Health effects of di(2-ethylhexyl)phthalate (DEHP)
Contents
Introduction
DEHP is an acronym for di(2-ethylhexyl) phthalate, a manufactured chemical that is commonly added to plastics to make them flexible. Other names for this compound are dioctyl phthalate (DOP) and bis(2-ethylhexyl) phthalate (BEHP). (Note that di-n-octyl phthalate, however, is the name for a different chemical.) Trade names used for DEHP include Platinol DOP, Octoil, Silicol 150, Bisoflex 81, and Eviplast 80. DEHP is a colorless liquid with almost no odor. It does not evaporate easily, and little will be present in the air even near sources of production. It dissolves more easily in materials such as gasoline, paint removers, and oils than it does in water. It is present in many plastics, especially vinyl materials, which may contain up to 40% DEHP, although lower levels are common. DEHP is present in plastic products such as wall coverings, tablecloths, floor tiles, furniture upholstery, shower curtains, garden hoses, swimming pool liners, rainwear, baby pants, dolls, some toys, shoes, automobile upholstery and tops, packaging film and sheets, sheathing for wire and cable, medical tubing, and blood storage bags. (Health effects of di(2-ethylhexyl)phthalate (DEHP))
Pathways for DEHP in the environment
DEHP can enter the environment through releases from factories that make or use DEHP and from household items containing it. Over long periods of time, it can move out of plastic materials into the environment. Therefore, DEHP is widespread in the environment; about 291,000 pounds were released in 1997 from industries. It is often found near industrial settings, landfills, and waste disposal sites. A large amount of plastic that contains DEHP is buried at landfill sites. DEHP has been found in groundwater near waste disposal facilities.
When DEHP is released to soil, it usually attaches strongly to the soil and does not move very far away from where it was released. When DEHP is released to water, it dissolves very slowly into underground water or surface waters that contact it. It takes many years before DEHP in buried or discarded materials disappears from the environment. Because DEHP does not evaporate easily, normally very little goes into the air. DEHP in air will bind to dust particles and will be carried back down to earth through gravity and rain or snow. Indoor releases of DEHP to the air from plastic materials, coatings, and flooring in home and work environments, although small, can lead to higher indoor levels than are found in the outdoor air.
DEHP can break down in the presence of other chemicals to produce mono(2-ethylhexyl)phthalate (MEHP) and 2-ethylhexanol. Many of the properties of MEHP are like those of DEHP, and therefore its fate in the environment is similar. In the presence of oxygen, DEHP in water and soil can be broken down by microorganisms to carbon dioxide and other simple chemicals. DEHP does not break down very easily when deep in the soil or at the bottom of lakes or rivers where there is little oxygen. It can be found in small amounts in fish and other animals, and some uptake by plants has been reported.
Exposure to DEHP
You can be exposed to DEHP through air, water, or skin contact with plastics that have DEHP in them. Food may also contain DEHP, but it is not certain how much.
It is not clear, but it is likely that a little DEHP is transferred by skin contact with plastic clothing or other articles that contain DEHP. Exposure through this route is expected to be low since plastic articles of clothing, like raincoats, do not have direct contact with your skin, and transfer is probably very low even if they do touch you.
You may be exposed to DEHP through drinking water, but it is not known how common this is. If you drink water from a well located near a landfill or waste site, you may be exposed to higher-than-average levels of DEHP.
You can breathe in DEHP that has been released to the environment. The average air level of DEHP is very low, less than 2 parts of DEHP per trillion parts of air (ppt) in cities and industrial areas. DEHP levels in the indoor air in a room with recently installed flooring could be higher than levels in the outdoor air. Workers in factories that make or use DEHP also breathe in higher-than-average levels of this compound.
DEHP also can enter your body during certain medical procedures, and medical exposures are likely to be greater than any environmental exposures. Blood products that are stored in plastic bags and used for transfusions contain from 4.3 to 1,230 parts of DEHP per million parts of blood (ppm). Other plastic medical products also release DEHP. Flexible tubing used to administer fluids or medication can transfer DEHP to the patient. The plastic tubing used for kidney dialysis frequently contains DEHP and causes DEHP to enter the patient's blood. DEHP also is present in the plastic tubing of respirators and is carried from it to the lungs.
Pathways for DEHP in the body
DEHP enters your body when you eat food or drink water containing this material or when you breathe in contaminated air. Small amounts of DEHP might enter your body by skin contact with plastics, but scientists are fairly certain that very little enters this way. Most DEHP that enters your body in food, water, or air is taken up into the blood from the intestines and lungs. DEHP can be introduced directly into your bloodstream if you get a blood transfusion, receive medicines through flexible plastic tubing, or have dialysis treatments.
After DEHP is ingested, most of it is rapidly broken down in the gut to MEHP and 2-ethylhexanol. Breakdown is much slower if DEHP enters your blood directly by way of a transfusion. Although some MEHP is absorbed into the bloodstream from the gut, MEHP is poorly absorbed, so that much of ingested DEHP leaves the body in the feces. The compounds that do enter the blood travel through the bloodstream to your liver, kidneys, testes, and other tissues, and small amounts might become stored in your fat and could possibly be secreted in breast milk. Most of the DEHP, MEHP, and 2-ethylhexanol leaves your body within 24 hours in the urine and feces.
Health effects of DEHP
To protect the public from the harmful effects of toxic chemicals and to find ways to treat people who have been harmed, scientists use many tests. You should know that one way to learn whether a chemical will harm people is to determine how the body absorbs, uses, and releases the chemical. For some chemicals, animal testing may be necessary. Animal testing may also help identify such health effects as cancer or birth defects. Without laboratory animals, scientists would lose a basic method for getting information needed to make wise decisions that protect public health. Scientists have the responsibility to treat research animals with care and compassion. Scientists must comply with strict animal care guidelines because laws today protect the welfare of research animals.
Additionally, there are vigorous national and international efforts to develop alternatives to animal testing. The efforts focus on both in vitro and in silico approaches and methods. For example, the National Toxicology Program (NTP) at the National Institute of Environmental Health Sciences (NIEHS) created the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) in 1998. The role of NICEATM is to serve the needs of high quality, credible science by facilitating development and validation—and regulatory and public acceptance—of innovative, revised test methods that reduce, refine, and replace the use of animals in testing while strengthening protection of human health, animal health and welfare, and the environment. In Europe, similar efforts at developing alternatives to animal based testing are taking place under the aegis of the European Centre for the Validation of Alternative Methods (ECVAM).
DEHP, at the levels found in the environment, is not expected to cause adverse health effects in humans. A man who voluntarily swallowed 10 g (approximately 0.4 ounces) of DEHP had stomach irritation and diarrhea. Most of what we know about the health effects of DEHP comes from studies of rats and mice that were given DEHP in their food, or the DEHP was placed in their stomach with the aid of a tube through their mouth. In most of these studies, the amounts of DEHP given to the animals were much higher than the amounts found in the environment. Rats and mice appear to be particularly sensitive to some of the effects of DEHP. Thus, because certain animal models may not apply to humans, it is more difficult to predict some of the health effects of DEHP in humans using information from these studies.
Breathing DEHP does not appear to have serious harmful effects. Studies in rats have shown that DEHP in the air has no effect on lifespan or the ability to reproduce. As mentioned previously, almost no DEHP evaporates into air. You probably will not have any health effects from skin contact with DEHP because it cannot be taken up easily through the skin.
Short-term oral exposures to levels of DEHP much higher than those found in the environment interfered with sperm formation in mice and rats. These effects were reversible, but sexual maturity was delayed when the animals were exposed before puberty. Short-term exposures to low levels of DEHP appeared to have no effect on male fertility.
Studies of long-term exposures in rats and mice have shown that high oral doses of DEHP caused health effects mainly in the liver and testes. These effects were induced by levels of DEHP that are much higher than those received by humans from environmental exposures. Toxicity of DEHP in other tissues is less well characterized, although effects in the thyroid, ovaries, kidneys, and blood have been reported in a few animal studies. The potential for kidney effects is a particular concern for humans because this organ is exposed to DEHP during dialysis and because structural and functional kidney changes have been observed in some exposed rats. Since changes in the kidneys of long-term dialysis patients might be due to the underlying kidney disease, and kidney changes have not been consistently seen in animals exposed to DEHP, the significance of the rat kidney changes is not clear.
Humans absorb and breakdown DEHP in the body differently than rats and mice. Therefore, many of the effects seen in rats and mice after exposures to DEHP might not occur in humans and higher animals like monkeys (primates).
No studies have evaluated the potential for DEHP to cause cancer in humans. Eating high doses of DEHP for a long time resulted in liver cancer in rats and mice.
The Department of Health and Human Services (DHHS) has determined that DEHP may reasonably be anticipated to be a human carcinogen. EPA has determined that DEHP is a probable human carcinogen. These determinations were based entirely on liver cancer in rats and mice. The International Agency for Research on Cancer (IARC) has recently changed its classification for DEHP from "possibly carcinogenic to humans" to "cannot be classified as to its carcinogenicity to humans," because of the differences in how the livers of humans and primates respond to DEHP as compared with the livers of rats and mice.
Health effects in children
This section discusses potential health effects from exposures during the period from conception to maturity at 18 years of age in humans.
Children can be exposed to DEHP if they eat food or drink water contaminated with DEHP or if they breathe in the chemical from ambient or indoor air. Small children can also be exposed by sucking on or skin contact with plastic objects (toys) and pacifiers that contain DEHP, as well as by ingestion of breast milk containing DEHP. Children also can be exposed to DEHP if they undergo certain medical procedures that require the use of flexible tubing such as that used to administer fluids or medication to the patient. However, there is no conclusive evidence of adverse health effects in children exposed to DEHP in any of these ways.
In studies of pregnant mice and rats orally exposed to large doses of DEHP, effects on the development of the fetus, including birth defects and even fetal death, were observed. Researchers observed alterations in the structure of bones and of parts of the brain, and in the liver, kidney, and testes of the young animals. These harmful effects suggested that DEHP or some of its breakdown products passed across the placenta and reached the fetus. Therefore, humans exposed to sufficiently high levels of DEHP during pregnancy could possibly have babies with low birth weights and/or skeletal or nervous system developmental problems, but this is not certain. Studies in animals also have shown that DEHP or some of its breakdown products can pass from mother to babies via the breast milk and alter the development of the young animals. This could also happen in humans because DEHP has been detected in human milk.
We do not know whether children differ from adults in their susceptibility to health effects from DEHP. However, studies suggest that young male animals are more susceptible than older ones to the adverse effects of DEHP on the sex organs.
Reducing risk of exposure to DEHP
DEHP is used in many products that are made from plastic, but especially a plastic known as polyvinyl chloride (PVC) or vinyl. When it is found in products, DEHP is at a higher level when that product is new. Less is found in products that are old. Items made from PVC include many plastic toys, some plastic furniture, car and furniture upholstery, shower curtains, some garden hoses, tablecloths, and some flooring (vinyl flooring). Not all PVC products contain DEHP, but it is found in many products. Because DEHP might be in some toys, there is a concern that children chewing on such toys might be exposed. One study has shown that DEHP can go from plastics to laboratory-simulated saliva.
Medical tests for exposure to DEHP
The most specific test that can be used to determine if you have been exposed to DEHP is the measurement of MEHP and other breakdown chemicals in your urine or blood (conduct of these tests constitutes biomonitoring). This test only provides a measure of recent exposure, since DEHP is rapidly broken down into other substances and excreted from your body. You also could be tested for another breakdown product (phthalic acid), but this test would not be specific for DEHP. One or 2 days after exposure, your feces could be tested for the presence of DEHP metabolites. These tests are not routinely available through health care providers.
Further Reading
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