Does NDMA Cause Cancer?

N-nitrosodimethylamine (NDMA) is classified as a probable human carcinogen, based on results of laboratory tests, according to the U.S. Food and Drug Administration (FDA). NDMA, a known environmental contaminant, is found in the air, water, foods (including meats, dairy products, and vegetables), and alcoholic beverages such as beer and whiskey.

It was formerly used in the production of liquid rocket fuel, antioxidants, additives for lubricants, and softeners for copolymers, but is not currently produced or commercially used in the United States, except for research purposes.

What Is NDMA?

NDMA is a semi-volatile organic chemical that forms in both industrial and natural processes. It is also known by the names dimethylnitrosamine (DMNA), nitrosodimethylamine, N-methyl-N-nitrosomethanamine, and N,N-dimethylnitrosamine.

A yellow liquid that has no distinct odor, NDMA is an N-nitrosamine, a type of compound that has the generic chemical structure R₂N–N=O, a deprotonated amine bonded to a nitroso group.

N-nitrosamines are generally formed when a secondary or tertiary amine reacts with a nitrosating agent. The compounds are found at low levels in certain foods and beverages, such as roasted meats, cheese, and beer, due to cooking and fermentation processes.

People are exposed to NDMA in many ways, but the main sources tend to be tobacco, cured meats such as bacon, fermented foods such as beer and cheese, shampoo and cleansers, and detergents and pesticides. In bacon, for example, NDMA formation occurs when nitrite preservatives react with amines and amino acids in the meat during cooking.

Since NDMA is classified as a group 2A carcinogen, or “probably carcinogenic to humans,” according to the International Agency for Research on Cancer, it means that there isn’t any direct evidence that the compound causes cancer in humans, but it’s likely that it does since it has caused cancer in animals.

NDMA may increase the risk of cancer if people are exposed to it above the acceptable level and over a long period of time, but a person taking a drug that contains NDMA at-or-below the acceptable daily intake limit, every day for 70 years, is not expected to have an increased risk of cancer.

NDMA in Food and Water

NDMA is an unintended byproduct of the chlorination of wastewater and drinking water at treatment plants that use chloramines for disinfection.

As of March 2011, NDMA had been detected in 1,787 samples out of 17,900 samples obtained from public water systems, which were monitored as part of the unregulated contaminant monitoring rule (UCMR).

The U.S. Environmental Protection Agency (EPA) uses the UCMR to monitor contaminants that are suspected to be present in drinking water, but that do not currently have health-based standards under the Safe Drinking Water Act.

NDMA may be present in waste discharges of such industries as rubber manufacturing, leather tanning, pesticide manufacturing, food processing, foundries, and dye manufacturing, as well as in sewage treatment plant effluent. Almost all of these waste discharges are released into water.

The most common method of treating NDMA in drinking water systems is photolysis by ultraviolet (UV) radiation in the wavelength range of 225 to 250 nanometers.

With food and alcoholic beverages, NDMA can be found in many processed foods such as cured meats or fish, bacon, and cheeses. Ingesting food that contains alkylamines can cause NDMA to form in the stomach. Malt beverages, such as beer and whiskey, may contain low levels of nitrosamines formed during processing.

NDMA in Medications

In the past few years, NDMA and other N-nitrosamine contaminants have been found in various drugs around the world. In 2018, the first discovery was made in a drug containing the active pharmaceutical ingredient valsartan, an angiotensin receptor blocker (ARB) used to treat high blood pressure.

Since this discovery, NDMA and similar compounds have been found in at least six drugs that are taken by tens of millions of people each year. Because these N-nitrosamine contaminants are possible carcinogens, regulatory agencies have been branding the drugs unsafe and have been recalling them.

Valsartan was recalled in July 2018, followed that October by irbesartan, and in November by losartan, two other ARBs also found to contain NDMA, and the related compound N-nitrosodiethylamine (NDEA).

In September 2019, the FDA alerted the public to the presence of NDMA in certain lots of ranitidine, available over the counter as Zantac, and it was removed from shelves within the next few months.

Nizatidine, another heartburn medication, was recalled by manufacturer Mylan in January 2020. And most recently, the FDA suggested that manufacturers of ranitidine recall all lots and types of these medications.

NDMA has also been found in metformin, a diabetes drug taken by more than 15.8 million people worldwide. Since May 2020, various companies have recalled more than 170 products containing metformin.

Experts in the pharmaceutical field point to multiple sources of NDMA contamination, including side reactions from drug syntheses, the breakdown of unstable drug compounds, and contamination from recycled solvents used in manufacturing.

Furthermore, the amount of NDMA that’s been found in pharmaceuticals has varied widely and depended on who did the testing, which manufacturer the drug came from, and what batch of medication was tested. The FDA plans to publish guidance on the matter in the near future.

Other Sources of NDMA

In addition to drinking water, certain foods and beverages, and medications, the general population may be exposed to NDMA from environmental, consumer, and occupational sources.

To date, NDMA has been found in at least 1 out of 1,177 hazardous waste sites on the National Priorities List (NPL) in the U.S. Under certain conditions, NDMA may be found in outdoor air, surface waters (rivers and lakes, for example), and soil.

However, the primary, non-food sources of human exposure to NDMA are tobacco smoke, chewing tobacco, toiletries and cosmetic products (for example, shampoos and cleansers), interior air of cars, and various other household goods, such as detergents and pesticides.

NDMA Cancer Risk

When rodents and other animals ate food, drank water, or breathed air containing lower levels of NDMA for periods more than several weeks, liver cancer and lung cancer, as well noncancerous liver damage, occurred.

Mice that were fed NDMA during pregnancy had offspring that were born dead or died shortly after birth. However, it is not known whether NDMA could cause the death of human babies whose mothers are exposed during pregnancy.

Although there are no reports of NDMA causing cancer in humans, there is an association with certain cancers and it is reasonable to expect that exposure to NDMA may cause cancer in humans. Several studies have linked NDMA to cancer incidence in humans.

A prospective study of 23,363 participants published in 2011 in The American Journal of Clinical Nutrition found that dietary NDMA was associated with a higher gastrointestinal cancer incidence, specifically rectal cancer. There were 3,268 incident cancers after a mean follow-up of 11 years.

An older study published in 2000 in the journal Occupational and Environmental Medicine, which featured 8,933 rubber workers, found that workers who were exposed to high levels of nitrosamines in factories had an increase in mortality from cancers of the esophagus, oral cavity, and pharynx.

A 2015 meta-analysis of 22 articles, of which 11 featuring NDMA were included, examined potential links between dietary consumption of nitrates, nitrites, and nitrosamines and gastric cancer risk. It was published in the journal Nutrients. It found that increased ingestion of nitrites and NDMA seemed to be a risk factor for cancer.

It should be noted, however, that exposure to NDMA does not mean that any effect on health will definitely occur. More long-term research involving humans and NDMA exposure and consumption is needed before the extent of risk and the specific risks are known.

Prevention

The most important, and probably the most harmful, way of coming into contact with NDMA seems to be by eating contaminated food or drinking contaminated water, according to the CDC. Therefore, it is suggested to limit your intake of foods such as smoked or cured meats and processed cheeses, as well as the consumption of beer and whiskey.

According to the World Health Organization (WHO), NDMA has been occasionally measured in drinking water, but typically at low concentrations that are unlikely to affect our health. The amount of NDMA in the aforementioned foods is found in far greater concentrations than in drinking water.

NDMA can be detected in water using a variety of methods. The most common method for removing NDMA is ultraviolet (UV) light and biological degradation. In addition, water is sometimes treated to remove the chemicals that may form NDMA (called NDMA precursors).

As for potentially contaminated medication, the FDA suggests the following:

• Don’t abruptly stop taking prescription medications without first talking with your healthcare provider.
• People who take non-prescription drugs can consider taking other over-the-counter products to treat their condition. Check with your healthcare provider or pharmacist.
• If you have a question about your medication or want to find out if it’s been recalled, call your pharmacist or the FDA’s Division of Drug Information (DDI), at 1-855-534-DRUG (3784).
• If your medication has been recalled, call your pharmacy. They’ll know if the specific batch dispensed to you is part of the recall. You may be able to switch to another medication.

A Word From Verywell

It can be concerning to learn that a medication you rely on has been recalled for a possible carcinogen. Understanding the risks and the purpose of the recall can help you take action and adjust to any changes your healthcare provider recommends.