Koch, HM, H Drexler, and J Angerer. 2003. An estimation of the daily intake of di(2-ethylhexyl)phthalate (DEHP) and other phthalates in the general population. International Journal of Hygiene and Environmental Health 206:77-83.

Background on phthalates

Koch and his colleagues report strikingly high phthalate levels in a sample of German men and women. They conclude that their results "unequivocally prove that the general German population is exposed to DEHP to a much higher extent than previously believed." By their calculations, 31% of the subjects had values higher than the reference dose for DEHP of 20 µg/kg body weight/day of the U.S. EPA. Twelve percent of subjects exceeded the European Union's "Tolerable Daily Intake" level of 37 µg/kg.

According to Koch et al., their findings are of great public health importance. "We are not aware of any other environmental contaminant for which the TDI and RfD are exceeded to such an extent within the general population.

What did they do? Koch et al. obtained urine samples from 85 people living in the southern German city of Erlangen. None of the subjects had been exposed occupationally to phthalates.

Using a new technique out of analytical chemistry called "multidimensional liquid chromatography tandem mass spectrometry" they detemrined the levels of a series of phthalate metabolites in the urine sample. Based on those measurements, they then calculated an estimate of the daily exposure to different phthalates that would have been required to produce the levels measured in the urine. Those calculations were based on previous studies in which people's urine levels were monitored following ingestion of known quantitites of phthalates.

What did they find? All people sampled had phthalate metabolites in their urine, with metabolites of DEHP being highest.

What does it mean? If data from the US about phthalate exposures were not already sufficient to raise concerns, these results from Germany should put public health authorities on notice that phthalate exposures in the general population are likely to be much higher than realized. Their "intake calculations demonstrate beyond doubt that an unexpectedly high share of the general population is exposed to DEHP and exceeds the TDI of the CSTEE and the RfD of the EPA."

The TDI and RFD concentrations are derived from data on experimental effects on animals, specifically on an estimate of what level is low enough so that no adverse effect can be observed in exposed animals (the no observed adverse effect level, or NOAEL). A series of safety factors are then used to add a margin of safety because of uncertainties about how applicable the animal results are to humans. The resulting TDI and RFDs then become the goals for exposure regulation, to make sure that people's exposures do not come close to a level at which adverse effects are likely.

The fact that 30% and 12% of calculated exposures for DEHP exceed the RFD and TDI levels, respectively, is a clear signal that something is wrong in the way that DEHP is being used and regulated. The data for DnBP, while indicating a larger gap between prevailing exposures and levels of concern, also raise flags about the adequacy of current regulations.

Sources of exposure to DEHP are ubiquitous. Its principal use is as a plasticizer for polyvinyl chloride, to make PVC plastic more flexible. Flexible PVC products include "wall coverings, tablecloths, floor tiles, furniture upholstery, shower curtains, garden hoses, swimming pool liners, rainwear, baby pants, dolls, toys, shoes, automobile upholstery and tops, packaging film and sheet, sheathing for wire and cable, medical tubing, and blood storage bags. Polyvinyl chloride is also used to produce disposable medical examination and surgical gloves, the flexible tubing used to administer parenteral solutions, and the tubing used in hemodialysis treatment," according to the US ATSDR.

Considerable research is underway on the toxicological effects of phthalates, especially DEHP, which is thought to be the most hazardous chemical in the family. The main concern arises because of DEHP's ability to interfere with androgens, particularly during fetal development. Experiments with animals reveal a range of adverse effects on the developing male fetus, especially with respect to growth of the reproductive tract.