Phthalate Di-butyl phthalate

5. What health effects can DBP cause in laboratory animals?

If DBP is swallowed, about 90% is rapidly absorbed and excreted in the urine within 48 hours. Very little is eliminated via the faeces. About 60% of a dose of DBP applied to the skin of rats is absorbed into the blood and is excreted via urine within 7 days and about 12% via faeces. Human skin absorbs DBP more slowly than rat skin.

There is no information on absorption after the inhalation of DBP.

After absorption into the blood, DBP passes to the liver and from there can be excreted into the gut via bile, and absorbed into the blood again. In this way it “recirculates” in the body. But DBP does not accumulate in the tissues. The major part of DBP is broken down in the gut before absorption of some DBP and its breakdown products into the blood. DBP and its main breakdown product have been shown to cross the placenta and reach the embryo but it does not accumulate in the embryo.

A single dose, of DBP which is breathed in, swallowed, or absorbed through the skin has a low toxicity. DBP as appeared not to be irritating to the skin, eye or airways nor sensitising to skin. However, a 28-day study on rats showed that inhalation of DBP can cause local effects in the upper respiratory tract, but no sign of inflammation.

Repeated oral exposure to DBP mainly affects the blood, liver and kidney. No effects were seen at a dose of 152 mg/kg body weight/day. Some studies in rats show effects on the testis at 250 mg/kg body weight. Several laboratory tests show that DBP does not cause damage to the inherited genetic material in cells (chromosomes and DNA).

DBP has not been tested in mice or rats to see if it causes cancer, but, as has been observed with DEHP and DINP, it might be expected to cause liver tumours in rodents. However, the mechanism by which the phthalates affect the liver in rodents does not apply in humans. Thus, there does not seem to be concern about cancer in humans.

DBP is toxic to the embryo and fetus and causes malformations at high doses that are also toxic to the mother. There were no adverse effects on the embryo and fetus at 100 mg/kg body weight (NOAEL). There is also evidence from studies on rats that DBP affects aspects of development that are dependent on male hormones in male offspring at oral doses of 100 mg/kg body weight or more. There were no effects at 50 mg/kg body weight/day.

In a rat reproduction study, specifically designed to identify substances affecting hormones, slight toxicity to the embryo was seen at 52 mg/kg body weight. Thus, based on all available studies an overall lowest observed adverse effect level (LOAEL) of 52 mg/kg body weight can be established for oral exposure to DBP. More...