"The Association between Asthma and Allergic Symptoms in Children an Phthalates in House Dust: A Nested Case-Control Study." Environmental Health Persepectives

Dermal Absorption of Phthalate Diesters in the Rat. ELSISI, A. E., CARTER, D. E., AND SIPES, I. G. (1989). Fundam Appl. Toxicol. 12, 70-77. This study examined the extent of dermal absorption of a series of phthalate diesters in the rat. Those tested were dimethyl, diethyl, dibutyl, diisobutyl, dihexyl, di(2-ethylhexyl), diisodecyl, and benzyl butyl phthalate. Hair from a skin area (1.3cm in diameter) on the back of male F344 rats was clipped, the [14C]phthalate diester was applied in a dose of 157 {micro}mol/kg, and the area of application was covered with a perforated cap. The rat was restrained and housed for 7 days in a metabolic cage that allowed separate collection of urine and feces. Urine and feces were collected every 24 hr, and the amount of [14C] excreted was taken as an index of the percutaneous absorption. At 24 hr. diethyl phthalate showed the greatest excretion (26%). As the length of the alkyl side chain increased, the amount of [14C] excreted in the first 24 hr decreased significantly. The cumulative percentage dose excreted in 7 days was greatest for diethyl, dibutyl, and diisobutyl phthalate, about 50-60% of the applied 14C; and intermediate (20-40%) for dimethyl, benzyl butyl, and dihexyl phthalate. Urine was the major route of excretion of all phthalate diesters except for diisodecyl phthalate. This compound was poorly absorbed and showed almost no urinary excretion. After 7 days, the percentage dose for each phthalate that remained in the body was minimal and showed no specific tissue distribution. Most of the unexcreted dose remained in the area of application. These data show that the structure of the phthalate diester determines the degree of dermal absorption. Absorption maximized with diethyl phthalate and then decreased significantly as the alkyl side chain length increased.