Concerns about both health and the environment are having an impact on products in the cleaning industry.
The use of toxic materials and those that cause cancer are being restricted. Chemicals that damage the ozone in the upper atmosphere are being phased out.
Emissions from volatile organic compounds (VOCs) that result in smog formation at lower levels of the atmosphere are being restricted under the Clean Air Act. The ongoing testing is resulting in lowered Permitted Exposure Levels (PELs).
Let’s take a look at the chemistry involved in formulating cleaning chemicals, changes taking place and why it is happening.
Surfactants (or surface active agents) are basic cleaning agents that work by lowering the surface tension of water. This permits the water to spread out and penetrate dirt and soil and help remove them.
Surfactants are classified by the charge they carry in solution. Soap is a common example of a surfactant and it carries a negative charge. Until the 1940s, soap was used as the primary cleaning agent, but it suffered from some inherent drawbacks. For instance, its effectiveness is reduced when used in hard water. Materials that overcame the drawbacks were added. These are called builders.
In the early 1950s, alkyl benzene sulfonate (ABS) was the surfactant of choice. Because of its branched complex structure, it broke down slowly by natural biological action and was discharged into the environment. In the mid-1960s, this was replaced by linear alkyl sulfonates (LAS), which have a simpler straight-line molecular structure. They are easily broken down through biological activity; in other words, they are readily biodegradable.
Another surfactant type primarily used in hot water extraction cleaners are alcohol ethoxylates (AE). These are non-ionic, in that they do not carry an electrical charge when mixed in water. Each molecule of the AE carries an oil loving and a water-loving group. By changing the concentration and ratios of these groups, varied properties of the end product can be obtained.
If the structure of an AE molecule is linear, like a straight line, these are termed as linear alcohol ethoxylates (LAEs). If the structure is a branched-ring type, it is referred to as nonylphenol ethoxylates (NPEs). Both types of alcohol ethoxylates are biodegradable, with the LAEs being far more biodegradable than the branched NPEs.
Alkyl polyglycosides surfactants (APGs), are non-inonics based on vegetable feed stock (corn and tropical oils, a renewable source), and may replace or supplement traditional non-ionics that are petroleum based. There are a number of specialty surfactants available that are not only biodegradable but mild as well. There is a trend toward milder surfactants.
Builders are materials, which are added to surfactants to enhance cleaning and give it desirable properties primarily in assisting with soil removal. In 1946, the first surfactant/phosphate builder combination was introduced in the U.S. This vastly improved performance, making them suitable for heavy-duty cleaning.
Among the builders, the most controversial are the phosphates (compounds of phosphorous). Because of their unique combination of performance, economy and safety, they would be the builder of choice. Unfortunately, phosphates are believed to contribute to “eutrophication” (from Greek words meaning “to nourish well”) of water. The result is accelerated algae growth, which robs water of oxygen. Oxygen, of course, is essential to marine life.
Different municipalities and states have banned the use of phosphates in home laundry detergents and even dish washing detergents. Industrial and institutional products are also being restricted. In some states, the laws are written so that they specifically restrict the use of phosphates in carpet or upholstery cleaning chemicals.
Attempts were made to replace phosphates, resulted in substituting NTANa3 (a complex organic salt) in the late 1960s. In 1971, studies showed NTANa3 caused cancer in both rats and mice. The cleaning industry, until the spring of 1980, voluntarily abstained from using it. California, under the 1986 Safe Drinking and Toxic Enforcement Act, regulates NTANa3 as a carcinogen and requires products containing this ingredient to carry a warning on the label.
Other replacement builders include soda ash, sodium sulfate, sodium citrate, silicates and zeolites.
Current trends include the use of oxygen-based, color-safe bleaches. These are being added to compounded formulations to remove stubborn stains and brighten colors. Some of these color-safe bleaches need catalysts to activate them.
Another trend is to add soil release agents, generally polymer-based, to remove soil, prevent redepositing of soils and increase the efficiency of surfactants.
Enzymes are also being added to detergents to help remove certain soils, especially proteins. Enzymes work well at low temperatures.
To reduce packaging sizes, more super concentrates, compacts or ultra-compacts are being offered. Companies are advertising minimum residue or no measurable residue left after the carpet is cleaned, indicating a trend toward more concentrates that can take a higher dilution.
By definition, a solvent dissolves another substance without undergoing any chemical change. For the purpose of this article, we will refer to solvents as organic compounds — generally synthetic, not natural in this context, compounds primarily composed of carbon and hydrogen) — other than water. Some solvents are completely soluble in water, such as rubbing alcohol. Some have limited solubility, such as methyl ethyl ketone (MEK); some are virtually insoluble, such as mineral spirits or gasoline.
Most solvents will de-fat skin. Most solvents, whether natural or synthetic, pose risks to health and the environment because most solvents emit VOCs.
Some VOCs are photochemically reactive and contribute to ozone and smog formation at ground level. Some solvents harm the protective ozone layer in the upper atmosphere. Both are considered undesirable properties.
Hydrocarbon solvents that have open, straight chain structures are called aliphatics. Examples include VM&P naphtha and mineral spirits. Solvents that have a ring-like structure, like toluene and xylene, are called aromatics and have distinct odors. Those with a structure between the two, like limonene (also called d-limonene), are called alicyclics and can be natural or synthetic. Hydrocarbon solvents, which contain a chlorine atom, are called chlorinated hydrocarbons; examples include perchlorothylene and methylene chloride.
If the hydrocarbon contains an oxygen atom, depending on the structure, it can be alcohol, like rubbing alcohol; glycol ether like “butyl,” ketone like “MEK,” or acids like citric or acetic acid. Depending on the way the atoms are structured, different products can be obtained.
Now, let us turn our attention to chlorinated solvents. Methylene chloride (dichloromethane,) perchloroethylene (tetrachloroethylene) and trichloroethylene (TEC) are the three most widely used chlorinated solvents in the industry.
Their popularity resulted from their excellent solvency and relatively low flammability. Unfortunately, there is a down side to these solvents. Chlorinated solvents are skin and eye irritants and can adversely affect the central nervous system. In addition, some of them are known to cause cancer. 1,1,1, Trichloroethane, also called methyl chloroform (MCF), depletes the protective ozone layer in the upper atmosphere.
The U.S. Occupational Safety and Health Administration (OSHA), the agency that oversees workers’ health, has significantly reduced the permitted exposure levels (PEL) for chlorinated hydrocarbons.
Methyl chloroform (MCF) was phased out at the end of 1995. Most states, such as California, do not consider methylene chloride to be contributing to smog or ozone formation at ground level and are not considered VOCs. Trichloroethylene (TCE), methylene chloride and perchloroethylene are classified as carcinogens.
Chlorofluorocarbons (CFCs) can be liquids or refrigerant gases. When they were discovered, they were considered a panacea. These products were considered non-toxic, non-flammable, had high solvency and were non-corrosive. Freon-12 or CFC-12 replaced toxic refrigerants of the day like ammonia and sulfur dioxide. The CFC solvents replaced toxic and flammable solvents. Mineral Spirits and odorless mineral spirits are 10 times more toxic than some CFC solvents. CFC-12 was used to freeze chewing gum. The CFC solvents were also used in high-grade, fast-acting dry cleaners and as carriers for protective finish in textiles.
CFCs had one basic flaw: They were rapidly depleting the protective ozone layer.
Under the Montreal Protocol, CFCs are carrying a hefty federal excise tax and are phased out. The tax has made the product cost prohibitive and has dissuaded the industry from using CFCs.
For freezing chewing gum, some manufacturers have switched over to HCFC-22, called HCFCs; others to 152-A, called HFCs. Both have drawbacks. HCFC-22 damages the protective ozone layer but not to the extent CFC-12 does. HCFCs are also being phased out under the Montreal Protocol, but at a later date than CFCs. 152-A does not damage the ozone layer but is highly flammable.
Glycol ethers are excellent de-greasers. They are used in cleaners by themselves, as co-solvents or as processing aids. Glycol ethers are readily absorbed through the skin. A clear distinction should be made between the proplylene based glycol ethers (called the P-series) and the ethylene based glycol ethers (called the E-series). Although both types are similar in their chemical structure, the E-series are far more toxic and are regulated under the SARA Act.
The E-series are toxic to sperm producing cells in the testes, bone marrow, thymus and spleen and are also reproductive toxins. They are known animal teratogens (cause birth defects). The higher member of the E-series, the best known of which is butyl cellosolve (or 2-Butoxyethanol) — commonly referred to as butyl or wet solvent — is less teratogenic than its lower member siblings, such as cellosolve and the methyl cellosolve, but does cause blood disorders.
P-series glycol ethers have not shown the levels of toxicity associated with the E-series, even after being subjected to high levels of exposure. As E-series glycol ethers have been linked to reproductive disorders, both users and producers are voluntarily phasing them out. Now, even P series glycol ethers are being restricted.
Let us now look at some statistics.
A leading scientist stated 98 percent of all cancer is environmentally related. Since 1978, there has been a 50 percent increase in skin cancer attributable to increased UV radiation as a result of damage to the protective ozone layer in the upper atmosphere.
Where do we go from here?
Phosphorous is an essential trace element to sustain life. It is added to processed food. It is an essential nutrient in fertilizers. Its salts (phosphates) are exceptional builders in detergents with the most desirable properties, yet it (together with other elements) causes eutrophication, indirectly killing marine life in water by fertilizing algae, which uses up the available oxygen.
Here, too much of a good thing has changed the natural balance. It seems phosphates are on their way out as detergent builders. A number of municipalities and states have restricted their use. Phosphates are being replaced with benign and safer ingredients that will give the desired properties in the detergents without the undesirable side effects.
An ideal solvent should have low toxicity (chronic and acute), low flammability, excellent cleaning ability, fast drying, recyclable, low potential to form smog, available from renewable sources, low global warming potential and does not deplete the protective ozone layer in the upper atmosphere.
The technical industry must educate the carpet cleaner that safer products do not necessarily provide the optimum desired performance. For instance, by substituting limonene or mineral spirits in place of MCF, the drying times are slower and the substitutes are combustible.
Generally, the replacements for E-series glycol ethers are the P-series glycol ethers. Some companies offer less toxic substitutes like dibasic esters, M-pyrol solvents, organic carbonates, alkyl esters, etc. Others are offering various blends. The thing to remember is that without the chlorine in the molecule, the solvent can be highly flammable and can form explosive mixtures in the air or it will have a low evaporation rate.
One safe and effective alternative to toxic solvents is the rapidly growing role of limonene. It is a renewable resource and relatively harmless to humans, but is considered a VOC. The Food and Drug Administration (FDA) classifies it as a generally safe material. CFCs, HCFCs and some chlorinated solvents under the Montreal Protocol are being phased out. Restrictions under the Clean Air Act are being imposed on VOCs, especially the ones that are photochemically reactive, such as regular or odorless mineral spirits, which result in ozone and smog formation at ground level. Restrictions are being imposed on a number of chemicals that are reproductive toxins or known to cause cancer.
A number of chemical companies are making available environmentally-friendly and safer ingredients. Some companies are offering aqueous (water-based) and semi-aqueous products to replace solvent based systems. Solvent-based systems are becoming closed systems in which vapors and solvents do not escape into the environment. The spent solvent is then recovered and recycled.
Different technologies (some operating, some experimental) are being employed, like a combination of microwave and ultrasonic cleaning systems. Recently, a company announced a water-based system with ozone to remove soils and stains.
Some companies have begun offering bio-surfactants. HFCs (these are related to CFCs and HCFCs but do not harm the protective ozone layer) are becoming available, although initially at very high prices.
Then there is a new generation of fabrics that do not soil easily, and can safely be cleaned by either water-based or solvent-base systems.
One day, technology may be developed where liquefied carbon dioxide can be used to extract soils from carpet or laundry. Water at the right pressure and temperature can become an extremely effective solvent for oil-based materials. Someday, this technology may be developed for carpet cleaning.
There is a lot of discussion of indoor air quality and sick building syndrome. Chemical companies that make products for the cleaning industry are moving away from solvent-based systems to water-based systems.
A number of laws have been passed to curtail emissions and waste disposal. Fines under the Clean Air and Clean Water Act approach $25,000 per day for each violation.
The EPA, in addition to civil penalties, is enforcing criminal prosecution for violators. “Not in my backyard” syndrome is being replaced by public awareness and intolerance for environmental crime. Some laws carry a “Bounty Hunter” provision, which means the person reporting the crime gets a reward from fines collected.
To meet the air quality standards in more than 100 non-attainment areas designated by the EPA, carpet and upholstery cleaners will have to install devices to control chemicals that contribute to the ground level ozone.
Eventually, the trend will be toward water-based cleaning systems and products derived from renewable sources that, when put back in nature, do not upset the natural balance. The laws are here to stay. To reduce the threat to the survival of the human race, we all have to do our part to restore the ecological balance on this Earth.
Companies have begun to get their products certified by third parties such as the EPA’s Design for the Environment (DfE) and Green Seal, etc. Some of the larger companies do not participate in this type of certification. The general assumption is these certified products are not only more expensive but also not as effective as the traditional cleaners.
Companies will tend to use only certified products only in cities or states that mandate it. As one big supplier said, “Customers will purchase the certified product for the show but use the traditional product for performance.”
Aziz Ullah, Ph.D., MBA is the president of Fabpro Manufacturing, a formulator of top-quality carpet and upholstery cleaning products. He is a member of the American Chemical Society, senior member of the American Association of Textile Chemists and Colorists and a member of The Textile Institute (UK). He can be reached through his website at www.FabPro.com