Detergents – the Science and Regulations (UK / EU)
Introduction
Detergents, with or without biocidal active ingredients are essential to keep our homes, workplaces and objects clean. We use them to wipe tables, clean windows, remove stains etc and perhaps take for granted the chemistry involved.
There is a degree of overlap with cosmetics (hand soap), biocides (toilet cleaner) and lots of grey areas where dual or multiple regulations may apply (sanitising wet-wipes with emollients?), but the definition of a detergent is based around the presence of surface-active substances.
The other over-riding feature of detergents is the assumption that all of the product will enter waste water systems and ultimately get into the environment.
Although fully covered by REACH and CLP, detergents need additional assessment in view of the high potential for exposure to consumers and to the environment and specific labelling is needed to ensure correct use and importantly, to reduce the risk of over-use with clear instructions for safe use.
Ultimately, despite legal requirements and the problems in working out if ingredients fit into specific types of substance, the supplier must ensure that the detergent product does what it claims to do, is of low risk to users and is of no long-term risk to the environment.
The legal bit….
The original Directives were replaced by Regulation (EC) No 648/2004 and this too is under review as part of the European Commission ‘refit’ process to assess whether regulatory processes can be simplified to provide the same protection but with less administration. In the case of the Detergents Regulation, an area of concern is the need to provided technical data sheets and make labelling easier, but this is the future. (Of course, SDS will be still be needed to comply with REACH as applicable.)
The existing EU Regulation is here
The UK fully adopted Regulation (EC) No 648/2004 and for now there are no plans to update. A link is here
The definition of a detergent will remain the same (EU and UK), specifically:
Article 2
‘Detergent’ means any substance or mixture containing soaps and/or other surfactants intended for washing and cleaning processes. Detergents may be in any form (liquid, powder, paste, bar, cake, moulded piece, shape, etc.) and marketed for or used in household, or institutional or industrial purposes.
Solvent cleaners containing no surfactants are therefore not technically ‘detergents’.
A surfactant is also defined :
6. ‘Surfactant’ means any organic substance and/or mixture used in detergents, which has surface-active properties and which consists of one or more hydrophilic and one or more hydrophobic groups of such a nature and size that it is capable of reducing the surface tension of water, and of forming spreading or adsorption monolayers at the water-air interface, and of forming emulsions and/or microemulsions and/or micelles, and of adsorption at water-solid interfaces.
There are many ‘dual use’ detergents that are also Biocides or Cosmetics and in these cases, the respective Regulations will apply; for biocidal cleaners, these need to meet both the Biocidal Products Regulations (with Approval of the actives and Authorisation of the product). Cosmetics will need notification and a Cosmetic Product Safety Report (CPSR).
The science
The definition above sums it up fairly well in that all the different types of surfactant have in common are fat soluble (hydrophobic) and water soluble (hydrophilic) portions. By dissolving both in fats and water, the surfactant effectively allows the fat to be dispersed in the water phase and therefore rinsed away.
The four types of surfactant noted in the Regulation are:
- Non-ionic with no dissociation under normal conditions; examples include fatty alcohol ethoxylates
- Cationic where the main molecule carries a positive charge, such as a quaternary ammonium ion; examples include alkylbenzene ammonium chloride
- Anionic where the main molecule carries a negative charge, such as a sulphonate; examples include sodium alkylbenzene sulphonate
- Amphoteric surfactants will have positive and negative charges; examples include betaines
Since dirt is typically more complicated than just fat, other things need adding to the detergents we use, and these include sequestering agents (interact with metals and inorganic ions), alkaline builders (help make fatty acids into ‘soaps’), enzymes (to start to digest complex organic matter like proteins) and so on. It is an interesting science and one we take for granted all the time with commercial cleaning products.
The Detergent Regulation provides a list of ‘functional’ substances found in detergents and these need to be identified on labelling and technical data sheets (more later on this). Most of the chemical types are common, but some need defining in more detail and even reasonably experienced chemists can get the surfactant type mixed up:
The substances ‘of interest’ can be split into groups:
- Phosphates and phosphonates are a source of phosphorous that will lead to enhance nutrition of surface water (eutrophication) as the phosphorus will not be removed by water treatment systems
- Anionic, cationic, amphoteric and non-ionic surfactants will provide much of the cleaning power and create foaming
- Oxygen-based and chlorine-based bleaching agents are chemically reactive and can be acutely hazardous (such as bleach)
- Sequestering agents such as EDTA and NTA (nitrilotriacetic acid) and their salts along with zeolites are substances that will have a potential to pick up metal ions and therefore can have biological significance.
- Phenols, halogenated phenols, paradichlorobenzene, aromatic hydrocarbons, aliphatic hydrocarbons and halogenated hydrocarbons have the potential to be hazardous to health and although not found in domestic products, will be present in some specialist biocidal cleaning products.
- Soap is an alkaline metal salt of a fatty acid and effectively the most simple of all surfactants; in fact, this surfactant has been in use for centuries.
- Polycarboxylates and related sugar-based ingredients are finding their way into ‘ecological’ products as dispersing aid
There are other more generic classes of constituent that need to be identified irrespective of their concentration, including enzymes, disinfectants (if none of the above), preservatives, optical brighteners and importantly perfumes (especially ingredients known to be sensitisers).
One class of substance not identified here is colourants; these do not need to be specifically listed, but as with all the ingredients listed so far, they must be biodegradable or at least ‘labile’ in the environment. This is discussed below.
Biodegradation and removal mechanisms for the environment
The problem with cleaning products is that by their nature of intended use, a lot of the chemicals will end up in the environment. For household chemicals, we assume it goes down the drain (washing up liquid, laundry products etc) and even for outdoor uses, it will still end up in surface water drains (car cleaning, patio cleaners etc).
Either way, once in the environment due to repeated use by many people, it is important that the ingredients do not persist and certainly do not accumulate.
Biodegradation of organic ingredients is therefore a key requirement for any detergent, and the Regulations include details on how biodegradation needs to be assessed and provides target levels of degradation to allow organic ingredients to qualify for use in detergents. As well as the list of ingredients indicated above, any organic substance present must be ‘rapidly’ biodegradable. This includes colourants and as a warning, may dyes are not rapidly biodegradable.
Various methods for assessing the biodegradation of organic substances exist and it is a key study for REACH Registration. The process is considered ‘rapid’ if 60% of the substance is lost as carbon dioxide in a 10 day period during the 28 day study. Even if vailing this criteria as ‘readily biodegradable’ the term ‘rapid’ can be applied using CLP definitions if expert assessment suggests it is rapid.
There is of course interpretation in this, but an example could be a substance that does not quite manage 60% loss in a 10 day period, but over 80% disappears during the study and assessment of the structure and metabolic mechanisms suggest there will be complete removal. Sometimes a slower than expected rate of degradation may be cause by poor solubility, but the final assessment suggest it will go away quickly. This is called ‘expert judgement’.
Part of any expert judgement will be to consider the identity of degradation products if there is not complete degradation. The classic example in this case is with the (now banned) alkyl phenol ethoxylates. These can show biodegradation of 60% or more, but the remaining 40% may be a potentially persistent and accumulative metabolite. So, assessment of biodegradation is more than just a number.
The other problem is how to assess inorganic substances and organo-metals and in this case, CLP also has an answer- it is rather obscure, but is based on whether a metal or other element will ‘biotransform’ in the environment. In other words, do natural systems have a way of avoiding accumulation of these elements in soils, sediments and importantly, the food chain.
The assessment of potential transformation is again part of ‘expert judgement’, but a simple way to look at it is to consider if the element has a biological function. Some are obvious such as sodium, calcium, iron, copper, chlorine etc that are abundant in nature as their ions and which are considered essential elements for animals and plants. Even if such elements are toxic at high dose, such as copper, if we eat too much copper then our bodies will take what it needs and excrete the rest.
Mercury, lead, cadmium, etc are not used by organisms and therefore not ‘labile’ and will be considered potentially accumulative. And of course, not used in detergents; Silica is perhaps the odd one out in that the element has not known biological function in most organisms, but is abundant in nature and will be consumed and excreted by organisms.
Labelling and communication of hazards
As well as REACH SDS requirements and CLP classification and labelling, Detergents have additional requirements in terms of labelling and in the provision of a product data sheet. The need for product data sheets may go away in the revision of the Regulation and is actually something many suppliers are unaware of; not difficult to do but it does provide a chance to communicate chemical and safety details.
So, as well as CLP requirements, the label will need to identify the presence of key chemical types (as described above) and also provide clear instructions for use; these instructions for use are to help ensure both efficiency as well as to try to prevent over-use (leading to further pollution).
The actual text for the inclusion on labelling is given here.
LABELLING AND INGREDIENT DATA SHEET
A. Labelling of contents
The following provisions on labelling shall apply to the packaging of detergents sold to the general public.
The following weight percentage ranges:
— less than 5 %,
— 5 % or over but less than 15 %,
— 15 % or over but less than 30 %,
— 30 % and more,
shall be used to indicate the content of the constituents listed below where they are added in a concentration above 0,2 % by weight:
— phosphates,
— phosphonates,
— anionic surfactants,
— cationic surfactants,
— amphoteric surfactants,
— non-ionic surfactants,
— oxygen-based bleaching agents,
— chlorine-based bleaching agents,
— EDTA and salts thereof,
— NTA (nitrilotriacetic acid) and salts thereof,
— phenols and halogenated phenols,
— paradichlorobenzene,
— aromatic hydrocarbons,
— aliphatic hydrocarbons,
— halogenated hydrocarbons,
— soap,
— zeolites,
— polycarboxylates.
The following classes of constituent, if added, shall be listed irrespective of their concentration:
— enzymes,
— disinfectants,
— optical brighteners,
— perfumes.
If added, preservation (although this is a CLP requirement)
Of course, if any of these ingredients are hazardous and are above CLP thresholds for reporting on a label, then the chemical is needed in addition to the chemical class description.
Conclusions: Reverting to first principles
The ‘first principles’ in relation to the supply of any chemical product is that any risk to users or the environment is acceptable in terms of the benefit of the product; the benefit of cleaners (and of course especially disinfecting cleaners) is clear to understand, but the potential for harm to users or the environment must also be considered.
Risk to users can be mitigated by careful instruction for use and communicated through the use of SDS (professional products) and recommendations for personal protective equipment (consumers will take no notice, of course). However, when it is likely that all detergents will find their way into the environment, even the best instructions for use or recommendations for disposal etc will be unlikely to have much impact and the only real way to reduce risk is to legislate against the use of persistent and accumulative ingredients.