Effective Strategies for Monitoring and Regulating Chemical Mixtures and Contaminants Sharing Pathways of Toxicity

Arjun Venkatesan,Rolf Halden

doi:10.3390/ijerph120910549

Abstract

Traditionally, hazardous chemicals have been regulated in the U.S. on a one-by-one basis, an approach that is slow, expensive and can be inefficient, as illustrated by a decades-long succession of replacing one type of organohalogen flame retardants (OHFRs) with another one, without addressing the root cause of toxicity and associated public health threats posed. The present article expounds on the need for efficient monitoring strategies and pragmatic steps in reducing environmental pollution and adverse human health impacts. A promising approach is to combine specific bioassays with state-of-the-art chemical screening to identify chemicals and chemical mixtures sharing specific modes of action (MOAs) and pathways of toxicity (PoTs). This approach could be used to identify and regulate hazardous chemicals as classes or compound families, featuring similar biological end-points, such as endocrine disruption and mutagenicity. Opportunities and potential obstacles of implementing this approach are discussed.

Highlights

IntroductionMore than 84,000 chemicals are included in the U.S Toxic Substances Control Act (TSCA)
Today, more than 84,000 chemicals are included in the U.S Toxic Substances Control Act (TSCA)inventory, and approximately 10% of these chemicals are associated with cancer [1,2]
Two classic approaches to address toxicity resulting from chemical mixtures are concentration addition (CA) and independent action (IA), for which information on both the individual chemical toxicity and concentration of the chemical in the respective mixture of interest is needed [5,6]

Summary

Introduction

More than 84,000 chemicals are included in the U.S Toxic Substances Control Act (TSCA). Research has shown that the presence of certain congeners (e.g., PCB 153) in mixtures antagonized the effects of TCDD, highlighting some major limitations for the use of additive TEF approach [7] These approaches of estimating toxicity require extensive ecotoxicological data for individual chemicals and a thorough characterization of the chemical mixtures. The large number of congeners, their varying toxicity (depending on the degree of halogenation), the possibility of inter-transformation of congeners from a higher to a lower halogenation state, and presence of impurities (such as dioxins and furans), make monitoring and legislative actions for OHFRs exceptionally complicated Managing this group of problematic chemicals has proven to be a challenge, as indicated by 45 years of still ongoing legislative actions for PBDEs. Relevant challenges and legislative initiatives are highlighted in the following, using OHFRs as an illustrative case study of lessons learned from monitoring practices and chemical regulations

Organohalogen Flame Retardants and Current Regulations

Future Monitoring Strategies

Findings

Conclusions