Environmental Chemicals: Integrative Approach to Human Biomonitoring and Health Effects

In recent decades, citizen awareness of toxic chemicals has been a topic of interest, particularly concerning national and international policy decision makers, expert/scientific platforms, and health protection organizations (WHO, UNEP, CDC, EFSA, IPEN, etc [...].

interact with the tissues, have been reported. In addition, the increasing incidence of neurodegenerative diseases, immune disorders, and cancers may also be related to the increased exposure microplastics and their co-contaminants [19]. The effects of exposure in human health are influenced not only by the type and concentration of the chemicals but also by the effects and complexity of mixtures and, more importantly, by the timing of exposure. Indeed, there is an increased vulnerability to chemical exposure in windows of greater susceptibility, especially during childhood and pregnancy, which may impair lifetime health. Therefore, there is a need to biomonitor and evaluate all exposures across lifespans and its interaction with our own unique characteristics, the 'exposome'.
As a complex field, researchers continue to wrestle with important issues, which requires an integrative and multidisciplinary research approach to this problematic, resorting to complementary methodologies to measure human exposure to environmental chemicals and to assess their health effects. One can define three main pillars: (1) environmental chemical analysis and development of new detection methods, with the identification and quantification of biomarkers of exposure and/or effect and/or susceptibility and development of new analytical methodologies for the detection of biomarkers in several human matrices (e.g., blood, plasma, serum, urine, and adipose tissue); (2) evaluation of biological effects, through the assessment of exposure impact on human health (e.g., general population, and people with obesity or diabetes) and/or resorting to experimental and mechanistic approaches (in vitro/in vivo models); and (3) data management and statistical analysis, namely in study design and sampling in the human population.
Biomonitoring studies are a good example of this complementarity, encompassing the measurement of internal levels of chemicals/metabolites in easily accessible biological fluids or tissues, and aiming to understand environmental health threats and to assist policy measures, namely in susceptible populations such as children. It requires analytical methods of high selectivity and high sensitivity due to low concentrations and limited sample volumes. Toxic chemicals cover a wide range of chemical groups with different physical-chemical properties. Therefore, scientific literature presents several analytical methods even for the same substance groups. Depending on the chemical group, the human biomonitoring biomarkers are either parent compounds or metabolites. A large variety of matrices have been analyzed (blood, urine, adipose tissue, hair, nails, breast milk, etc.). This complexity calls for the urgent need to carry out further studies on the appropriate analytical methods for each group of compounds and matrices. Biomonitoring studies identify new chemicals in human tissues, monitor the distribution of exposures among the general population, and provide a measure of potential health risk.
Preventing diseases arising from chemical environments requires the development of a consistent and rational approach to human biomonitoring as a complementary tool to assist in providing evidence-based public health and environmental measures, confirming the health effects of toxic chemical exposures, and validating regulatory actions and policies.
Author Contributions: All authors contributed equally in all statements. All authors have read and agreed to the published version of the manuscript.

Conflicts of Interest:
The author declares that he has no known competing financial interests or personal relationships that could influence the work reported in this paper.