Phthalates are chemicals made from phthalic acid. They are mainly used as plasticizers, which are substances added to plastics to make them more flexible, clear, strong, and long-lasting. Phthalates are most often used to soften a type of plastic called polyvinyl chloride (PVC). Although phthalates are widely used as plasticizers, not all plasticizers are phthalates. These two terms describe different things and are not used interchangeably.
In the United States, Canada, and the European Union, lower-molecular-weight phthalates are often replaced in many products because of health concerns. These are being replaced by higher-molecular-weight phthalates and other types of plasticizers that are not phthalates.
Phthalates are often eaten in small amounts through food. One well-known type of phthalate is bis(2-ethylhexyl) phthalate (DEHP). In many countries, DEHP is considered a harmful substance and is banned from use in certain products, such as cosmetics, children’s toys, medical devices, and food packaging.
There are many types of phthalates that are not controlled by governments.
Production
Phthalate esters are made in factories by mixing phthalic anhydride with extra alcohol. Often, the phthalic anhydride is in a liquid state. The first step of the reaction happens quickly, but the second step is slower. To help the reaction proceed, the process is done at high temperatures to remove water. Common catalysts used include compounds based on tin or titanium, such as alkoxides or carboxylates.
The properties of phthalates can change depending on the type of alcohol used. Around 30 different phthalates have been or are currently important for commercial use. Although phthalates' share of the global plasticizer market has decreased since about 2000, the total amount produced has increased. In 2015, about 5.5 million tonnes were made, compared to around 2.7 million tonnes in the 1980s. This increase is mainly because the overall demand for plasticizers has grown, especially due to rising production of PVC, which nearly doubled between 2000 and 2020. The People's Republic of China is the largest user, accounting for about 45% of all phthalate use. Europe and the United States together use about 25%, while the rest of the world uses the remaining amount.
Uses
Between 90 and 95% of all phthalates are used as plasticizers to make flexible PVC. Most of these are found in films and cable coverings. Flexible PVC can contain more than 85% plasticizer by weight, but unplasticized PVC (UPVC) must not contain any. Phthalates were the first widely used materials for this purpose, which helped them become common in flexible PVC technology. Among common plastics, PVC is special because it can hold large amounts of plasticizer, allowing it to change gradually from a hard solid to a soft gel. Phthalates made from alcohols with 7–13 carbon atoms are often used as general-purpose plasticizers for most flexible PVC uses. Phthalates with more than 13 carbon atoms do not work well with PVC, and di(isotridecyl) phthalate is the largest one that can still be used. Plasticizers made from alcohols with 4–6 carbon atoms are too volatile to use alone but are sometimes added to other materials to improve flexibility at low temperatures. Plasticizers from alcohols with 1–3 carbon atoms are not used in PVC because they release too much vapor during processing (usually 180–210 °C).
Historically, DINP, DEHP, BBP, DBP, and DIHP were the most important phthalates. However, many of these are now being restricted or phased out due to regulations. Almost all phthalates made from alcohols with 3–8 carbon atoms are considered toxic by ECHA. This includes Bis(2-ethylhexyl) phthalate (DEHP or DOP), which was once the most widely used phthalate, with production starting in the 1930s. In the EU, DEHP is limited under REACH and can only be used in specific cases if approved; similar rules apply in other regions. Despite these restrictions, DEHP is still the most commonly used plasticizer, with about 3.24 million tonnes produced globally in 2018. DINP and DIDP are often used as alternatives to DEHP because they are not classified as hazardous. Non-phthalate plasticizers are also being used more frequently.
Phthalates are used as plasticizers in other materials, such as coatings like lacquers, varnishes, and paints. Adding phthalates makes these materials more flexible and less likely to chip. Phthalates made from alcohols with 1–4 carbon atoms are used in cellulose-based plastics, such as cellulose acetate, nitrocellulose, and cellulose acetate butyrate. These are commonly found in products like nail polish. Most phthalates also work well with alkyds and acrylic resins, which are used in both oil-based and water-based paints.
Other materials that use plasticizers include polyvinyl butyral (used in laminated glass), PVA and its copolymers like PVCA. They are also compatible with nylon, polystyrene, polyurethanes, and certain rubbers, though their use in these materials is limited.
Phthalates can soften ethyl cellulose, polyvinyl acetate phthalate (PVAP), and cellulose acetate phthalate (CAP), which are used to make enteric coatings for medicines. These coatings protect drugs from stomach acid but allow them to be absorbed in the intestines.
Phthalate esters are widely used as solvents for highly reactive organic peroxides. Large amounts are used each year for this purpose. A key benefit of these esters is that they act as phlegmatizers, which reduce the risk of explosions from certain chemical compounds. Phthalates have also been used to make plastic explosives like Semtex.
Some phthalates are used in small amounts in personal-care products such as eye shadow, moisturizers, nail polish, liquid soap, and hair spray. Low-molecular-weight phthalates like dimethyl phthalate and diethyl phthalate are used to help perfumes last longer. Dimethyl phthalate has also been used as an insect repellent, especially against ticks that cause Lyme disease and certain mosquitoes like Anopheles stephensi, Culex pipiens, and Aedes aegypti.
Diallyl phthalate is used to make vinyl ester resins with strong electrical insulation properties. These resins are used to produce electronic components.
History
In 1846, the creation of cellulose nitrate plastic caused the patent of castor oil in 1856 for use as the first plasticizer. By 1870, camphor became the most commonly used plasticizer for cellulose nitrate. Phthalates were introduced in the 1920s and quickly replaced camphor because camphor easily evaporated and had a strong smell. In 1931, the commercial availability of polyvinyl chloride (PVC) and the development of di(2-ethylhexyl) phthalate (DEHP) started the rapid growth of the plasticizer PVC industry.
Properties
Phthalate esters are a type of chemical made from phthalic acid, which is also known as 1,2-benzenedicarboxylic acid. This should not be confused with similar chemicals called terephthalic or isophthalic acids. The word "phthalate" comes from "phthalic acid," which is named after "naphthalene." When added to plastics, phthalates help polyvinyl polymers move past each other, making the plastic more flexible. Phthalates are clear, syrupy liquids that do not dissolve easily in water but dissolve well in oils. They do not evaporate easily. The carboxyl group in phthalates has little effect on their physical properties unless the attached groups (like ethyl or methyl) are very small. Phthalates are colorless and have no smell. They are made when phthalic anhydride reacts with alcohols.
Since the 1960s, scientists have studied how phthalates and similar chemicals make polar polymers flexible. This happens through interactions between the charged parts of the phthalate molecule (the C=O group) and the positively charged areas of the polymer chain, usually near the carbon-chlorine bond. To achieve this, the polymer must be heated above its glass transition temperature (Tg) and then melted. This allows the polymer and phthalate to mix thoroughly, forming strong interactions. When cooled, these interactions remain, preventing the PVC chains from reorganizing (as they do in unplasticized PVC). The long chains in phthalates also help keep the PVC chains separated. These interactions and separation occur during the manufacturing process.
Because phthalates are not chemically attached to the plastic, they can be released from the material with gentle methods. For example, they can be removed using organic solvents or through handling.
Phthalate esters are nearly ideal plasticizers because they are inexpensive, not harmful in small amounts, colorless, noncorrosive, biodegradable, and can be easily adjusted for different physical properties. Other plasticizers include dioctyl terephthalate (DEHT), a type of terephthalate similar to DEHP, and 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), a version of DINP that is hydrogenated. Both DEHT and DINCH are used in large amounts in products like medical devices, toys, and food packaging as alternatives to DEHP and DINP. DEHT and DINCH are more hydrophobic than other phthalate alternatives, such as bis(2-ethylhexyl) adipate (DEHA) and diisodecyl adipate (DIDA). Because DEHT and DINCH are more likely to attach to organic matter and dust indoors, exposure to them often happens through eating food or touching dust.
Many plasticizers made from vegetable oil have been developed as alternatives to traditional phthalates.
Occurrence and exposure
Plastic products are common in daily life, and people often come into contact with phthalates, chemicals used to make plastics more flexible. Studies show that most Americans tested by the Centers for Disease Control and Prevention have signs of phthalate exposure in their urine. Women and people of color are more likely to be exposed to phthalates. Research found differences in how phthalates might affect blood sugar levels among Mexican-Americans, African-Americans, and Caucasian-Americans. Mexican-Americans had the highest increase in fasting blood glucose (FBG), followed by African-Americans, then Caucasian-Americans. These findings suggest that certain groups may have a higher risk of health issues related to blood sugar and insulin. The study concluded that phthalates could affect how the body manages blood sugar and how sensitive it is to insulin. Higher levels of some phthalate chemicals were linked to higher FBG, insulin levels, and insulin resistance. Non-Hispanic Black women and Hispanic women had higher levels of some phthalate metabolites.
Homes with children who have asthma or allergies had higher levels of DEHP, a type of phthalate, in their dust compared to homes of healthy children. A study found that higher DEHP levels were connected to wheezing in children over the past year. Phthalates were found in nearly every home tested in Bulgaria. The same study found higher levels of DEHP, BBzP, and DnOP in homes where polishing products were used. While data on flooring materials was collected, no significant differences were found between homes with PVC or linoleum flooring and those with wood flooring. However, frequent dusting reduced phthalate levels in dust.
Children are more exposed to phthalates than adults. A 1990s study in Canada estimated that infants received 9 micrograms of DEHP per kilogram of body weight each day, toddlers 19 micrograms, children 14 micrograms, and adults 6 micrograms. Infants and toddlers are at greater risk because they often put objects in their mouths. Body-care products for babies, like lotions and shampoos, are a source of phthalate exposure. A 2008 study found that using these products was linked to higher levels of phthalate metabolites in infants' urine, especially in younger babies. Researchers noted that young infants are more vulnerable to phthalate effects because of their smaller size, developing systems, and higher exposure per body surface area.
Infants and hospitalized children may face higher phthalate exposure due to medical devices. Some medical tools, like IV tubes and gloves, contain up to 40% DEHP, which can leak when heated. The FDA found that neonates (newborns) might be exposed to five times the allowed daily limit of DEHP. This led the FDA to conclude that children undergoing certain medical procedures may be at greater risk from DEHP.
In 2008, Denmark found phthalates in erasers and warned about health risks if children chew on them regularly. However, the European Commission noted that swallowing small pieces of erasers is unlikely to cause harm.
In 2008, the U.S. National Research Council recommended studying the combined effects of phthalates and other chemicals that cause similar health issues, even if they work differently. It criticized earlier guidelines that limited such studies to chemicals with similar structures or effects.
Phthalates are found in food, especially fast food. A 2024 study found phthalates in nearly all tested grocery items and fast food. Phthalates enter the body mainly through food, particularly fatty foods like milk, butter, and meat. Some phthalates can also be absorbed through the skin or inhaled. Fast food packaging, vinyl gloves, and PVC tubing used in food handling may contribute to phthalate exposure.
A study of 9,000 people found that those who ate fast food had higher levels of DEHP and DiNP in their urine. Even small amounts of fast food increased these levels. For example, people who ate fast food occasionally had 15.5% higher DEHP levels and 25% higher DiNP levels than those who did not eat fast food. Those who ate large amounts had even higher increases. Phthalates leave the body quickly, so their presence in urine likely shows ongoing exposure rather than long-term buildup.
Phthalate levels in outdoor air are higher in cities than in rural areas. They do not cause immediate harm. Common phthalates like DEHP are not easily released into the air. Higher temperatures increase phthalate levels in the air. PVC flooring can release BBP and DEHP into dust, which children may inhale or ingest. A 2012 study in Sweden found that children absorbed phthalates from PVC flooring, showing that exposure can occur through breathing and skin contact, not just food.
Some plants and microorganisms naturally produce small amounts of phthalates, called endogenous phthalates. Scientists believe this happens through a chemical process called the Shikimate pathway. However, the extent of this natural production is not fully understood.
Phthalates do not stay in the environment for long because bacteria break them down quickly. Aerobic and anaerobic bacteria convert phthalates into other chemicals, which then degrade further. Even without bacteria, phthalates can break down in soil through processes like hydrolysis. Sunlight also helps break down phthalates.
Research
Phthalates are being studied as a group of possible hormone-disrupting chemicals that may interfere with normal hormone function in different environmental conditions. Concerns about these chemicals have led to calls for banning or limiting their use in baby toys.
A 2024 study found that mothers exposed to environmental phthalates may experience negative effects on pregnancy, such as a higher chance of miscarriage and lower birth weights. Another study showed small decreases in lung function among children and teenagers who had been exposed to phthalates.
A 2017 study suggested ways to reduce phthalate exposure: (1) eating a healthy, balanced diet to avoid consuming too many hormone-disrupting chemicals from one source, (2) avoiding canned or packaged foods to reduce intake of DEHP phthalates that may leak from plastic packaging, and (3) avoiding personal products like lotions, perfumes, or makeup that contain phthalates. Exposure to phthalates may increase the risk of asthma.
A 2018 study found that exposure to phthalates during childhood development may harm the function of fat tissue and disrupt the body’s ability to balance energy, possibly increasing the risk of obesity.
Legal status
The governments of Australia, New Zealand, Canada, the United States, and California have decided that many phthalates are not harmful to human health or the environment when found in typical amounts. Because of this, these substances are not legally regulated in these areas. However, regulation mainly focuses on diethyl phthalate (DEHP), which is considered a cancer-causing substance and requires control.
The European Chemicals Agency (in the European Union, or EU) considers certain phthalates, including DEHP, dibutyl phthalate, diisobutyl phthalate, and benzyl butyl phthalate, to possibly harm fertility, unborn babies, and the endocrine system. The EU also regulates some phthalates to protect the environment.
A 2017 study of food and packaging in Australia and New Zealand found DEHP and diisononyl phthalate to be possible contaminants that could harm human health. This led to new rules about these phthalates in both countries. Australia has banned certain children’s products containing DEHP because it is considered dangerous if swallowed by children under three years old.
In 1994, Health Canada found DEHP and another phthalate, B79P, to be harmful to human health. The Canadian government banned their use in cosmetics and limited their use in other products, such as soft toys and baby items. In 1999, DEHP was added to Canada’s List of Toxic Substances under the Canadian Environmental Protection Act, 1999. In 2021, DEHP was classified as a risk to the environment and is now on the List of Ingredients Prohibited in Cosmetic Products.
Out of 28 phthalate substances reviewed in national screening programs, 20 are considered possible risks to human health or the environment. As of 2021, no environmental regulations for DEHP or B79P have been created.
Since 1999, the European Union has limited the use of certain phthalates in children’s toys. DEHP, BBP, and DBP are not allowed in any toys, while DINP, DIDP, and DNOP are restricted only in toys that can be put in a child’s mouth. These phthalates must not exceed 0.1% of the plastic part of the toy.
High molecular weight phthalates, such as DINP, DIDP, and DPHP, are registered under REACH and have been shown to be safe for current uses. They are not classified as harmful to health or the environment.
Low molecular weight phthalates, including BBP, DEHP, DIBP, and DBP, were added to the REACH Candidate List of Substances for Authorization in 2008–2009. In 2012, they were added to Annex XIV, meaning they cannot be produced in the EU without special permission. These chemicals may still be imported in consumer products. An effort to ban their import was being planned by the European Chemicals Agency and Danish authorities, with a submission expected by April 2016.
Since 2021, the European Waste Framework Directive requires companies that use phthalates on the REACH Candidate List to notify the European Chemicals Agency.
In November 2021, the European Commission added endocrine-disrupting properties to DEHP and other phthalates. This change requires companies to apply for REACH authorization for certain uses, such as in food packaging, medical devices, and drug packaging, that were previously exempt.
In August 2008, the U.S. Congress passed the Consumer Product Safety Improvement Act (CPSIA), signed by President George W. Bush. Section 108 of the law banned children’s toys and child care items containing more than 0.1% DEHP, DBP, or BBP. It also banned toys that can be placed in a child’s mouth from containing more than 0.1% DINP, DIDP, or DNOP. The law also created a permanent review board to assess the safety of other phthalates. Before this law, the Consumer Product Safety Commission had removed DEHP and DINP from teethers, pacifiers, and rattles, reducing risks to children and advising against a full phthalate ban.
In 1986, California voters approved the Safe Drinking Water and Toxic Enforcement Act (Proposition 65). In December 2013, DINP was added to California’s list of chemicals known to cause cancer. Starting in December 2014, companies with ten or more employees that sell products containing DINP must provide warnings to consumers. California’s Office of Environmental Health Hazard Assessment sets a “No Significant Risk Level” of 146 μg/day for DINP.
In 2011, the CDC released a public health statement about diethyl phthalate, outlining regulations and guidelines for its potential health risks. Under Superfund laws, the Environmental Protection Agency classified diethyl phthalate as a hazardous substance. The Occupational Safety and Health Administration limits the amount of diethyl phthalate in workplace air to 5 milligrams per cubic meter during an 8-hour workday and 40-hour workweek.
Identification in plastics
Phthalates are used in some types of PVC, but not all. There are no rules about labeling phthalates on these products. PVC plastics are often used for containers, hard packaging, medical tubing, and bags. These items are labeled "Type 3." However, labels do not show whether phthalates or other chemicals are used to make the plastic flexible. Only unplasticized PVC (uPVC), which is mainly used for hard construction materials, does not contain plasticizers. If more precise testing is needed, chemical analysis, such as gas chromatography or liquid chromatography, can identify phthalates.
Polyethylene terephthalate (PET, PETE, Terylene, Dacron) is the main material used for packaging bottled water and many sodas. Products made with PETE are labeled "Type 1" (with a "1" in the recycle triangle). Although the word "phthalate" appears in the name, PETE does not use phthalates as plasticizers. The terephthalate polymer in PETE and phthalate ester plasticizers are chemically different. However, many studies have found phthalates, such as DEHP, in bottled water and soda. One possible explanation is that these chemicals may have entered the products during the recycling process.