The fields of reproductive and developmental toxicology have found a great many examples of toxicant exposures causing adverse consequences that are expressed from one generation to the next. Lopez-Rodriguez et al. (2021) provide two important examples of how neural and endocrine toxicity can be expressed across generations, one persistent and one emergent.
They reported a persisting effect with developmental exposure to an endocrine-disrupting mixture in which an effect (reduced maternal behavior) that was present in the F1 generation was also seen in the F2 and F3 generations. Toxicant effects can persist in a variety of ways across generations, including the neural and epigenetic changes seen by these investigators. Importantly, they showed with cross-fostering studies that toxicant-induced changes in maternal care by the F1 generation caused changes in maternal care by their offspring and subsequent generations. The deficits were not apparent with cross-fostering. Thus, it appears that the persistence of the effect across generations was carried through behaviorally due to the repetition of lessened maternal care in each generation. Toxicant-induced changes in maternal and other social behavior like those in other animals can have cascading effects in humans that are relayed across generations long after the toxicant exposure has ended.
These investigators also documented an interesting case of emerging toxicity (delayed sexual maturation and follicular development in adulthood) expressed across generations. They found that that low-dose developmental exposure to a mixture of endocrine-disrupting compounds did not cause delayed sexual maturation in the F1 generation but did cause this effect in F2 and F3 generations. This is not a persistence of effect, but rather an emergence of effect across generations. This effect may be due to low-dose exposure causing adaptations in development that compensated for the exposure effects in the F1 generation but that were maladaptive in later generations when the endocrine disruption was not present.
As we advance toxicology by investigating lower-dose effects, we...