Quats – better not?

Let’s start with the in vitro study². 

There is a big difference between exposing individual cells to a chemical substance in vitro and the effect of the same substance on a human from normal day-to-day exposure.

First, let’s consider where mitochondria are located—inside cells. For a substance to get to mitochondria it must enter the cell by crossing the cell membrane. The cell membrane is a good barrier to substances with an electrical charge, and quats are positively charged. So can quats cross the cell membrane? Does this happen in live tissues? In human tissues?

Second, the mode of exposure needs to be considered. In this study, cells were incubated directly with the undiluted substance whereas in the real world, humans are most likely to encounter quats as part of a formulated products via skin contact, eye contact or inhalation. What is the actual exposure of human cells to quats? And which cells?

Third, what about the quat doses used in the study? How does this relate to actual human exposure?

What about the rodent results?^3,4

There are many question marks concerning this study. Like the atypical and extremely complex experimental design. High oral doses that don’t represent normal human exposure. And no clear dose-response or ‘no-observed adverse effect level’ (NOAEL) is identified.

No link between the findings and actual human exposure is established or indeed is possible.

And what about the mouse oligodendrocytes?⁵

Again, this was early experimental work, mainly in vitro. Much more evidence is needed, based on realistic doses, exposure routes and durations, before any conclusions can be drawn on potential human effects.

So what does this all mean?

It is not yet time to panic! Despite the irresponsible news headlines. Click here for some tips on how to read media, beyond the sensational headlines. 

Much more research is needed. For example, the results should be independently replicated, further investigation of the in vitro results in animal models is needed, and exposure scenarios that are replicable and can be related to normal human exposure are required.

In Australia, quats are regulated for public health and safety by the Australian industrial chemicals (AICIS) and therapeutic goods (TGA) regulators.

Many individual quats are listed on the Australian Inventory of Industrial Chemicals. This is a database of chemicals that can be used in products regulated by AICIS, like cosmetics, personal care and household cleaning products, including Australian-made and imported products.

AICIS has conducted many assessments of different quats for their health effects. These assessments reviewed scientific studies covering numerous aspects of human health. In its 2022 assessment of benzalkonium halides, no concerns relating to impacts on fertility or brain health were noted.⁹

Quats are also scheduled via the national Poisons Standard,¹⁰ which is administered by the TGA. The Poisons Standard is for substances requiring additional controls, by limiting access and/or requiring warnings or specific packaging requirements. Quats generally, when at 5% or less in a product are not listed on the Poison Standard, at 5–20% are on Schedule 5 (requires a ‘CAUTION’ warning) and at more than 20% are on Schedule 6 (‘POISON’). Benzalkonium chloride is scheduled separately, with the only difference being that it is Schedule 5 at 5–10% and Schedule 6 at greater than 10%.

Poisons Standard – what do the warnings signify?

‘CAUTION’: Substances with a low potential for harm but require appropriate packaging, labeling, and handling to minimize risk. The label alert users to handle the product with care but does not indicate significant health risks under normal use.

‘POISON’: Substances with moderate potential for harm that require stronger warnings and safety precautions to reduce the risk of harm. The label emphases the need for careful storage and use.

In other words, low levels of quats (below 5%) are not deemed to need any special precautions or warnings; higher levels need to be handled appropriately.

What about products you come in contact with – what levels of quats are in those?

In its 2022 evaluation of benzalkonium halides, AICIS stated that rinse-off cosmetics can contain up to 7% (but usually < 3% in rinse-off hair products) and leave-on cosmetics can contain up to 1% (but usually < 0.1% as a preservative). Household cleaning products can contain up to 20%. Does 20% sound high? AICIS isn’t worried, concluding that ‘the public is unlikely to regularly be exposed to high concentrations (>10%) of these chemicals in domestic cleaning products, but this may occur when diluting concentrated products prior to use…where domestic cleaning products are used as directed, exposure is not expected to be significant’.⁹

Both AICIS and the Federal Health Department monitor new scientific studies regarding chemicals and take action when warranted.

Quats are well studied, globally. They have been assessed for human health impacts by groups such as the US Environmental Protection Agency (US EPA), the US Food and Drug Administration (FDA) and the EU Scientific Committee on Consumer Safety (SCCS).

Related to the quats mentioned above…

…the US EPA conducted a risk assessment of DDAC (and related quats) in disinfectant and deodorant products.¹¹ This considered relevant research data and, specifically relating to developmental toxicity, concluded that studies on rats and rabbits did ‘not indicate increased susceptibility in rats or rabbits from in utero and postnatal exposures to DDAC’.

…the US FDA announced in 2017 that cetylpyridinium chloride (CPC) could no longer be used in consumer antibacterial wash products sold in the USA.¹² However, this wasn’t based on new evidence of safety concerns, but because ‘manufacturers didn’t provide the data necessary to demonstrate that [it is] both safe for daily use over a long period of time and any more effective than plain soap and water in preventing illnesses and the spread of certain infection’¹³. CPC can still be used in other categories of products.

…again on CPC, the SCCS reviewed evidence on its use as a preservative in cosmetic products (oral hygiene products, skin lotions & creams and antiperspirants). In its 2015 Opinion,¹⁴ the SCCS determined ‘that the use of [CPC] in a single cosmetic product for oral or dermal application is safe for the consumer’. The SCCS did not consider simultaneous exposure to all these products to pose a risk.

In Europe, cosmetic regulations list maximum allowable concentrations for some specific quats, depending on the product type and application, e.g. leave-on vs rinse-off; face vs hair.¹⁵