Di-n-butyl phthalate is an odorless and colorless oily liquid. It is a man-made chemical that is added to plastics and other chemical products. Di-n-butyl phthalate has been used to make soft plastics, carpet backing, paints, glue, insect repellents, hairspray, nail polish, and rocket fuel.
Structural diagram: National Institutes of Health
Fate & Transport
Di-n-butyl phthalate does not evaporate easily, but small amounts do enter into the air as a gas. Di-n-butyl phthalate also gets into air by attaching to dust particles. In air, di-n-butyl phthalate usually breaks down within a few days. Di-n-butyl phthalate does not dissolve easily in water, but can get into water by attaching to dirt particles. In water and soil, bacteria break down di-n-butyl phthalate. This may happen in a day, or may take up to a month. The length of time it takes to break down di-n-butyl phthalate in soil or water depends on the kind of bacteria present and the temperature.
Because di-n-butyl phthalate has so many uses in modern society, it has become widespread in the environment, and most people are exposed to low levels in air, water, and food. In most cases, the largest source of exposure is from food that contains di-n-butyl phthalate. Some di-n-butyl phthalate in food comes from the plastics used to package and store the food, and some of it comes from di-n-butyl phthalate taken up by fish, shellfish, or other foods. Levels of di-n-butyl phthalate in food have been found to range from around 50 to 500 parts per billion (ppb).
Another way you can be exposed is by breathing air containing di-n-butyl phthalate. Low levels (0.01 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 inside homes, especially when products containing di-n-butyl phthalate, such as nail polish, are used. Di-n-butyl phthalate is present in some drinking water supplies, usually at levels of around 0.1 to 0.2 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. However, if you were exposed to higher-than-usual levels of di-n-butyl phthalate, this might be of concern. 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 by 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 release into the air, water, and soil is also of concern at garbage dumps and landfills. This is because large amounts of di-n-butyl phthalate-containing materials are thrown away at these sites, and the di-n-butyl phthalate can slowly come out of the products and get into air, water, or soil.
If you eat or drink di-n-butyl phthalate in food or water, 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 enters your body through the lungs, but this has not been studied in detail. Di-n-butyl phthalate can also enter the body through 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.
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. Di-n-butyl phthalate can cause death of unborn animals. 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. Exposure to high levels of di-n-butyl phthalate might cause similar effects in humans as in animals, but this is not known. There is no evidence that di-n-butyl phthalate causes cancer, but this has not been thoroughly studied.
Di-n-butyl phthalate appears to have relatively low toxicity, and large amounts are needed to cause injury. The levels of di-n-butyl phthalate which 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. If you were to eat di-n-butyl phthalate at levels equal to those at which effects were seen in animals, about 1-2% of what you eat every day would have to be di-n-butyl phthalate. Large amounts of di-n-butyl phthalate repeatedly applied to the skin for a long time may also cause mild irritation.
Information excerpted from:
Toxicological Profile for Di-n-butyl Phthalate December 1990