Chemical Substitution Examples
Substituting hazardous chemicals with safer ones offers substantial benefits to companies that handle them. It reduces costs by lowering expenditure on protective measures, storage and disposal.
It also improves working conditions and the physical environment. The process can be facilitated by legal provisions such as the REACH regulation. Tools useful for alternatives assessment and substitution are available and there is a growing pool of shared experience in the field.
1. Ethylene glycol
Ethylene glycol is a clear, colorless liquid with a sweet taste. It is soluble in water, but its low vapor pressure precludes substantial inhalation exposure and it does not persist in ambient air or soil (half-life in air is about 24 hours). Ingestion of monoethylene glycol is poisonous; untreated ingestion can be fatal.
It is used as a solvent, freeze-thaw stabilizer and a corrosion inhibitor. It is an ingredient in automotive antifreeze and engine coolants and in aircraft de-icing and de-icer solutions. It is also an important precursor to polyethylene terephthalate, which is used in the manufacture of plastic bottles for soft drinks.
2. Polyethylene glycol
Poly(alkylene glycol)s are water-soluble, oily liquids that find their way into environmental and wastewater systems. They are not readily metabolized, but rather retain their ether bonds in the biodegradation process (apart from those linked to sugar molecules). They are typically labeled by their average molecular weight or Mn, indicated by a number after the polymer name.
PEG has several beneficial characteristics, including its low toxicity, nonadsorptive properties, and resistance to protein binding. Its uncharged, hydrophilic, and sterically inert structure also helps to reduce the formation of aggregates and other unwanted effects from biological reactions. It is the basis for many biomedical applications, such as a gel designed to treat periodontitis by encapsulating stem cells and promoting tissue regeneration. PEGs with a long terminal hydroxyl group can be used to generate reactive groups such as acrylic (PEGDA) and methacrylic acids (PEGGDMA). They have also been used to construct polymer scaffolds for tissue engineering.
3. Propylene glycol
Propylene glycol, also known as propane-1,2-diol, is a chemical that’s used to control the viscosity of cosmetic products. It’s also an important ingredient in aircraft de-icing fluid, and it is sometimes found in antifreeze and other automotive fluids.
In the event of a spill or leak, propylene glycol can enter surface water via production and processing facility wastewater, as well as from aircraft deicing fluid runoff. It has been shown to adsorb and leach to sediment in surface water systems, but is not expected to volatilize from the water’s surface(SRC).
When ingested in high doses, propylene glycol can cause brain-related symptoms such as seizures. This type of toxicity is considered to be iatrogenic, meaning it is the result of medical treatment rather than caused by exposure to the chemical itself.
4. Butylene glycol
Butylene glycol (or butane-1,3-diol) is a colorless, syrupy liquid. It’s a multi-tasking ingredient that performs many roles in cosmetic products including solvent, humectant and viscosity reducer.
It’s a good choice for skin care because it smoothes and conditions the skin. It also helps other ingredients to absorb faster and deeper into the skin.
Like propylene glycol, butylene glycol is derived from fossil fuels by using acetaldehyde (which is produced through conventional synthetic methods and is a probable carcinogen). Genomatica’s fermentation process produces pure R-enantiomer butylene glycol, avoiding the need for acetaldehyde use. This is a big environmental benefit, especially because butylene glycol has a low toxicity and is a safe chemical for cosmetics use. Older studies suggest it can cause allergic contact dermatitis in some people, so sensitive skin types should consider formal patch testing before starting a new product with this ingredient.
5. Butadiene glycol
Mitsubishi Chemical is able to produce 14BG (1,4-Butanediol, 1,4-Butylene glycol) from butadiene using its proprietary technology. 14BG is used as raw material for polyurethane resins of controllable color and high performance characteristics.
This molecule is also used as an antimicrobial agent inhibiting the growth of gram-negative and gram-positive microorganisms, molds, and yeasts but it is not sporicidal. It is also used as an intermediate in the manufacture of butadiene from acetadol.
Like propylene glycol, butadiene glycol is toxic and should be handled with care. It irritates the skin, eyes, and throat. It can also corrode steel containers, so it’s important to keep butadiene glycol in tightly closed bottles. It’s also a suspected carcinogen and may be absorbed through the skin. It’s recommended that workers wear gloves when handling this substance.