There is a growing body of evidence demonstrating that chemicals can affect epigenetic processes in organisms (e.g. DNA methylation, histone tail modifications, microRNAs, etc) and subsequently alter the way an organism responds to a stressor. These epigenetic effects may result in long-term impact on phenotypes, fitness, health and disease in living organisms both within generations (from embryogenesis to adulthood) and in a trans-generational fashion. While most research in this area has focused on plant or vertebrate systems (including human and fish), an increasing number of studies has recently been published in invertebrate species. The results of these studies indicate that the epigenome and epigenetic regulatory mechanisms in invertebrates may be different compared with vertebrates and plants.
The aim of the part II is to discuss a number of questions remain to be answered, despite the substantial amount of research published in this area particularly in the context of long-term impact on human health and ecological risk assessment of chemicals:
(i) What is the biological variability/natural variation of epigenetic traits? When can we classify a chemical as hazardous by way of causing significant epigenetic abnormalities with biological relevance?
(ii) Which epigenetic endpoints and bioassays are most informative for chemical risk assessment? How should we standardise procedures and protocols for testing epigenetic effects (including transgenerational epigenetic effects) of chemicals?
(iii) What evidence is available on the nature of dose response relationships for epigenetic effects in humans and environmental species exposed to chemicals?
(iv) What is the potential for cross-species extrapolation regarding epigenetic effects? Is there phylogenetic conservation of core epigenetic processes? How these processes are influenced by chemicals across the animal and plant kingdoms?
(v) Should chemicals that are designed to cause epigenetic modifications (e.g. epidrugs) be considered as potentially hazardous when they enter the environment?
(vi) What is the relationship between epigenetic changes and adverse outcome pathways/toxicity pathways leading to developmental, reproductive, carcinogenic and, eventually trans-generational and multigenerational effects? Can adverse outcome pathways including adverse changes to the epigenome?
(vii) What are the potential relevant in vivo and in vitro assays that can be used for the screening and testing of chemicals for potential epigenetic effects in a validated and standardised manner?
These questions will be discussed during the sessions by the speakers in their talks and through interactions with the audience while the final panel debate will serve as open discussion to summarize the findings from this symposium and the steps that need to be taken to further research and regulatory practices.