Chemical Profile: Quaternary Ammonium Compounds

Quaternary ammonium compounds, commonly known as quats or QACs, encompasses a large category of chemicals found in various personal care products. The chemicals in this group are widely recognized for their use as disinfectants. The COVID-19 pandemic resulted in a significant increase in the use of quaternary ammonium compounds due to their prevalence in cleaners recommended by the Environmental Protection Agency (EPA) for their ability to kill bacteria and viruses. Research on this group of chemicals has also increased in recent years. In one study, the level of quaternary ammonium compounds in household dust was observed to have roughly doubled when compared to pre-COVID levels ^[1].

There is widespread concern across the scientific community as to what increased use of these compounds could mean for the environment. Many quaternary ammonium compounds are environmentally persistent and are linked to various adverse health effects – could disinfectant cleaners be doing more harm than good? Here, we discuss the hazards of quaternary ammonium compounds and what you can do to limit your exposures.

Ammonium quaternary compounds may be found in disinfectant wipes and sprays, household and industrial/medical cleaners, hand sanitizers, hand soaps, moisturizers, shampoos and conditioners, baby wipes, mouthwashes, and more. Many products contain a mixture of two or more quats.

There are multiple potential routes of exposure to quaternary ammonium compounds. Exposure to quats can occur through inhalation or dermal exposure, depending on a product’s purpose and how it’s applied or used. Ingestion is also a means of exposure to quaternary ammonium compounds, even aside from ingestion during use of a mouthwash containing QACs. After a surface has been disinfected with a quat-based cleaner (or even utensils or equipment cleaned with quat-based detergents and other products), it can have residues of the compounds, and these residues can ultimately travel to food and become ingested ^[7]. Similarly, if food packaging contains quats, they can migrate to the food they are in contact with.

Some quats, such as benzalkonium chloride, are linked to developmental and reproductive toxicity in mice ^[8]. Research on quats suggests that two of the most commonly used quats, alkyl dimethyl benzyl ammonium chloride (ADBAC) and didecyldiemethylammonium chloride (DDAC), may be endocrine active ingredients that impact fertility in mice from ambient exposure ^[9]. The EPA and European Union also classify ABDAC and DDAC as skin and eye irritants under acute exposures, and some quats are recognized to be skin sensitizers as a result of long-term exposures ^[7].

A more recent study investigated these two compounds in combination at low, environmentally relevant doses. Synergistically, they exhibited the formation of neural tube birth defects in mice and rats in early gestation and decreases in pup size and survivability in late gestation ^[10]. While this research isn’t comprehensive, it suggests that quat compounds are developmental and reproductive toxicants and could be endocrine active within the human body, too ^[2][8]. Animal studies can be important indicators of potential impacts on humans due to the biological and genetic similarities between humans and mammals. While more research is needed to fully understand the potential harm of quats on humans, specifically, the negative effects seen in the animal data is a cause for concern and a case that further investigation is essential.

Some quats are known to accumulate in human blood ^[7][11], and thirteen quaternary ammonium compounds have been found in human breast milk, suggesting a plausible pathway for quats to reach infants ^[2][12]. There are also concerns that quats can give rise to bacteria and viruses resistant to antimicrobials; exposure to high concentrations of quats in an isolated laboratory setting has shown bacterial resistance to quats and antibiotics ^[13].

Other quats are “formaldehyde releasers” meaning they can release formaldehyde, a known carcinogen ^[14][15][16], within the formulation. They can also be lung irritants under chronic exposure, contributing to asthma and breathing problems. Increased occurrences of asthma have been reported in healthcare workers exposed to disinfectants ^[2], with exposure to quats presenting a heightened risk for occupational asthma and nasal symptoms, surpassing that posed by other hazardous chemicals or allergens, such as chlorinated bleach products, latex gloves, and glutaraldehyde ^[7]. Harmful chemicals such as benzyl chloride, a classified carcinogen by California Proposition 65, may be used as intermediates in the manufacturing of quats ^[17].Quats may also cause the formation of carcinogenic nitrosamines ^[18].

Quaternium-15, a quaternary ammonium salt, is a skin allergen known for causing dermatitis in over-exposed skin ^[2][19]. It also releases formaldehyde, a known carcinogen ^[20]. Many quats, like quaternium-15, are persistent in the environment and in marine ecosystems where they are toxic to aquatic life ^[2][21]. They easily adsorb to environmental compartments, like soil, sediments, and sewage sludge ^[2][21]. Toxicity of some quats to freshwater crustaceans has been observed at environmentally relevant concentrations, and these compounds have been shown to cause mortality or inhibit growth in aquatic life through oxidative stress or disruption of the cell membrane and other molecular components ^[2][22][23].

Quaternary ammonium compounds are a large, complex class of chemicals. For this reason, there are many existing data gaps in their research. MADE SAFE examines each compound individually with the aim to close these data gaps, using our  360° Ecosystem Approach Screening. Compounds are evaluated for human, terrestrial, and aquatic toxicity; environmental persistence; bioaccumulation (buildup of chemicals in human or animal tissues), and risk of problematic impurities. Example quaternary compounds not permitted by MADE SAFE:

• Benzalkonium chlorides (BACs). Also called alkyl dimethyl benzyl ammonium chlorides (ADBACs)
• Benzethonium chloride
• Cetalkonium chloride
• Cetrimonium chloride
• Ditallow dimethyl ammonium chloride (DTDMAC). Also called quaternium-18
• Didecyl dimethyl ammonium chloride (DDAC)
• Quaternium- 7, 15, 26, 31, 60 

Identifying quaternary ammonium compounds on ingredient labels can be a difficult task, considering they are a large class of chemicals with varying names which may not easily indicate they are a quat compound. To get started, avoid the example quats listed above. To avoid the uncertainty surrounding difficult-to-pronounce ingredients, start here:

• Shop MADE SAFE or MADE WISE Certified products.
• Avoid any ingredients with “quaternium” in the name, followed by a number (e.g., quaternium-15)
• Avoid any ingredients with “ammonium chloride” in the name or any names ending in “-onium” (e.g., didecyldimethylammonium chloride, benzethonium chloride). Also avoid any ingredients with “ammonia” or “ammonium” in the name – while these do not always represent quats, it is generally best to avoid all  ammonia and ammonium compounds.
• Avoid using conventional disinfectants and opt for simple ethanol, hydrogen peroxide, or citric acid-based cleaners when disinfecting surfaces. These are safer active ingredients that are registered with the EPA to be effective against numerous bacteria and pathogens, including SARS-CoV-2. Be aware that quats are active ingredients in more than 200 disinfectants registered with the EPA to be effective against many bacteria and viruses, making it imperative to read product labels.
• Wash hands with plain soap and water. This is one of the most important steps you can take to avoid spreading germs and getting sick. The CDC recommends scrubbing hands for at least 20 seconds (the amount of time it takes to sing “Happy Birthday” in your head).
• Try to avoid products labeled or marketed as “antimicrobial,” “odor fighting,” “germ-killing,” or “antibacterial” for everyday use.
• Reserve antibacterial cleaners for situations that present a human health hazard. Choose a simple soap-based all-purpose cleaner for everyday cleanliness and care.