde is a colorless gas with a strong smell. It is most commonly known for its use in building materials and is also a consequence of some environmental pollutants. Other sources of formaldehyde include:
When formaldehyde is dissolved in water, it becomes formalin, which is commonly used as a disinfectant as well as a preservative in funeral homes and medical labs. Formalin is also used as a preservative for food, and it can be produced during the cooking and smoking process.
Living creatures, including humans, produce formaldehyde through normal metabolic functions. For example, a process called the “one-carbon cycle” uses folate to enable the synthesis of amino acids and DNA precursors. One byproduct of this process is formaldehyde.
Similarly, plants and animals (including those you eat for food) may produce formaldehyde as part of their metabolic processes. It is also found naturally in the environment (related to plant decomposition). It breaks down quickly in the air.
Most of the time, formaldehyde in food is a completely natural occurrence. It’s simply the byproduct of the processes going on inside a living, breathing organism—be it a plant or animal.
Formaldehyde is also approved as an indirect food additive. This means it’s used in certain materials that have contact with food. Currently, the Food and Drug Administration (FDA) lists it as approved for use in defoaming agents, which are used to prevent foam on certain liquids and other foods.
The FDA has also approved liquid formalin for use in the fishing industry. It is used as an anti-parasitic water treatment for certain types of fish you might eat, including salmon and catfish. It’s also used as an antifungal treatment on fish eggs.
There is no withdrawal time between the use of formalin on fish and its entry into the food system, which causes concern among some people. However, formalin does not accumulate in the bodies of fish. There are also specific guidelines in the U.S. as far as percentages of formalin used in these products and the length of time for application.
Fish from other countries may be more concerning, though. While it is prohibited, some fisheries abroad use formaldehyde treatment as a preservative on their fish to extend the time to spoilage.
Theoretically, fish containing high levels of formaldehyde should not be accepted into the U.S. food supply, but there have been occasional media reports of imported fish testing for higher-than-normal levels of formaldehyde.
The European Food Safety Authority (EFSA) notes that natural levels of formaldehyde in food vary widely depending on the type of product. Here are some common examples, listed in milligrams (mg) to kilograms (kg) of the food product (i.e. 6 mg/kg means there is 6 mg of naturally occurring formaldehyde in 1 kg of the food):
With minimal exposure, the body is actually quite efficient at enacting several lines of defense. When you breathe in formaldehyde, the cells lining your respiratory tract work quickly to break it down. If you’re only breathing in small amounts from everyday environmental exposure, your body usually breaks it down so quickly that little to none reaches the bloodstream.
When you ingest formaldehyde in food, it is rapidly absorbed and metabolized in the gastrointestinal tract. Most formaldehyde in food is also bound in a way that makes it unusable and unlikely to cause any side effects.
In large amounts, formaldehyde can be toxic. While most people are not at risk for formaldehyde exposure, toxicity may occur in indoor settings where the gas is released by products containing formaldehyde. However, the trace amount of formaldehyde in food is unlikely to cause formaldehyde poisoning.
Formaldehyde poisoning is rare, but it can occur if someone is exposed to high levels of the substance. Extreme cases of formaldehyde poisoning may cause low blood pressure, abnormal heart rhythm, irregular breathing, restlessness, unconsciousness, coma, and in rare cases, death.
In the U.S., the minimal risk level for humans is set at 0.2 mg/kg/day of chronic exposure, which is a conservative estimate of the daily human exposure that is considered to be safe. In addition, the EFSA states that food intake would be unlikely to exceed 100 mg/day at a maximum level, which would still only equate to around 1.5 mg/kg for a 150-pound person.
The greatest risk of formaldehyde exposure comes from frequent, high concentration inhalation, rather than ingestion of food, according to the World Health Organization.
The most common way to be exposed to formaldehyde is by inhaling air that contains it. Some factory workers can be exposed to formaldehyde through the treatment of textiles and the production of resins. Other at-risk groups may include healthcare workers, medical lab technicians, and mortuary workers. In addition, some teachers and students who work with biological specimens preserved with formalin are at risk for exposure.
Research is mixed on the degree of risk, however. One study examined data from a large group of chemical workers who had various degrees of exposure to formaldehyde. It concluded that there was no risk of excess death from nasopharyngeal cancer or myeloid leukemia at typical occupational exposure levels.
At the highest exposure category, however, a small risk for myeloid leukemia was observed. In addition, a 2015 review published in BMC Cancer found significant connections between formaldehyde exposure and sinonasal cancer.
The National Cancer Institute (NCI) concluded that "based on data from studies in people and from lab research, exposure to formaldehyde may cause leukemia, particularly myeloid leukemia, in humans." Still, it's important to keep in mind that this warning refers to high levels of occupational risk via inhalation—not the levels of formaldehyde you might naturally breathe through the air in your home.
The average person is unlikely to be exposed to toxic amounts of airborne formaldehyde.
The risk of ingesting a poisonous amount of formaldehyde is unlikely. When it comes to ingestion of formaldehyde, side effects and risks are only evident at high doses.
The Agency for Toxic Substance and Disease Registry notes that excessive ingestion could cause reduced food intake, kidney and liver side effects, gastrointestinal lesions, and (in extreme cases) increased risk of death. However, the agency notes that toxic effects are thought to begin at levels of 50 to 100 mg/kg/day of ingested formaldehyde.
The WHO estimates a person’s average intake of formaldehyde via food at 1.5–14 mg/day for an average adult. At the highest end of this range for a 150-pound person, that would be about 0.2 mg/kg, which is well below the levels related to side effects.
There is very little risk associated with the natural formaldehyde occurring in the food you eat. But if you’re still concerned about the amount of formaldehyde in your food, follow these simple guidelines to help minimize your exposure.
If you're concerned about formalin in farm-raised fish, it's important to note that it's used as a disinfectant in aquaculture practices around the world, including the U.S. Research shows that formalin may produce fish toxicity, but the implications for human health are not fully understood.
Because the greatest risk from formaldehyde comes from inhalation, you may wish to focus on reducing that type of exposure instead. Here are a few things you can do:
In 2016, the use of formalin as a food preservative was banned in the European Union due to its potential as a carcinogen. Elsewhere, formaldehyde is illegal in foods beyond trace amounts. Many foods like fruits, vegetables, meats, and milk that contain naturally occurring formaldehyde are legal around the world.
Like other food manufacturers, certain fast-food chains may use formalin as a food preservative. However, the toxic food packaging used by some fast food restaurants is likely more hazardous to your health than any trace amounts of formaldehyde found in these foods.
Naturally occurring formaldehyde in food is generally safe and relatively common. It is produced naturally by living organisms and is unlikely to cause formaldehyde poisoning. Most foods that have been preserved with formalin should be safe for consumption in the U.S.
The only time to really be concerned about formaldehyde exposure is when excessive amounts are inhaled over time. But most people shouldn't have to worry about inhaling or ingesting dangerous amounts of formaldehyde from the foods they eat or the air they breathe.
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By Chrissy Carroll, RD, MPH
Chrissy Carroll is a registered dietitian and USAT Level I Triathlon Coach, and the author of "Eat to Peak: Sports Nutrition for Runners and Triathletes."
