Children's phthalate intakes and resultant cumulative exposures estimated from urine compared with estimates from dust ingestion, inhalation and dermal absorption in their homes and daycare centers

Abstract

Total daily intakes of diethyl phthalate (DEP), di(n-butyl) phthalate (DnBP), di(isobutyl) phthalate (DiBP), butyl benzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP) were calculated from phthalate metabolite levels measured in the urine of 431 Danish children between 3 and 6 years of age. For each child the intake attributable to exposures in the indoor environment via dust ingestion, inhalation and dermal absorption were estimated from the phthalate levels in the dust collected from the child's home and daycare center. Based on the urine samples, DEHP had the highest total daily intake (median: 4.42 µg/d/kg-bw) and BBzP the lowest (median: 0.49 µg/d/kg-bw). For DEP, DnBP and DiBP, exposures to air and dust in the indoor environment accounted for approximately 100%, 15% and 50% of the total intake, respectively, with dermal absorption from the gas-phase being the major exposure pathway. More than 90% of the total intake of BBzP and DEHP came from sources other than indoor air and dust. Daily intake of DnBP and DiBP from all exposure pathways, based on levels of metabolites in urine samples, exceeded the Tolerable Daily Intake (TDI) for 22 and 23 children, respectively. Indoor exposures resulted in an average daily DiBP intake that exceeded the TDI for 14 children. Using the concept of relative cumulative Tolerable Daily Intake (TDI(cum)), which is applicable for phthalates that have established TDIs based on the same health endpoint, we examined the cumulative total exposure to DnBP, DiBP and DEHP from all pathways; it exceeded the tolerable levels for 30% of the children. From the three indoor pathways alone, several children had a cumulative intake that exceeded TDI(cum). Exposures to phthalates present in the air and dust indoors meaningfully contribute to a child's total intake of certain phthalates. Such exposures, by themselves, may lead to intakes exceeding current limit values.

Figure 1. Cumulative frequency distributions for the estimated intakes of phthalates.

Distributions are shown for the intakes on the day before urine sampling by different indoor exposure pathways and the total intakes calculated from the metabolite concentrations measured in urine (DI_urine). A) DEP, B) DnBP, C) DiBP, D) BBzP and E) DEHP. The solid horizontal line indicates the TDI value. The TDI value for BBzP (500 µg/d/kg-bw) is not indicated in the plot.

Figure 2. Cumulative frequency distribution of the ratio of the daily intake to the TDI for each of the five phthalates.

The solid diamonds depict the relative cumulative tolerable daily intake (TDI_cum) for DnBP, DiBP and DEHP; A) daily intakes calculated from the excreted amount of phthalates in the urine (DI_urine), B) average daily intakes from a week-long exposure in the indoor environment through dust ingestion, inhalation and dermal absorption. Values above the solid horizontal line (100%) exceed the TDI of the given phthalate or the TDI_cum for the three phthalates.