How Alternatives to Animal Testing Increases our Understanding of Human Health Risk

Human biology played an increasingly fundamental role at the International Society for Exposure Science annual meeting

I know I say this every year, but it really is an exciting time for exposure science. And risk assessment in general, for that matter. Why? Because we are finally moving beyond the old paradigm of risk assessment. The old-school thinking of “what’s the hazard level, what’s the exposure, and is one bigger than the other?” is becoming supplanted by a more holistic approach to understanding how people interact with chemicals in the world around them, and what that means for human health.

For my money, the program at this year’s annual meeting of the International Society for Exposure Science (ISES) at Utrecht was the best I’ve ever seen. It’s always a hectic week for Creme Global, and this year between my colleagues Conor McGauran, Giulia Vilone and I, we had a stand, a workshop, three presentations, and a number of other ISES-related meetings and events.

The theme of the meeting was “Interdisciplinary Approaches for Health and the Environment”, and it was certainly an appropriate description. As our understanding of human health and risk assessment becomes more refined, so does the analysis become more of a continuum. At times I felt like I could equally have been at a conference on toxicology or systems biology; it all depends on how you choose to view things. Many of the talks I attended discussed how external exposure can be linked to internal exposure, sometimes going all the way down to a cellular level. Modern toxicology often uses alternative approaches to characterising chemicals hazards rather than the more traditional animal testing. These include computational approaches such as Physiologically Based Pharmacokinetic (PBPK) models, which quantify the time course of a chemical in the body, the very useful Threshold of Toxicological Concern (TTC) concept, and in vitro or lab-based methods. Equally, at conferences on toxicology, exposure is becoming more and more a consideration as a fundamental part of risk assessment.

Amongst the Creme Global talks on some of our core areas of cosmetics and pesticides, I also co-organised a symposium this year on these new techniques in toxicology. As we move towards different techniques for measuring hazards, we need to understand what that means for exposure science. This is both from a technical perspective, where we have new metrics of hazard requiring us to modify our exposure models in order to better align them with toxicology, and equally we need to understand the overall significance of a risk assessment using novel toxicological methods in conjunction with exposure assessment.

It’s been said many times before, but it bears repeating; exposure is a key component of risk assessment that is all-too-often overlooked. Exposure is key because it quantifies to what extent humans interact different stressors (chemicals, microorganisms etc) with the potential to cause harm to human health. And exposure is not a number; it is a dynamic, changing, and varying quantity. So when we talk about risk, we need to accept that this cannot be magically shrunk into one number – and it can be very unhelpful to do so. We now have a wealth of understanding about human biology, the mechanisms of toxicology, and exposure science has become a mature field where we can provide very refined estimates of human exposure to external stressors.

Tragically enough, the “public” (that ambiguous swathe of people scientists like to refer to when they are annoyed with some sort of rhetoric they don’t agree with), don’t always accept that a degree of risk an essential component of life. Hopefully though, given the rate at which the field is advancing, we as scientists should be able to provide assurance that we really do have a handle on what the risks to human health are, and therefore our overlords in risk management have the information and tools to keep those risks under wraps.

Written by Cian O'Mahony on November 2 2016

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