Health effects of di-n-butyl phthalate
Contents
- 1 Introduction
- 2 Pathways for di-n-butyl phthalate in the environment
- 3 Exposure to di-n-butyl phthalate
- 4 Pathways for di-n-butyl phthalate in the body
- 5 Health effects of di-n-butyl phthalate
- 6 Reducing risk of exposure to di-n-butyl phthalate
- 7 Medical tests for exposure to di-n-butyl phthalate
- 8 Further Reading
Introduction
Di-n-butyl phthalate is an odorless and colorless or faintly yellow oily liquid that does not occur in nature. It is a chemical that is added to hard plastics to make them soft. The plastics that di-n-butyl phthalate is used most in are called polyvinyl chloride plastics and nitrocellulose lacquers. These plastics are used to make many products that we use every day such as carpets, paints, glue, insect repellents, hair spray, nail polish, and rocket fuel. In 1994, more than 17 million pounds (i.e., 7.8 million kilograms) of di-n-butyl phthalate were made. (Health effects of di-n-butyl phthalate)
Pathways for di-n-butyl phthalate in the environment
Di-n-butyl phthalate enters the environment in many ways. Di-n-butyl phthalate is in many items made of plastics such as carpets, paint, and nail polish. When paint dries or new carpets are installed, a small amount of di-n-butyl phthalate enters the air. Di-n-butyl phthalate also gets into air by sticking to dust particles. In air, di-n-butyl phthalate usually breaks down within a few days, but not if it is stuck to dust. When it is on dust, di-n-butyl phthalate can move with the wind for many miles before dust drops to the ground. Di-n-butyl phthalate can get into soil when people throw out certain plastic items containing di-n-butyl phthalate and they get buried. In water and soil, bacteria break down di-n-butyl phthalate. This may happen in a day, or may take up to a month. How long it takes to break down di-n-butyl phthalate in soil or water depends on many factors. These factors include the outside temperature, because di-n-butyl phthalate breaks down more slowly when it is cold than when it is hot. If di-n-butyl phthalate does not break down in soil, it can get into groundwater and contaminate wells.
Exposure to di-n-butyl phthalate
Because di-n-butyl phthalate has so many uses, it is widespread in the environment. Most people are probably exposed to low levels in air. Some people may also be exposed to di-n-butyl phthalate in water, food, or both. Most of the time, the largest source of exposure is from air that contains di-n-butyl phthalate. Low levels (0.01 parts per billion [ppb]) are present around the globe, and levels of 0.03 to 0.06 ppb are often found in city air. Higher levels can occur temporarily inside homes and offices, especially when products containing di-n-butyl phthalate, such as nail polish, are used or when new carpet containing di-n-butyl phthalate is installed. Di-n-butyl phthalate is present in some drinking water supplies, usually at levels of around 0.1 to 0.2 ppb.
Another way you can be exposed is by eating food containing di-n-butyl phthalate. Some di-n-butyl phthalate in food comes from the materials used to package and store the food. Some comes from di-n-butyl phthalate taken up by fish and shellfish. Levels of di-n-butyl phthalate in food have been found to range from about 40 to 570 ppb. The levels of di-n-butyl phthalate found in air, water, and food are usually low enough that they are not expected to cause any harmful effects.
Exposure to high levels could occur at a number of places. For example, if you live near a factory that makes or uses di-n-butyl phthalate, you could be exposed if the factory allowed di-n-butyl phthalate to escape into the air that you breathe or into the water that you drink. If the factory spilled or disposed of any di-n-butyl phthalate on the ground, you could also be exposed by getting the soil on your skin. You could be exposed to elevated levels of di-n-butyl phthalate in these same ways if you live near a chemical waste site that has allowed di-n-butyl phthalate to escape into the environment. Di-n-butyl phthalate released into the air, water, and soil is also of concern near garbage dumps and landfills. This is because large amounts of products that have di-n-butyl phthalate in them are thrown away at these sites, and the di-n-butyl phthalate can slowly come out of these products and get into air, water, or soil.
Pathways for di-n-butyl phthalate in the body
If you eat or drink food or water containing di-n-butyl phthalate, nearly all of the di-n-butyl phthalate rapidly enters your body through the digestive system. If you breathe air containing di-n-butyl phthalate, it is likely that most of what you breathe in will enter your body through the lungs, but this has not been studied in detail. Di-n-butyl phthalate can also enter the body through the skin, although this occurs rather slowly. Inside the body, di-n-butyl phthalate is changed into other chemicals. Most of these are quickly removed from the body in the urine. The rest are removed in the feces. Most of the di-n-butyl phthalate that enters the body is removed within 24 hours, and virtually all of it is gone by 48 hours after exposure.
Health effects of di-n-butyl phthalate
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).
Di-n-butyl phthalate appears to have relatively low toxicity, and large amounts are needed to cause injury. Adverse effects on humans from exposure to di-n-butyl phthalate have not been reported. In animals, eating large amounts of di-n-butyl phthalate can affect their ability to reproduce. In male animals, sperm production can decrease after eating large amounts of di-n-butyl phthalate. However, when exposure to di-n-butyl phthalate stops, sperm production seems to return to near normal levels. The levels of di-n-butyl phthalate that cause toxic effects in animals are about 10,000 times higher than the levels of di-n-butyl phthalate found in air, food, or water. Exposure to high levels of di-n-butyl phthalate might cause similar effects in humans as in animals, but this is not known. In animals, large amounts of di-n-butyl phthalate repeatedly applied to the skin for a long time cause mild irritation. Although the available data do not indicate that di-n-butyl phthalate causes cancer, this needs to be more thoroughly studied.
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. Potential effects on children resulting from exposures of the parents are also considered. Very few studies have looked at how di-n-butyl phthalate can affect the health of children. It is likely that the health effects seen in children exposed to di-n-butyl phthalate will be similar to the effects seen in adults. We do not know whether children differ from adults in their susceptibility to di-n-butyl phthalate. We do not know if exposure to di-n-butyl phthalate will result in birth defects or other developmental effects in people. Birth defects have been observed in animals exposed to high levels of di-n-butyl phthalate during development. The developing animal is sensitive to di-n-butyl phthalate. Death, low body weights, skeletal deformities, cleft palate, and damage to the testes have been observed in the offspring of animals ingesting large amounts of di-n-butyl phthalate. We have no information to suggest that there are any differences between children and adults in terms of how much di-n-butyl phthalate will enter the body, where di-n-butyl phthalate can be found in the body, and how fast di-n-butyl phthalate will leave the body. We do not know if di-n-butyl phthalate can be transferred from the mother to an infant in breast milk or whether it can cross the placenta.
Reducing risk of exposure to di-n-butyl phthalate
This section discusses potential health effects from exposures during the period from conception to maturity at 18 years of age in humans. Potential effects on children resulting from exposures of the parents are also considered. Very few studies have looked at how di-n-butyl phthalate can affect the health of children. It is likely that the health effects seen in children exposed to di-n-butyl phthalate will be similar to the effects seen in adults. We do not know whether children differ from adults in their susceptibility to di-n-butyl phthalate. We do not know if exposure to di-n-butyl phthalate will result in birth defects or other developmental effects in people. Birth defects have been observed in animals exposed to high levels of di-n-butyl phthalate during development. The developing animal is sensitive to di-n-butyl phthalate. Death, low body weights, skeletal deformities, cleft palate, and damage to the testes have been observed in the offspring of animals ingesting large amounts of di-n-butyl phthalate. We have no information to suggest that there are any differences between children and adults in terms of how much di-n-butyl phthalate will enter the body, where di-n-butyl phthalate can be found in the body, and how fast di-n-butyl phthalate will leave the body. We do not know if di-n-butyl phthalate can be transferred from the mother to an infant in breast milk or whether it can cross the placenta.
Medical tests for exposure to di-n-butyl phthalate
Tests are available that can detect di-n-butyl phthalate in blood and body tissues, and the major breakdown products of di-n-butyl phthalate can be measured in urine. These tests are known as biomonitoring. However, there is not enough information at this time to use the results of such tests to predict the nature or severity of any health effects that may result from exposure to di-n-butyl phthalate. Since special equipment is needed, these tests cannot be performed routinely in your doctor's office.
Further Reading
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