Multimedia modeling of human exposure to chemical substances: The roles of food web biomagnification and biotransformation

Abstract

The Risk Assessment IDentification And Ranking (RAIDAR) model is refined to calculate relative human exposures as expressed by total intake, intake fraction (iF), and total body burden (TBB) metrics. The RAIDAR model is applied to three persistent organic pollutants (POPs) and six petrochemicals using four mode-of-entry emission scenarios to evaluate the effect of metabolic biotransformation estimates on human exposure calculations. When biotransformation rates are assumed to be negligible, daily intake and iFs for the nine substances ranged over six orders of magnitude and TBBs ranged over 10 orders of magnitude. Including biotransformation estimates for fish, birds, and mammals reduced substance-specific daily intake and iF by up to 4.5 orders of magnitude and TBB by more than eight orders of magnitude. The RAIDAR iF calculations are compared to the European Union System for the Evaluation of Substances (EUSES) model iF calculations and differences are discussed, especially the treatment of food web bioaccumulation. Model selection and application assumptions result in different rankings of human exposure potential. These results suggest a need to critically consider model selection and to include reliable biotransformation rate estimates when assessing relative human exposure and ranking substances for priority setting. Recommendations for further model evaluations and revisions are discussed.

The precautionary principle and chemicals management: The example of perfluoroalkyl acids in groundwater

“…For small non-polar molecules in water-respiring organisms this is generally the case, as the excretion of such a compound is via passive diffusion leading to similarity across species after allometric scaling (Nagilla and Ward, 2004). For chemicals eliminated primarily via metabolism, BCF FISH is often conservative with respect to higher organisms as metabolism is generally more rapid in higher organisms than in fish (Arnot et al, 2010). However, BCF FISH may not be conservative for higher organisms in food webs where there is significant biomagnification of the chemical arising from dietary exposure.…”

Assessment and improvement of biotransfer models to cow’s milk and beef used in exposure assessment tools for organic pollutants

“…ingestion of food for the input, and for the output faeces excretion, urination, milk excretion and metabolism ( Fig. 1) (Czub and McLachlan, 2004;Hendriks et al, 2007;Arnot and Mackay, 2008;Arnot et al, 2010).…”

“…The mean value of the metabolic rate in fish (k met Fish ) from EPI-HL and IFS-HL was adopted for the predictions. Each metabolic rate was then converted to the metabolic rate in cattle being multiplied by the interspecific correction factor (ICF) based on Arnot et al (2010) which previously assumed the cattle metabolic rate 5 times faster than the fish metabolic rate.…”

“…Another case for filling the data gaps is using parameter values obtained from other species, called species read-across in this study. For example, Arnot et al (2010) used the measured metabolic rate in fish as a substitute for avian and mammalian species with the biological explanation of each metabolism. These substitution techniques should also be useful for estimating the cattle metabolism of a wide scope of organic pollutants targeted by the regulatory authorities.…”

Modeling bioaccumulation in coupled pelagic–benthic food chains: Past insights and future directions

“…Third, this model inspired further development of bioaccumulation models for different trophic levels and types of food chains under both steady-state and temporal scenarios [16][17][18][19] and classes of chemicals including substances susceptible to biotransformation [20][21][22][23][24][25][26]. Moreover, food-chain models have become increasingly used in region or site-specific assessments to inform policy and remedial options [27][28][29][30][31][32][33][34][35][36][37][38] as well as in prioritization and risk assessment of chemicals in commerce [39][40][41][42].…”