Despite the name, dry cleaning is a process that uses liquids other than water to clean clothes, bedding, upholstery and other types of fabrics. Water can damage certain fabrics — such as wool, leather and silk — and a washing machine can wreak havoc on buttons, lace, sequins and other delicate decorations. Enter dry cleaning.
Dry cleaning chemicals
Dry cleaners use a variety of solvents to clean fabric. Early solvents included gasoline, kerosene, benzene, turpentine and petroleum, which were very flammable and dangerous, according to the State Coalition for Remediation of Drycleaners (SCRD), a group whose members share information about cleanup programs. The 1930s saw the development of synthetic, nonflammable solvents — such as perchloroethylene (also known as perc or PCE) and decamethylcyclopentasiloxane (also known as GreenEarth) — which are still used today.
Detergents are typically added to the solvents to aid in the removal of soils, according to an SCRD report titled "Chemicals Used in Drycleaning Operations." Detergents aid dry cleaning in three ways:
- Carrying moisture to aid in the removal of water-soluble soils.
- Suspending soil after it has been removed from the fabric so it won't be reabsorbed.
- Acting as a spotting agent to penetrate the fabric so that the solvents will be able to remove the stains.
Detergents are either added into the solvent before dry cleaning begins or added into the process at specific times.
Dry cleaning process
Dry cleaning machines consist of four parts, according to the Drycleaning & Laundry Institute (DLI), an international trade association for garment care professionals:
- The holding tank or base tank that holds the solvent.
- A pump that circulates the solvent through the machine.
- Filters that trap solid impurities and soils removed from either the solvent or the fabric.
- A cylinder or wheel where the items that are being cleaned are placed.
During dry cleaning, the pump pulls solvent from the tank and sends it through the filters to remove any impurities. The filtered solvent then enters the cylinder, where it interacts with the fabrics and removes any soil. The solvent then travels back into the holding tank so it can begin the process again.
After the items complete the cleaning cycle, the machine goes through an extraction cycle, which removes excess solvent. During this process, the rotation rate of the cylinder increases, much like the final spin cycle on a home washing machine.
After the extraction cycle completes and the cylinder stops moving, the clothes are either dried within the same machine (if it is a closed system) or transferred into a separate drier. The excess solvent is collected, filtered and transferred back into the holding tank.
History of dry cleaning
Dry cleaning dates back to ancient times, according to the DLI. Records about methods for cleaning delicate items have been found in the ruins of Pompeii, decimated by the eruption of Mount Vesuvius in the year 79. In those days, many clothes were made from wool, which was known to shrink in water. Professional clothes cleaners, known as fullers, used solvents such as ammonia (produced from urine) and lye, as well as a type of clay called fuller's earth, which excelled at absorbing dirt, sweat and grease stains.
According to the DLI, the earliest reference to anything resembling modern dry cleaning was a story about a clumsy maid who spilled some kerosene on a greasy tablecloth. The kerosene quickly evaporated, and she noticed how much cleaner the spot where the chemical fell was. People performed many experiments after that incident to determine what types of solvents were best at cleaning greasy stains. These substances included turpentine spirits, kerosene, petroleum-based fluids, gasoline and camphor oil, according to the SCRD.
The credit for being the first commercial dry cleaner goes to the firm of Jolly-Belin, which opened in 1825 in Paris, according to the Handbook of Solvents. In Paris, of course, fashion was an important part of society. The clothes were soaked in vats filled with turpentine, then put into a sort of predecessor to the washing machine and then air dried so that the turpentine could evaporate.
The first dry cleaner in the United States showed up around the same time. Thomas Jennings, a U.S. tailor and inventor, as well as the first known African-American to receive a patent in the United States, used a method called "dry scouring" to clean clothes that traditional cleaning methods would damage. His process was patented in 1821, and Jennings ran a highly successful tailoring and dry cleaning business in New York City.
The underlying issue with petroleum-based solvents was their extreme flammability, so alternatives were sought. Michael Faraday, an English physicist and chemist, first synthesized PCE in 1821. However, it wasn't readily used in dry cleaning until the early 1930s, after William Joseph Stoddard, a U.S. dry cleaner, further developed PCE as a dry cleaning solvent. Its use grew in the late 1930s and early 1940s due to a petroleum shortage during World War II.
Environmental and health concerns
While it is the most popular choice for dry cleaning, perchloroethylene has been found to be dangerous for both health and the environment. According to the Occupational Safety & Health Administration (OSHA), coming into contact with perc puts dry cleaning employees at high risk of health complications. Exposure to perc vapors may occur when an employee loads dirty clothes into a machine, removes items before the drying cycle completes, cleans lint or button traps, changes the filters, or performs maintenance on the machines.
Those who have their clothes and uniforms dry cleaned regularly may also experience the side effects of perc. Inhaling these vapors for a prolonged period can cause dizziness, drowsiness, loss of coordination, mild memory loss, visual perception and blistering of the skin after prolonged contact.
People in the dry cleaning business also face a risk of certain types of cancer. Long-term exposure, according to the National Library of Medicine, may lead to certain types of cancer, including esophageal, cervical, bladder, multiple myeloma and non-Hodgkin's lymphoma. There are also potential links to cervical and breast cancers.
Damage to the central nervous system, liver, kidneys and lungs may also develop.
Studies, such as one published in 2014 in the journal Environmental Health Perspectives, discuss links that have been found between perc and cancer, especially in the dry cleaning business. After going over many similar past studies, and after studying the effects of perc on rats, the researchers in the 2014 study concluded that perc exposure did have a strong correlation with certain types of cancer. Similar to the EPA's 2012 classification, the 2014 study characterized the substance as "likely to be carcinogenic to humans," no matter how someone came in contact with the chemical.
Another 2014 study, also appearing in Environmental Health Perspectives, specifically examined the risk of bladder cancer in people exposed to perc. The researchers also found strong correlations between dry cleaners who use perc as a solvent and an increased risk of bladder cancer. This held true even after taking into account cigarette smoking, another known risk factor in the development of bladder cancer.
The EPA also stated that there is some evidence, while inconclusive, that perc affects the reproductive system in both men and women, resulting in altered sperm structures and reduced fertility. There has also been some research into birth defects caused by perc, but the studies are few and have many limitations.
Perc can be released into the air, water and soil in the environment around where it is produced or used, including the neighborhood dry cleaner. According to the Agency for Toxic Substances and Disease Registry, most of the perc in the atmosphere comes from the dry cleaning industry. The compound breaks down very slowly in the atmosphere, so it can travel long distances.
Perc can enter the water system by liquid waste that may be contaminated with the solvent. Typically, most of the perc evaporates quickly from the water, and the leftovers break down slowly in the water. The chemical also breaks down slowly in soil, where it concentrates after seeping out at waste-disposal sites.
The future of dry cleaning
Today, there are at least 36,000 dry cleaners in the United States alone, according to IBISWorld, a market-research company. However, according to several sources, including a story published on American Drycleaner, many areas in the United States are losing dry cleaners. The article indicates that rising rents, casual attire becoming the new norm, more-durable fabrics being used for clothing and cheap clothing are just a few of the reasons for the shrinking number of dry cleaning stores in the United States.
Another reason is that many dry cleaners are small, family-owned businesses. As the older generation retires, the younger generation looks for other types of jobs. Environmental concerns are also changing the industry. California, for example, is phasing out the use of perc in dry cleaning in favor of less-toxic choices, including water-based and carbon dioxide cleaning.
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Rachel Ross is a science writer and editor focusing on astronomy, Earth science, physical science and math. She holds a Bachelor of Arts in Philosophy from the University of California Davis and a Master's degree in astronomy from James Cook University. She also has a certificate in science writing from Stanford University. Prior to becoming a science writer, Rachel worked at the Las Cumbres Observatory in California, where she specialized in education and outreach, supplemented with science research and telescope operations. While studying for her undergraduate degree, Rachel also taught an introduction to astronomy lab and worked with a research astronomer.