Environmental Engineering Reference
In-Depth Information
Reproductive Toxicity Studies
The critical end-points relate to potential toxic effects on reproductive parameters,
including effects on mating behaviour (both sexes), on fertility (both sexes), the
implantation of blastocysts, embryonic and fetal development and survival, partu-
rition, lactation, and postnatal survival and development. Thus, a range of repro-
ductive parameters need to be assessed in one or more generations, depending on
whether the study is a one-generation (OECD Test Guideline 415), two-generation
(OECD Test Guideline 416) or three-generation test. Important end-points to assess
within each generation include: time after pairing to mating; mating behaviour;
percentage of females pregnant; number of pregnancies going to full term; litter
size; number of live births; number of stillborns; pup viability and weight at par-
turition, and postnatal days 4, 7, 14 and 21 days of age; the fertility index (% of
matings resulting in pregnancy); gestation index (% of pregnancies resulting in live
litters); viability index (% of pups that survive 4 or more days); and lactation index
(% of pups alive at 4 days that survived to day 21, i.e., weaning); gross necropsy
and histopathology on some parents (sires and dams), with attention paid to the
reproductive organs; and gross necropsy on weanlings
Developmental Toxicity Studies
The critical end-points in developmental toxicity studies relate to potential devel-
opmental effects in utero, including death, malformations, functional deficits and
developmental delays in fetuses. The following parameters are some of those
assessed: number of live litters; number of live fetuses/litter (total and by sex); sex
ratio of fetuses; fetal body weights; and litter weights. In addition to the above
developmental parameters other reproductive parameters are assessed including
the following; number of females pregnant; number of corpora lutea/dam; num-
ber of implants/dam; and number and percentage of pre-implantation loss/litter.
OECD Test Guideline 414 outlines the protocol for a standard developmental or
“teratology” study.
Special Studies
Different classes of contaminants may require special toxicology studies that are
not part of the “standard” package of studies. For example, it is common to test
organophosphate (OP) pesticides for their ability to cause delayed neuropathy by
conducting tests in hens (OECD Test Guideline 419), since this species is especially
sensitive to OP pesticide inhibition of neuropathy target esterase.
Toxicokinetic and Metabolism Data
Toxicokinetic (absorption, distribution and elimination) and metabolic data on the
handling of the contaminant in the test species, can be very useful in the evaluation
and interpretation of sub-chronic and chronic exposure study data.
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