Modified ACCHUMANsteady bioaccumulation model: Plastic ingestion as a vector of exposure for organic chemicals and implications to human health

A modified Excel version of the ACCHUMAN steady state bioaccumulation food web model.  The model includes capability to simulate the ingestion of microplastic particles that include plastic additive chemicals.  The size, amount and percent inclusion of plastic additive chemicals can be adjusted.  Ingestion of microplastic particles can occur via fish, cows and/or humans.  The modifications to the model thus enable an evaluation of the relative importance of ingesting microplastic as a vector of exposure to chemicals as compared to other exposure pathways, such as via the diet and/or respiration.  When the exposure to chemicals occurs only via ingestion of plastic, for instance, the relative contribution of exposure to plastic additive chemicals can be seen to represent >99% of the overall exposure.  However, when released to the environment, the chemicals in the plastic are assumed to be capable of reaching steady state with the surrounding environment, which can signficantly reduce the relative contribution that ingesting microplastic may represent as a source of exposure to the same chemicals.  The exposure to plastic additive chemicals can thus be complex, influenced by a variety of factors.  Given that the model estimates the steady-state body burden concentration of chemicals in humans, it is further possible to evaluate how much microplastic would be needed to exceed a specific point of departure and/or a toxicological threshold of concern.  The model presented here has been modified from the original Excel version of ACCHUMAN, however, future iterations will work towards developing a Python version of the model, which is identified as important given the complexity encountered with the existing VBA code.  For anyone wishing to use the model please contact the authors for additional details.