Phthalate Di-isodecyl & Di-isononyl phthalates

5. What health effects can DIDP and DINP cause in laboratory animals?

If DIDP or DINP are swallowed, about 50% of it is absorbed from the gut into the blood. Absorption through the skin is very low in rats (about 4%) and even lower in humans. About 75% of DIDP or DINP inhaled as aerosols are absorbed. DIDP and DINP are rapidly eliminated and do not accumulate in tissues. DIDP and DINP themselves are not found in the urine but their breakdown products (metabolites) are excreted in urine. In faeces, both DIDP and DINP as well as their major breakdown product can be detected. A study on female rats suggests that swallowed DIDP may possibly transfer into mother's milk.

A single dose of DIDP or DINP which is breathed in, swallowed (for example as a contaminant in food) or absorbed through the skin has a low toxicity. DIDP and DINP are not irritant to skin, eyes or respiratory system, nor do they cause skin or respiratory sensitization.

In rodents and dogs, toxicity to the liver is the main result of repeated oral exposure to DIDP or DINP. No liver changes are observed at exposures of up to 60 mg/kg body weight/day in rats or 15 mg/kg body weight/day in dogs for DIDP. For DINP, no effects were observed at up to 88 mg/kg body weight/day. Effects on the kidney are only seen at higher exposures.

DIDP and DINP have not been shown to cause damage to the inherited genetic material in cells (chromosomes and DNA) as shown by several laboratory tests.

DIDP was found to cause liver cancer through a mechanism that is specific to rodents and does not affect humans. It also causes a certain type of leukaemia in rats which never occurs in humans. Similarly it causes tumour in the kidney of male rats by a mechanism which does not operate in humans. Thus, there does not seem to be a concern about cancer in humans through those processes. DIDP has not been tested in mice or rats to see if it causes cancer, but in-vitro tests suggest it may cause the same type of tumours in the liver of rodents as DINP.

No adverse effects of DINP or DIDP on human fertility are anticipated, based on the results of studies on rats, mice and monkeys.

Exposure of pregnant rats to high doses of DIDP or DINP (1 000 mg/kg body weight/day) caused slight malformations in the fetuses, but there were no effects at 500 mg/kg body weight/day.

In rat reproduction studies, reduced survival of the offspring was seen, but there were no effects at concentrations up to 33 mg DIDP/kg body weight/day or159 mg DINP/kg body weight/day.

DIDP does not affect reproductive hormones. DINP does not have an effect on female hormones, however in a rat reproduction study, the development of male offspring, monitored specially for effects controlled by male hormones, was abnormal in a small proportion (7.7%) of the offspring. More...