Data, prenatal

Tetrachlorodibenzo-p-Dioxin (8-D). Prenatal Effects. Data from 2 experiments conducted with 0.125-16 / g/kg/day doses of... 

KHERA AND RUDDiCK Polychlowdihenzo-p-dioxins and 2-Chlorodibenzo- -Dioxin Prenatal Data... 

Children s Susceptibility. Data needs relating to prenatal developmental exposures are discussed above in the Developmental Toxicity subsection. 

The Guidelines for Developmental Toxicity Risk Assessment (US-EPA 1991) outline principles and methods for evaluating data from animal and human studies, exposure data, and other information to characterize risk to human development, growth, survival, and function because of exposure prior to conception, prenatally, or to infants and children. 

In order to fully assess the hazardous properties of a substance with respect to reproductive toxicity, the key data requirements are a two-generation study and a prenatal developmental toxicity (teratogenicity) smdy in two species (EC 2003). 

Rats and rabbits are the preferred species for prenatal toxicity studies because of the accumulated experience in developmental toxicity studies over many years. However, other species should be considered if the available metabolism or pharmacokinetic data show that they are more relevant to the human (see Note 1). 

The first phase of ToxCast profiled a 309-chemical library consisting mostly of pesticidal actives as well as several other compounds of high interest. The acceptance criteria for chemical selection for inclusion in Phase I were as follows (a) availability of in vivo data from bioassays on chronic/cancer, multigenerational reproductive, and/or prenatal developmental toxicity (95% Phase I chemicals met this criteria) (b) solubility in DMSO (the vehicle for HTS assays) with a log of the octanol/water partition coefficient (logP) between -1 and +6 (97.5% met this criteria) (c) molecular weight in the range of 250-1,000 (90% met this criteria) and (d) commercially available at a purity >90% (98% met this criteria) (16). Current information about the Phase I (and Phase II) chemical library can be found at the NCCT website address http //www. epa.gov/ncct/toxcast/chemicals.html. 

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